假臭草幼苗生长对水氮耦合效应的响应

Growth response of Praxelis clematidea seedlings to water and nitrogen coupling

为揭示入侵植物假臭草(Praxelis clematidea)幼苗生长对不同水、氮养分耦合模式的响应机制,探讨其与入侵性的关系,以假臭草为供试材料,设计3个供水量水平、4个供氮量水平共12个处理,比较假臭草的形态、生物量分配和叶绿素含量等生长指标对不同水氮耦合效应的可塑性反应。结果显示,假臭草幼苗生长受水氮耦合影响显著(P<0.05),在适宜水分和养分条件,如中水中氮处理(沙土饱和含水量60%~70%,供水量60 mL·kg^(-1),供氮量0.30g·kg^(-1))处理下,假臭草幼苗株高、茎粗、叶面积、总根长度和根表面积等根、茎、叶形态指标表现较好,生物量积累较多,植株生长较好。低水处理(沙土饱和含水量30%~40%,供水量30 mL·kg^(-1))和高水处理(沙土饱和含水量90%~100%,供水量90mL·kg^(-1))的各个氮含量处理的假臭草植株的各项根、茎、叶形态及生物量指标均差于中水处理。假臭草叶绿素对氮素较为敏感,随着氮素增加其积累量也相应增多。研究结果表明,假臭草入侵植物喜好一定的水、氮环境,过多或不足的水分或养分则不利于假臭草的生长发育,但仍有一定的分布,这与其入侵性密切相关。

The response mechanism of invasive species of Praxelis clematideaseedling growth to different water and nitrogen（WN）coupling models were investigated by determining the relationship between WN and bio-invasion.This experiment incorporated three irrigation levels and four levels of nitrogen,for a total of 12 processes to study the coupling effect of different WN processing on P.clematideaparameters including morphological,biomass and chlorophyll content.P.clematideaseedlings were significantly affected by the WN coupling（P〈0.05）.The seedlings grew better with higher root,stem and leaf morphological indexes,such as plant height,stem diameter,leaf area,total root length and root surface area,and more biomass accumulation under suitable moisture and nutrient conditions,such as treatment with the intermediate level of WN（saturated sand water content 60%-70%,water supply 60 mL·kg^-1,nitrogen supply 0.30 g·kg^-1）.P.clematideaseedlings exposed to each nitrogen treatment coupled with low level of water（saturated sand water content 30%-40%,water supply 30 mL·kg^-1）or high level of water（saturated sand water content 90%-100%,water supply 90 mL·kg^-1）displayed lower root,stem and leaf morphological indexes and less biomass accumulation than the corresponding nitrogen treatment coupled with the intermediate level of water.Leaf chlorophyll content of P.clematidea was more sensitive to nitrogen,which increased with the increase of nitrogen.We can draw the conclusion that P.clematidea easily invades an environment with a certain content of WN,but has more restricted distribution in an environment with excessive or insufficient water or nutrients,which is closely related to its invasion.