PG Thesis

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    Impact of biofertilizers and nutrients on the quality and shelflife of tomato (Solanum lycopersicum L.) and on the fruit shelflife regulator (SIFSR) gene expression under elevated CO2 condition
    (Department of Plant Physiology, College of Agriculture , Vellayani, 2024-03-16) Haripriya, S.; Manju, R V
    The study entitled “Impact of biofertilizers and nutrients on the quality and shelflife of tomato (Solanum lycopersicum L.) and the Fruit Shelflife Regulator (SlFSR) gene expression under elevated CO2 condition” was undertaken with the objective of elucidating the effects of biofertilizers and nutrients on the quality and shelf-life of tomato and the Fruit Shelf-life Regulator (SIFSR) gene expression under elevated CO2 condition. The experiment was conducted using the Open Top Chamber (OTC) system facility in the Department of Plant Physiology, College ofAgriculture, Vellayani during 2022-2023. In the experiment, quality and shelf-life of tomato under elevated CO2 environment, as influenced by nutrients and biofertilizers were evaluated. The experiment was laid out in CRD consisting 5 treatments with three replications under ambient and elevated conditions. The treatments comprised of T1: POP, KAU+AMF, T2: POP, KAU+ PGPR Mix-1,T3: POP, KAU+Azolla T4: POP, KAU+50 ppm B + 50 ppm Zn+60 ppm Ca water spray (40, 55 and 70 DAS.) and T5: POP,KAU Control. The experimental results revealed, plant height after 75 days of sowing, specific leaf area and total dry matter increased significantly under elevated CO2 condition. Foliar spray with 50 ppm B + 50 ppm Zn + 60 ppm Ca along with POP, KAU recommendation recorded the highest plant height at 75 DAS. AMF treated plants were found to improve specific leaf area at 60 DAS and 75 DAS. Root to shoot ratio was reduced under elevated CO2 condition compared to ambient condition. Among the treatments, soil incorporation of PGPR before transplantation of seedlings resulted in the highest accumulation of dry matter. Among the physiological and biochemical parameters, total chlorophyll content, total carbohydrate content and chlorophyll stability index recorded higher values under elevated CO2 compared to open condition. However, a significant reduction was noted in total soluble protein content under elevated CO2 compared to open condition. PGPR mix 1 treated plants had recorded the highest chlorophyll and total carbohydrate content but plants foliar sprayed with 50 ppm B+50 ppm Zn+60 ppm Ca recorded the best results with respect to chlorophyll stability index. Exposure to elevated CO2 was found to increase the days for first flowering. Application of biofertilizers and nutrients reduced the days to flowering significantly. Plants came to flowering 40 DAS in the cases of PGPR mix-1 treated plants under eCO2 and AMF treated plants under aCO2. Due to high temperature associated with CO2 enrichment, pollen viability was lost and there was no fruit production inside OTC. Yield parameters such as number of fruits, fruit weight, fruit setting percentage and yield per plant showed significant difference among treatments. Among the treatments, PGPR mix-1 treated plants recorded significant increase in fruit weight, number of fruits and yield. Application of biofertilizers and nutrients had significant impact on quality of fruit and the most effective treatment was incorporation of PGPR mix-1 along with POP, KAU in terms of increased accumulation of lycopene, β-carotene, vitamin C, total sugars, pectin, moisture content, shelf-life and reduced physiological loss in weight. Foliar spray had the same impact as that of PGPR mix-1 treatment in the cases of vitamin C and beta carotene contents. Though AMF was found to increase P content of the fruits significantly, Fe content in fruits was influenced by foliar sprayed and PGPR mix-1 treatment.CO2 enrichment was found to have no influence on expression levels SlFSR gene in leaf tissues but the application of biofertilizers and nutrients was found to affect expression levels in fruits. Lowest level of expression was noted in fruits collected from azolla treated plants under ambient condition. The increase in atmospheric temperature due to increasing CO2 concentration can hasten perishability in the case of farm products. Efforts towards shelf-life extension to make fruit safe for long periods, keeping its original quality is of paramount importance today. The present programme clearly indicates that the shelf-life of tomato variety Vellayani Vijay can be enhanced by 85% through the soil incorporation of PGPR mix-1 before transplanting. This is a great achievement considering the higher perishability of tomato. Application of the biofertilizer, azolla which resulted in the 22.22% increase in shelf-life lead to down regulation of the GRAS transcriptional factor, SlFSR which controls fruit shelf-life by regulating expression of cell wall modifying genes and metabolism of pectin and cellulose. The significant extension of shelf-life achieved through the application of PGPR and AMF could be mediated through the down regulation of ethylene biosynthesis and cell wall degrading enzyme activities. Combined application of calcium, boron and zinc contributes towards firmness of fruit tissues and extended shelf-life to the same degree. The findings of the present programme revealed that application of azolla, PGPR mix-1 and AMF and combined application of calcium, boron and zinc improved the quality and shelf-life of tomato significantly. The result also proves SlFSR gene as a potential biotechnological target for the control of fruit shelf-life. The outcome of the programme will help to develop agricultural practices for improving the shelf-life and quality of tomato which is of paramount importance in the scenario of increasing atmospheric temperature and climate change.
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    Management of elevated CO 2 induced high temperature through nutrient and biofertilizer application in tomato (Solanum lycopersicum L.)
