The mechanism of high yield of winter wheat in the field at late growth period was investigated by measuring the photosynthetic characteristics of photosystem II (PSII) and xanthophylls cycle, which could provide physiological reference for breeding. Weimai 8 (W8), a super high yield cultivar, and Lumai 14 (L14), a control cultivar were object. The photosynthetic rate (Pn), parameters of chlorophyll fluorescence and chlorophyll content were measured. The Pn, maximum photochemical efficiency of PSII (Fv/Fm), quantum yield of PSII electron transport ( PSII), efficiency of excitation energy capture by open PSII reaction centers (Fv′/Fm′), and photochemical quenching coefficient (qP) were higher in Weimai 8 compared to that in Lumai 14, a commercial high yield cultivar. Furthermore, Weimai 8 showed a lower nonphotochemical quenching coefficient and a lower de-epoxidized ratio of the xanthophyll cycle pigments than of Lumai 14 at late growth period. At mature stage, chlorophyll content of different leaves decreased both in Weimai 8 and Lumai 14. Chlorophyll content in flag, second and third leaf from the top of plant decreased more in Lumai 14 than in Weimai 8. These results suggested that Weimai 8 had more antenna pigments to absorb light energy, and had higher photosynthetic capability and photochemical efficiency of PSII. The yield of Weimai 8 was also higher than that of Lumai 14.
SUI NaLI MengMENG Qing-weiTIAN Ji-chunZHAO Shi-jie
In cyanobacteria and higher plants, NdhS is suggested to be an electron donor-binding subunit of NADPH dehydrogenase(NDH-1) complexes and its absence impairs NDH-1-dependent cyclic electron transport around photosystem I(NDH-CET). Despite significant advances in the study of NdhS during recent years, its functional role in resisting heat stress is poorly understood.Here, our results revealed that the absence of NdhS resulted in a serious heat-sensitive growth phenotype in the unicellular cyanobacterium Synechocystis sp. strain PCC6803. Furthermore, the rapid and significant increase in NDH-CET caused by heat treatment was completely abolished, and the repair of photosystem II under heat stress conditions was greatly impaired when compared to that of other photosynthetic apparatus in the thylakoid membrane. We therefore conclude that NdhS plays an important role in resistance to heat stress, possibly by stabilizing the electron input module of cyanobacterial NDH-1 complexes.
Jiaohong ZhaoFudan GaoZijian QiuQuanxi WangWeimin Ma
