ISHS Acta Horticulturae 493: I ISHS Workshop on Water Relations of Grapevines
RELATIONSHIPS BETWEEN LEAF WATER POTENTIAL AND PHOTOSYNTHETIC ACTIVITY OF FIELD-GROWN GRAPEVINES UNDER A MEDITERRANEAN ENVIRONMENT |
| Author: | C. M.A. Lopes |
| Keywords: | stomatal conductance, irrigation, water stress |
| Abstract:
In order to verify the dependence of net assimilation rate (A) and stomatal conductance (gs) on leaf water potential (  ), physiological data from a training system and irrigation experiment conducted during 1991 and 1992 are correlated.
In 1991, a very hot and dry season caused a high water stress, which induced premature leaf senescence and low photosynthetic rates on the remaining leaves and, consequently, reduced berry sugar accumulation.
The irrigation applied in 1992 positively affected grapevine physiology, growth and yield without changing wine quality.
In stress conditions, A and (gs measured during the summer on sun leaves at three different periods of the day were highly correlated with predawn leaf water potential (pd). In non-irrigated plants the correlations between the diurnal values of and A or (gs), measured at the same time, were also significant but the coefficients were lower than those found on the correlation with the pd. In the irrigated vines there were no significant correlations between values and A or gs measured during the photoperiod.
Under water stress conditions, pd was a very sensitive indicator of the physiological activity of sun leaves.
During the photoperiod, leaf water status was a poor indicator of sun leaf photosynthetic activity and its relative importance decreases with the increase in soil water availability.
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