菊科几种入侵和非入侵植物种子需光发芽特性差异

The differences in light-demanding germination features of seeds between invasive and noninvasive alien plants within Compositae

对入侵菊科植物(假苍耳、薇甘菊、紫茎泽兰、飞机草)以及非入侵菊科植物(扫帚梅、天人菊、金鸡菊、麦秆菊、翠菊、黑心菊)对比研究发现,入侵组种子往往是需光发芽,即有光条件下平均高出无光条件发芽率40%(P<0.01),而非入侵组的需光发芽特性不明显,即有光和无光条件下种子发芽率差异不显著(P>0.05)。以入侵植物假苍耳为例对其种子需光发芽的特性研究发现:红光有利于提高种子的萌发率(萌发率为62%),而蓝光起到相反的作用(萌发率37%);当以全光的25%照射种子时,最能够促进种子的萌发(萌发率59%),更高的光强抑制种子萌发(100%光强时,发芽率为21%)。适宜浓度水杨酸SA处理(0.01mmol/L)可以起到与光照类似的效果而促进种子萌发(提高30%发芽率),而PEG和低温处理对其不存在显著影响,说明这种需光发芽的机理可能与SA处理影响种子萌发存在一定的联系。研究证实了入侵和非入侵菊科植物之间确实存在需光发芽的差异,其生理生化差异及是否有利于入侵植物的快速入侵需深入研究。

Many introducing alien plants from the family of Compositae are used as gardening or pasture materials.Some of them had became invasive plants causing serious influence to ecological environment and vegetation health,while others became useful local-like species without any bad biological influence.The reason why some Compositae plants had much higher invasive ability than others of close taxonomic relation was a hot issue in the study of biological invasion.Seed germination is the first step for colonizing a new environment for any introducing species and high performance of seed germination may be also important for the success of invasive Compositae plants comparing with non-invasive species.High light habitats are typical colonizing sites for the invasive plants,favoring the fast invasion of these species.The aim of this study was to check the possible light influences on seed germination of invasive and non-invasive Compositae introduced plants and analogical illustration of possible underlying mechanism for such observed differences by one typical specie.For approaching this aim,the differences in light-demanding germination features of seeds between several alien invasive（Iva xanthifolia,Mikania micrantha,Eupatorium adenophorum,Eupatorium odoratum）and noninvasive plants（Cosmos biginnatus,Gaillardia pulchella,Coreopsis basalis,Helichrysum bracteatum,Callistephus chinensis,Rudbeckia hybrida）within Compositae were studied in this paper and seed germination experiments of these species were carried out under light or in dark.The results showed that the seeds of invasive plants germinated difficultly without light,and the germination percentage under light was averagely 40%（P0.01）higher than that in dark,on the contrary,no significant differences in the seed germination percentage in dark and under light were found in non-invasive plants（P0.05）.Taking the typical invasive plant,Iva xanthifolia as an example,experiments were designed to find the influence of light quality（red light,green light,orange light,yellow light,blue light,purple light and white light control）and light intensity（increasing pieces of gauzes to set 100%、75%、50%、25%、0% of outside light about 78800lx）on the seed germination parameters,and different treatments of low temperature,PEG（polyethylene glycol,PEG-6000）as well as SA（salicylic acid）soaking were used to find possible mechanism underlying the light-demanding germination of invasive Compositae plants.The data showed that red light was more benefitable for germination（62% in germination percentage）,but blue light strongly restrained the germination（37%）,and such difference between two lights were statistical significant（P0.05）.Different light intensity also directly affected the germination performance,under the condition of 25% of full light,the germination percentage increased to 59%,and the length of the seedling was the largest comparing with those in other light conditions.On the contrary,higher light intensity would restrain the germination of seeds（full light,21%;75% of full light,37%;50% of full light,30%）,and seedling length under full light was the shortest.Data from the treatments of different SA concentration,different PEG concentration and different low temperature showed an alternative method stimulating seed germination instead of light treatment;i.e.,SA treatment（0.01 mmol/L）could play the similar role as light to promote germination（30% higher germination percentage than that in dark）.However,PEG and low temperature treatments had no effect on seed germination and could not take the place of light in stimulating the seed germination.These findings imply that there might be some correlation between the mechanism of light-demanding germination and the effect of SA treatment.In all,a marked difference in light-demanding seed germination between invasive plants and noninvasive plants were supported by our data,but more researches are needed to testify whether or not such light-demanding differences could benefit the rapid invasion of these species comparing the non-invasive species within the family of ompositae.