    (Department of Plant Physiology, College of Agriculture , Vellayani, 2021-12-17) Arunima, A S; R V, Manju
    The study entitled “Management of elevated CO 2 induced high temperature through nutrient and biofertilizer application in tomato (Solanum lycopersicum L.)” was undertaken with the objective of improving flowering and fruit set of tomato under elevated CO 2 condition through nutrient and biofertilizer application. The experiment was conducted using the Open Top Chamber (OTC) facility at the Department of Plant Physiology, College of Agriculture, Vellyani during 2020-2021. In the experiment, flowering and fruiting in tomato under elevated CO 2 environment, as influenced by nutrients and biofertilizers were evaluated. The experiment was laid out in CRD with nine treatments and three replications. The treatments comprised of T 1 :50 ppm B + 50 ppm Zn + water spray, T 2 :75 ppm B + 75 ppm Zn, T 3 : POP 150% N:125%P:125% K, T 4 : Azolla (soil application), T 5 :Azolla biofertilizer extract (20%) (foliar application), T 6 : Azolla biofertilizer extract(20%)(seed treatment), T 7 :POP, KAU+ PGPR1, T 8 : Control (water spray) and T 9 : Absolute control. Experimental results revealed that plant height, number of branches, number of leaves and specific leaf area increased significantly under elevated CO 2 condition at 75DAS. Among the treatments, foliar spray with 50ppmB+50ppm Zn+ water spray at 40, 55and 70 DAS recorded higher plant height (57.56%) at 75DAS. Nutrient application of 150%N:125%P:125%K found to improve the number of branches (91.82%), leaves (98.56%) and specific leaf area (40.03%) at 75DAS. Among the physiological and biochemical parameters, total chlorophyll content, total carbohydrate, photosynthetic rate, water use efficiency, chlorophyll fluorescence, chlorophyll stability index and proline content recorded higher values inside OTC compared to open condition. However, a significant reduction was noted in transpiration rate and total soluble protein content inside OTC compared to open condition. The foliar spray of 50ppm B+50ppm Zn+ water spray recorded high values for chlorophyll content (1.58 mg g -1 ) and cell membrane stability index (53.83%) compared to open condition at 75DAS. The application of POP 150% N:125% P:125% K recorded significantly higher photosynthetic rate (21.03μmol CO 2 m -2 sec -1 ), total carbohydrate(50.04mgg -1 ), chlorophyll stability index(135.38%) and chlorophyll fluorescence (0.74Fv/Fm). Also foliar application of 20% Azolla biofertilizer extract was found to significantly improve the relative water content (96.15%) and water use efficiency(6.82 mmol CO 2 mol -1 H 2 O) in tomato plants under elevated CO 2 conditions. Inside OTC, flowering delayed by 2 days and the total number of flower clusters (5.96) also increased compared to control (4.12). Reduction in pollen viability (82.42%) observed at higher CO 2 compared to control. But it was found to improve under treatment T1 (50ppm B+ 50ppm Zn + water spray) which resulted in highest fruit setting percentage (53.01%) as against the control (39.92%). Fruiting was delayed by 3 days inside OTC. However, the fruit weight was found to increase with water spray (54.46%), extra NPK(55.89%) and foliar spray of 50ppm B+ 50ppm Zn+ water spray(57.51%). Foliar application of Azolla biofertilizer extract (20%)(T5), 150% N:125% P:125% K(T3) than the recommended dose, as well as foliar application 50ppm B + 50ppm Zn+ water spray (T1) improved the yield per plant by 55.79%, 63.08% and 65.22% respectively compared to control. All these treatments also improved the quality parameters like lycopene, vitamin C, beta carotene and minerals (P, Fe) in tomato fruits under elevated CO 2 condition. The present study indicated the improved performance of tomato variety Vellayani vijay upon exposure to elevated CO 2 . But flowering, fruit set and ultimately the total yield were negatively influenced by elevated CO 2 induced high temperature. The impact of application of extra N, P and K than the recommended doses as well as foliar application of B and Zn indicate the changing nutrient requirement of tomato under the current scenario of increasing atmospheric CO 2 concentration. The response of experimental plants to foliar application of Azolla extract (20%) strongly suggest the effectiveness of this biofertilizer in overcoming the impacts of elevated CO 2 induced high temperature and thereby improving the plant performance. Recommendations based on the best treatments can be developed by extending the study to field condition since the treatments were found to improve the yield and quality even under ambient condition
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    Management of button shedding in coconut by root feeding of nutrients and growth regulators
    (Department of Plant Physiology, College of Agriculture , Vellayani, 2021-12-13) Shanmugapriya, D; Roy Stephen
    The study entitled “Management of button shedding in coconut by root feeding of nutrients and growth regulators” was conducted to determine the physiological management of button shedding in coconut by using nutrients and growth regulators through root feeding and to determine the role of beneficial microbes on auxin production in coconut. Two experiments were conducted at Coconut Research Station, Balaramapuram during 2020-2021. Survey was conducted for the first experiment to select the palms with uniform age having significant button shedding. The respective solutions were prepared and administered to the palms through root feeding. The yield parameters, biochemical and physiological parameters were estimated and recorded for the first six months. The results shown that the yield parameters such as the number of female flowers and the number of buttons retained showed non siginificant variation in all the treatments. The percentage of button shedding also showed non siginificant variation during 5th and 6th month. Among the 7 treatments, T2 [Hoagland solution - 2X] reported the lowest button shedding percentage (22.9, 24.2, 28.4 and 31.1%) for the first four months respectively followed by T6 [Salicylic acid-200ppm] and T5 [Borax (0.5 g palm-1 ) + 2, 4- D (50 ppm)] .T1 [Control] reported the highest level of button shedding percentage (32.88, 37.21, 44.25 and 50%) for the first four months respectively. The physiological parameters such as transpiration rate shown the highest level (3.8, 4.0, 4.3, 4.2, 4.3, 4.4 mmol H2O m-2 sec-1 ) in the T2 treatment followed by T6 respectively for the first six months. T2 reported the maximum photosynthetic rate (4.4, 4.6, 4.9, 4.8, 4.9 and 5.2 µmol CO2 m-2 sec-1 ) for a period of first six months respectively which was on par with T6. T1 reported the minimum photosynthetic rate and transpiration rate for the first six months. The biochemical parameters such as carbohydrate content was maximum (21.84,79.65, 77.42, 84.33,96.66 mg g-1 ) in the T2 treated palms respectively except 2nd month. There was no significant variation in between the treatments during 2nd month. The macronutrients such as N (2.07, 2.26, 2.5, 2.37, 2.41, and 2.54 %), K (1.27, 1.46, 1.7, 1.65, 1.87, 2.14%), Mg (1.56, 1.74, 1.95, 1.6, 1.78, and 1.89 %), Ca (0.57, 0.88, 1.05, 0.88, 1.08 and 1.16%) and S (0.57, 0.75, 1.06, 0.86, 1.01 and 1.19%) were higher in T2 treated palms respectively for six months. T7 [SA (200 ppm) + 2, 4- D (50ppm)] recorded the maximum phosphorus content (0.13, 0.14, 0.18, 0.08, 0.15, and 0.22 %) during the observation of first six months respectively. Micronutrients such as Fe (158.5, 175.45, 240, 234, 258.33 and 275.66 ppm), B (15.06, 19.16, 26.93, 20.33, 25.33 and 31.33ppm) and Mn (169.55, 179.66, 188.66, 181.92, 186.66 and 195.33 ppm) was also higher in the T2 treated palms for the first six months respectively. Except 1st month, T2 reported higher copper content (54, 67.66, 61.66, 71, 81.33ppm) from 2nd to 6th month. T5 [Borax (0.5 gm palm-1 ) + 2, 4- D (50 ppm)] reported the highest Zinc content (42.33, 43.9, 55.34, 46.43, 53.32 and 62.06 ppm) for the first six months respectively. T1 reported the lowest level of carbohydrate content and nutritional (macro and micro) content in the leaf during the six months period. The second experiment was performed to evaluate the role of beneficial microbes on auxin production in coconut. Piriformospora indica vermiculite mixture and Rhizobium radiobacter suspension were prepared and inoculated in the 3 months old coconut seedlings and the colonization was evaluated after 15 days of inoculation and recurred until the result was obtained. The results revealed that the chlamydospores similar to the P. indica were colonized in the cortex region of the root hairs of the coconut seedlings. Colonization of Rhizobium radiobacter were not observed in the roots of coconut seedlings. In coconut, considerable loss in yield had been observed due to the phenomenon of shedding of buttons. It varies from 55 to 95 per cent depending on the conditions prevailing, and on the variety of the coconut. In my study, root feeding of Hoagland solution (2X) recorded 43.03, 53.6, 55.7, 60.7% lower button shedding percentage over the control during the first four months respectively. Salicylic acid-200 ppm and [Borax (0.5 g palm-1 ) + 2, 4- D (50 ppm)] was also able to control the button shedding effectively.
