Leaf photosynthesis and chlorophyll fluorescence in four clones (400 series) of Hevea brasiliensis during low temperature period in Tripura.

摘要

This present investigation was aimed at comparing the extent of variation in single leaf net photosynthetic rate (P_N) and its relative dependence on mesophyll capacity to fix carbon in four new clones of Hevea brasiliensis (RRII 414, RRII 422, RRII 429 and RRII 430) which were grown under the agro-climatic condition of Tripura. Photosynthesis and fluorescence parameters were measured during low temperature period. There were significant variations in P_N measured at various irradiance levels. The compensation irradiance (CI) and apparent quantum yield of CO₂ assimilation ( Phi c) calculated from P_N/PFD response curves showed significant variation among these four clones. Photosynthetic rate at saturated Ci (P_maxCi), in vivo carboxylation efficiency (CE) and CO₂ compensation concentration ( Gamma ) calculated from P_N/Ci response curves showed significant variation. A strong positive correlation existed between P_N saturated with radiant energy (P_sat) and carboxylation efficiency (CE). A negative relationship between Gamma and CE was observed in these clones. A clone with large P_sat, high CE and low Gamma may be more biomass producer. Diurnal pattern of dark adapted Fv/Fm was also monitored during peak winter period to assess the extent of acclimation to low temperature. Results indicate that RRII 429 with high P_sat, high CE and low Gamma showed relatively better acclimation compared to other clones. However, RRII 430 was also found to be promising at early growth stage.