Photosynthesis and Related Physiological Characteristics Affected byExogenous Glucose in Wheat Seedlin<I>G</I><SUP>s</SUP> under Water S<I>T</I><SUP>r</SUP>ess

Abstract

Drought, one of the main adverse environmental factors, obviously affects plant growth and development. Previous studies have shown one of the plant mechanisms conferred stress tolerance is the rapid accumulation of soluble sugar (glucose, fructose and sucrose) during water stress. A large number of stress responsive genes have been reported to be induced by glucose, indicating the role of sugars in environmental responses. Although it has already been shown that sugars act as signaling molecules in plants to modulate growth, development, and stress responses, little is known about the mechanisms by which plants respond to them under water stress. To investigate the regulational relation between glucose and drought resistance in wheat, the effects of exogenous glucose on growth and photosynthesis in wheat (Triticum aestivum L.) seedlings under water stress were studied. Wheat seedlings were treated with Hoagland solution (T0), 15% PEG-6000 (T1), 15% PEG-6000+100 μmol L-1 Glc (T2), and 15% PEG-6000+300 μmol L-1Glc (T3), respectively. Effects of exogenous glucose on the leaf water potential and relative water content, photosynthesis, photosynthetic pigment content, soluble sugar and proline content in leaves, as well as growth of seedlings and roots were analyzed. The leaf water potential and leaf photosynthesis decreased significantly, and the growth of seedlings was inhibited when the plants were subjected to water stress. However, the leaf water potential, photosynthetic pigments content increased in T2 and T3 treatments. Simultaneously, the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), and water use efficiency (WUE) in leaf increased. However, the but transpiration rate (Tr) decreased when the seedlings were treated with exogenous glucose under water stress and rewatered after water stress. Moreover, the levels of proline and soluble sugar in leaves increased by glucose treatment under water stress. Exogenous glucose treatment increased the number of lateral roots, and the length of adventitious roots, and the plant dry matter increased by 14.32–40.39% compared to the drought treatment alone. These results indicate that exogenous glucose may improve drought resistance by increasing roots growth and photosynthesis in leaves under water stress.