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    Deciphering the mechanistic role of plant neurotransmitters in rice
    (Department of Plant Pathology, College of Agriculture ,Vellayani, 2024-01-15) Sharmila, S; Parvathi M Sreekumar
    Rice, a fundamental dietary staple food for over half the global population, particularly in developing nations. It has developed intricate and sophisticated mechanisms to confront environmental stresses such as drought, heat and salinity. In response to stress conditions, rice plants showcase diverse adaptive strategies. Melatonin and dopamine serve as pivotal signaling molecules, contributing significantly to diverse physiological processes in plants, alongside stress ameliorative potentials. The present study was aimed at deciphering the mechanistic roles of these plant neurotransmitter-like ameliorants in rice. The first experiment was conducted at the Department of Plant Physiology, College of Agriculture, Vellanikkara laid out in a Completely Randomized Design (CRD) with nine treatments, with three replications. Rice seedlings were exposed to three stressors in petriplates namely Methyl Viologen (MV; 2.5 μM and 5 μM for oxidative stress), Dithiothreitol (DTT; 2.5 mM and 5 mM for endoplasmic reticular stress) and Antimycin A (ANT A; 10 µM and 20 µM for chloroplast and mitochondrial stress). Melatonin and dopamine, at concentrations of 100 µM and 0.4 µg/mL, respectively, were used to investigate their ameliorative potentials against the three stressors. The study examined various traits such as growth patterns, biochemical changes and stress tolerance mechanisms to elucidate the potential protective or ameliorative effects of melatonin and dopamine under the given stress conditions. The seedling assays indicated that the growth of non-stressed ameliorant-treated seedlings exceeded that of stressed ones. Dopamine was effective in mitigating damage caused by oxidative and ER stress, while melatonin demonstrated superior performance in alleviating chloroplast and mitochondrial stress. Malondialdehyde (MDA) content increased significantly under oxidative stress induced by 5.0 μM MV treatment and decreased in the control. Under ER stress, MDA was higher in DTT treated seedlings @ 2.5 mM with (84.13%) and without (94.83%) dopamine. In chloroplast and mitochondrial stress, MDA levels were 25.6% and 82.5% lower in dopamine-treated seedlings stressed with ANT A @ 10 and 20 μM, respectively. Histochemical observations revealed that, methyl viologen induced damage elevated ROS production, as indicated by prominent staining in stressed seedlings, with an ameliorant specific scavenging activity in shoots (melatonin) and roots (dopamine). Noticeably, dopamine outperformed melatonin at higher ER stress levels, in maintaining shoot and root growth, whereas t in chloroplast and mitochondrial stress, dopamine and melatonin had distinct roles in shoot and root growth maintenance, respectively. The second experiment was carried out in pots at the nethouse facility, Department of Plant Physiology, College of Agriculture, Vellanikkara, in Completely Randomized Design (CRD) with three replications. One month old rice plants were subjected to four treatments namely a mock/absolute control, Tween-20 (0.05%), Melatonin (100 μM) and Dopamine (0.4 μg/mL). Both dopamine and melatonin treatments constitute Tween-20 as a surfactant. Results indicated that the ameliorants have a distinct physiological role in stress alleviation over control. Plant height variations indicated a more significant increase with Tween-20, followed by melatonin and dopamine, compared to the unsprayed control. Ameliorant treated rice showed enhanced chlorophyll levels, with the highest content observed in Tween-20-treated plants, followed by melatonin and dopamine treatments. Likewise, dopamine treatment resulted in a higher net photosynthetic rate than melatonin, while Tween-20-treated plants displayed the highest net photosynthetic rate and stomatal conductance among all treatments. Soluble sugar and protein contents were on par across the four treatments. The research also focused on exploring the response of noble prize-winning mechanosensitive ion channel receptors such as TRPV1 and PIEZO mediating human sensory perception of temperature, touch, and cold, to exogenous application of melatonin and dopamine. Acknowledging the potential involvement of plant neurotransmitter-like molecules like melatonin and dopamine in orchestrating sensory responses, the study delved into the plant homologs of these receptors. Phylogenetic analysis of TRPV1 with diverse species indicated a 33% homology between Oryza sativa and Homo sapiens. Further, in silico expression analysis of TRPV1 under diverse stress conditions using the ePlant Stress Expression Browser was studied and interpreted. Mechanosensory receptor expression signatures (OsPIEZO, OsTRPV1, OsPMTR1) and basal transcriptional regulator responsiveness (OsTAF2, OsTAF4, OsTAF6, OsTAF9A, OsTAF9B, OsBTF3), were examined in melatonin and dopamine treated rice leaf tissues. OsTAF4, OsTAF6, OsTAF9A, OsTAF9B, OsBTF3, OsPIEZO, OsTRPV1 and OsPMTR1 were upregulated in dopamine-treated plants (0.4 µg/mL) compared to control, whereas OsTAF4 and OsTAF6 showed similar expression patterns under both dopamine and melatonin administration. OsTAF2 exhibited higher expression in Tween-20 treated leaf tissues. With dopamine treatment, OsTAF9B, OsPIEZO and OsPMTR1 displayed nearly three-fold change in transcript levels over control. OsTRPV1 exhibited one- and two-fold changes under melatonin and dopamine treatments, respectively, marking the first report of mechanosensory receptor responsiveness to plant neurotransmitter-like molecules in rice.
