The aim of this research project was to study the interactive effects of heat and water stress on grapevine growth and ripening.
Pot-grown Cabernet Sauvignon and Riesling grapevines were used. The following treatments were applied in growth chambers in a controlled environment:
– Control: no stress (C)
– Water stress only (WS) Soil moisture 10% lower than control
– Heat stress only (HS) Hourly temperatures elevated by 10°C above 10 year average
– Combined water and heat stress (WS + HS)
Treatments were applied for seven days before veraison, then stress relieved and vines allowed to recover. Repeated again during veraison. Various measurements were taken and berry samples collected before and after the treatments.
– Water stress reduced canopy growth and leaf gas exchange in both cultivars
– Heat stress only occasionally reduced canopy growth
– Heat stress increased transpiration in both cultivars, but only reduced photosynthesis in Riesling
– In both cultivars, stomata closed as water status declined
– The cultivars responded differently to the stresses when considering fruit ripening. Water stress advanced the onset of ripening in Cabernet Sauvignon, but heat stress had no effect. In Riesling, the opposite was observed, heat stress advanced the onset of ripening whereas water stress had no effect.
SIGNIFICANCE OF THE STUDY:
As climate changes in different grapevine growing areas, it is important to understand what these changes mean to the physiology of grapevines. This study gave further insights into how grapevines respond to water and heat stress.