Clonal variation in temperature response of photosynthesis in tea

Abstract

The effect of temperature on the photosynthetic characteristics of six tea clones (viz., 6017, B/5/63, B/6/61, B/6/62, CCS-26 and T-78), originally from different agro-climatic zones in India, was studied to determine the clonal variation in photosynthesis, if any. The results clearly indicated significant clonal differences in relation to temperature. Of the six clones, B/5/63 and B/6/61 were found to be relatively thermotolerant. Both stomatal and mesophyll components seemed to be responsible for the differences in temperature dependence of photosynthesis, however, their magnitude varied with the tea clones. Differences in water use efficiency were also observed between clones. However, differences became less pronounced at the higher temperature. Clone B/5/63 showed higher water use efficiency and lower values for stomatal conductance and transpiration. Thus this clone may be suitable for relatively dry and exposed sites. A 2–10-fold increase in dark respiration with increase in temperature was also observed. However, higher increase was associated with clones having higher photosynthetic rates, indicating an association between photosynthetic and respiratory rates. The results provide a valuable indication regarding clonal variation in temperature responses of photosynthesis and may be used to offer useful suggestions to tea growers in the initial selection of tea clones.