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    Elucidation of hormonal physiology underlying the differential response of indica and japonica rice to in vitro system
    (Department of Plant Physiology, College of Agriculture ,Vellanikkara, 2024-01-19) Anubharathi, K.; Krishna Kumar, G
    World is running towards 9 billion population by 2050 along with two serious issues in its hand– climate change and food insecurity. It can ultimately hamper the world to achieve Sustainable Development Goals (SGDs). High yielding and climate resilient crops are crucial towards accomplishing SDGs. Half of the world population relies on rice and it is also a model monocot crop which is widely used for the study of various crop improvement programs. Indica rice is the widely cultivated genotype across India. Improvement in quantitative and qualitative traits of rice is very important to battle against hunger and malnutrition. Micropropagation takes the lead towards crop improvement through various biotechnological approaches. In indica there is a research gap due to recalcitrant calli which is poor to regenerate under micropropagation conditions. The present study was undertaken to dissect the reason behind this limitation in indica. In the current study, IR64 an indica genotype along with a check japonica genotype, Nipponbare were used. The manually dehusked surface sterilized seeds were inoculated in the callus induction media with various dosages of 2,4-D (0, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mg/L). The response of the seeds to 2,4-D was examined by callus induction frequency (%), callus size (mm), and fresh and dry weight of callus (g). The calli from 3 mg/L 2,4-D had maximum callus induction frequency in IR64 while in Nipponbare it was 100 % at 1.5 mg/L 2,4-D. The size, fresh weight and dry weight of the callus was maximum at 3 mg/L of 2,4-D in both genotypes. Calli from IR64 was compact and larger than that of Nipponbare. Considering all the dosages, calli from 3 mg/L 2,4-D performed best in both genotypes. The maximum size and weight might be the due to aggressive cell division and growth of the calli. This uncontrolled cell division can possibly affect the development of embryogenic calli. Hence calli from suboptimal concentration i.e., 2.5 mg/L of 2,4-D was selected for regeneration process. Two to three week old calli from 2.5 mg/L 2,4-D were transferred to two regeneration media. The first media was supplemented with 0.05 mg/L NAA and 2, 2.5, 3 mg/L BAP, kinetin and the other with 0.5 mg/L NAA with same concentration of cytokinins as in the first set of treatments. The differential response of the callus to the media was determined by recording the number of green calli, shoots, brown and hairy calli, chlorophyll and carotenoid content, secondary metabolites, and endogenous hormonal homeostasis. In general, green calli were more in the media with 0.5 mg/L NAA in both genotypes. IR64 had maximum number of green calli at 0.5 mg/L NAA with 3 mg/L BAP and Nipponbare at 0.05 mg/L NAA with 3 mg/L BAP. No shoots were regenerated from IR64 in both regeneration media types tested. In the media with 0.5 mg/L NAA shoots from Nipponbare were regenerated. Number of brown calli were more in IR64 than Nipponbare in both media. Maximum number of brown calli were found in the media with 0.05 mg/L NAA in IR64. Total number of hairy calli were higher in Nipponbare than in IR64 irrespective of the media. Chlorophyll content in IR64 was maximum at 0.05 mg/L NAA and in Nipponbare at 0.5 mg/L NAA. In both cases, media with BAP had maximum chlorophyll content. Carotenoid content was high in IR64 at 0.05 mg/L NAA. In the media with 0.5 mg/L NAA, higher carotenoid was found at BAP in IR64 and kinetin in Nipponbare. Secondary metabolites had both positive and negative roles in the regeneration of calli. Total phenols were significantly high at 0.05 mg/L in IR64 than at 0.5 mg/L NAA. Nipponbare had maximum phenol content at 0.05 mg/L NAA and 3 mg/L BAP and with no significant difference in other treatments for both the media types. Alkaloid content of calli was collectively less in the media with 0.5 mg/L NAA than 0.05 mg/L NAA. In IR64 the alkaloid content exhibited a two-fold increase at 0.05 mg/L NAA. Nipponbare maintained steady alkaloid content in almost all treatments in both media. As auxin and cytokinin ratios are critically important, in this study auxin content and IAA oxidase activity were determined. Higher auxin content in both genotypes has recorded at the media supplemented with 0.05 mg/L. In the media 0.5 mg/L NAA the auxin content was reduced in IR64 and also had improved auxin homeostasis. After four weeks, shoots of Nipponbare were transferred to the ½ x MS media without NAA and 0.5 mg/L NAA. The efficacy of the rooting media was determined by observing root number, total root length, dry weight of roots and shoots. Media without hormone failed to produce roots however the media with 0.5 mg/L NAA had the positive effect of rooting irrespective of the shooted calli from different treatments. The present study points that IR64 exhibited considerably good green calli number, better accumulation of chlorophyll content than Nipponbare. But better regeneration of Nipponbare may be attributed to its friable nature of the calli along with steady maintenance of the secondary metabolites and auxin content. The poor performance of IR64 might be due to higher levels of phenolics and alkaloids accumulation. These findings also give insights into the importance of auxin-cytokinin signaling crosstalk and auxin transport during shoot regeneration.
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    Elucidating the role of growth promoting endophytic fungus Piriformospora indica for water stress tolerance in rice (Oryza sativa L.)
