The effects of water deficits on photosynthesis, plant growth and dry matter accumulation and distribution in the kiwifruit, cv Hayward, grown under controlled conditions in the glasshouse were studied. Water stress was imposed by irrigating the plants with 100~ 85%, 65% and 40% of water needed to reach pot capacity in the soil. Water deficits reduced the rate of photosynthesis by up to 53-64% in relation to the control. This decline was attributed to stomatal closure, since stomatal conductance was reduced significantly, or/and to inhibition of photosynthesis at chloroplast level. Severe water stress reduced plant height by 78-84%, total dry weight by 58-66% and total leaf area by 72-77%. The root to shoot ratio was 3.5 times higher in water-stressed plants, showing that water stress in kiwifruit alters the pattern of dry matter distribution favouring the roots. The decrease in growth induced by water deficits was a consequence of a reduction in both photosynthesis and photosynthates partitioning, which adversely affects leaf area development.The reduction in growth and yield by water stress has been well documented (Hsiao 1973;Fischer 1980;Kriedemann and Barrs 1981), although different physiological processes have been put forward to account for this reduction in different species. The onset of stress may initially cause a loss of cell turgor (Begg and Turner 1976;Hsiao et al. 1976), which in turn reduces gas exchange and leaf elongation, since both are turgor-dependent processes (Hsiao and Acevedo 1974;Bradford and Hsiao 1982). The result is a decrease in growth rate, since this is a function of photosynthetic rate and leaf area. Moreover, prolonged water stress may affect the growth by altering the pattern of allocation of photosynthates to different plant parts (Kramer 1983;Schulze 1986).Correspondence to: K. Chartzoulakis Kiwifruit, native to the Yangtse Valley, China, (Nihou11976) is now successfully grown in Greece and other Mediterranean countries. Its anatomical features, -low resistance to water flow, high transpiration rate and large size of leaves -, characterize it as a water consumptive plant. In Mediterranean climate, where atmospheric conditions during summer usually reach critical values, in combination with an inadequate water supply kiwifruit may grow under water deficit conditions. The objectives of this study were to investigate the factors influencing the vegetative growth of kiwi fruit under water stress, with particular regard to effects on leaf area development and photosynthetic capacity. We also examined the allocation of resources between plant components and the effects of water stress on this allocation.
Materials and methodsRooted cuttings of kiwifruit (Actinidia sinensis, P. var. deliciosa), cv Hayward, one year old were used. Before planting, the rooted cuttings were kept in a refrigerator at 3-4~ for six weeks in order to break dormancy. Then, plants were established in a glasshouse in 8.51 pots, freely drained, containing light soil (sandy-loam) with pot capacity 20.5% (v/v) an...
