Effect of soil water availability on root respiration in grapevines – importance for plant carbon balance

Abstract

The effect of water stress on photosynthesis and transpiration has been largely studied in the past. However, there is a lack of research on water stress effects on root respiration and vine carbon balance even though the importance of root respiration on the final carbon balance has been clearly shown. An experiment was carried out during 2013 to determine the effect of different levels of water availability on root respiration and plant carbon balance on two important grapevine cultivars ('Grenache' and 'Tempranillo'). Two irrigation treatments were established (moderate irrigation and drought or rain-fed). Root respiration and soil water content were measured at different phenological stages and different soil positions from each vine monitored. Results showed that root respiration rates for 'Tempranillo' and 'Grenache' were higher in the initial growth stages, with 'Tempranillo' exhibiting the highest levels. A decline in respiration rates was observed in both cultivars and treatments at veraison. Soil moisture heterogeneity around the irrigated vines determined changes in root respiration, being higher in the portion of soil close to the dripper than between rows. This could be explained by the distribution of root system activity according to greater moisture availability in these zones. The present study showed that about 15% of carbon fixed by photosynthesis was lost by root respiration.