Photosynthesis and ultrastructure of photosynthetic apparatus in tomato leaves under elevated temperature

Abstract

The microstructure of leaves and ultrastructure of chloroplasts were examined in tomato (Lycopersicon esculentum L.) plants treated with elevated temperature. Plants were exposed to 35ºC for 30 d after florescence. The plants grown continuously under 25ºC served as controls. Compared with the controls, the net photosynthetic rate (P N ) in stressed plants decreased significantly. Stomatal conductance, intercellular CO 2 concentrations, the rate of transpiration, and the limitation of stomatal conductance showed that the decrease in P N was caused mainly by nonstomatal restrictions. Meanwhile, stomata density increased significantly in the stressed plants. The stomata status of opening and closing became disorganized with a prolonged 35ºC exposure. The damage of chloroplast membrane occurred earlier and was more serious in the plants under elevated temperature. At the same time, the thylakoids were loosely distributed with lesser grana, but the number of lipid droplets increased in chloroplasts. The number of starch grains in chloroplasts increased first and then decreased. In addition, the length of the main nerve in leaves increased and the main vein showed distortion in the plants stressed by 35ºC. An increase was observed in the number of cells on the abaxial side of the main vein and these cells were overly congregated. The thickness of a vertical section became thinner in the stressed leaves. The cells of the upper epidermis thinned, and the ratio of palisade tissue to spongy tissue decreased. Generally, the photosynthetic apparatus of tomato changed significantly and the changed chloroplast ultrastructure might be one of the important reasons that caused the decrease of PN under 35ºC.

Influence of High Temperature on Photosynthesis, Antioxidative Capacity of Chloroplast, and Carbon Assimilation among Heat-tolerant and Heat-susceptible Genotypes of Nonheading Chinese Cabbage

“…7). These alterations of chloroplast ultrastructure can negatively and directly influence the photosynthetic apparatus function and inhibit the activities of membrane-associated electron carries and enzymes, which ultimately result in a reduced rate of photosynthesis (Zhang et al, 2014). The swollen chloroplasts and disordered lamellase were more severe in heat-susceptible 'sym', indicating that the chloroplast and thylakoid suffered from more damage than the chloroplast in heat-tolerant 'xd'.…”

Screening and validation of tomato genotypes under heat stress using Fv/Fm to reveal the physiological mechanism of heat tolerance

“…reduction in photosynthesis is linked to the decreases in chlorophyll content as a result of reduced antenna pigments, lowering the light harvest during heat stress (Herde et al, 1999;Camejo et al, 2006). On the other hand, the alteration of chloroplast ultrastructure can directly influence the state of the photosynthetic apparatus and the photosynthesis rate (Zhang et al, 2014). Heat stress destroyed the chloroplast structure by disordering the lamellae in the chloroplast and increased the plastoglobulus number (Xu et al, 2006;Gao et al, 2010).…”

“…The optimal growing temperature for tomato is between 25 C and 30 C during the daytime and 20 C during the night (Camejo et al, 2005). Cultivation of tomatoes under higher temperatures than the optimum has a negative impact on plant growth (Camejo et al, 2006;Zhang et al, 2014) and will decrease productivity (Peet et al, 1998;Sato et al, 2000Sato et al, , 2006. As a consequence of global warming, the impact of high temperatures on field-grown tomatoes has become an urgent issue.…”

Model for tomato photosynthetic rate based on neural network with genetic algorithm

“…Other microclimate factors, such as temperature, can have a direct or an indirect influence on photosynthesis and have been shown to influence the activity of a crop's Rubisco activase, stomatal conductance and chlorophyll content [25,26] . The CO 2 concentration can also affect the crop, including the dark reaction rate and dry matter accumulation [27] .…”