    (Department of Plant Physiology, College of Agriculture, Vellayani, 2022-10-03) Lekshmi Mohan S; Beena R
    The research work titled “Elucidating the role of growth promoting endophytic fungus Piriformospora indica for water stress tolerance in rice (Oryza sativa L.)” carried out at Department of Plant Physiology, College of Agriculture, Vellayani during 2020-2021 with the objective to elucidate the changes in morphological, physiological, biochemical and molecular mechanisms associated with water stress tolerance in Piriformospora indica-colonised rice. The roots of Ptb 23, Ptb 24, Ptb 29 and Ptb 30 varieties’ seedlings were appraised microscopically for root colonisation after germinating in trays containing P. indica-infused composted coir pith- cow dung (1:1) mixture maintained in temperature and humidity-controlled conditions. Isolated or chains of double walled pear shaped chlamydospores were observed in the root sections of seedlings in trays with P. indica after seven days of cocultivation. On treatment with Poly Ethylene Glycol (PEG) 6000 at concentrations of 0, 5,10, 15, and 20 per cent, the varieties on root colonisation with P. indica showed higher water stress tolerance while the water stress tolerant varieties Ptb 29 and Ptb 30 showed tolerance to water stress even in the absence of P. indica. Shoot length, shoot and root dry weight, number of root branches, SVI 1 and SVI 2 increased in P. indica-colonised plants than non-colonised plants under water stressed condition, while the root length decreased. Based on the observations on different parameters, Ptb 29 was considered as the best water stress tolerant variety and as Ptb 23 performed better than Ptb 24 under water stress condition, the former was selected as the best water-stress susceptible variety. The P. indica-colonised and non-colonised rice seedlings of Ptb 23 and Ptb 29 were the evaluated for water stress tolerance during the different growth stages by studying the morphological, physiological, biochemical, yield parameters and molecular aspects. P. indica-colonised plants under water stress exhibited higher shoot and root length, shoot and root dry weight, root-shoot ratio and root volume, however, it was more conspicuous in the water stress susceptible variety. The enhanced plant shoot-root growth and biomass production as well as other changes in plant morphology after P. indica-colonisation can be related to the plant response to increase auxin level in roots either produced by the fungus or by the plant due to stimulation by the endophyte. Relative water content was found to be higher in water stressed P. indica-colonised plants in both Ptb 23 and Ptb 29, although the effect of colonisation was more visible in Ptb 23. There was significant increase in the specific leaf area in P. indica-colonised plants of both varieties than non-colonised plants. In the current study, rice plants of Ptb 29 under water stressed condition had higher cell membrane stability index than Ptb 23. Plants in the presence of P. indica showed significantly reduced MDA content which indicates that P. indica lowers the adverse consequences of drought. Ptb 29 had lower MDA content than Ptb 23, which further established that Ptb 29 is more tolerant to water stress. Gas exchange parameters like stomatal conductance, transpiration rate and photosynthetic rate showed increase in P. indica-colonised plants than in non-colonsed plants. Retention of chlorophyll was significantly higher in water stressed plants of Ptb 29 than Ptb 23. The increased activity of antioxidant enzymes such as superoxide dismutase and catalase in P. indica-colonised plants during stressed condition reduced ROS levels in cells and thereby minimizing or preventing damage to cellular components. P. indica-colonised plants showed a reduced invertase activity than non-colonised plants. P. indica-colonisation improved the number of tillers, productive tillers as well the panicle length in plants under water stressed condition. The spikelet sterility was higher in non-colonised and water stressed plants. P. indica-colonisation contributed to a considerable increase in grain weight in Ptb 23. All these factors contributed to the final yield of the plant and unsurprisingly, P. indica-colonised plant sets produced more yield than non-colonised plant sets under water stressed conditions. Even though Ptb 29 produced more yield., P. indica-colonisation was more noticeable and effective in the water stress susceptible variety- Ptb 23. Keeping in view of our results, it can be emphasised that P. indica can mitigate the ill effects of water stress. The findings obtained from this study can be used as a foundation for future lines of research related to rational improvement of rice plants against water stress using endophytes.
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    Physiological effect of seed priming and foliar application of growth regulators in cowpea (Vigna unguiculata L.)
    (Department of Plant Physiology, College of Agriculture, Padannakkad, 2022) Swathy, P; Sudarsana Rao, G V
    An investigation entitled “Physiological effect of seed priming and foliar application of growth regulators in cowpea (Vigna unguiculata L.)” was carried out in two experiments during the period 2020-2021. The objective of the study was elucidation of influence of seed priming and foliar application of growth regulators on morpho-physiological changes, yield and quality in cowpea (Vigna unguiculata L.). Experiment-1 on seed germination and early seedling growth was conducted at College of Agriculture, Padannakkad. It was carried out in complete randomized design with eight treatments and three replications. Treatments included seeds primed with growth regulators viz., thiourea @ 500 ppm (T2); salicylic acid @ 50 ppm (T3); salicylic acid @ 100 ppm (T4); salicylic acid @ 150 ppm (T5); brassinolide @ 0.1 ppm (T6); brassinolide @ 0.3 ppm (T7); brassinolide @ 0.5 ppm (T8) and control (T1) without growth regulators. Minimum number of days taken for 50 per cent seed germination in T4, T6 and T7. 100 per cent seed sprouting and seed germination were recorded in T4 and T7. Maximum seedling survival was recorded in T4 and T7 which was on par with T5 and T6. Whole seedling dry weight and seedling vigour index were significantly enhanced in T7 followed by T4. Based on statistical analysis T4 and T7 were considered as best treatment for further field studies. Experiment-2 was conducted as field study at Instructional Farm II, Karuvacheri, College of Agriculture, Padannakkad. The best seed priming results obtained from Experiment -1 were further studied under field condition in Experiment- 2. It included 14 treatments viz., Standard POP recommendation without thiourea (KAU, 2016) (T1); standard POP with thiourea foliar spray @ 500 ppm (T2); T₁ + salicylic acid foliar spray @ 50 ppm (T3); seed priming with 100 ppm salicylic acid + salicylic acid foliar spray @ 50 ppm (T₄); T₁ + salicylic acid foliar spray @ 100 ppm (T₅); seed priming with 100 ppm salicylic acid + salicylic acid foliar spray @ 100 ppm (T₆); T₁ + salicylic acid foliar spray @ 150 ppm (T₇); seed priming with 100 ppm salicylic acid + salicylic acid foliar spray @ 150 ppm (T₈); T₁ + brassinolide foliar spray @ 0.1 ppm (T9); seed priming with 0.3 ppm brassinolide + brassinolide foliar spray @ 0.1 ppm (T₁₀); T₁ + brassinolide foliar spray @ 0.3 ppm (T₁₁); seed priming with 0.3 ppm brassinolide + brassinolide foliar spray @ 0.3 ppm (T₁₂); T₁ + brassinolide foliar spray @ 0.5 ppm (T₁₃) and seed priming with 0.3 ppm brassinolide + brassinolide foliar spray @ 0.5 ppm (T₁₄). The foliar sprays were given at 20 and 40 DAS. Regarding morphological observations, T6 and T14 significantly superior in plant height, leaf area per plant and number of compound leaves per plant at 25, 45 and 60 DAS. Minimum number of days taken for 50 per cent flowering in T₁₄ which was on par with T6. Minimum number of days for first harvest were recorded in T6 and T₁₄. Duration of crop and greater number of productive flower setting were significantly superior in T14 and T6 which was on par with T12. Efficient translocation of assimilates increased pod length and pod diameter in T6 which was on par with T14. Leaf area index and SPAD chlorophyll meter readings were maximum in T6 and T14 at 25, 45 and 60 DAS. The increase in net photosynthetic area and assimilate translocation, enhanced the total dry matter production, relative growth rate and crop growth rate in T14 followed by T6 during vegetative