长期不同放牧强度下荒漠草原优势种无芒隐子草叶片解剖结构变化

Leaf anatomical changes of Cleistogenes songorica under long-term grazing with different intensities in a desert steppe

为探讨长期(19年)放牧干扰下荒漠草原植物的响应与适生策略,该研究以荒漠草原优势种无芒隐子草(Cleistogenes songorica)作为研究对象,测量不同放牧强度(控制、轻度、中度、重度)下叶片解剖结构指标,探讨无芒隐子草叶片解剖结构对长期放牧干扰作出的响应。结果表明:(1)保护组织方面,角质层厚度、角质层厚度占叶片厚度比均随着放牧强度的增加呈先减小后增加趋势。泡状细胞厚度随着放牧强度的增加先减小后增加,与对照、中度、重度放牧区相比,轻度放牧区泡状细胞厚度显著减小。(2)维管组织方面,维管束面积、导管面积、韧皮部面积3个指标均随放牧强度的增加呈先增加后减小趋势。木质部面积随着放牧强度增加先减小后增加。维管组织占比方面,木质部占维管束面积比随着放牧强度增加而增加,而主导管占主脉维管束面积比随着放牧强度增加而减小。韧皮部面积随着放牧强度的增加呈先增加后减小趋势,与对照区相比,3种放牧区韧皮部面积显著减小。(3)花环结构面积随着放牧强度的增加呈增加趋势,与对照区相比,3种放牧区花环结构面积显著增加。上述结果表明无芒隐子草叶片各项解剖结构均对长期放牧干扰作出适当响应以确保自身在受放牧等人为干扰的荒漠草原脆弱生态系统中持续生存。

Aims Physiological responses at the leaf level are determined by anatomical structure.Quantitative analysis of the responses of leaf anatomy to grazing in desert steppe is of great theoretical implications to reveal the ecological adaptation mechanism of plants to harsh environment.Methods We measured 13 anatomical indices for leaves of Cleistogenes songorica,a dominant species in desert steppe under different grazing intensities,including control(CK),lightly grazing(LG),moderately grazing(MG),and heavy grazing(HG).Many indices measured were related to photosynthesis,including protective tissue,vascular tissue,and Kranz structure area.Comparative analysis for all the indices was made among different grazing intensities.Important findings The results showed that:(1)cuticle thickness,as well as the ratio of cuticle thickness to leaf thickness first decreased and then increased with increasing grazing intensity.The thickness of motor cells decreases first and then increases with the increase of grazing intensity,compared with control and moderately heavy grazing areas,the thickness of motor cells in lightly grazing areas significantly decreased.(2)In terms of vascular tissue,the area of vascular bundle,vessel area,and phloem area were firstly increased and then decreased with the increases of grazing intensity.xylem area first decreased and then increased with the increases of grazing intensity.In terms of vascular tissue proportion,the ratio of xylem to vascular bundle area increased with the increases of grazing intensity,while the ratio between dominant vessel to vascular bundle area decreased with the increases of grazing intensity.The phloem area increased first and then decreased with the increases of grazing intensity.Compared with the control,phloem area significantly decreased in the three grazing treatments.(3)The area of Kranz structure increased with the increases of grazing intensity.Compared with that in the control,the area of Kranz structure was significantly increased in the three grazing treatments.