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Greenhouse grown 1 year old potted M.9EMLA apple trees ( Malus pumila Borkh) were subjected to the soil compaction and, after growing under compacted or non compacted conditions for 6 weeks, were subjected to drought stress by withholding water for an additional six week period. Soil compaction and drought stress significantly reduced plant height, number of leaves, and leaf area. Although drought significantly inhibited photosynthesis and transpiration, compaction only depressed transpiration. Furthermore, the effects of drought on plant growth, photosynthesis and transpiration were much greater than the effects of compaction. The rate of water loss from compacted plants was lower than the rate from non compacted controls and this may explain the insignificant impact of compaction on photosynthesis. Sorbitol, glucose, and fructose concentrations increased over time during the drought stress period whereas sucrose concentration declined. In well watered controls, sucrose concentration was much higher in leaves of compacted plants than in the leaves on non compacted controls. For most of the sampling dates the leaf sorbitol concentration was lower in leaves on plants growing in compacted soil than in the leaves of those of the non compacted controls. Although interactions between the effects of compaction and drought were highly significant for plant growth variables during the onset of drought, interactive effects on photosynthesis, transpiration, relative water content and carbohydrate variables were inconsistent. Compaction and drought both have major effects on apple plants and the interactions between these two stresses are complex.
Greenhouse grown 1 year old potted M.9EMLA apple trees (Malus pumila Borkh) were subjected to the soil compaction and, after growing under compacted or non compacted conditions for 6 weeks, were subjected to drought stress by withholding water for an additional six week period Even though the significant of photosynthesis and transpiration, compaction only depressed output growth, photosynthesis and transpiration were much greater than the effects of compaction. The rate of water loss from compacted plants was lower than the rate from non compacted controls and this may explain the insignificant impact of compaction on photosynthesis. Sorbitol, glucose, and fructose concentrations increased over time during the drought stress period whereas sucrose concentration declined. In well watered controls, sucrose concentration was much higher in leaves of compacted plants than in the leaves on non compacted controls. Most of the sampling dates the leaf sorbitol concentration was lower in leaves on plants growing in compacted soil than in the leaves of those of the non compacted controls. Although interactions between the effects of compaction and drought were highly significant for plant growth variables during the onset of drought, interactive effects on photosynthesis, transpiration, relative water content and carbohydrate variables were inconsistent. Compaction and drought both have major effects on apple plants and the interactions between these two stresses are complex.