Differences in the photosynthetic and physiological responses of Leymus chinensis to different levels of grazing intensity

Min Liu,Chenchen Zhu,Xiangyang Hou,Biao Wang,Zihe Zhang,Bo Yang,Yong Ding,Jirui Gong

doi:10.1186/s12870-019-2184-1

Min Liu, Chenchen Zhu + Show 6 more

Open Access

https://doi.org/10.1186/s12870-019-2184-1

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Abstract

BackgroundGrazing is an important land use in northern China. In general, different grazing intensities had a different impact on the morphological and physiological traits of plants, and especially their photosynthetic capacity. We investigated the responses of Leymus chinensis to light, medium, and heavy grazing intensities in comparison with a grazing exclusion control.ResultsWith light grazing, L. chinensis showed decreased photosynthetic capacity. The low chlorophyll and carotenoid contents constrained light energy transformation and dissipation, and Rubisco activity was also low, restricting the carboxylation efficiency. In addition, the damaged photosynthetic apparatus accumulated reactive oxygen species (ROS). With medium grazing, more energy was used for thermal dissipation, with high carotene content and high non-photochemical quenching, whereas photosynthetic electron transport was lowest. Significantly decreased photosynthesis decreased leaf C contents. Plants decreased the risk caused by ROS through increased energy dissipation. With high grazing intensity, plants changed their strategy to improve survival through photosynthetic compensation. More energy was allocated to photosynthetic electron transport. Though heavy grazing damaged the chloroplast ultrastructure, adjustment of internal mechanisms increased compensatory photosynthesis, and an increased tiller number facilitated regrowth after grazing.ConclusionsOverall, the plants adopted different strategies by adjusting their metabolism and growth in response to their changing environment.

Highlights

Grazing is an important land use in northern China
The tiller number increased with increasing grazing intensity, and the difference was significant in the heavy grazing (HG) plots, whereas the mean internode length decreased gradually, and the difference was significant for all grazing intensities
Plant biomass and height decreased with increasing grazing intensity, and the differences became significant in the HG and medium grazing (MG) plots, respectively

Summary

Introduction

Grazing is an important land use in northern China. Different grazing intensities had a different impact on the morphological and physiological traits of plants, and especially their photosynthetic capacity. Grazing is the most common and important land use in Inner Mongolia that affects grassland productivity and vegetation dynamics [67, 83]. The over-grazing decreases vegetation cover and damages the soil, leading to Livestock grazing directly affects plant morphology. It reduces plant height, decreases the length of shoot internodes, and decreases leaf area [76, 88]. At the same time, grazed plants increase their tiller production to

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