CLONAL VARIATION IN TEMPERATURE RESPONSE OF PHOTOSYNTHESIS IN TEA

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), ori ginally from different agro-climatic zones in India, was studied to de termine the clonal variation in photosynthesis, if any. The results cl early indicated significant clonal differences in relation to temperat ure. 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 re sponsible for the differences in temperature dependence of photosynthe sis, however, their magnitude varied with the tea clones. Differences in water use efficiency were also observed between clones. However, di fferences became less pronounced at the higher temperature. Clone B/5/ 63 showed higher water use efficiency and lower values for stomatal co nductance and transpiration. Thus this clone may be suitable for relat ively dry and exposed sites. A 2-10-fold increase in dark respiration with increase in temperature was also observed. However, higher increa se was associated with clones having higher photosynthetic rates, indi cating an association between photosynthetic and respiratory rates. Th e results provide a valuable indication regarding clonal variation in temperature responses of photosynthesis and may be used to offer usefu l suggestions to tea growers in the initial selection of tea clones. ( C) 1998 Elsevier Science Ireland Ltd. All rights reserved.