Impact of changing climatic factors on physiological and vegetative growth

Abstract

Context and purpose of the study – scientific information on grapevine response to predicted levels of climate parameters is scarce and not sufficient to properly position the Wine Industry for the future. It is critical that the combined effects of increased temperature and CO2 on grapevines should be examined, without omitting the important link to soil water conditions. The purpose of this study is to quantify the effects of envisioned changes in climatic parameters on the functioning and growth of young grafted grapevines under controlled conditions, simulating expected future climate changes. Scientific knowledge of precisely how the newly-planted grapevine will react morphologically, anatomically and physiologically (at leaf, root and whole plant level) to the expected changes in important climatic parameters will enable producers to make better-informed decisions regarding terroir, cultivar and rootstock choices as well as the adaptation of current cultivation practices.

Material and methods – four glass house compartments were set up with combinations of the two main environmental factors, namely ambient temperature and CO2. Within each compartment, another treatment factor, water supply, was introduced. Young, grafted grapevines were established in pots in a randomized block design. Five growth cycles of 12 weeks each were monitored, with Shiraz as scion cultivar in three of them and Merlot in the other two. The rootstock used throughout was 101-14 Mgt. Vegetative and physiological growth parameters were measured throughout the growth cycles with critical sampling times at 4, 8 and 12 weeks after planting.

Results – a change in environmental growth conditions significantly affected physiological activity of the grapevine. Both increased CO2 levels and adequate water supply increased photosynthetic activity for all treatment combinations. Newly planted vines were photosynthetically more active and reacted more strongly to treatments than slightly older vines. The higher temperature treatment seemed to impair photosynthesis under comparable CO2 and H2O conditions, especially with regards to very young vines. The effect of temperature on vegetative growth was insignificant compared to the CO2 and H2O effects and only seemed to affect initial growth directly after planting. The availability of water was critical to root, shoot and leaf growth – higher CO2 levels further enhanced vegetative growth.
The results indicate that the importance and impact of the climatic variables and the vine reaction change during the growth season. The strong interactions found between weeks after planting, available water, ambient temperature and CO2 levels necessitate multi-variable research on the effect of changing climatic factors on the grapevine.