The heterosis of photosystem Ⅱ functions in Sorghum bicolor×S. sudanense seedlings under drought stress
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Abstract
The response of photosystem Ⅱ activity in leaves of Sorghum sudanense and S. bicolor×S. sudanense to drought stress was investigated by the fast chlorophyll fluorescence induction dynamics analysis. The results showed that the maximum photochemical efficiency (Fv/Fm) and the performance of PSⅡ activity (PIABS) in these two species decreased with the increasing intensity of drought stress, especially the PIABS reduction was significantly greater than Fv/Fm. Although the PSⅡ photochemical activity in leaves of both of these two species seedlings decreased under drought stress, the PSⅡ photochemical activity in S. bicolor×S. sudanense seedling leaves was significantly higher (P<0.05) than that in S. sudanense seedling. The possible reasons for these difference included that the rates of relative variable fluorescence increase at 0.15 and 0.3 ms on the OJIP curve of S. bicolor×S. sudanense seedlings were significantly less than that of S. sudanense seedlings under drought stress and that the impacts of drought on the complex activities of electron donor side OCE oxygen and thylakoid aggregation state in S. bicolor×S. sudanense seedlings was significantly less than those in S. sudanense seedlings which was important for the supply, transport and stability of electron in electron transport chain. In addition, the relative variable fluorescence of VJ and VI at 2 and 30 ms on the OJIP curve (J point and I point) of these two species forage seedlings significantly increased under drought stress suggested that the decrease of PSⅡ photochemical activity was correlated with the block of QA to QB transport in PSⅡ electron acceptor side and the decrease of the PQ library capability of accepting electron. However, there was significant difference between VJ and no significant difference between VI of S. bicolor×S. sudanense and S. sudanense leaves, indicating that the electron transfer body QB ability to accept electrons and the ability of transmitting electron of PSⅡ donor side of S. bicolor×S. sudanense seedlings were higher than those in S. sudanense under drought stress.
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