Characterizing the thermotolerance properties of Albizia procera in temporal and seasonal scale through physio-biochemical traits and spectral indices

Albizia procera is well recognized for timber, nutritious fodder for livestock and reforestation tree species with agroforestry importance. To reveal the inherent thermotolerance properties of A. procera through physio-biochemical traits and spectral indices, experiments were conducted under temporal and seasonal scale viz. pre-winter, winter and post-winter seasons. Effects of temporal and seasonal variation have been conspicuously noticed in physiological traits. Canopy temperature depression (CTD) increased with increase in atmospheric temperature. In winter season at low atmospheric temperature rate of CO₂ assimilation (A_max) and thylakoid electron transport rate (ETR) decreased. There were prominent effects of seasonal and temporal variations on leaf level spectral indices like Normalized Difference Vegetation Index (NDVI) and Photochemical Refelectance Index (PRI) as well. During pre-winter and post-winter season, NDVI and PRI were higher than in winter period. Thus, an overall impact of increasing temperature through temporal variation has been reflected on photosynthetic apparatus, intercellular biochemical reactions and spectral traits. Correlations among various traits indicated that NDVI and PRI may be useful to understand the physiological status of plants under such conditions if judiciously used. Our results demonstrated the inherent thermotolerance properties of A. procera which may help to understand the mechanistic insights involved in coping with elevated temperature under changing climate scenarios. To our knowledge, the association of PRI and NDVI in A. procera in the context of thermotolerance is being reported for the first time which is noteworthy.