Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology submitted time 2019-10-26 Cooperative journals: 《干旱区科学》
LIU Junjie1
WANG Xiaoping
RONG Zhanlei
GAO Yunfei
ZHANG Guangde
WANG Wenbin
GE Lijuan
MAO Yahua
GUO Zhaoxia
WANG Qingtao
ZHAO Chuanyan
Abstract：The non-rectangular hyperbola (NRH) equation is the most popular method that plots the photosynthetic light-response (PLR) curve and helps to identify plant photosynthetic capability. However, the PLR curve can't be plotted well by the NRH equation at different plant growth phases due to the variations of plant development. Recently, plant physiological parameters have been considered into the NRH equation to establish the modified NRH equation, but plant height (H), an important parameter in plant growth phases, is not taken into account. In this study, H was incorporated into the NRH equation to establish the modified NRH equation, which could be used to estimate photosynthetic capability of herbage at different growth phases. To explore photosynthetic capability of herbage, we selected the dominant herbage species Potentilla anserina L. and Elymus nutans Griseb. in the Heihe River Basin, Northwest China as the research materials. Totally, twenty-four PLR curves and H at different growth phases were measured during the growing season in 2016. Results showed that the maximum net photosynthetic rate and the initial slope of PLR curve linearly increased with H. The modified NRH equation, which is established by introducing H and an H-based adjustment factor into the NRH equation, described better the PLR curves of P. anserina and E. nutans than the original ones. The results may provide an effective method to estimate the net primary productivity of grasslands in the study area.
Subjects: Biology >> Botany submitted time 2019-06-20 Cooperative journals: 《干旱区科学》
Abstract： Potentilla anserina L. and Elymus nutans Griseb. are dominant species in the subalpine meadows of China. Grazing is one of the most important factors that influence community structure and productivity of subalpine meadows. Understanding how grazing changes photosynthetic capability is essential for preservation and restoration of grasslands. However, information about the effects of grazing on photosynthetic capability remains inadequate. Experiments were conducted in fencing and grazing areas in the Qilian Mountains, Northwest China. The leaf gas exchange and photosynthetic curves of P. anserina and E. nutans were measured at different growth stages. Results showed that grazing decreased the values of leaf gas exchange parameters, such as net photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO2 concentration of P. anserina and E. nutans. In addition, grazing decreased the values of net photosynthetic rate-photosynthetically active radiation (PN-PAR) curve parameters, such as light-saturated net photosynthetic rate, apparent quantum efficiency, light compensation point, light saturation point, and dark respiration rate. Our results demonstrated that grazing was the primary limiting factor for photosynthesis of dominant grassland species in the study area.
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