外来入侵杂草银胶菊种子萌发特性及无性繁殖能力研究

Seed germination characteristics and clone reproductive capacity of Parthenium hysterophorus L.

银胶菊Parthenium hysterophorus L.是一种危害性很强的外来入侵杂草,在我国南方多省均有分布,在山东省莒南县也大面积分布,目前已对发生地生态环境造成巨大影响。文章于2011年采用人工气候箱培养皿法和温室土壤盆栽相结合的方法,研究银胶菊的种子在不同pH、盐浓度、湿度、营养条件、不同埋藏深度等条件下种子萌发特性及其无性繁殖能力,以期为明确其入侵机制和适生环境提供依据。结果表明,银胶菊种子适宜的萌发环境为酸性,pH=6.0时发芽率最好,到pH=8.0时,种子不能萌发;盐对银胶菊种子的萌发影响很大,随着盐浓度的提高,发芽率下降明显,当盐浓度达到0.12 mol·Lˉ1时,种子不再萌发;但不同的营养条件和不同P水平对种子的萌发无显著影响;干旱或水涝均能降低种子发芽率;种子埋藏土层越深,其发芽率越低,土层深度达3.0 cm以上,银胶菊种子几乎无发芽率。银胶菊有较强的无性繁殖能力,根部、基部茎和上部茎等不同部位埋入土壤后均能发芽,基部茎的发芽率最高(为66.7%-88.9%),根部和上部茎发芽率较低(为22.2%-44.4%)。另外,从发芽后的生长来看,茎部(包括基部茎和上部茎)发芽后均能正常生长,但根部发出新芽后逐渐黄化死亡。由此可以看出,银胶菊种子适应力、耐贫瘠能力强,一般的农田、荒地环境均能萌发生长,但盐碱地的环境下不能萌发生长;散落在土壤表层的银胶菊种子萌发率最高,因此,没有人类扰动的荒地、沟渠更适宜其萌发和生长;由于其很强的无性繁殖能力,人工砍伐的防除措施不能将其彻底防除。这些都是银胶菊入侵后,能够在短时间内暴发成灾,且不易彻底防除的原因。

Parthenium hysterophorus, commonly distributed in southem China but also occurred in Junan of Shandong province, is an alien weed with strong invasiveness and is spreading rapidly in southern China at present. The successful invasion of the weed might be related to its reproductive traits and strong adaptability of seed germination to environmental conditions. Petri dish and pot experiments were conducted to determine the seed germination characteristics in different conditions and clone reproduction ability of P. hysterophorus in plant growth chamber and glasshouse. The results showed that its suitable seed germination condition was acidic, and the appropriate pH was 6.0. No germination was observed at pH 8.0. The seed germination rate decreased with the increase in salt concentration and there was no germination at the salt concentration up to 0.12 mol.L^-1. Any additional nutrition and sodium dihydrogen phosphate concentration had no effect on seed germination. Seed on the soil surface achieved the highest germination rate, while the germination decreased with the increase in soil depth and no seedling emerged when the seeds were planted at 3.0 cm deep. The P. hysterophorus had high clone reproductive ability, and all the parts （including the root, the lower and upper stem） could grow into a new plant when buried, but the new growth rate is different. The new growth rate of the lower stem was highest with 66.7%-88.9% more than the root and upper stem. The new growth plants derived from stem could grow very well, while plants from root went to yellowing and died finally. Conclusion, the seed adaptability and barren resistance ofP. hysterophorus were very strong; it could germinate in most farmland and wasteland except saline and alkaline land. The seed germination rate is highest when scattered in soil surface, therefore, undisturbed wasteland and channel are more suitable for its germination and growth. The plants could not be completely controlled by only cutting down due to high reproductivity. All of these factors contribute to the wide occurrence ofP. hysterophorus in its invasion area and difficulty to get rid of it.