Impact of seed priming on psychological and biochemical mechanisms under water stress condition in chilli (Capsicum annuum L.)

Abstract

A study entitled “Impact of seed priming on physiological and biochemical mechanisms under water stress condition in chilli (Capsicum annuum L)” was undertaken with the objective assessment of the effect of seed priming on physiological and biochemical mechanisms and yield components under water stress condition in chilli. For both experiments I & II seeds of the chilli variety ‘Vellayani Anugraha’ were primed with 2.5% potassium nitrate (KNO3), 3% silicon dioxide (SiO2), and unprimed were soaked in distilled water for 24 hours and subjected to control and water stress levels at flowering stage. The first experiment was carried out in a factorial completely randomized design (FCRD) with the first factor being stress levels and the second-factor being priming agents using different solutions replicated thrice. The seeds primed with 2.5% KNO3, 3% SiO2, and unprimed seed treatments were sown in protrays. Seedlings were transplanted to pots 35 days after sowing (DAS), irrigation, and other cultural practices were followed according to KAU POP (package of practices). Water stress was induced by withholding irrigation for three days where the relative water content (RWC) of leaves reached 70% during the flower initiation stage. The results of the first experiment revealed that seeds primed with 3% SiO2 resulted in early flowering and first fruiting. Under water stress conditions, seeds primed with 2.5% KNO3 recorded significantly higher values for RWC (69%), cell membrane stability Index (CMSI) (42.16%), malonaldehyde (0.62 μmole ml-1), H2O2 (0.62 μmol g-1), trehalose (0.15 μmol g-1 FW), α-amylase activity (14.68 μmol maltose formed min-1 mL-1), specific leaf area (15.99 cm2 g-1) total chlorophyll content (TCC) (1.92 mg g-1), superoxide dismutase (SOD) (491.3 units mg-1 of protein), total soluble sugars (TSS) (1.53 mg/g) and total soluble protein (TSP) (1.017 mg g-1) however 3% SiO2 primed seeds recorded significantly higher values for total proline content (3.12 μmoles of proline g-1 of tissue). 136 Under control conditions, 2.5% KNO3 primed seeds recorded significantly high values for RWC (92%), trehalose (0.17 μmol g-1 FW), α-amylase activity (16.76 μmol maltose formed min-1 mL-1), specific leaf area (20.88 cm2 g-1) total chlorophyll content (TCC) (4.54 mg g-1), superoxide dismutase (SOD) (491.32 units mg-1 of protein), total soluble sugars (TSS) (3.22 mg g-1) and total soluble protein (TSP) (2.06 mg g-1) however 3% SiO2 primed seeds recorded significantly higher values for total proline content (1.31 μmoles of proline/g of tissue) and CMSI (91.0%). Under water stress conditions, capsaicin content was recorded higher in seeds primed with 2.5% KNO3 (144.6 μg g-1), and ascorbic acid was recorded the highest in seeds primed with 3% SiO2 (3.89 mg g-1). In contrast, in control, both capsaicin content (224.0 μg g-1) and ascorbic acid content (4.81 mg g-1) were recorded higher in seeds primed with 2.5% KNO3. Under water stress conditions, the yield components were higher in seeds primed with 2.5% KNO3. The plant height (60 cm), number of flowers plant-1 (24 number), number of fruits plant-1 (20 number), and fruit yield (44.29 g), were recorded as significantly higher in seeds primed with 2.5% KNO3. however, the seed yield (3.60 g) was recorded as significantly higher in seeds primed with 3% SiO2, and the number of flowers plant-1 (22 number) was found the highest in unprimed seeds. Whereas in control, 2.5% KNO3 primed seeds recorded significantly higher plant height (65.3 cm), fruit yield (90.4 g), number of fruits plant-1 (23.4), and 3% SiO2 primed seeds recorded significantly higher seed yield (4.03g). The second experiment was carried out in a factorial randomized block design (FRBD) with the first factor being stress levels and the second factor being priming using different solutions which were replicated thrice. the seeds primed with 2.5% KNO3, 3% SiO2, and unprimed seeds treatments were sown in protrays. Seedlings were transplanted to the field 35 days after sowing (DAS) and irrigation and other cultural practices were followed according to KAU POP. Water stress was induced by withholding irrigation for seven days where the (RWC) of leaves reached 70% during the flower initiation stage. During this period, physiological parameters were taken from the stress and control plants. The results revealed that seeds primed with 3% SiO2 recorded early flowering whereas seeds primed with 2.5% KNO3 recorded the first fruiting stage. Under water stress conditions, seeds primed with 2.5% KNO3 recorded significantly high values for RWC (68.16%), CMSI (46.66%), malonaldehyde (0.73 μmole ml-1), H2O2 (0.71 μmol g-1), trehalose (0.13 μmol g-1 FW), α-amylase activity (13.93 μmol maltose formed min-1 mL-1), Specific leaf area (13.47 cm2 g-1) TCC (1.93 mg g-1), SOD (520.03 units mg-1 of protein), TSS (1.55 mg g-1) and TSP (1.05 mg g-1) where 3% SiO2 primed seeds recorded significantly higher values for total proline content (3.12 μmoles of proline g-1 of tissue). For control conditions, 2.5% KNO3 primed seeds recorded significantly high values for (RWC) (79 %), trehalose (0.17 μmol g-1 FW), α-amylase activity (14.77 μmol maltose formed min-1 mL-1), Specific leaf area (18.47 cm2g-1) TCC (3.86 mg g-1), SOD (405.60 units mg-1 of protein), TSS (3.16 mg/g) and TSP (2.0 mg/g) however 3% SiO2 primed seeds recorded significantly higher values for total proline content (1.31 μmoles of proline/g of tissue) CMSI (91.16%).Under water stress conditions, capsaicin content was recorded higher in seeds primed with 2.5% KNO3 (90.5 μg g-1), and ascorbic acid was recorded the highest in seeds primed with 3% SiO2 (3.78 mg g-1). In control, capsaicin content (232.0 μg g-1) and ascorbic acid content (4.75 mg g-1) were recorded higher in seeds primed with 2.5% KNO3.Under water stress conditions, the yield components were recorded as higher in seeds primed with 2.5% KNO3 like plant height (55 cm), number of flowers plant-1 (22.8 number), number of fruits plant-1 (19 number), and the fruit yield (45.3 g), were recorded as significantly higher in seeds primed with 2.5% KNO3. The seed yield (3.16g) was recorded as significantly higher in seeds primed with 3% SiO2, under, the control condition, 2.5% KNO3 primed seeds recorded significantly higher plant height (60 cm), fruit yield (84.93 g), number of fruits plant-1 (22.4) and 3% SiO2 primed seeds recorded significantly higher seed yield (3.18 g). According to our results, seed priming with 2.5% KNO3 and 3% SiO2 enhanced the capacity of the plant to absorb water by preserving the least amount of cell damage and shielding the macromolecular structures from membrane damage, Thus, seed priming with 2.5% KNO3 and 3% SiO2 can be recommended.