PEG预处理对青稞种子萌发和幼苗生理特性的影响

摘要

In our experiment, 28 hulless barley cultivars were choose to study their water consumption rate and dehydration rate when the first leaf spread out. A drought-tolerant and a water-sensitive hulless barley cultivar were selected. To understand the regulating effect of polyethylene glycol (PEG) under drought stress , we examined the effects of 5%-~30% PEG pretreatment on the seed germination, seedling growth and physiological characteristics of different barley varieties. The results were as following: (1)Relative water content of 28 hulless barley varieties increased gradually, while dehydration rate showed the opposite trend. The relative water content ranked the highest (60. 16%) and dehydration rate ranked the lowest (8. 80%) in Handizi,while relative water content ranked the lowest (38. 98%) and dehydration rate ranked the highest (20. 20%) in Dama, it indicated Dama was greatest sensitive to water and Handizi was least sensitive to water. (2) Germination and rooting rate in hulless barley seed, root length, shoot height and fresh weight in hulless barley seedlings showed 'rises first,falls later' with the increase of PEG concentration. The best treatment concentration on Handizi hulless barley and Dama were 15% and 10% respectively and the difference was significant with the control (P<0. 05). The best treatment concentration on root length,shoot height and fresh weight in two hulless barley seedlings was 10% and no significant difference was found between the treatments and the control in Dama. (3)Soluble protein and chlorophyll content of Handizi hulless barley leaves was correlation with PEG concentration and malondialdehyde (MDA) presented negatively correlation. They were obvious at 0. 01 degree in 30% PEG. Soluble protein and chlorophyll content of Dama hulless barley leaves showed 'rises first, falls later', and the MDA showed the opposite change. 20%PEG was the best treatment. To sum up, low concentration of PEG pretreatment promoted seed germination, seedling growth and improvement of physiological function of hulless barley; high concentration of PEG inhibited seed germination, seedling growth and improvement of physiological function of hulless barley. The variety with stronger drought tolerance had a strong resistance to PEG and self regulation ability from the beginning of seed germination period,and the variety with weak drought tolerance had a weak resistance and self regulation ability when subjected to higher degree of stress. So the treatment of appropriate PEG concentration not only could significantly promote the seed germination and seedling growth of hulless barley, but also could improve the physiological function, including protein, chlorophyll, MDA content and relative conductivity,which could enhance the resistance ability. The results of this study suggested that it can make dormant seed rapidiy activing using a proper concentration of PEG solution to soak,and improve the efficiency of seed breeding,which lays a foundation for the PEG widely application in agriculture.%选择国内外28份青稞品种材料幼苗第一片展开叶,分别测定其相对含水量和失水率,并选择其中对水分胁迫敏感与不敏感的材料各1份,研究不同浓度(5％～30％)聚乙二醇(PEG)预处理对青稞种子萌发、幼苗生长和生理特性的影响,探讨短期水分胁迫对青稞生长发育的调节作用.结果显示:(1)28个青稞材料中‘旱地紫青稞’幼苗叶片的相对含水量最高(60.16％)、‘大麻青稞’最低(38.98％),而离体失水率‘旱地紫青稞’最低(8.80％)、‘大麻青稞,最高(20.20％).说明‘大麻青稞’对水分胁迫最敏感,而‘旱地紫青稞’最不敏感.(2)随着胁迫程度的增加,青稞种子的萌发率和生根率,幼苗的根长、苗高和鲜重均呈先增加后降低的趋势,‘旱地紫青稞’和‘大麻青稞’种子分别在15％和10％ PEG处理下发芽和生根最佳且均与对照差异显著(P＜0.05),两品种的幼苗根长、苗高和鲜重均在10％ PEG处理下表现最佳,但‘大麻青稞’与对照差异不显著.(3)‘旱地紫青稞’幼苗叶片可溶性蛋白和叶绿素含量随PEG处理浓度增加而逐渐增加,而丙二醛含量和相对电导率则逐渐降低,并在30％ PEG处理下效果差异极显著(P＜0.01)；‘大麻青稞’叶片可溶性蛋白和叶绿素含量随PEG处理浓度增加呈先增加后降低的趋势,丙二醛含量和相对电导率呈先降低后增加的趋势,并在20％PEG处理下最佳.研究表明,短时间低浓度PEG处理对青稞种子萌发、幼苗生长及可溶性蛋白、叶绿素、丙二醛含量和相对电导率等生理指标的改善均有一定的促进作用；高浓度PEG处理却具有抑制作用,且高浓度PEG胁迫条件下,耐旱性强比耐旱性弱品种的自我调控能力更强.