Grazing integrates multiple processes including bruising,defoliation,and the deposition of saliva, which may affect the regrowth of forage grasses.In this study,alfalfa plants defoliated at different intensities were treated with exogenous inorganic salts and with thiamine (treatment groups ),and deionized water and sheep saliva (control groups).The aim of this study was to determine whether a herbivorous animal's (sheep) saliva,especially its components (inorganic salts and thiamine)positively affect alfalfa regrowth.We also ana-lyzed how the defoliation and sheep saliva interaction induced compensatory regrowth,and evaluated the mor-phological and physiological differentiation of defoliated alfalfa after treatment with inorganic salts and thia-mine.Our results showed that,compared with alfalfa in the defoliation-only treatment,that in the saliva+de-foliation treatment showed significantly better regrowth due to an effective ingredient in saliva (thiamine ). Compared with defoliated alfalfa treated with exogenous inorganic salts,that treated with thiamine grew bet-ter,as indicated by the significantly greater aboveground biomass,4.3-7.9-times greater stem/leaf ratio,and 1.56-times higher total tiller number at the 80% defoliation level.The physiological characteristics of defolia-ted alfalfa did not vary widely among treatments.In all treatments,the chlorophyll content of defoliated alfalfa was close to 49 .3 mg/g.At the 20% defoliation level,alfalfa plants treated with sheep saliva and with water showed significantly increased soluble sugars contents in the roots,compared with those in the inorganic salts and thiamine treatments.Treatment with inorganic salts led to a progressive increase in peroxidase activity as the defoliation intensity increased,while treatment with thiamine did not affect peroxidase activity.These re-sults increase our understanding of the functional mechanism of the alfalfa response to herbivore grazing.These results provide a reference for improving the status of artificial grassland and for improving the agricultural effi-ciency of cultivated forage grasses.The results of this study provide theoretical support for the development of ecologically sound grazing regimes.%放牧活动是包含牧食折损、枝叶去除、唾液沉积等多个过程的融合,而觅食者分泌的唾液对牧草具有潜在影响.本试验选择外源无机盐与硫胺素处理作为试验组,以去离子水与羊唾液处理为参考对照,并将4种溶液涂抹作用于不同枝叶去除水平的紫花苜蓿截面处,探究植食性动物(羊)唾液中的无机盐与硫胺素是否对紫花苜蓿的再生性产生影响,分析枝叶去除与羊唾液是如何诱导植物的补偿再生,同时探寻紫花苜蓿从形态与生理上对无机盐和硫胺素的差异响应.试验结果表明,1)与单一的枝叶去除处理相比,在羊唾液的催化作用下,枝叶去除后的紫花苜蓿再生能力明显提高,其中硫胺素是羊唾液中的有效成分;2)相对于外源无机盐,硫胺素对枝叶去除紫花苜蓿牧草有更为显著的正效应,紫花苜蓿地上累积生物量显著增加,茎叶比差异也达到了4.3~7.9倍;在80%枝叶去除水平下,总分蘖数大约是无机盐组的1.56倍;3)不同处理下紫花苜蓿的生理指标差异性不均一.在各项处理中,紫花苜蓿的叶绿素含量值都接近49.3 mg/g;在20%枝叶去除水平下,清水与羊唾液处理均促进根系可溶性糖含量大幅度增加;对于无机盐组,POD活性随着枝叶去除水平呈递增变化,而硫胺素处理没有引起POD活性的改变.通过本研究,期望进一步了解紫花苜蓿响应放牧的内在机制,为改善人工草地现状和提高牧草的农业效益提供参考,同时也为放牧生态学的发展提供理论支持.
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