Abstract: By using fast OJIP chlorophyll a (Chl a) fluorescence transients, this paper studied the effects of short-term high temperature stress on the flag leaf photosystem Ⅱ (PSⅡ) functions of high-yielding winter wheat cultivar 01-35 at its late grain filling stage. The results showed that with the temperature raised from 37 ℃ to 43 ℃, the extent and velocity of Q_A reduction enhanced gradually, being 23.89% and 24.09% higher at 43 ℃ than at room temperature, respectively, which suggested that the electron transport from Q_A to Q_B was inhibited. The electron acceptor pool of PSⅡ including Q_A, Q_B and PQ at 43 ℃ decreased to 47.4% of that at room temperature, indicating its being damaged. The electron donor side of PSⅡ was not damaged from 37 ℃ to 43 ℃. When temperature raised to 46 ℃, the extent and velocity of Q_A reduction were 13.95% and 20.48% higher than those at room temperature, respectively, but decreased obviously, compared with those at 43 ℃. In contrast, the electron acceptor pool of PSⅡ at 46 ℃ had no obvious change, compared with that at 43 ℃, indicating that the electron donor side of PSⅡat 46 ℃ was damaged. Comparing with cultivar Lumai 14, the light harvesting complex (LHCⅡ) of high-yielding wheat cultivar 01-35 could harvest more sun energy, and distributed more absorbed energy into electron transport, suggesting that the LHCⅡ of cultivar 01-35 could endure a certain higher temperature, and maintain higher electron transport capacity.

Key words: Orchid, Mycorrhiza, Secretion, Extraction