Abstract
BackgroundThe electron transport chain, Rubisco and stomatal conductance are important in photosynthesis. Little is known about their combined responses to heat treatment at different temperatures and following recovery in grapevines (Vitis spp.) which are often grown in climates with high temperatures.Methodology/FindingsThe electron transport function of photosystem II, the activation state of Rubisco and the influence of stomatal behavior were investigated in grapevine leaves during heat treatments and following recovery. High temperature treatments included 35, 40 and 45°C, with 25°C as the control and recovery temperature. Heat treatment at 35°C did not significantly (P>0.05) inhibit net photosynthetic rate (P n). However, with treatments at 40 and 45°C, P n was decreased, accompanied by an increase in substomatal CO2 concentration (C i), decreases in stomatal conductance (g s) and the activation state of Rubisco, and inhibition of the donor side and the reaction center of PSII. The acceptor side of PSII was inhibited at 45°C but not at 40°C. When grape leaves recovered following heat treatment, P n, gs and the activation state of Rubisco also increased, and the donor side and the reaction center of PSII recovered. The increase in P n during the recovery period following the second 45°C stress was slower than that following the 40°C stress, and these increases corresponded to the donor side of PSII and the activation state of Rubisco.ConclusionsHeat treatment at 35°C did not significantly (P>0.05) influence photosynthesis. The decrease of P n in grape leaves exposed to more severe heat stress (40 or 45°C) was mainly attributed to three factors: the activation state of Rubisco, the donor side and the reaction center of PSII. However, the increase of P n in grape leaves following heat stress was also associated with a stomatal response. The acceptor side of PSII in grape leaves was responsive but less sensitive to heat stress.
Highlights
High temperature negatively affects plant growth and survival and crop yield
The decrease of photosynthetic rate (Pn) in grape leaves exposed to more severe heat stress (40 or 45uC) was mainly attributed to three factors: the activation state of Rubisco, the donor side and the reaction center of photosystem II (PSII)
The increase of Pn in grape leaves following heat stress was associated with a stomatal response
Summary
Photosynthesis is known to be one of the most heat-sensitive processes, and it can be inhibited by high temperature before other symptoms of stress are detected [1,2]. Inhibition of photosynthesis by heat stress has long been attributed to an impairment of electron transport activity, especially the inhibition of photosystem II (PSII) activity [3,4]. Heat stress damages the oxygen-evolving complex of PSII [5,6], and impairs electron transfer within the PSII reaction centres [7,8,9] and downstream of PSII. Some authors [10,11] have suggested that the initial site of the inhibition is associated with a Calvin cycle reaction, especially inactivation of Rubisco [12,13,14,15]. Little is known about their combined responses to heat treatment at different temperatures and following recovery in grapevines (Vitis spp.) which are often grown in climates with high temperatures
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