Abstract
Poa alpigena is a dominant grass species in alpine meadows, which is sensitive to environmental conditions. In this study, we analyzed the characteristics of the anatomical structure of the stems and leaves of Poa alpigena in overgrazed and enclosed conditions in order to determine the dwarfing morphological mechanism associated with overgrazing. The results show that leaf thickness, leaf epidermal thickness, epidermal cell area, and phloem thickness increased with increased grazing intensity (p < 0.05). In contrast, xylem thickness, mesophyll cell area, and guide wall thickness decreased with an increase in grazing intensity (p < 0.05). Mesophyll cell density was relatively unaffected by grazing intensity. Additionally, the plasticity indices of leaf area, upper epidermal cutin layer thickness, and leaf xylem thickness were higher than 0.5. The plasticity indices of stem tube diameter, epidermal cell size, and epidermal cuticle thickness were greater than 0.4. The results of our study indicate that the structural stem and leaf changes in Poa alpigena are induced by the water and mechanical stresses that occur under grazing conditions. Thus, plateau plants adapt to grazing stress by increasing the thickness of their leaves, cuticles, and phloem. The mesophyll cell area, as well as the stem epidermal cell area of Poa alpigena decreased in response to minor variations in grazing intensity, yet overgrazing did not change its density. However, overgrazing induced a shortening of the leaves and stems, indicating that overgrazing has a dwarfing effect on Poa alpigena.
Highlights
Dwarfing is a common adaptive response of plants to environmental stresses [1,2,3,4,5].Dwarf grassland plants exhibit several traits, including shortened stature under overgrazing conditions, narrow and short leaves, short internodes, stiff leaves, narrow thickets, and a shallow root distribution [6,7]
Leaves are one of the main organs involved in plants’ important functions, and they are very sensitive to environmental conditions [18]
We observed that the leaves were thicker in the samples collected from the open grazing site than in the samples collected from the enclosed grazing locations (p < 0.05)
Summary
Dwarfing is a common adaptive response of plants to environmental stresses [1,2,3,4,5]. Dwarf grassland plants exhibit several traits, including shortened stature under overgrazing conditions, narrow and short leaves, short internodes, stiff leaves, narrow thickets, and a shallow root distribution [6,7]. Changes to the main plant characteristics and the mechanism regulating the development of the dwarf phenotype of grassland plants have not been fully characterized. A thorough analysis of the mechanism responsible for the dwarfing of grassland plants is necessary. Alpine plants mainly grow in special climatic conditions such as the alpine and low-temperature conditions on the Qinghai-Tibet Plateau. It is of great ecological significance to study alpine plants under such special climatic conditions [8,9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
