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Drought, heat, and their combined stress reduce the productivity and alter the photosynthetic characteristics of different alpine meadow plants
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  • Li Ma,
  • Zhonghua Zhang,
  • Bingrong Zhou,
  • Manhou Xu,
  • H Zhou
Zhonghua Zhang
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Bingrong Zhou
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H Zhou
Northwest Plateau Institute of Biology, Chinese Academy of Sciences
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Alpine meadow plants, which are adapted to humid and cold environments, are more sensitive to environmental factors such as drought and high temperatures. However, excluding species competition, the physiological responses of individual alpine meadow species to drought and heat stress remain unclear. In this study, four representative species of typical functional groups in an alpine meadow of the Qinghai-Tibet Plateau were selected as experimental materials. Heat (H1, H2), drought (D1, D2), and combined heat and drought stress (D1H1, D2H2) treatments were implemented to reveal the physiological characteristics’ response to a constant drought and heat environment. Our results showed that the leaf water content (LWC) of Kobresia humilis and Poa annua increased significantly under heat stress and the compound heat and drought stress (P<0.05). Additionally, the aboveground biomass (AGB) of Oxytropis ochrocephala and Saussurea pulchra decreased significantly under compound stress (P<0.05). The response patterns of the net photosynthetic rate (Pn) and transpiration rate (Tr) of K. humilis and P. annua under various stress treatments were similar; as were those of O. ochrocephala and S. pulchra. The stomatal conductance (Gs) variation in K. humilis, P. annua, O. ochrocephala, and S. pulchra were the same under three kinds of stress treatments. The photosynthetic characteristics were more sensitive to the effects of composite than of single factors. The drought × heat × species treatment had a significant influence on various indexes except on height and the belowground biomass (P<0.01). Within a certain range, daytime temperature (DT) promoted the height and increased the LWC of the plants, while it inhibited their AGB and intercellular CO2 concentration. The Pn, Tr, and Gs were more sensitive to soil moisture than to DT. Our results help improve understanding of the physiological response regularity of representative alpine meadow plant species to continuous drought and high temperature conditions.