Effects of exogenous glucose on photosynthesis and key enzyme activities in carbon and nitrogen metabolism of flue-cured tobacco at fast-growing stage under high temperature and high light intensity
In order to investigate the regulation mechanism of exogenous glucose on the photosynthesis mechanism and carbon and nitrogen metabolism of flue-cured tobacco leaves at fast-growing stage under high temperature and high light intensity, a pot experiment in an artificial climate chamber was conducted by simulating the high temperature and high light intensity environment of flue-cured tobacco at fast-growing stage in central Henan tobacco-planting areas. The effects of exogenous glucose (0.5 mmol/L) on the contents of photosynthetic pigments, including chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll [Chl(a + b)], carotenoids (Car), the photosynthetic parameters, including net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), intercellular CO2 concentration (Ci), chlorophyll fluorescence parameters, including initial fluorescence (Fo), nonphotochemical quenching coefficient (NPQ), actual photochemical quantum efficiency of PSⅡ ( Φ PSⅡ), photosynthetic electron transfer efficiency (ETR), photochemical quenching coefficient (qp), maximum photochemical efficiency of PSⅡ (Fv/Fm), glutamine synthase activity (GS) and 1,5-diphosphate ribulose carboxylase (Rubisco) activity of flue-cured tobacco were studied. The results showed that spraying exogenous glucose under high temperature and high light intensity significantly promoted the contents of Chla, Chlb, Chl(a+b) and Car, noticeably raised Pn, Gs, E, remarkably reduced Ci, Fo and NPQ; Φ PSⅡ, ETR, qp were increased significantly, in which the increase extent of Fv/Fm was relatively smaller. Furthermore, the activities of GS and Rubisco were improved. Therefore, spraying exogenous glucose under high temperature and high light intensity promotes the photosynthetic performance, carbon and nitrogen metabolism balance and the growth of tobacco, and alleviates the adverse effects of high temperature and high light intensity stress on tobacco.
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