Effects of high temperature and high light on photosystem II activity in leaves of two Bauhinia species

Abstract

It is, so far, unclear whether lianas and trees differ in photosynthetic thermotolerance and response to high temperature and high light. Here, photosynthetic thermotolerance was compared in the leaves of Bauhinia brachycarpa (tree) and Bauhinia comosa (liana). Moreover, the combined treatments of four temperatures (25, 35, 40, and 45°C) and two light intensities [500 and 2,000 μmol(photon) m-2 s-1] were used to investigate the effects of high temperature and high light on PSII activity. The results showed that B. brachycarpa leaves exhibited higher photosynthetic thermotolerance, leaf mass per area, and Ca2+ concentration than those of B. comosa. As the temperature and light intensity increased, maximum quantum yield of PSII decreased significantly, particularly with greater declines in B. comosa than that in B. brachycarpa. Our results suggested that PSII was more sensitive to high temperature and high light in liana species B. comosa than in the congener tree species B. brachycarpa.

Keywords

• global warming; heat stress; photoinhibition; photoprotection.