Browsing by Author "Delphy Rocha"

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Fine root dynamics and associated carbon and nutrient flux in 12 year old acacia mangium at varying stand densities
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2017) Delphy Rocha; Kunhamu, T K
Foliar uptake and accumulation of nanoplastics and its effect on growth and physiology in selected tree seedlings
(Department of Forest Biology and Tree improvement, College of Forestry, Vellanikkara, 2025-04-26) Archana Abraham; Delphy Rocha; Misha Davis, A
The persistent nature of plastics, combined with inadequate waste management practices, poses a significant and escalating threat to both terrestrial and marine ecosystems worldwide. This study investigated the foliar uptake, accumulation and physiological effects of nanoplastics (NP) in seedlings of Tectona grandis, Gmelina arborea, and Macaranga peltata. Five-month-old seedlings were subjected to foliar application of NP solutions (0.1 mg L⁻¹ and 1 mg L⁻¹) for 21 days, with control plants serving as a baseline. Confocal Laser Scanning Microscopy confirmed the uptake and systemic transport of nanoplastics in leaves, stems, and roots of all species. Growth parameters, including height and collar diameter, showed significant reductions in Tectona grandis, while physiological parameters such as photosynthesis, stomatal conductance, transpiration, and chlorophyll content declined across all species, with the most pronounced effects observed at higher nanoplastic concentrations. Biochemical analyses revealed reductions in total soluble sugars, proteins, and phenolic content, particularly in Tectona grandis and Gmelina arborea, suggesting oxidative stress and metabolic disruptions. The results highlighted strong correlations between nanoplastic exposure and impaired physiological functions. These findings provide crucial insights into the species-specific responses of trees to airborne nanoplastic contamination, emphasizing the need for further research on the ecological consequences of nanoplastics in forest ecosystems. By examining these effects, the research aims to provide insights into the potential risks posed by airborne nanoplastics to plant health.
Functional trait variations and drought tolerance among teak (Tectona grandis Linn.f.) provenances
(Department of Forest Biology and Tree Improvement, College of Forestry, Vellanikkara, 2024-11-27) Muhammed Ajsal, K K; Delphy Rocha
The present study investigated, functional trait variations among six provenances of Tectona grandis L. f, in the 90 year old provenance trial plot at Aravallikavu, Nilambur consisting of Anamalai, North Burma, Nilambur, South Bombay, South Burma and Travancore provenances. In addition, genetic diversity among these six teak provenances using ISSR markers and drought tolerance of these six provenances were also studied. Functional traits such as height, GBH, crown width, and self-pruning activity of teak provenance showed significantly different variation. However, leaf thickness not showed significantly different variations among the provenances. The South Burma provenance showed highest height (28.48m), crown width (9.05m) and self-pruning activity (0.82), whereas Nilambur provenance showed highest GBH of 168.06cm. The South Burma provenance showed highest stem straightness. In addition, foliar nitrogen concentration showed significantly different variations among the provenances. South Bombay provenance showed highest leaf nitrogen concentration of (2.54%). However, both phosphorous and potassium concentration did not significantly vary among provenances. Genomic DNA from six teak provenance was extracted using the modified CTAB protocol, yielding DNA concentrations ranging from 117.3 to 284.11 ng µL-1, with OD260/280 values between 2.06 and 2.21. Amplified bands resulted in 37 observed alleles, of which 32were polymorphic, demonstrating genetic diversity, while 5 were monomorphic. The Jaccard dissimilarity coefficient between Anamalai and South Bombay was 0.43, suggesting their genetic similarity. Whereas highest dissimilarity was observed between South Bombay and South Burma with coefficient of 0.67. Morpho-physiological and biochemical responses of teak ramets to drought stress were evaluated. Based on morphological indicator (percent leaf retained), Anamalai and South Bombay provenances were classified as "moderately Tolerant," whereas South. Burma was "Susceptible". Photosynthesis varied, with South Bombay maintaining the highest rate (3.27μmol CO2 m-2 s-1) and Travancore exhibiting the lowest (1.75μmol CO2 m-2 s-1) under xvi drought. Provenance displayed diverse responses under drought for relative water content (56.61%- Travancore to 84.62%-South Bombay) and total chlorophyll content (4.94 mg g⁻¹ South Bombay to 2.84 mg g⁻¹-Travancore). Maximum proline was produced by South Bombay (9.11μg g-1). Similarly, South Bombay displayed higher peroxidase activity (8.53μmol min-1). Hierarchical cluster analysis categorized teak provenances into Susceptible (Nilambur and Travancore), Moderately Tolerant (North Burma and South Burma), and Highly Tolerant (Anamalai and South Bombay) categories. The study enhances understanding of the functional trait, genetic variations and drought tolerance of six teak provenances contributing valuable information for breeding programs and sustainable forest management. The multidisciplinary approach integrating physiological, biochemical, and genomic analyses offers a comprehensive framework for understanding and improving teak cultivation, ensuring sustainable production in the face of environmental challenges.
