Abstract
In C-3 plants, carbon isotope composition (delta C-13) is influenced by isotopic effects during diffusion from the atmosphere to the chloroplasts and carboxylation reactions. This work aimed to demonstrate if delta C-13 of leaf soluble carbohydrates (delta C-13(leaves)) and of dry matter from new-growth shoots (delta C-13(shoots)) of Prunus plants subjected to a period of water deficit was related to water use efficiency (WUE). For this purpose, three interspecific Prunus hybrids rootstocks (6-5, 7-7 and G x N) were gradually subjected to drought and then rewatered. Soil water content (SWC) decreased from 26.1 to 9.4% after 70 days of water shortage, when plants reached values of predawn leaf water potential (LWP) ranging from-3.12 to-4.00 MPa. Gas exchange, particularly net photo-synthetic and transpiration rates, differed among the three hybrids, leading to different values of WUE. After 70 days of drought, a significant delta C-13 increase of 5.86, 4.28 and 4.99 parts per thousand was observed in 6-5, 7-7 and G x N, respectively. Significant correlations between 813C and other parameters (substomatal CO2/atmospheric CO2 ratio, stomatal conductance and stem water potential) were found in all hybrids. The rewatering phase caused a recovery of the physiological status of the plants. The isotope composition of delta C-13 (shoots) was correlated with the average WUE measured during the whole experiment. delta C-13(leaves) and delta C-13(shoots) were positively related (r = 0.87; p < 0.001). The isotopic signature was a reliable screening tool to identify Prunus genotypes tolerant to drought stress. The results suggest the possibility of using delta C-13 as an integrated indicator of level of drought stress in plants subjected to prolonged stress conditions.
NSTL
Elsevier