紫茎泽兰提取物对3种杂草的化感胁迫作用

为探讨紫茎泽兰(Eupatorium adenophorum)提取物对植物种子萌发和早期幼苗生长的影响及其生理机理,以稗草(Echinochloa crusgalli)、灰绿藜(Chenopodium glaucum)和反枝苋(Amaranthus retroflexus)3种常见的田间杂草为材料,采用根悬空培养等方法,研究了不同浓度紫茎泽兰提取物对3种杂草种子萌发和幼苗生长、根尖组织结构、根系边缘细胞(root border cell,RBC)生理特性和根冠果胶甲基酯酶(pectin methyl esterase,PME)活性的影响。结果发现:紫茎泽兰提取物对3种植物种子萌发均具有明显的抑制作用;1000 mg/L紫茎泽兰提取物处理后,3种杂草幼苗的根尖均有不同程度的伤害,如根尖肿胀、抽缩或变形;根尖表层细胞脱落、内层细胞排列混乱。紫茎泽兰提取物处理能显著抑制3种杂草幼苗根尖RBC的数量(分别比对照降低了44.5%、48.3%和64.0%);诱导RBC凋亡(凋亡率分别达到81.7%、91.3%和97.1%)并显著增加RBC的黏胶层厚度(分别比对照增加了99.0%、65.5%和61.1%)及诱导PME活性升高。这些结果表明:紫茎泽兰提取物抑制了3种杂草根边缘细胞的产生,并诱导了根尖边缘细胞凋亡,因而破坏了根边缘细胞对根尖的保护系统,最终抑制了根系的生长发育。研究为将紫茎泽兰提取物用于植物源除草剂的开发提供了理论依据。

Physiological mechanisms of the allelochemical stress to three weed species caused by Eupatorium adenophorum extracts

To explore the inhibitory effects of Eupatorium adenophorum extracts on weed seed germination and early seedling growth, three common weed species, Echinochloa crusgalli, Chenopodium glaucum, and Amaranthus retroflexus, were chosen as materials to investigate seed germination and seedling growth, morphological characteristics of root tip cells and root border cells(RBCs), and pectin methyl esterase(PME) activities in the root cap using suspension cultures. The results indicated that Eupatorium adenophorum extracts significantly inhibited the seed germination, and damaged the root tips, including swelling, shrinking, and deformation of root tips, loss of epidermal root tip cells, and disordered distribution of internal root tip cells. Moreover, Eupatorium adenophorum extracts obviously inhibited RBC number; the RBC number of the three weed species decreased by 44.5%(E. crusgalli), 48.3%(C. glaucum), and 64.0%(A. retroflexus), respectively, compared with the untreated control). Eupatorium adenophorum extracts also induced RBC apoptosis; the RBC apoptosis rate of the three weed species decreased by 81.7%(E. crusgalli), 91.3%(C. glaucum), and 97.1%(A. retroflexus), respectively, compared with the untreated control. In addition, Eupatorium adenophorum extracts increased the thickness of RBC adhesive layers, and improved PME activity. Taken together, these findings indicate that Eupatorium adenophorum extracts inhibited RBC development and induced RBC apoptosis, thereby weakening the protective effects of RBC on root tips, and eventually inhibiting the growth and development of the whole root system. Our findings shed light on the development of bioherbicides derived from Eupatorium adenophorum extracts.