麦冬草对草甘膦耐药性的形态学机制

麦冬、土麦冬和阔叶土麦冬都对草甘膦具有较高的天然耐药性,其耐药性的主要机制是由于EPSPS基因结构差异、基因多拷贝以及高表达量,但是,靶标机制并不能完全解释阔叶土麦冬的耐药性最高,麦冬的耐药性最低,土麦冬居于中间。为了进一步揭示其耐药性的非靶标机制,采用光镜和扫描电镜观察了麦冬、土麦冬和阔叶土麦冬的叶表皮显微结构,发现麦冬、土麦冬和阔叶土麦冬的气孔主要分布于叶片下表皮,气孔密度分别为37.6、36.15和23.92个/mm~2。但是,土麦冬和阔叶土麦冬的气孔在叶片上表皮也有分布,并且阔叶土麦冬上表皮的气孔明显多于土麦冬。麦冬草气孔带和非气孔带细胞在细胞长度、面积和长宽比等方面均存在差异。麦冬气孔周围的表皮细胞平周壁具明显瘤状突起,导致气孔下陷;土麦冬气孔周围的表皮细胞平周壁呈波浪状突起,使气孔略下陷;阔叶土麦冬气孔周围的表皮细胞平周壁基本无突起,气孔下陷不显。这些结构特征差异可能与麦冬草对草甘膦的耐药性差异有一定的相关性。

Morphological Mechanism of Natural Glyphosate-Tolerance of the Lilyturfs

Three lilyturfs,Ophiopogon japonicas (OJ),Liriope spicata (LS)and Liriope platyphylla (LP)were reported to have evolved high natural tolerance to glyphosate.The main mechanism is attributed to a combination of unique EPSPS structure and increased EPSPS gene copy number and expression.This target-site mechanism,however,appears insuffi-cient to explain the differences in glyphosate-tolerance among those three lilyturfs with the highest level observed in LP and the lowest in OJ (LS has intermediate tolerance).To further investigate the non-target site mechanisms conferring glyphosate tolerance in the three lilyturfs,microscopic and submicroscopic structure of leaf epidermis were observed using LM and SEM.The stomata mainly distribute in the lower leaf epidermis of the three species with stomatal densities of 37.6,36.2 and 23.9 mm-2 in OJ,LS and LP,respectively.Furthermore,there were more stomata in the upper epidermis of LP than that of LS.There are also differences in cell length,area,and length-width ratio of stomatal and non-stoma-tal bands in the three lilyturfs.The periclinal wall of epidermis cells around stomata forming obviously strumous protuber-ances resulted in sunken stomata on leaves of OJ.The periclinal wall of LS had wavy protuberances and the stomata were only partially sunken.On the contrary,the periclinal wall of LP almost had no protuberances and the stomata were not sunken.These features may contribute to the different tolerance to glyphosate in three lilyturf species.