短花针茅分蘖特征对载畜率变化的响应及其机制的研究

Over grazing induced grassland degeneration has become a global issue. Tillering plants play a critical role in grassland ecosystem response to grazing, and also have important effects on community structure and ecosystem function. However, its molecular mechanism is still unclear. Over grazing induced grassland degeneration has become a global issue. Tillering plants play a critical role in grassland ecosystem response to grazing, and also have important effects on community structure and ecosystem function. Thus far, grazing induced mechanisms of plant tiller’s change are still poorly understood. Therefore, we designed an experiment with different stocking rates in Siziwang Research Station, Inner Mongolia Academy of Agriculture and Animal Sciences, China, to determine the mechanisms and responses of tillering traits for Stipa breviflora to stocking rates. At the individual level, we focus on the response of S. breviflora to different stocking rates in branching characteristics and resources allocation patterns. At the physiology and molecular level, we concentrate on changes in content of three main plant hormones and key genes which related to plant tillers. Our experiment expects to reveal the response strategy and molecular mechanism of S. breviflora tiller. We further probe the effect of different plant hormones and key related genes of S. breviflora tillering structure. The findings of current project can provide theoretical guidance for grazing management and degraded grassland restoration. It could also providing basic information for forage breeding and selection, tame pasture establishment, and ecological restoration of degraded grassland by related species.

过度放牧导致草原退化已经成为一个全球性问题。分蘖植物在草地生态系统对放牧响应的过程中发挥着重要作用，对群落结构和生态系统功能有着重要影响。但是迄今，关于放牧引起植物分蘖变化的机制尚不明确。本项目以内蒙古荒漠草原为对象，依托内蒙古农牧科学院四子王旗放牧实验平台，研究生长季不同载畜率水平下建群种短花针茅的分蘖特征对载畜率的响应和机制，分析不同载畜率下调控短花针茅分蘖结构及资源分配格局变化和分蘖相关的三种植物激素以及关键基因与表达的变化。明确短花针茅分蘖特征对放牧响应的策略及其分子机制，探讨不同放牧压力下不同植物激素和相关基因与表达对短花针茅分蘖结构的影响，厘清放牧响应过程中各种激素之间相互协调作用，为草地放牧管理和退化草地恢复提供依据，为繁育和培植草原优良牧草和建植人工草地以及应用相关物种对退化草原进行生态修复提供理论指导。

荒漠草原是内蒙古草原的重要组成部分，放牧是该草原最主要、最直接和最经济的利用方式之一。本项目依托内蒙古农牧科学院四子王旗长期放牧试验平台，采用对照、轻度、中度和重度放牧4个载畜率的随机区组实验设计，采用野外生态学调查和室内分析相结合的方法，从形态、生理和分子水平研究荒漠草原建群种短花针茅分蘖特征对不同放牧压力的响应，以植物分蘖调控激素及相关功能基因及其表达为切入点，探讨短花针茅分蘖对不同放牧强度的响应模式及机制。结果表明：.（1）短花针茅种群高度、盖度、地上生物量、植株营养枝高度与生殖枝高度均随载畜率增大而呈现出降低的趋势，但短花针茅密度呈现出随载畜率增加而增加的趋势。与对照相比，轻度放牧降低了短花针茅种群高度、营养枝与生殖枝高度；中度放牧降低了短花针茅种群高度、盖度、单株分蘖数、营养枝枝条数、株丛径、营养枝与生殖枝高度、营养枝单枝重和生殖枝单枝重，增加了短花针茅生殖枝、株丛径、叶面积、叶片干重；而重度放牧降低了短花针茅种群高度、盖度、地上生物量、叶形指数、营养枝与生殖枝高度，但增加了种群密度、叶片卷曲度。此外，短花针茅茎基贮藏还原糖随载畜率增大而降低，茎基粗蛋白含量随载畜率增大而增加；茎基中贮藏养分高于根系贮藏养分。.（2）与对照相比，轻度和中度放牧增加了短花针茅净光合速率、蒸腾速率、气孔导度值、胞间CO2浓度，降低了气孔限制值，但重度放牧则增加气孔限制值。此外，放牧增加了短花针茅各内源激素含量，且内源激素含量随载畜率增大而增加。与对照相比，中度和重度放牧叶片热值降低，且重度放牧下MOC1基因表达量显著降低。4~9月短花针茅所释放的热值呈现出逐渐增加的趋势。.（3）短花针茅单株分蘖数与净光合速率、CTK/IAA呈正相关关系，与气孔导度、内源IAA和内源CTK含量均呈负相关关系；短花针茅分蘖数量随MOC1基因表达量增加而增多。