stage and reproductive stage as well. Maximum relative leaf water content was observed in T6 which was on par with T5, T8, T12 and T14 at 25 DAS and T5, T8, T12, T13 and T14 at 60 DAS. The ratio of variable fluorescence to maximum fluorescence (Fv/Fm) was recorded maximum in T14 which was on par with T6 and T12 at 25 DAS. The maximum effective quantum yield of PS II (Y (II)) were recorded maximum in T6 and T14 which were on par with T10 and T12 at 25 DAS. At 45 DAS, T14 was on par with T6, T8, T10 and T12. At 60 DAS, T14 was on par with T4, T6, T8, T9, T10, T11, T12 and T13. Electron transport rate (ETR) were observed maximum in T6 and T14 which were on par with T8, T10 and T12 at 25 DAS. At 45 DAS, T14 was on par with T6, T8, T10 and T12. At 60 DAS, T14 was on par with T2, T4, T6, T8, T10, T11, T12, and T13. A perusal of biochemical data showed that T6 and T14 had maximum leaf chlorophyll content at 25 DAS. At 45 DAS, T6 had the highest chlorophyll content which was on par with T8, T12 and T14. At 60 DAS, maximum chlorophyll content was recorded in T6 which was on par with T14. Maximum proline content was recorded in T1 at 25, 45 and 60 DAS. Regarding yield parameters average number of pods per plant and average number of seeds per plant were recorded maximum in T6 and T14, Seed yield was found to be increased by 43 per cent in T6 when salicylic acid @ 100 ppm seed priming and foliar application were given and 42.11 per cent increase in seed yield was noticed in T14 when seed priming was given with brassinolide @ 0.3 ppm and foliar spray at 0.5 ppm. Among only foliar spray of growth regulators without considering seed priming, brassinolide @ 0.5 ppm (33.74 per cent) and salicylic acid @ 100 ppm (33.29 per cent) were recorded maximum increase in seed yield. Foliar spray of thiourea was increased the yield by 26.32 per cent over control. Maximum net returns were obtained from treatment of seed priming and foliar spray with salicylic acid 100 ppm (T6) followed by T8 and T5. Even though, the gross returns were maximum from brassinolide treated plants, the net return was less due to higher cost of brassinolide. The highest BC ratio was from salicylic acid treated plants T6 (2.86) followed by T8 (2.73) and T4 (2.67). Among foliar sprayed treatments T5 recorded maximum BC ratio (2.66) and thiourea treatment recorded BC ratio 2.52. Results of the study revealed that seed priming and foliar spray of salicylic acid 100 ppm was significantly superior to all other treatments with respect to yield and net return. It can be concluded that among the treatments seed priming and foliar application of salicylic acid 100 ppm and seed priming with brassinolide @ 0.3 ppm and 0.5 ppm foliar spray showed the best results. Among foliar spray without seed priming salicylic acid 100 ppm and brassinolide 0.5 ppm superior in all parameters. Maximum economic returns were recorded from salicylic acid treated plants, even though highest seed yield and gross returns observed from brassinolide treatment because of high cost of chemical, net returns were minimised. Therefore, seed priming and foliar application of salicylic acid (100 ppm) significantly enhanced seed yield and net returns in cowpea
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    Differential and dynamic response of rice variety uma under varying drought stress regimes
    (Department of Plant Physiology, College of Agriculture, Vellanikkara, 2021) Akshaya Ramakrishnan; Parvathi M Sreekumar
    Rice has the evolutionary advantage of being semi-aquatic, making it one of the world's most important crops. As a result, it has fewer water-scarcity responses and is especially vulnerable to drought stress. Climate change has put rice production in jeopardy today. According to recent studies, rice yield decreases as result of climate change such that when drought frequency and rainfall pattern changes, rice output is lowered. Rice is the principal staple grain grown in Kerala, with around 600 types used across the state's paddy fields. Uma (MO 16), developed by Kerala Agricultural University's Rice Research Station, Moncompu, is one of the most popular rice varieties in Kerala, which is currently planted in more than 60% rice growing areas in the state. It also has adaptability towards wide range of environmental conditions as well, even though environmental variations limit the potential yield of variety Uma. In this context, the present study on differential and dynamic response of variety Uma under drought stress at vegetative stage and its impact on stress responses of progeny, were attempted with the main objective of identifying potential drought stress specific biomarkers representing a trend in metabolite dynamics across generations. This approach was aimed to demonstrate in a simple way that a natural drought stress exposure can influence stress responses of rice variety, Uma in the present as well as future generations, with an aim of identification and selection of potential traits for inclusion in crop improvement programmes. The study was carried out at the Department of Plant Physiology, College of Agriculture, Vellanikkara, Thrissur as two experiments- a drought stress imposition study in the net house facility and a laboratory study in the next generation. As part of the first experiment, drought stress (60% field capacity; FC) was imposed to rice variety, Uma at vegetative stage by gravimetric approach, simultaneously maintaining a nonstressed control at 100% FC by regular watering. The experiment was laid out in completely randomized design in customized rain-out shelter like structures in the net house. Physiological parameterswere assessed immediately after stress exposure for assessment of stress damage and it was noted that there was a significant reduction in chlorophyll content (36.2%), membrane thermostability (78.5%) and relative water content (23.5%) under stress in comparison to non-stressed control tissues, ensuring effective stress exposure. Biochemical markers such as proline and malondialdehyde (MDA) estimated immediately after stress and after recovery across different phenophases, revealed a differential pattern in their regulation. The levels of both the biomarkers were significantly higher (14% and 70.7% respectively) under stress which dropped drastically at panicle initiation stage, followed by an increase in the grain filling stage. However, it was interesting to note that correspondingly both the biomarker metabolites exhibited lesser accumulation (95.1% and 25.2% respectively) in comparison to the non-stressed control plants in grain filling stage. The differential dynamics of proline as well as MDA over different phenophases when related to the protein levels estimated at panicle initiation stage, revealed that there was no concomitant recovery in protein levels even after stress recovery. The non-stressed control and stressed plants were raised to maturity and harvested seeds were used for the second experiment for assessing the stress memory response in the next generation. Yield attributes assessed also showed significant difference between the stressed and non-stressed plants. The second experiment to assess the stress memory response aimed at comparative stress response assessment under salinity as well as osmotic stresses at seedling stage in the next generation. In this context, a standardization experiment was carried out using different concentrations of NaCl and polyethylene glycol (PEG 6000) to impose salinity and osmotic stresses respectively, to uniformly germinated seedlings of rice variety, Uma, to ascertain sub-lethal stress levels. From the standardization experiment, sub-lethal levels of salt (100 mM NaCl) and osmotic (-4 bar) stresses were arrived at based on the percent reduction in growth over control. The progenies of the first experiment along with a lot of fresh seeds were exposed to stress using the standardized doses of salt as well as osmotic stresses. Priorto stress exposure, germination speed and the vigour index of the seedlings were estimated, which led to the discovery of two classes of stress exposed plants of first experiment with their seeds differing in vigour viz. moderate and high vigour. Four classes of seed materials- control and stressed (high and moderate vigour) seed sets from first generation and a fresh set of seeds of rice variety, Uma were used for the stress response experiment using the sub-lethal stress levels ascertained. The high vigour seedlings from the stressed plants showed better growth under