4种多年生禾本科牧草种子萌发对Na2CO3胁迫的响应

Germination Characteristics of Four Perennial Grasses(Poaceae) Seeds in Responses to Sodium Carbonate Stress

采用培养皿室内培养方法,研究了4种多年生根茎型耐旱植物俄罗斯新麦草(Elymus junceus Fisch)、苇状羊茅(Festuca arundinacea Schreb)、羊草(Leymus chinensis Trin.Tzvel.)和高冰草(Agropygron elongatum Host Nevski)种子对不同浓度(0、25、50、75和100mmol·L-1)Na2CO3胁迫及胁迫解除后种子发芽率和幼苗生长的响应。结果表明,4种牧草发芽率均在没有Na2CO3胁迫时最高,且以苇状羊茅最高达到96.8%,羊草最低73.1%;随着胁迫浓度的增加发芽率呈下降趋势,高冰草在100mmol·L-1Na2CO3下发芽率仍达到14.9%,而其他3种牧草在此浓度下没有观察到萌发的种子。4种牧草的发芽速率均与Na2CO3浓度呈显著负相关,相同Na2CO3浓度下,4种牧草中苇状羊茅最高,羊草最低。Na2CO3胁迫对根长的抑制明显高于苗长,且对不同物种影响不同;75mmol·L-1Na2CO3胁迫下,除了高冰草根长为3.4cm之外,其他3个物种根的伸长几乎完全被抑制。解除胁迫后,羊草种子发芽恢复最快,且发芽率与原Na2CO3浓度成正比;高冰草、俄罗斯新麦草和苇状羊茅几乎均为0。上述结果说明,4种牧草中,种子萌发期以高冰草耐Na2CO3能力最强,其次是俄罗斯新麦草和苇状羊茅,羊草种子最差;但当胁迫解除后,羊草种子具有较高的萌发恢复率,这也是其适应盐碱环境的一个重要原因。

Elymus junceus, Festuca arundinacea, A gropygron elongatum, Leymus chinensis are all perennial rhizome drought tolerant grasses （Poaceae） with great economic and ecological significances. Songnen Plain of Northeast China is the largest alkali sodic soil distribution area in the world where the sodium carbonate （Na2CO3） is one of the main composition salts. Seed germination and seedling growth of the four grasses in response to different concentrations of 0, 25, 50, 75 and 100 mmol·L^-1 Na2CO3 were investigated. Highest germination percentages of the four species were all obtained under non-stress conditions and with the increase of the concentration, germination percentages all decreased. F. arundinacea had the highest germination percentage at 0 mmol·L^-1 concentration reaching 96.8%. A. elongatum was more salttolerant with germination percentage of 14.9% in 100 mmol·L^-1 Na2CO3 while there was no germinated seed for the other three species at this concentration. The salt stress inhibited the root elongation more severely than that of shoot. Almost no radicle emerged when the Na2CO3≥75 mmol·L^-1 with the exception ofA. elongatum which was 3.4 cm at 75 mmol·L^-1 concenration. When transferred from stressed solutions to distilled water, seeds of L. chinensis germinated quickly and showed positive relationship between the germination percentage and the pre-trans-ferred concentration of Na2CO3. However, after being transferred to distilled water, the germination of A. elongatum was poor while no germination was found in E. junceus and F. arundinacea. These results indicated that E. junceus, and F. arundinacea had comparatively higher germination in low salinity and A. elongatum also had higher germination in hyper-salt conditions. Seeds of L. chinensis could keep viable with long-time exposure to salty condition which was one of the main reasons for its adaptation to alkali sodie soil condition.