Gas exchange characteristics of tea (Camellia sinensis) in subtropics

by Dr. N. G. Hajra | J. Plant Biol. 29 (2): 169 – 173. 2002

Abstract

The patterns of net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), leaf water potential (ψL) and water use efficiency (PN/E) of intact leaves and stem diameter in field grown tea (Camellia sinensis (L) O. Kuntze), clone T78 representing “China” jat were evaluated at monthly intervals during 1999 and 2000. The maximum value of PN was recorded in October when relative humidity was very high, air temperature, soil moisture (Sm) were moderate and photosynthetic photon flux density (PPFD) was maximum, PN was lowest in August, when humidity and soil moisture were highest, and PPFD were lowest. Higher values of gs were recorded during July/August (rains) and lowest in March/April (summer). ψL decreased from –1.6 MPa in August to –2.8 MPa in May. Decrease in E was more pronounced during March and April. The maximum value of PN was recorded up to a VPD of 2.3 in October; there after PN declined slowly. In general, a reduction in gs with higher VPD values was observed. Maximum PN/E observed in March and decreased during rains. PN was positively correlated with PPFD, E, gs, PN/E and VPD. A positive correlation between Chl content and PN also existed. Higher rate of stem diameter (SD) increment observed during June to August (rains) and lowest increment was recorded during December (winter), January, and April/May. The correlation between SD and PN was found negative. In general, higher SD coincided with higher ψLand E.