Effects of non-stomatal components on photosynthesis in soybean [Glycine max] under salt stress
2001
Umezawa, T. (Tsukuba Univ., Ibaraki (Japan)) | Shimizu, K. | Kato, M. | Ueda, T.
Abstract To elucidate the physiological mechanism of inhibition of photosynthesis by salt stress in soybean (Glycine max (L.) Merr.), the photosynthetic activity, Na+ accumulation and ABA content of two soybean cultivars, Lee (salt-tolerant) and Enrei (salt-sensitive), were investigated. After 4 weeks of exposure to various NaCl concentrations, photosynthesis and growth in Enrei were more strongly inhibited by salt stress (50 mM NaCl) than in Lee. The evolution of oxygen was inhibited by salt stress only in Enrei. Therefore, the reduction of photosynthesis in Enrei can be partly explained by the increase in the involvement of non-stomatal components Since the Na+ concentration in Enrei leaves was increased remarkably under 50 mM NaCl treatment, it was assumed that a high Na+ content might contribute to non-stomatal components. Lee may also be endowed with some mechanism(s) of prevention of Na+ accumulation m shoots since Lee accumulated more Na+ in roots than Enrei. These results suggested that the difference in salt tolerance between these two soybean cultivars was due to the inhibition of photosynthesis by non-stomatal components caused by Na+ accumulation in shoots. On the other hand, the leaf ABA content in Lee increased significantly under salt stress, while that in Enrei showed only a slight increase. It is thus possible that ABA enhances salt tolerance in soybean.
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