【作者】 王强；

【导师】 陈存根；

【作者基本信息】 西北农林科技大学 ， 生态学， 2009， 硕士

【摘要】 榆科树种是我国分布最广泛的树种,在榆林地区常见的榆科榆属树种主要有沙地榆(U. pumila var.sabulosa)、旱榆(Ulmus. glaucescens Franch)、白榆(Ulmus. pumila Linn)、春榆(Ulmus.propinqua Koidz)等4种,作为榆林乡土树种,它们在当地世代繁衍,与榆林的气候、土壤环境融为一体,所以特别能够忍耐风沙侵袭、霜寒雪冻等各种自然灾害。但近年来,由于人为破坏和病虫害治理不力,目前榆林地区的榆属树种已处在濒危状态。本文利用WP4露点水势仪、Li-6400便携式光合分析系统和CM1000 chlorophyⅡmeter叶绿素测定仪,对上述4种榆属树种苗期抗旱特性进行了研究,结果表明:(1)无水分胁迫条件下,4种榆属树种水势日变幅的大小排序为:白榆>春榆>旱榆>沙地榆;在干旱胁迫下,沙地榆叶片相对含水量高,饱和亏最小,保水能力最强,白榆叶水势降低显著,保水能力差,春榆和旱榆居中。(2)轻度干旱胁迫在一定程度上能够提高所测4种树种光合能力,但在严重干旱胁迫条件下,水分亏缺抑制了4种榆属树种的光合作用,其中白榆光合生理指标变化最为显著,净光合速率和水分利用效率下降迅速,而沙地榆即使在严重干旱胁迫下仍能够保持较高的光合能力。(3)4种榆属树种的光补偿点、光饱和点、CO2补偿点对干旱胁迫反映敏感,白榆在极端干旱胁迫条件下,光补偿点和CO2补偿点分别是无胁迫条件下的2倍和1.6倍,光饱和点是无胁迫条件下的1/7;沙地榆变幅最小,其光补偿点和CO2补偿点分别是无胁迫条件下的1.8倍和1.2倍,光饱和点是无胁迫条件下的1/5。(4)干旱胁迫对4种榆属树种的叶绿素荧光参数影响较大,在中度干旱胁迫下白榆和春榆的最大光能转化效率、实际光能转化效率、线性电子传递的量子效率和光化学荧光猝灭明显降低,而沙地榆在严重干旱胁迫下其叶绿素荧光参数才有明显变化。(5)轻度的干旱胁迫能够促使4种榆属树种叶绿素相对含量增大,但随着干旱胁迫的加剧,各树种叶绿素相对含量都有降低,在极端干旱胁迫下,白榆比其处理一降幅达16.9%,沙地榆仅降低6.9%,旱榆和春榆降幅分别为12.1%和13.8%。(6)干旱胁迫对4种榆属树种叶片重量、苗高和地径等形态学指标的影响程度不同,其对苗高的影响最大,地径次之,对叶片重量影响较小;一定的干旱胁迫可以促使4种榆属苗木的上述3个指标增大,但在严重干旱胁迫下,所测苗木的叶片重量、苗高和地径与其对照比较,下降幅度均显著,其中白榆下降幅度最大,旱榆和春榆次之,沙地榆最小。经过对4种榆属苗木的水分胁迫实验研究,我们得出沙地榆苗期抗旱能力最强,而白榆抗旱性相对较差,这为榆林的风沙地区造林提供理论依据。更多还原

【Abstract】 Ulmaceae tree species is one of the most widely distributing species in China. In Yulin region, the common Ulmaceae species are mainly the following four species: Ulmus. pumila var.sabulosa、Ulmus. glaucescens Franch、Ulmus. pumila Linn and Ulmus.propinqua Koidz. Elm, one of the native tree species, reproduces from generation to generation and integrates with the climate and soil environment in the local. So, elm can endure natural disasters, particularly, sand invasion and frozen injury. But, in recent years, elm has been in the endangered state and became a rare plant in Yulin region, because of destructive influences of man and weak control of diseases and insect pests.In this paper, potential WP4 dewpoint instrument, Li-6400 portable photosynthesis system and CM1000 chlorophyⅡmeter were used to study the drought-resistance characteristics of the above-mentioned four species seedling. The results showed that:Under non-water stress, diurnal change range of water potential of four elm species was listed in descending order as follow: Ulmus. pumila L.> Ulmus.propinqua Koidz >Ulmus. glaucescens Franch>Ulmus. pumila var.sabulosa. Under the water stress condition, the relative water content of leaves of Ulmus. pumila var.sabulosa was the highest, the saturated deficit of that was the least, and the water retention capacity of that was the strongest. The leaf water potential of Ulmus. pumila Linn decreased significantly; the water retention capacity of that was the weakest, that of Ulmus.propinqua Koidz and Ulmus. glaucescens Franch was intermediate.To some extent, the photosynthetic capacity of four elm species was improved under the light water stress. But water deficit inhibited the photosynthesis of four species under the sever water stress, among which the change of photosynthetic physiological index of Ulmus. pumila Linn was the most significant, net photosynthetic rate and water use efficiency decreased rapidly. However, Ulmus.pumila var.sabulosa could maintain a high photosynthetic capacity even under the sever water stress condition.Light Compensation Point (LCP), Light Saturation Point (LSP) and CO2 Compensation Point (CCP) of four Ulmaceae species were sensitive to drought stress. Under the extreme water stress , LCP and CCP of Ulmus. pumila Linn were respectively as 2 times and 1.6 times as that of non-water stress, and LSP was one-seventh as that of non-water stress. The variation of Ulmus. pumila var.sabulosa was smallest, of which LCP and CCP were respectively as 1.8 times and 1.2 times as that of non-water stress, and LSP was one-fifth as that of non-water stress.Drought stress had great influences on Chlorophyll fluorescence parameters of four species. Under moderate drought stress, PSⅡlargest solar energy conversion efficiency, the actual conversion efficiency of light energy, linear electron transport in quantum efficiency and photochemical fluorescence quenching coefficient of Ulmus. pumila Linn and Ulmus.propinqua Koidz decreased significantly. However, the chlorophyll fluorescence parameters only changed significantly under severe drought stress.Relative content of chlorophyll of four elm species increased under light drought stress; but with the aggravation of drought stress, relative content of chlorophyll of four elm species decreased; under severe drought stress, that of Ulmus. pumila L, Ulmus.propinqua Koidz, Ulmus. glaucescens Franch,and Ulmus. pumila var.sabulosa decreased respectively by 16.9%, 13.8%, 12.1% and 6.9%.After the experimental study of water stress on four Ulmaceae seedlings, the results showed that seedlings of U. pumila var.sabulosa had the strongest drought-resistance, but seedlings of Ulmus. pumila L had a relatively weaker drought-resistance, which provide a theoretical basis for afforestation in Yulin sandy area.Drought stress had different influences on leaf weight, height and diameter of the seedlings of four species. The impact of its height was the most, followed by diameter, weight of leaves was less affected. A certain degree of drought stress can promote the four indexes above-mentioned.But under severe drought stress, the four indexes above-mentioned had a significant decrease comparing with the control, of which the largest decrease was U. pumila L, followed by Ulmus.propinqua Koidz and Ulmus. glaucescens Franch,Ulmus. pumila var.sabulosa decreased smallest.更多还原