Low morning temperature limits photosynthesis and growth in cool climate grapevines

Abstract

Photosynthesis and growth of grapevines (Vitis vinifera cvs. Riesling) was studied in relation to temperature in a cool climate vineyard near Murrumbateman, NSW. The grapevines were planted in rows oriented north-south such that eastern and western halves of the canopy were exposed to direct sunlight in the morning and afternoon, respectively. Leaf photosynthesis and relative vine productivity were compared between east and west facing shoots on individual vines and between vines grown on two sites differing by 1 to 1.5 °C in minimum temperature. East and west-facing leaves intercepted similar amounts of light, but temperatures were lower in the morning than in the afternoon. On most days, low morning temperatures caused east -facing leaves to have lower rates of electron transport and higher levels of non-photochemical dissipation than west-facing leaves intercepting similar amounts of light, but at warmer leaf temperatures in the afternoon. Vines at the warmer site had relative growth rates higher than the cooler site vines throughout the early growth period. When expressed on a degree-day basis, differences in growth between sites were attributable to temperature. Summing the average daily CO2 assimilation for east- and west-facing leaves showed that vines at the cooler site fixed 14% less CO2 than the warmer site. The majority of this difference was attributable to effects of low morning temperature on the rate of CO2 assimilation by east facing leaves. Thus it appears that low morning temperature limits the rate of photosynthesis and hence growth of grapevines in north- south oriented rows.