Drought is the most significant limiting factor for plant cultivation. Greenhouse-grown 1-year-old potted M.9EMLA apple trees (Malus domestica Borkh.) (after growing for 6 weeks) were subjected to drought stress by withholding water for an additional six-week period. The photosynthesis, carbohydrates and the nitrogen (N), phosphorus (P) absorb in the upper, middle and lower leaves of the seedlings were determined. The results revealed that drought stress obviously decreased the photosynthesis and carbohydrates contents in the leaves at all sections of shoot compared with the control. Sorbitol and glucose concentrations increased over time and was kept at a higher level during the drought stress period whereas sucrose concentration declined. N content in the leaves kept a flat trend and was higher than that of the control while P concentration decreased compared with the control. These results demonstrated that drought stress prevented N and P absorbtion and decreased RWC of apple leaves, which caused the decline of photosynthesis and transpiration. Thus, the direct phenotype was the slowed growth which was specifically expressed in decreased plant height, number of leaves, average leaf area and stem diameter.
Key words: Malus domestica Borkh, sorbitol, water deficit, transpiration.
ET, Evapotranspiration; Pn, photosynthesis; E, transpiration; RWC,relative water content; DPS, data processing system.
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