Transpiration rates and hydraulic conductance of two olive genotypes with different sensitivity to drought

Abstract

Although some mechanisms of leaf dehydration tolerance are known in olive (Olea europaea L.), insights on adjustments in stem and root hydraulic conductance (K) in response to drought are yet to be explored. This work investigated transpiration mechanisms and K regulations in two olive genotypes showing different sensitivity to drought stress. In 2017, one-year-old potted ‘Nocellara del Belice’ (NB) and ‘Cerasuola’ (CE) plants were set in a greenhouse and double-bagged to avoid evaporation from soil surface. Half of the plants were drought-stressed (DS, no irrigation) for more than 30 days and the remaining plants were well-watered (WW). At the end of the drought period, stem and root portions were separated and used to determine hydraulic conductance (K). Results were then normalized using stem cross-sectional area and expressed as sapwood specific conductance (Ks). NB plants were able to keep a normalized transpiration rate (TN) stable until a lower transpirable soil water fraction (Wfraction) than CE plants, indicating lower tolerance to sudden drought events in the former. Dry matter content sensibly increased after drought in NB, not in CE. Also, drought increased root/leaf ratio in NB, not in CE. Regardless of the genotype, there was an 100% increase of stem Ks in DS plants compared to WW plants. Conversely, root Ks was not affected by drought, suggesting that xylem modifications in response to water deficit occur mainly in above-ground organs. Overall, these results show than the two olive genotypes use different mechanisms to cope with drought and confirm that the CE genotype tolerates quick tissue dehydration better than NB. © 2019 International Society for Horticultural Science. All rights reserved.