外来杂草小花山桃草种子休眠萌发特性

Seed dormancy and germination characteristics of Gaura parviflora,an exotic weed species in China

种子萌发和出苗是植物一生中对环境胁迫最为敏感的阶段,外来植物在这一时期对环境条件的适应能力是决定其入侵能力大小的关键因素之一。通过室内外试验研究了小花山桃草种子休眠特性以及贮藏时间、果皮、温度、p H值、水势、盐分和埋土深度对其种子萌发、幼苗生长和出苗的影响。结果表明:小花山桃草蒴果中4粒种子的大小差异显著(P<0.01),但它们的活力和萌发率差别不大,4粒种子活力均高达96%以上。休眠解除后,萌发率均高达98%以上;坚硬果皮的机械阻碍是引起种子休眠的主要原因;在室温储藏条件下,种子萌发率随贮藏时间的增加先增加后降低。贮藏1个月,萌发率提高到54%(贮藏前为0)。贮藏3—6个月时,萌发率达最大值(98.5%—99%)。贮藏1a后,萌发率和萌发速度显著下降,但萌发率仍高达90%以上;在室外,有10.5%的蒴果前两粒种子(果实柱头端)同时萌发出苗。室外埋藏1a后,蒴果中未萌发的3粒种子的发芽率分别为45.5%、90.5%和88.5%;小花山桃草种子萌发的温度范围为5—35℃,15—25℃最适于种子萌发,25℃最有利于幼苗生长;小花山桃草能忍受一定的盐胁迫和干旱胁迫,盐浓度和水势为0.15 mol/L和-0.5 MPa时,种子萌发率分别为33.5%和9%。种子萌发和幼苗生长最适宜的土壤含水量为50%;小花山桃草对p H值具有较广泛的适应性,在p H值为5—9范围内均可萌发;小花山桃草种子在土壤表面的出苗率为43%,埋土深度2 cm时,出苗率最高(89.5%),埋土深度大于10 cm时,不再出苗。小花山桃草种子休眠萌发特征以及出苗特点是其快速入侵的基础。研究结果为预测小花山桃草潜在分布范围以及提出科学合理的综合治理措施提供了理论依据。

Seed germination and early seedling growth are the stages in a plant’s life cycle during which it is most sensitive to environmental stresses. The adaptability of an alien plant at this stage to unfavorable environmental conditions is one of the key factors determining its invasiveness. In this study,experiments were conducted to evaluate the effects of dormancy features,storage time,pericarp,temperature,p H,osmotic stress,salt stress and seed burial depth on seed germination,seedling growth and seedling emergence in Gaura parviflora. Although the four seeds of each capsule were found to differ significantly with respect to weight（ P 〈 0.01）,their vigor and germination rates were similar to one another. Seed vigor was greater than 96%,and germination was higher than 98% after release from dormancy. The pericarp of G. parviflora affected seed germination via physical obstruction,and was the major cause of seed dormancy. After storage at room temperature,G. parviflora seed germination initially increased; at longer storage times,however,it decreased. Prior tostorage,no germination occurred. After one month of storage,germination rates as high as 54% were observed,with maximum germination（ 98.5% —99%） taking place after 3—6 months of storage. Germination rate and germination speed decreased significantly after one year of storage,although the germination rate was still greater than 90%. The first two seeds of G. parviflora capsules germinated（ 10. 5%） and emerged at the same time under outdoor conditions. After one year of burial in the soil,germination rates of the remaining second,third and fourth ungerminated seeds averaged 45.5%,90.5%and 88.5%,respectively. Gaura parviflora seeds germinated at temperatures ranging from 5 ℃ to 35 ℃,with optimum germination occurring at 15—25 ℃,and optimum seedling growth taking place at 25 ℃. Gaura parviflora seeds were fairly tolerant of high salt stress and low water potential,with germination rates of 33.5% and 9% observed at a salinity level of0. 15 mol / L and an osmotic potential of- 0.5 MPa,respectively. The optimum soil moisture content for seed germination and seedling growth was 50%. Gaura parviflora seeds were able to germinate over a broad range of p H values,ranging from p H 5 to 9. When seeds were placed on the soil surface,the seedling emergence rate was 43%. Maximum seedling emergence（ 89.5%） occurred at a burial depth of 2 cm. No seedlings emerged when a burial depth of 10 cm was used. Seed dormancy,seed germination and seedling emergence are the critical factors responsible for the rapid invasion characteristics of this species. Our results should be helpful for predicting potential distribution areas of G. parviflora and for developing effective management strategies for this species.