PHOTOSYNTHESIS, PLANT GROWTH AND CARBON ALLOCATION IN KIWI, CV HAYWARD, AS INFLUENCED BY WATER DEFICITS

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 field capacity in the soil. Water deficits reduced the rate of photosynthesis by 53–64% in relation to the control. This decline was attributed either 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 at water stressed plants, which shows that water stress in kiwi 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 photosynthesis, leaf area development and photosynthates partitioning.