EFFECTS OF SHADING ON GAS-EXCHANGE, SPECIFIC LEAF WEIGHT AND CHLOROPHYLL CONTENT IN 4 KIWIFRUIT CULTIVARS UNDER FIELD CONDITIONS

Diurnal changes of incident photosynthetic photon flux density (PPFD), transpiration rate (E), photosynthetic rate (Pn), stomatal conductanc e (Cs) and water use efficiency (WUE), together with a number of envir onmental factors, were measured on individual leaves at well exposed a nd shaded positions within the canopy for four cultivars of kiwifruit (Actinidia sinensis, P). Pn and E rates were much lower in the shaded leaves for all cultivars due to extremely low PPFD values reaching the se leaves. Cs followed a trend similar to that for Pn. Exposed leaves showed a significantly higher WUE in the morning, while no difference was observed between exposed and shaded leaves around midday. Specific leaf weight (SLW) was lower in shaded leaves, which had a greater chl orophyll content than exposed leaves.