Water relations and non-structural carbohydrate responses to the combined effects of defoliation and progressive drought
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Water relations and non‑structural carbohydrate responses to the combined effects of defoliation and progressive drought in a dioecious tree Yuanbin Zhang1 · Gang Xu2 · Shuming Peng3 · Jingwen Bai1 · Qi Lu1 · Baoli Duan1 Received: 17 January 2020 / Accepted: 5 October 2020 © Springer Nature B.V. 2020
Abstract Increases in drought frequency and insect defoliation are emerging threats that typically affect the plantation production of Populus yunnanensis, which is an endemic dioecious tree species in China. Nevertheless, it is difficult to predict which sex of P. yunnanensis will be more affected by the combined effects of water limitations and defoliation. In this study, we examined the combined effects of progressive drought and defoliation on water relations, growth, gas exchange and leaf carbohydrate reserves in P. yunnanensis females and males to test whether defoliation alters the effects of drought and and how this response varies between genders. The experimental design included two watering regimes (well-watered and drought-stressed) and two levels of defoliation (leaves untouched and 60% defoliated). Defoliation exacerbated drought stress in females by decreasing photosynthesis, dry mass accumulation and leaf non-structural carbohydrate (NSC) concentration. In contrast, the total biomass of males grown under drought combined with defoliation was not significantly altered when compared to those grown under drought alone. These results suggest that defoliation does not aggravate the drought effects on males. The males presented a high capacity to maintain foliar water status through stomatal control under drought conditions irrespective of defoliation treatment. The conservative water use strategy in males resulted in a gradual reduction in leaf water potential, gas exchange rates and NSC. Our data showed that the different responses of the females and males to drought and defoliation were influenced by plant water status and consequent effects on changes in carbon assimilation and leaf non-structural carbohydrate reserves. Keywords Compensatory mechanisms · Defoliation · Drought · Non-structural carbohydrate · Water relations * Baoli Duan [email protected] 1
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
2
School of Life Sciences and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
3
State Environmental Protection Key Laboratory of Synergetic Control and Joint Remediation for Soil & Water Pollution, College of Environment and Ecology, Chengdu University of Technology, Chengdu 610059, China
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New Forests
Introduction Increases in drought frequency and insect herbivory are emerging threats to forest production under global climate change (Adams et al. 2009; Rehfeldt et al. 2009; Carnicer et al. 2011; Allen et al. 2010; Quentin et al. 2012). The effects of drought on tree growth have been well documented. Previous research has shown that the capacity for stomatal conductance regulation coul
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