Sex-specific physiological and growth responses to water stress in Hippophae rhamnoides L. populations

Dioccious plant species and those occupying diverse habitats may present special analytical problems to determine effects of environmental stress. Here, sex-specific physiological and growth responses of two contrasting sea buckthorn (Hippophae rhamnoides L.) populations were recorded after exposure to different watering regimes. The populations used were from wet and dry climate regions in China, respectively. In the semi-controlled environmental study, the well-watered and water-deficiency plants which were watered to 100% and 50% field capacity were used, respectively. Sexual differences in height growth (HT), dry matter accumulation (DMA), root/shoot ratio (RS), specific leaf area (SLA), net photosynthesis (A), transpiration (E), instantaneous water use efficiency (WUEi) and carbon isotope composition (delta(13)C) between the male and female individuals were detected under water-deficiency treatment in both populations tested. However, these sexual differences were not detected under well-watered treatment. On the other hand, compared with the wet climate population, the dry climate population showed lower HT, DMA, SLA, A and E, and higher RS under both watering regimes. The dry climate population also showed higher WUEi and delta(13) Cas affected by water deficit than the wet climate population. These morphological and physiological responses to drought showed that the different populations and the different sexual individuals may employ different Survival strategies under environmental stress. The male individuals and the dry climate population would have a conservative water-use strategy in response to drought stress.