光和不同打破种子休眠方法对紫茎泽兰种子萌发及幼苗状态的影响

紫茎泽兰是著名的外来入侵植物,作为入侵的第一步,发芽及其幼苗生长应该与其强入侵能力有关.基于此,通过不同光照强度处理和不同打破休眠方法的双因素实验,旨在探讨紫茎泽兰种子是否具有需光萌发特性以及低温、水杨酸、聚乙二醇,硝酸钾等常规打破休眠方法和光照如何共同影响其萌发、幼苗生长等问题.结果表明:在全光照条件下,不同处理的紫茎泽兰种子的萌发率均大于63％,铝箔纸覆盖的遮光条件(0.23％光照)萌发率均大于60％,而在完全黑暗条件下,其萌发率较低(均小于30％),这表明紫茎泽兰种子具有需光萌发的特性.有别于以往对其它植物种子的报道,低温处理、水杨酸处理、聚乙二醇处理和硝酸钾处理不能代替光照打破种子休眠,显示紫茎泽兰种子可能处于一种强迫休眠状态(种子静态).全光照与水杨酸处理、PEG处理对幼苗生长具有交互影响:黑暗下水杨酸处理浓度与幼苗生物量成正相关(P＜0.05),但全光照和加铝箔下不相关(P＞0.05)；全光照下PEG处理浓度与根长显著正相关(P＜0.05),而加铝箔和黑暗下不相关(P＞0.05).紫茎泽兰种子需光萌发特征及其幼苗生长特点是人为破坏表土壤、深层土壤种子库地表化导致快速入侵的基础.结果也为通过引入适宜树种造林来控制光照因子对紫茎泽兰进行生态控制提供了理论依据.

Impacts on seed germination features of Eupatorium adenophorum from variable light stimulation and traditional dormancy-broken methods

Eupatorium adenophorum (Crofton weed) is a notorious invasive species worldwide, as the first step colonizing in a new habitat, seed germination and growth of seedlings should be related to its strong invasiveness. Combining experiments on different light intensity and different traditional dormancy-breaking treatments were carried out in this paper. We are aiming to answer two questions, i.e., whether or not germination of the weed is light-required, and how traditional dormancy-breaking methods and light intensity interactively affect germination and seedling growth. Crofton weed had the feature of photoblastic seed germination. Germination under different treatments was higher than 63% under full light, and higher 60% under aluminum foil-covered treatments (0.23% light transmittance), while germination was lower than 30% under dark treatments. Different from previous reports on other species, the low temperature, SA, PEG and KNO₃ treatments cannot take the place of light in breaking seed germination, indicating that Crofton weed was in the form of forced dormancy (seed quiescence). Light with SA and PEG treatments had interactions on seedling growth: SA treatments were linearly related with seedling biomass at dark (P<0.05), while no correlations were found under full light and aluminum foil treatments (P>0.05). Similarly, significantly linear correlation between PEG concentration and root length under full-light treatments was found (P<0.05), but no correlations were found in the aluminum foil treatments and dark treatments (P>0.05). This photoblastic seed germination and seedling growth characteristics play a key role in forming soil seed bank, and also the basis of fast-invasion of this species in disturbed soil, where seeds in deep soil come to surface after disturbance. Our finding also supports the ecological control of this invasive species by introducing suitable trees to influence light environment around Crofton weed.