【作者】 曾彦军；

【导师】 王彦荣；

【作者基本信息】 兰州大学 ， 草业科学， 2010， 博士

【摘要】 我国西北干旱荒漠区植被退化、物种濒危形势严重。植被恢复、植物保护已成为国家生态建设的重要工作。西北干旱荒漠区拥有许多天然旱生植物,大多具有独特的生态适应性。其中包括特殊的种子萌发特性以及幼苗存活对策。深入研究这类植物种子萌发生态,对深刻理解植物适应环境的机理具有科学意义。唐古特白刺(Nitraria tangutorum Bobr.)、西伯利亚白刺(N. sibirica Pall)、骆驼蓬(Peganum harmala L. )、匍根骆驼蓬(P. nigellastrum Bunge)、沙蓬(Agriophyllum squarrosum (L.) Moq.)均是西北干旱荒漠区优势种植物。几种植物在栖息地偏好上和地理分布上有明显差异。因此设想,通过综合比较几种植物种子萌发特性的共同特征和差异,有望归纳出植物种子萌发适应干旱环境的基本特性。白刺属植物种子萌发困难,给利用该属植物造成很大不便。研究该属植物种子的休眠特性、破除方法、生活力测定方法和程序无疑也具有科学意义和实用价值。本研究以采集于阿拉善高原荒漠的上述几种植物种子为研究对象,通过系统比较种子萌发对温度、水分、盐分胁迫的响应特征,两种白刺种子休眠对预先冷冻、预先干热、硝酸钾(KN03)、赤霉素(GA3)、浸种、硫酸处理等6方法共23种处理的响应,以及2种种胚暴露方法的四唑染色效果,旨在验证上述设想、确定白刺属种子休眠类型、研发白刺种子休眠破除和生活力四唑测定的适宜方法。取得了如下主要结果或结论：(1)适应阿拉善高原干旱荒漠自然环境的种子萌发基本特征可概括为：种子具有休眠特性；限制水分条件下萌发缓慢、萌发率低；变温和高温条件下发芽率高。(2)种子萌发适宜温度唐古特白刺和匍根骆驼蓬均为25/35℃变温,西伯利亚白刺25-30℃恒温和20/30℃变温,骆驼蓬为15/25℃、20/30℃、25/35℃变温,沙蓬为20/30℃变温。三次方程曲线模型较二次方程曲线模型和直线模型能更好拟合种子萌发率与干旱和盐分条件的关系。(3)水分限制条件对参试所有植物种子萌发均产生抑制作用。种子萌发的最低水分渗透势胁迫(PEG溶液模拟)阈值：唐古特白刺为-0.9 MPa,西伯利亚白刺为-1.5 MPa,骆驼蓬为-0.6--1.21MPa,匍根骆驼蓬为-0.9--1.5 MPa。(4)轻度盐分条件(-0.3 MPa, NaCI溶液模拟)对西伯利亚白刺种子萌发有促进作用,但对其他4种植物均产生抑制作用。种子萌发的最低盐分渗透势胁迫阈值：唐古特白刺为-1.2 MPa；西伯利亚白刺为-1.8 MPa；骆驼蓬为-0.9 MPa；匍根骆驼蓬为-1.5 MPa。(5)浸种是破除两种白刺属种子休眠的适宜方法。两种白刺种子的休眠属生理休眠类型,休眠程度唐古特白刺比西伯利亚白刺为重。(6)从核果钝端起约1/3种子长的位置处横切,于蒸馏水中浸泡4 h取出胚,是实现用四唑染色法测定白刺种子生活力的适宜预处理方法。更多还原

【Abstract】 The situation of vegetation degradation and plant species endangerment has been serious in arid desert region of northwest China these years. Vegetation recovery as well as natural resource conservation had become the key work the government encountered. There were many valuable native xerophytes in the arid desert region. Most of them possess unique eco-adaptations to the adverse environments, including the special germination characteristics as well as the strategies for seedling survival. Studies in deep on the ecology of seed germination of these plants will benefit the better understanding of the adaptation mechanisms of these plants. All of the five plant species, Nitraria tangutorum Bobr., N. sibirica Pall., Peganum harmala L. P. nigellastrum Bunge and Agriophyllum squarrosum (L.) Moq., are dormant plant species in arid desert of northwest China. Their habitat preference as well as geographical distribution of these species differed. The hypotheses proposed that, the key characteristics of seed germination for seeding survival in this area can be concluded by comparing seed germination responses of these species to key environmental elements. Moreover, seeds of Nitraria showed slow and dispersive germination patterns, with dormancy. The hard endocarp makes it hard to cut and expose embryos for tetrazolium testing. Consequently little is known about seed quality evaluation in Nitraria species; the use of the seed has been seriously impeded. So it should be valuable do studies on seed dormancy and dormancy breaking, as well as developing the methods of topographical tetrazolium testing for seed viability of Nitraria.Mature seeds of the five species used in this study were collected from their mother plant in Alashan plateau, which is one of the typical desert (cold desert) region of northwest China. Aims to verify the proposed hypotheses and determine the appropriate methods for dormancy breaking and tetrazolium testing for seed viability for the two species of Nitraria. Experiments were used to compare the followings:seed germination responses to. temperature, water limitation and salinity stress for the five tested species; seed germination responses to prichilling, preheating, soaking, KNO3, GA3, alternating temperature and acid scarification as well as the effects of two approaches to expose tissues for staining in tetrazolium solution for evaluation of seed viability for the two species of Nitraria. The main results and conclusions were listed as followings:(1) The key characteristics of seed germination of dominant species for adapting Alashan arid desert climates should be: seed should have dormancy; seed should show reduced or delayed germination under water limiting conditions; seed germinating selected alternating and high temperature.(2) The optimum temperature of seed germination for both N. tangutorum and P. nigellastrum were 25/35℃alternating temperature; for N. sibirica,25-30℃constant temperatures and 20/30℃; for P. harmala,15/25℃、20/30℃and 25/35℃; for A. squarrosum,20/30℃. The cubic curve model fitted the relationship between seed percentage germination and drought stress or salinity stress better than did of linear model or quadratic model.(3) Water limitation had negative effects on seed germination for all tested species. The most negative osmotic potential (PEG 6000 solution) under which seed could germinated was-0.9 MPa for N. tangutorum;-1.5 MPa for N. sibirica;-0.6--1.2 MPa for P. harmala and -0.9--1.5 MPa for P. nigellastrum.(4) For N. sibirica, seed germination was promoted under light salinity condition (-0.3 MPa NaCI solution); however, salinity stress had negative effects on seed germination for other tested species. The most negative osmotic potential of NaCI solution under which seed could germinate was-1.2 MPa for N. tangutorum;-1.8 MPa for N. sibirica;-0.9 MPa for P. harmala and-1.5 MPa for P. nigellastrum.(5) Soaking is one of the most effective methods to breaking dormancy for the two Nitraria species. Seeds of tested Nitraria species possess physiological dormancy, and the dormancy degree of N. tangutorum was deeper than that of N. sibirica.(6) The key of exposure tissue for tetrazolium testing for seed viability for two Nitraria species should be transversely cut one third of the drupe at the lower part of the drupe, soak in water for 4 hours, then squeeze embryos out carefully.更多还原