胜红蓟化感作用研究Ⅵ.气象条件对胜红蓟化感作用的影响

在田间条件下 ,胜红蓟化感作用与光、温、水等气象要素显著相关 ,有利的光、温、水生长条件使得其化感作用减弱 ,反之增强 .春夏季温度和降水有利胜红蓟的生长 ,其化感作用减弱 ,而秋冬季温度和降水不利胜红蓟生长 ,其化感作用增强 .实验表明 ,30 0 μg·ml-1高浓度胜红蓟挥发油使受试植物不能生长 ,而6 0 μg·ml-1低浓度影响较小 ,在高温、低温和遮光等不利植物生长的条件下 ,低浓度的胜红蓟化感物质对受试植物的抑制效应显著增强 ,显示在不利的生长条件下 ,受试植物对胜红蓟化感物质的抵御能力减弱 .研究表明 ,在不利于胜红蓟及受试植物生长的气象条件下 ,胜红蓟化感作用增强 ,受试植物抵御化感物质的能力降低 ,使得胜红蓟群落中其它植物难以正常生长 ,相应地提高了胜红蓟在自然群落中的竞争优势 .化感作用和光、温、水、气象条件的共同作用是胜红蓟在自然群落中成为优势种群的重要原因之一 .

Allelopathy of Ageratum conyzoides Ⅵ. Effects of meteorological conditions on allelopathy of Ageratum cony

In the field, allelopathic potential of A. conyzoides correlated significantly with sunshine time, temperature and rainfall. Allelopathic potential of A. conyzoides grew in favorable combinate condition of temperature, rainfall and sunshine time, allelopathic potential of A. conyzoides reduced, and vice versa. Allelopathic potential of A. conyzoides decreased because of favorable growing seasons in spring and summer. On the contrary, autumn and winter were unfavorable growing seasons, and the allelopathic potential of A. conyzoides increased. Under laboratory experiments, the volatile oil of A. conyzoides made the tested plants not survive at high concentrations of 300 micrograms.ml-1, but volatile oil of A. conyzoides inhibited the tested plants slightly at low concentrations of 60 micrograms.ml-1. However, under high or low temperatures and shading conditions, inhibitory effects of allelochemicals of A. conyzoides on tested plants intensified significantly at low concentration. It revealed that under unfavorable growing conditions, tested plants resistant ability to the allelochemicals of A. conyzoides decreased. When A. conyzoides and tested plants both grew under unfavorable meteorological conditions, allelopathic potential of A. conyzoides increased, and the tested plants resistant ability to allelochemical decreased. Thus, other plants growing among A. conyzoides in natural community were difficult to grow, and it was relatively improved competitive ability of A. conyzoides in natural communities. Joint effect of allelopathic potential and some meteorological factors such as sunshine time, temperatures, and rainfall was one of the important factors that A. conyzoides was dominated in natural communities.