Yin Jingjing, Li Xiliang, Guo Huiqin, Zhang Jize, Kong Lingqi, Ren Weibo
School of Ecology and Environment, Inner Mongolia University, Hohhot, China.
Institute of Grassland Research, Chinese Academy of Agriculture Sciences, Hohhot, China.
PeerJ. 2020 Jun 17;8:e9266. doi: 10.7717/peerj.9266. eCollection 2020.
Grazing, one of the primary utilization modes of grassland, is the main cause of grassland degradation. Historical overgrazing results in dwarf phenotype and decreased photosynthesis of perennial plants. However, it remains unknown what the mechanism underlying of this legacy effect is, and the role of stomata in the resulting decreased photosynthesis also remains unclear. To address these questions, differences in stomatal density, length and width on both adaxial and abaxial epidermis were compared between overgrazing and ungrazed offspring by using rhizome buds cultivated in a greenhouse, and the correlation between photosynthetic capacity and stomatal behavior was also investigated. Our results showed that historical grazing significantly impacted phenotype, photosynthesis and stomatal traits of . The offspring plants taken from overgrazed parents were dwarfed compared to those taken from ungrazed parents, and the photosynthesis and stomatal conductance of plants with a grazing history decreased by 28.6% and 21.3%, respectively. In addition, stomatal density and length on adaxial and abaxial leaf surfaces were significantly increased; however, stomatal width on abaxial leaf surfaces of overgrazed was significantly decreased compared with ungrazed individuals. Moreover, the expression patterns of eight genes related to stomatal regulation were tested: seven were down-regulated (2-18 times) and one was up-regulated (three times). Genes, involved in ABC transporter and receptor-like serine/threonine protein kinase were down-regulated. These results suggest that legacy effects of historical grazing affect the stomatal conductance by decreasing the stomatal width in progeny plants, which thus results in lower photosynthesis. Furthermore, changes of stomatal traits and function were regulated by the inhibition of ABC transporter and serine/threonine protein kinase. These findings are helpful for future exploration of the possible mechanisms underlying the response of grassland plants to long-term overgrazing.
放牧是草地的主要利用方式之一，也是草地退化的主要原因。历史上的过度放牧导致多年生植物出现矮化表型并降低光合作用。然而，这种遗留效应的潜在机制是什么以及气孔在由此导致的光合作用下降中所起的作用仍不清楚。为了解决这些问题，通过在温室中培养根茎芽，比较了过度放牧和未放牧后代在叶片上表皮和下表皮的气孔密度、长度和宽度差异，并研究了光合能力与气孔行为之间的相关性。我们的结果表明，历史放牧对后代的表型、光合作用和气孔特征有显著影响。与从未放牧亲本获取的后代相比，从过度放牧亲本获取的后代植株出现矮化，有放牧历史的植株的光合作用和气孔导度分别下降了28.6%和21.3%。此外，叶片上表皮和下表皮的气孔密度和长度显著增加；然而，过度放牧植株叶片下表皮的气孔宽度与未放牧个体相比显著减小。此外，还测试了八个与气孔调节相关基因的表达模式：七个基因下调（2至18倍），一个基因上调（三倍）。参与ABC转运蛋白和类受体丝氨酸/苏氨酸蛋白激酶的基因下调。这些结果表明，历史放牧的遗留效应通过减小后代植株的气孔宽度来影响气孔导度，从而导致光合作用降低。此外，气孔特征和功能的变化受ABC转运蛋白和丝氨酸/苏氨酸蛋白激酶抑制的调节。这些发现有助于未来探索草地植物对长期过度放牧响应的潜在机制。
