Physiological determinants for adaptive potential of turmeric (Curcuma longa) for its growth and yield under different regimes of shade in semi-arid Region of Central India

Abstract

We have conducted the present experiment to find out the physiological determinants for shade adaptive potentials of turmeric (Curcuma longa) by growing it in four different regimes of light viz. 100% incident light (open), 33% shade, 50% shade and 75% shade in field of three category of shade-net houses and without shade (adjacent open field). Plant height, leaf length and shoot biomass significantly increased under shade. Although, fresh weight of rhizome was more under shade than in open condition, the turmeric yield (dry weight of rhizome) was highest under 50% shade and similar trend was observed with shoot biomass and chlorophyll content index. PPFD (Photosynthetic photon flux density) saturated rate of CO₂ assimilation (Amax) was highest under 50% shade. Physiological efficiency of turmeric plants under shade was noted to be higher than open condition (100% sun light) as we observed higher rate of photosynthesis (CO₂ assimilation), PS2 quantum yield, low co-efficient of non-photochemical quenching (qN) with sustained photochemical quenching (qP) and optimum thylakoid electron transport rate (ETR) of turmeric plants under shade. Shade adaptive potential of turmeric has been well corroborated with leaf protein profiling that indicated more thicker protein bands around 55 kDa and 17 kDa under shade which mostly linked with RUBISCO (Ribulose bisphosphate carboxylase-oxygenase) and LHCP (Light Harvesting complex protein). The present study revealed the physiological basis of shade adaptive potential of turmeric plants. For its better physiological efficiency turmeric could be grown as a shade tolerant crop (partial shade regimes from 33 to 50%) under light limiting environment like agroforestry or intercrop practices.