I admit it, I’m partial to a glass of red wine in the evening. And Shiraz is one of my favourites, so the idea that climate change might threaten my favourite tipple is worrying, to say the least. Shiraz is very much the signature grape of Australian wine, and produces hearty red wines with intense fruit flavours. (This is making me thirsty.) Looking at the problem in a slightly broader way, the Australian wine industry is the world’s fourth largest exporter of wine producing approximately 750 million litres a year, and the wine industry is a significant contributor to the Australian economy.
Rising global temperatures can be accompanied by smaller, but significant, changes in soil surface temperatures and this has the potential to affect root physiology and root activity. In particular, a gradual rise in night-time air temperature over the past few decades has probably resulted in an increase in soil temperature during the night and early morning, depending on soil depth. Root growth, water uptake, nutrient uptake and availability and signal transduction are all influenced by the temperature of the soil. These processes affect above-ground growth and productivity. As a result, analogous to air temperature, soil temperature can limit the geographical distribution of plants and crops.
A new free Open Access paper in Annals of Botany assesses the foliar gas exchange response of ‘Shiraz’, a grapevine variety originating from temperate Bordeaux, France, and grown widely in warm climates across southern Australia and Argentina. So will climate change threaten my (and possibly your) drinking habits?
You’ll have to read the paper to find out.
Free Open Access article: Nocturnal and daytime stomatal conductance respond to root-zone temperature in ‘Shiraz’ grapevines. Annals of Botany (2013) 111 (3): 433-444. doi: 10.1093/aob/mcs298
Daytime root-zone temperature may be a significant factor regulating water flux through plants. Water flux can also occur during the night but nocturnal stomatal response to environmental drivers such as root-zone temperature remains largely unknown. Here nocturnal and daytime leaf gas exchange was quantified in ‘Shiraz’ grapevines (Vitis vinifera) exposed to three root-zone temperatures from budburst to fruit-set, for a total of 8 weeks in spring. Despite lower stomatal density, night-time stomatal conductance and transpiration rates were greater for plants grown in warm root-zones. Elevated root-zone temperature resulted in higher daytime stomatal conductance, transpiration and net assimilation rates across a range of leaf-to-air vapour pressure deficits, air temperatures and light levels. Intrinsic water-use efficiency was, however, lowest in those plants with warm root-zones. CO2 response curves of foliar gas exchange indicated that the maximum rate of electron transport and the maximum rate of Rubisco activity did not differ between the root-zone treatments, and therefore it was likely that the lower photosynthesis in cool root-zones was predominantly the result of a stomatal limitation. One week after discontinuation of the temperature treatments, gas exchange was similar between the plants, indicating a reversible physiological response to soil temperature. In this anisohydric grapevine variety both night-time and daytime stomatal conductance were responsive to root-zone temperature. Because nocturnal transpiration has implications for overall plant water status, predictive climate change models using stomatal conductance will need to factor in this root-zone variable.