Division of Crop Sciences, Central Research Institute for Dryland Agriculture, Hyderabad-500659
Primary racemes of dryland castor develop during later part of rainy season and secondaries and tertiaries develop during post-rainy season. The reproductive phase is therefore subjected to variation in soil moisture availability and solar radiation intensity. The objective of the study was to find out the influence of fluctuation in solar radiation intensity on photosynthetic rate, transpiration rate, transpiration efficiency, stomatal conductance and leaf water potential during early and late reproductive phase of castor. When photosynthetically active radiation was less than 1000 µmol m−2 s−1, transpiration efficiency decreased because reduction in photosynthesis rate was more than that in transpiration rate. Transpiration efficiency also decreased, when radiation was above 1500 µmol nr−2 s−1 because of increase only in transpiration rate. Leaf water potential was higher during early than during late reproductive phase at similar radiation intensity. Transpiration rate was lower and transpiration efficiency was more during early phase when radiation was above 1500 µmol m−2 s−1. Photosynthetically active radiation and leaf water potential were inversely related.
