Dry dirt and hot air: how grapevines respond

Researchers have known for some time that different varieties of grapes respond in different ways to soil water stress. Varieties such as Grenache are able to reduce transpiration and conserve water when stressed. Others, such as Shiraz, respond less and lose more water.

CRCV researchers wanted to see if atmospheric water stress, due to hot, dry air, would have the same effect.

Samples of leaves and roots from Shiraz and Grenache were taken and analysed over three hot and three cooler days. Soil moisture was the same for both varieties.

The study found that, while there was little difference under cool conditions, Grenache reduced its transpiration and water loss significantly more than Shiraz when the climate became more stressful.

Levels of Abscisic acid (ABA), the signalling hormone that tells the leaves to conserve water, confirmed the results. An investigation of gene activity in root and leaf tissues pointed to the ABA originating in the leaves of the vines and not, as previously supposed, being transported to the leaves from the roots.

New research is now investigating a wide range of popular grape varieties to assess their responses to water deficits and will help in fine-tuning deficit irrigation systems such as regulated deficit irrigation (RDI) and Partial Rootzone Drying (PRD) to suit individual cultivars.

This research is being supported by the Grape and Wine Research and Development Corporation.

Reference: Grape vine varieties Shiraz and Grenache differ in their stomatal response to VPD: apparent links with ABA physiology and gene expression in leaf tissue, C.J. SOAR, J. SPEIRS, S.M. MAFFEI, A.B. PENROSE, M.G. MCCARTHY and B.R. LOVEYS, 2006. Australian Journal Of Grape And Wine Research, 12, 2-12.

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