Influence of host plant on the physiological attributes of field grown sandal (santalum album L.).
(Department of Tree Physiology and Breeding,College of forestry, Vellanikkara, 2011) Delphy Rocha; Ashokan, P K
Effects of host plant, casuarina on the carbon assimilation, water and nutrient absorption in field grown sandalwood was studied at College of Forestry, Kerala Agricultural University, Vellanikkara, Thrissur during the year 2009-2011. Radioisotopic study to understand the trans-haustorial translocation from the host to field grown sandalwood tree and anatomical studies of sandalwood haustoria were also taken up during the investigation. The investigations were carried out in a six year old sandal-field, where sandalwood tree with and without host were established as a part of an earlier research project. The experiment was laid out with single tree plants, in RBD with three treatments viz, T1 - Sandalwood tree without host (Casuarina) (Host plant dead naturally within 2 years after establishment of sandal), T2 - Sandalwood tree with host (Casuarina), T3 - Sandalwood tree with host (Casuarina) and the host plant cut and removed at six year stage of growth. The host plant casuarina did not influence the height and diameter (dbh) of the sandalwood tree significantly during its six years growth. Sandalwood trees growing with host showed higher rate of photosynthesis (carbon assimilation) than sandalwood trees growing without host. Sandalwood tree growing without specific host can extend its root for finding a host in its vicinity, and forming haustorial connections, for meeting its water and nutrient requirements. Sandalwood trees grown with host showed higher plant water potential than sandalwood trees grown without host. Plant water potential has decreased significantly after the removal of host plant from the sandalwood pit. It also resulted in leaf wilting and leaf fall in sandalwood tree, indicating the contribution of the host in maintaining higher water potential in sandalwood trees. Sandalwood trees growing with host showed higher leaf N, P and K content. The N, P and K content of the sandalwood tree leaf decreased considerably after the removal of the host plant. The removal of host did not show any significant effect on leaf micronutrient content of sandalwood tree. Sandalwood growing without host also formed haustoria with roots of host plants growing in the adjacent pit. The sandalwood growing with host in the same pit showed higher number of haustoria. Total number of haustoria was higher on the primary root of the host followed by secondary and tertiary roots. Size of the haustorium, the depth of the penetration, the length of the penetration peg and area of coverage of endophyte was higher in the case of secondary root haustoria than in tertiary. Anatomical study of sandalwood haustoria showed that elongated parenchyma cells of the haustorium projected towards the host root xylem, making vascular connection between sandalwood tree root and the host plant root. Radioactive phosphorus (32P) labelling on host plant, casuarina and tracing in sandalwood tree and other hosts revealed that there is inter-translocation of nutrients between sandalwood and host plants, sandalwood and sandalwood, host and host. The data indicated that a network of roots of sandalwood tree and the hosts are formed through haustorial connection resulting in xylem-translocation. Peak count of 32P was obtained on the eighth day of its application. Radiotracer studies on different sandalwood tree-host associations showed that association of sandalwood and cocoa as host was efficient in haustorial translocation of 32P. Labelling of wild grasses growing around sandalwood tree with 32P revealed that, sandalwood also depends on wild grass for meeting its nutrient requirements.