Articles
VALIDATION OF A SIMPLE BIOLOGICAL INDICATOR OF PLANT WATER STATUS TO DETERMINE IRRIGATION TIMING OF GRAPEVINES
Article number
646_9
Pages
77 – 89
Language
English
Abstract
The ability to manipulate winegrape quality in response to seasonal water deficits through use of the relative transpiration index (RTI) was evaluated during two consecutive years in container-grown Shiraz grapevines installed inside a commercial vineyard.
The RTI (Relative Transpiration Index) assesses water loss from plants experiencing water deficits relative to that from well watered controls and was used as an indicator of the plant water stress and for irrigation timing.
The treatments were: T1: no stress, T2: moderate stress from fruit set to veraison (FV) and T3: moderate stress from veraison to harvest (VH). Midday (LWPm) and predawn (LWPp) leaf water potential were also measured.
The effects of the treatments on the yield components, vegetative and reproductive growth and specific phenolic compounds of the berries were determined.
There was no significant effect of the treatment during FV and moderate stress was reached in T3 vines during VH according to RTI and LWPp -criteria.
In T2 and T3 the main shoots showed reduced growth due mainly to a reduction in node number.
Shoot growth rate was reduced by water deficit by 20 and 30% during FV and VH periods respectively.
In relation to T1, the pruning weight of T2 and T3 was 43.7% and 49.3% less.
No significant differences among treatments were found in the yield components but the weight loss in ripening berries was more evident in T3. The number of clusters initiated was not affected.
No significant differences in polyphenolic content was observed among treatments, nor in degree of tannins polymerization . Nevertheless, a relative increase in flavonol content was observed during harvest 2000 due to the effect of late restriction and in harvest 2001 a relative increase in anthocyanins, flavonols, proanthocyanidins and also in flavonol monomers due to moderate stress during preveraison was observed.
During the two seasons the RTI behaved as a sensitive and accurate indicator of the plant water availability and a simple tool for irrigation timing.
The RTI (Relative Transpiration Index) assesses water loss from plants experiencing water deficits relative to that from well watered controls and was used as an indicator of the plant water stress and for irrigation timing.
The treatments were: T1: no stress, T2: moderate stress from fruit set to veraison (FV) and T3: moderate stress from veraison to harvest (VH). Midday (LWPm) and predawn (LWPp) leaf water potential were also measured.
The effects of the treatments on the yield components, vegetative and reproductive growth and specific phenolic compounds of the berries were determined.
There was no significant effect of the treatment during FV and moderate stress was reached in T3 vines during VH according to RTI and LWPp -criteria.
In T2 and T3 the main shoots showed reduced growth due mainly to a reduction in node number.
Shoot growth rate was reduced by water deficit by 20 and 30% during FV and VH periods respectively.
In relation to T1, the pruning weight of T2 and T3 was 43.7% and 49.3% less.
No significant differences among treatments were found in the yield components but the weight loss in ripening berries was more evident in T3. The number of clusters initiated was not affected.
No significant differences in polyphenolic content was observed among treatments, nor in degree of tannins polymerization . Nevertheless, a relative increase in flavonol content was observed during harvest 2000 due to the effect of late restriction and in harvest 2001 a relative increase in anthocyanins, flavonols, proanthocyanidins and also in flavonol monomers due to moderate stress during preveraison was observed.
During the two seasons the RTI behaved as a sensitive and accurate indicator of the plant water availability and a simple tool for irrigation timing.
Authors
R.C. Vallone, L. Nijensohn, J.B. Cavagnaro, E.E. Merlo, J.A. Maffei, H. Ojeda, E.E.A. Mendoza
Keywords
grapevine, regulated deficit irrigation, relative transpiration index, shoot growth, berry growth, berry ripening, phenolic compounds
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