Heat Resistance in Photosynthesis of Sorrel Vine(Cayratia japonica(Thunb.)Gagn.) Leaf, Chloroplasts and Photosystem II Particles.

Abstract

The sorrel vine (Cayratia japonica (Thunb.) Gagn.), a winder plant (liana) in the Vitaceae family, was heat resistant in photosynthetic oxygen (O2) evolution. The O2 evolution of leaf, chloroplasts and photosystemII particles of sorrel vine was little affected by heating at 45°C for 5min, while the O2 evolution of spinach and many other plants was inhibited at 45°C. Inhibition of the O2 evolving center of a heated leaf was monitored with greater depression of chlorophyll-fluorescence induction, reflecting the depression of plastoquinone photoreduction by photosystem II (PS II). The leaf fluorescence of spinach, pumpkin, maize, sorrel (Rumes japonicus) and arrowroot (Pueraria lobata Ohwi) was depressed and modified in a rising pattern, while the fluorescence rise of sorrel vine leaf was little affected by heating at 45°C; this indicated that sorrel vine leaf was more heat resistant than others tested. Heating of spinach and sorrel leaf, and their chloroplasts and/or PS II particles to 45°C destroyed the O2 evolving center so that most of the essential Mn and the 18-, 24- and 33-kDa extrinsic peptides of the center were lost, while the center of the sorrel vine was protected from the destruction at 45°C.