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Two cultivars of spring wheat (Triticum aestivum L.) with known drought-resistance rankings (cv. Dingxi 24 more tolerant than cv. Longchun 8139) were subjected to progressive field water stress throughout their growth. Except at the seedling stage, cv. Dingxi 24 showed a higher leaf water potential compared with cv. Longchun 8139 during the stress period. Leaf water potential, inorganic ions (Na+, K+, Ca2+, Mg2+, Cl−), proline, betaine, soluble sugars and ATP content were studied in the two cultivars at various developmental stages. Contrary to the sensitive cv. Longchun 8139, consistent changes in K+ and Cl− levels and selective accumulation in K+ and Na+ were observed in Dingxi 24 mesophyll and bundle sheath cells evaluated by X-ray microanalysis and in leaves measured by atomic absorption spectrophotometer at the seedling and jointing stages. The responses of the two wheat cultivars to a decline in leaf water at the seedling and jointing stages of development included a net accumulation of inorganic ions and soluble sugar, while at the heading and grain-filling stages, there was an accumulation of betaine and proline. These results suggest that the changes in solute levels in different cultivars were closely related to their drought tolerance at different developmental stages. Mechanisms involved in solute accumulation in different cultivars and the relationship between solute accumulation and ATP consumption at different developmental stages during water stress are also discussed. |
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