salt stress compared to control set of seedlings from first generation as evidenced by lesser percent reduction in growth as well as recovery responses. Subsequently, biochemical marker MDA was estimated in the different treatments revealing that moderate as well as high vigour seedlings of the stress class accumulated lesser (64.5% and 18.6% respectively) MDA levels in comparison to the non-stressed control, with a consistent pattern under salinity stress. GC-MS/MS analysis was performed using shoot tissues of the seedlings across the different treatments, with an attempt to unravel any possible stress responsemechanism. GC spectra displayed a number of highly abundant as well as uniquely present compounds in the plants. Diphenyl sulfone, a potent sulfone derivative with antioxidant activity was differentially detected in all classes of plant materials used for the stress response study. There were corroborative inferences from the fold changes in diphenyl sulfone as well as the MDA contents, wherein there were proportional variations in the two especially in NaCl induced salinity stress in all treatments, indicating its probable role in maintaining lower MDA levels in the progenies of plants that were subjected to a prior drought stress exposure in the previous generation. A round of stress exposure at vegetative stage in rice variety, Uma influenced several morpho-physiological and biochemical parameters at different stages of the crop. There was an indication of the transmission of stress induced signal even in the next generation as evidenced by profuse growth and lower MDA contents under different stresses at seedling stage. It will be rewarding to observe the stress response/acclimation behaviour of Uma, under different abiotic stress exposure regimes across different phenophases.
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    Elucidation of antioxidant fractions in leaves of Dendrophthoe falcata L. and standardisation of tape method of control
    (Department of Plant Physiology, College of Agriculture, Vellanikkara, 2021) Aswathi Gopal; Parvathi M Sreekumar
    Dendrophthoe falcata is a partial stem parasite belonging to Loranthaceae family, which is considered as a destructive pest of many economically important fruit trees such as mango, sapota, sugar apple and guava. They cause damage to the host plants by depleting nutrients, releasing toxins, and limiting their growth. Though several management strategies have been suggested by previous researchers which include pruning of its branches, base banding using 2,4-D and spray of ethrel in combination with organosilicone (non-ionic surfactant), the latter gave a promising response in comparison to others without affecting the host. Because of its destructive nature, some of the potential pharmaceutical features of the parasite often go unnoticed; if prospectively exploited it will automatically open up avenues for targeted removal of the parasitizing aerial parts of D. falcata. Plants are thought to be one of the most important sources for discovering and developing pharmaceuticals that are both effective and safe compared to currently available synthetic drugs. Traditional and folk medicines are gaining favour over contemporary therapy due to fewer side effects and a higher safety margin. Dendrophthoe falcata, a widely distributed plant in India, is one of nature's many plants with medicinal characteristics. The potential medicinal property of Loranthus has been reported in Ayurveda. It is reported to have diuretic, wound healing, anti-microbial, anti-helminthic, anti-fertility, antioxidant, anti-cancer, anti-diabetic, anti- hyperlipidemic and anti-hypersensitive activities. Medicinal properties of mistletoes are host specific. The antioxidant property of these parasitic plants might be due to their phenolic compounds including tannins and flavonoids. However, it will be very interesting to identify the novel antioxidant principles in the context of specific host associations. The present study was envisaged with a major aim of characterisation and elucidation of bioactive antioxidants from D. falcata leaves by invitro assays and identification of bioactive compounds through GC-MS/MS with prospective pharmaceutical applications, and standardization of efficient and non-regenerative method to control Loranthus.The experiments were carried out in Department of Plant Physiology, College of Agriculture, Vellanikkara, Thrissur. In the first experiment the leaf samples of Dendrophthoe falcata inhabiting different hosts namely mango, jackfruit, cocoa and sapota were collected, powdered and extracted in various organic solvents such as chloroform, petroleum ether, ethyl acetate, methanol and water followed by computation of extract yields. Aqueous extracts of D. falcata inhabiting all the hosts showed significantly higher (10.2 to 14.8%) yields compared to other solvents. Extract yield in case of petroleum ether and ethyl acetate were reported to be lowest (1.6 to 2.9% respectively) compared to other solvents indicating polar inorganic extraction to be advantageous, although novel and unique bioactive compounds could be effectively extracted in the latter. D(Sapota) showed lowest extract yield in petroleum ether (1.6%) and ethyl acetate (1.7%), whereas D(Jack) and D(Cocoa) had higher extract yields of 14.8% and 14.4% in water respectively. Free radical inhibition activity of D. falcata were assessed using DPPH radical scavenging assay in different hosts across various solvent extractions at different time intervals. Chloroform and water extracts of D. falcata showed an increasing trend in inhibition activity with time. However, ethyl acetate extracts marked a reduction in inhibition activity after two hours of incubation. Qualitative phytochemical screening of different extracts of D. falcata on the four hosts namely mango, jackfruit, cocoa and sapota were carried out to detect the presence of alkaloids, phenols, saponins, flavonoids, terpenes, tannins and steroids. There was a differential display of possession of different classes of phytochemicals by D. falcata across different host associations which varied with the nature of solvent used for extracting the antioxidant fractions. Chloroform extract of all the four hosts infested with D. falcata contained alkaloids, phenols, flavonoids, terpenes and steroids. Ethyl acetate extract had comparatively lesser phytochemicals, whereas methanolic extract had alkaloids, saponins, phenols, flavonoids, terpenes and steroids. Water extract yielded tannins along with other phytochemicals. Based on the antioxidant potential of the different extracts and host specificities, eight samples were shortlisted for GC- MS/MS analysis. Bioactive substances were detected in different extracts of D. falcata during GC-MS/MS analysis. Two common and abundant bioactive principles viz. cis- vaccenic acid and n-hexadecanoic acid were extracted in higher abundance in the petroleum ether extracts of D(sapota) and D(jack) for the former and D(jack) for thelatter. Petroleum ether extraction resulted in the best profiling for both the bioactive compounds from D(jack), indicating the association of D. falcata with jack as the most potential one to be tapped for pharmacological uses. The second experiment was carried out at Cocoa farm of Cocoa Research Centre, Kerala Agricultural University, Thrissur where the cocoa trees infested with Loranthus were tested for efficient management by impregnating the super absorbent polymer, super absorbent cotton and super absorbent paper with a combination of Ethrel and surfactants like oraganosilicone (OS)/alcohol ethoxylate (AE) @ 25mL/L of Ethrel + 0.5 mL/ L OS/AE and developed as a tape. Fresh and 1 week dried tapes were comparatively assessed, of which fresh application performed better than dried. The rate of defoliation also increased with time and after a while the number of leaves defoliated remained constant. Among the applicant material used, super absorbent polymer was found to be superior to super absorbent cotton and paper. Percent defoliation due to both surfactants revealed that AE performed better than OS. Ethrel along with surfactant alcohol ethoxylate (AE) as a sticky tape using superabsorbent polymer as the impregnating material can be used as an effective management strategy as AE is more eco-friendly than organosilicone. The tape method can also be an alternative to spraying even in the event its longer time for defoliation, provided if it ensures similar regrowth restriction efficiencies.
