Can a small differential in canopy temperature influence performance of Semillon in a vineyard?

Vegetative and reproductive growth responses of vineyard-grown Vitis vinifera cv. Semillon vines to canopy temperatures were followed. Canopies were controlled at means of 29.8°C, 31.5°C and 32.7°C. Stem and leaf growth were affected; length and canopy leaf area was maximal in the warmest treatment and smallest in the coolest treatment. Accumulation of biomass of leaves, stems and bunches was highest in the coolest treatment and lowest in warm conditions. Berry expansion was affected by treatment temperatures but most reduced in the warm treatment, whereas accumulation of sugar in the berries was highest in the coolest treatment. There were treatment differences in yield, with a marked reduction in the warm treatment. Clearly, there were detrimental growth responses to the higher temperatures. The temperature differential between treatments of 3°C was comparable with what might occur with climate change and the study shows such a difference can be detrimental to vine growth and development.