(143) Drought Acclimation of Leaf Gas Exchange in Jalapeno and Big Chili Pepper

Abstract

Drought is a major constraint to chili production in a variety of cropping systems worldwide. A greenhouse study was conducted to understand mechanisms underlying drought acclimation of leaf gas exchange in two popular chili cultivars, `Big Chili' and `Jalapeno'. Unstressed `Big Chili' had 27% greater net photosynthesis (Pnet), 60% higher stomatal conductance (gw), and 18% higher transpiration (E), but only 3% greater intercellular CO2 concentration (Ci) than `Jalapeno'. Light compensation point was 43.3 and 31.6 μmol·m-2·s-1 in `Big Chili' and `Jalapeno', respectively, although light-saturated assimilation (Amax) and photosystem II efficiency (F'v/F'm) were the same in the two cultivars. Maximum rubisco-mediated carboxylation, Vcmax, was 66.3 and 69.1 μmol·m-2·s-1 in `Big Chili' and `Jalapeno', respectively. During drought, 50% of plants wilted to zero Pnet in 5 days in `Big Chili', and 7 days in `Jalapeno'. However, at wilting, relative water content was the same at 66%, with 97% less gw than unstressed plants, in each cultivar. `Jalapeno' had 9% greater F'v/F'm than `Big Chili', at wilting. Four days after rewatering, Pnet, gw and F'v/F'm were 27%, 47%, and 8% less in `Big Chili', but only 11%, 19%, and 4% less in `Jalapeno', than unstressed plants, respectively. `Jalapeno' shows greater acclimation of gas exchange to drought than `Big Chili' through rapid recovery of photosystem II, carbon assimilation and stomatal activity.