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    Drought mitigation in Okra (Abelmoschus esculentus L.) through chemical approach
    (Department of Plant Physiology, College of Agriculture, Padannakkad, 2021) Fathimath Suhaila; Sudarsana Rao, G V
    Okra or Bhindi (Abelmoschus esculentus L.) is one of the most popular summer vegetable crop grown widely in Kerala for its edible green fruits. Drought is a major yield limiting factor in agriculture and vegetables are more sensitive to drought stress as compared to most of the field crops because of their high water requirement. Hence, the study entitled “Drought mitigation in okra (Abelmoschus esculentus L.) through chemical approach” was carried out with the objective to investigate the influence of different chemicals namely, salicylic acid, ascorbic acid and thiourea on mitigation of drought and to evaluate their effect on morphological, physiological and yield charcteristics of okra. The field experiment was laid out in randomized block design with 8 treatments and 3 replications at RARS, Pilicode during December 2019 to March 2020. The okra variety Arka Anamika was raised as per standard package of practices recommendations of Kerala Agricultural University and also under soil test based nutrient management system. The experiment consisted of 8 treatments viz., normal irrigation (T 1 ) as control, drought stress (T 2 ), T 2 + salicylic acid foliar spray @ 1 mM (T 3 ), T 2 + salicylic acid foliar spray @ 2 mM (T 4 ), T 2 + ascorbic acid foliar spray @ 1 mM (T 4 ), T 2 + ascorbic acid foliar spray @ 2 mM (T 5 ), T 2 + thiourea foliar spray @ 500 ppm (T7), T 2 + thiourea foliar spray @ 1000 ppm (T8). Foliar application of chemicals were given at 10, 20 and 30 DAS and stress was induced by withholding irrigation from 25 days of sowing and re-irrigation was given at 50 per cent field capacity. Morphological, physiological and biochemical parameters were recorded at 25, 50 and 75 DAS and the yield and fruit quality characters were recorded at the time of harvest. A perusal of morphological data showed that T 3 had maximum plant height, number of leaves plant -1 , number of pickings and highest duration of the crop followedby T 6 when compared to all other treatments. The maximum number of branches per plant and the highest root volume were recorded in T 1 which was on par with T 3 followed by T 6 . Foliar spray of chemicals did not significantly influence number of days for 50 per cent flowering and first harvest. Up to 75 DAS, maximum relative growth rate was observed T 3 . All the treatments performed better than drought stress treated crops. At all the growth stages, maximum specific leaf weight was exhibited T 3 . Leaf area was observed maximum for T 3 and was on par with T 4 , T 5 , T 6 at 25 DAS and T 1 , T 4 and T 6 at 50 DAS and T 6 at 75 DAS. The relative leaf water content was recorded the highest for T 3 at 25 DAS and for T 1 at 50 and 75 DAS. At 50 DAS, T 1 was on par with T 3 , T 6 and T 7 and at 75 DAS T 1 was followed by T 3 and T 6 . T 3 had maximum total dry matter production which was on par with T 1 and T 4 .at 25 and 50 DAS, respectively. Root shoot ratio was recorded maximum in T 3 which was on par with T 1 at 25 and 50 DAS. SPAD chlorophyll meter reading (SCMR) was recorded maximum in T 3 at 25 and 50 DAS and in T 1 at 75 DAS. T 1 was on par with T 3 , T 4 and T 6 at 75 DAS. Considering the yield and fruit quality attributes, T 4 recorded maximum value for fruit length and was on par with T 1 , T 7 and T 8 . The highest average fruit girth and fruit weight were exhibited in T 3 and lowest was in drought stressed crop (T 2 ). The treatment T 1 , T 3 , T 4 and T 6 recorded maximum number of fruits plant -1 which were on par with T 5 and T 7 . The highest total fruit yield was recorded in foliar spray of salicylic acid (1 mM) followed by ascorbic acid (2 mM). These treatments recorded 45 per cent and 41 per cent higher yield over drought stressed treatment, respectively. The crude fibre content was recorded highest for drought stressed crops (T 1 ) and the lowest was recorded in T 3 . The ascorbic acid content was observed maximum in T 1 followed by T 5 and T 6 . The highest net returns and BCR was obtained in T 3 followed by T 6 . The frequency of irrigation given was highest in T 1 followed by T 2 and T 8 . The lowest frequency of irrigation given were in T 3 , T 6 and T 7 . The irrigation interval was more with T 3 , T 6 and T 7 (5 days).It can be concluded that morphological, physiological, biochemical and yield traits of okra were severely affected under drought stress. Among the three drought mitigating chemicals, salicylic acid (1 mM) recorded maximum values for morphological traits viz., plant height, number of leaves plant -1 , root volume and duration of crop, followed by ascorbic acid (2 mM), which also significantly improved morphological traits of okra compared to all other treatments. Physiological traits such as total dry matter production, leaf area plant -1 , relative growth rate, specific leaf weight, root shoot ratio and SPAD chlorophyll meter reading increased over drought stress crop when sprayed with salicylic acid (1 mM) and ascorbic acid (2 mM). Salicylic acid (1 mM) and ascorbic acid (2 mM) is beneficial for getting higher fruit yield and maximum economic returns over drought stressed and normal irrigated crops. Therefore, application of salicylic acid (1 mM) and ascorbic acid (2 mM) significantly mitigated the harmful effect of drought stress in okra.