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半干旱区典型植物对气候变化与CO2浓度升高的响应与适应

Responses and Adaptations of Typical Plants to Climate Change and CO2 Concentration Enrichment in Semi-arid Region

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【Author in Chinese】 许振柱

【Supervisor】 张新时周广胜

【Author's Information】 中国科学院研究生院(植物研究所), 生态学, 2003, 博士

【Abstract in Chinese】 1. 羊草对土壤水分的响应与适应羊草生物量随着土壤水分含量的降低逐渐降低,后期的降低幅度远远大于前期。干旱促进鞘分配增加,增加了在处理初期的根的分配,但到后期则使之减少,表明羊草在经历较长期的持续干旱后通过增加根部的比重来提高抗旱性的能力逐渐降低。轻度(LD)、中度干旱(MD)对羊草叶片相对含水量(RWC)、气孔密度、光合参数、荧光猝灭参数和群体日交换速率无显著影响,但严重土壤干旱使它们显著降低。羊草叶片的可溶性蛋白质以中度干旱的最高,严重干旱(SD)特别是极严重干旱(VD)使之显著降低,游离氨基酸含量(FAA)的变化与之相似。随着土壤水分含量的降低硝酸还原酶(NR)活性逐渐下降,而谷氨酰胺酶合成酶(GS)的活性变化则是LD和MD使之分别增加了25. 75%和12. 22%,SD和VD则分别减少了8. 21%和28. 72%,说明了NR的活性变化对土壤干旱较敏感,而GS的活性则对适度的干旱有一定程度的适应性。LD处理没有增加天冬酰胺酶(AE)和内肽酶(EP)两种酶的活性,但MD、SD和VD使两种水解酶的活性显著增加,说明轻度土壤干旱对蛋白质和氨基酸的分解作用有稍降低作用,但随着土壤干旱程度的加剧,又极大地促进了这个分解过程。严重和极严重土壤干旱显著降低了叶片的总核酸含量和RNA的含量,暗示严重程度的土壤水分胁迫限制了核酸的合成代谢,加强了其分解代谢,严重土壤干旱还显著增加了丙二醛(MDA)的含量,说明提高了羊草叶片叶肉细胞的膜质过氧化水平。2. 羊草对土壤干旱和复水的响应与适应羊草受到适当的干旱驯化可促进生长,但过长时间的干旱处理,复水后未能补偿损失的生物量和叶面积。羊草叶片的气孔密度以中度干旱持续期(Mtd)处理的最高,其次是短期干旱持续期(Std),二者分别比没有经过土壤干旱的处理(对照)增加了14. 90%和3. 61%,但长期干旱持续期(Ltd)却使之减少了27. 19%,气孔指数亦有类似的趋势。复水增加羊草叶片的光合速率、气孔导度、蒸腾速率,近期复水的激发效应明显大于前期,而对夜晚的呼吸作用影响不显著。水分利用率(WUE)的日变化动态呈“M”字型曲线,以Mtd的WUE值的峰值最大,以三次曲线拟合WUE的24小时日进程最佳。叶绿素荧光动力学的分析结果表明,复水,特别是最近的复水可显著改善羊草叶片的PSⅡ性能,增加叶绿素a,b的含量及其比值,提高碳酸酐酶的活性。许振柱:半干早区典裂植物对气候文化与C02浓度升商的响应与适应 羊草含氮量以叶片的最高(4 .40%),根部的最低(1 .99%),枯叶、茎鞘和根茎的含量差异较小(2.26礴.40%)。所有器官的含氮量对土壤水分处理的响应基本一致,以对照处理的最低,Std的最高。各器官的碳氮比都是以对照的最高,而其它土壤水分处理相差不显著,给于一定时间的土壤干旱处理可使羊草获得较强的氮代谢能力。Std的氮素总拥有量最多,和对照相比,绿叶、枯叶、茎鞘、根茎和根分别提高了35.58、26.88、23.49、31.“、40.75%,而Ltd的含氮总量呈下降趋势,说明短时间的土壤水分干旱处理可明显促进羊草各器官和植株的氮素积累,而较长时间的土壤干旱则不利于氮素的积累。羊草各器官氮素绝对量占整株的百分比从大到小依次为:绿叶(42.42一44.00%)、根茎(20.13一23.69%)、根(15.43一17.18%)、枯叶(10.07一11.30%)和茎鞘(7 .27一8.67%),表明叶片的氮素存量占植株的一半以上。Mtd处理增加了叶片的氮素贡献率,减少了茎鞘和根茎的贡献率,有利于加强叶片的光合性能。 以中度干旱持续期(Mtd)处理的叶片可溶性蛋白质含量、谷氨酞胺合成酶(GS)活性、RNA含量为最高,但中长期的土壤干旱处理再复水后则显著降低了羊草叶片内肤酶(EP)的活性和MDA的含量,说明给于一定时间的土壤干旱处理可使羊草叶片保持较高的蛋白质代谢水平,降低膜脂过氧化水平。3.羊草对昼夜温差与土壤水分交互作用响应与适应 昼夜温差减少使单株羊草的生物量降低21.3%,分孽和根的生物量减少,而鞘的生物量稍增加,显著降低了严重和极严重条件下的生物量。温差缩小降低了分粟和根的投资比例,减少植株的地下部分生物量,而增加新叶、鞘和分粟光合产物的比例,表明温差的减少将抑制光合产物向地下部分的转移。温差减少对充足土壤水分和轻度干旱处理的放射性比强影响较小,但减少了其它3种干旱处理的放射性比强。其原因主要是减少了植株鞘、根和根茎的放射性比强,显著增加了饲喂叶和J自叶的放射性比强,表明温差的缩小阻止了“源”的光合产物向“库”的转移,降低对分孽和根的投资,不利于羊草对千旱逆境的适应。 昼夜温差缩小使羊草叶片的气孔密度降低4.01%,而且减少了土壤干旱对气孔密度的影响。较高的昼夜温差和较低的昼夜温差相比,羊草叶片的光合速率和WUE分别增加了7.37%和20.09%;而气孔导度、胞间CO:浓度和蒸腾速率分别降低了14.03%、2.57%和10.80%。昼夜温差减少降低了土壤干旱的6’3c值,说明可能减少处在干旱条件下的植株WUE,暗示减小昼夜温差不利于增大羊草叶片对土壤水分亏缺的耐性。昼夜温差的缩小主要影响了下午羊草群体的CO:交换速率,增加了

【Abstract】 1. Responses and adaptations of Leymus chinensis to soil moistureLeaf relative water content (RWC) was increased subtly by light and moderate soil drought, but reduced significantly by severe drought. Soil drought reduced biomass of plant, especially at the later growth stage. It was suggested that the leaf water status may be regulated adaptively by soil drought, and the growth was limited by extreme soil drought. The sheath allocation decreased gradually with growth development, but did oppositely for rhizome, suggesting the translocation from the matter in stored sheath to rhizome. Soil drought increased the root allocation and ratio of shoot to root in the earlier period, but did oppositely in the later period, indicating that the higher capacity of plant drought resistance through increasing root distribution decreased gradually after enduring long period of soil drought. Light drought (LD), moderate drought (MD) did not significantly affect leaf RWC, stomatal density, photosynthetic parameters, fluorescence parameters and community CO2 daily net exchange rate, but severe soil drought (SD) significantly reduced them.The soluble protein of Leymus chinensis leaf at MD was the greatest, but those at SD, especially very soil drought (VD) significantly were reduced, and the trend of free amino acid (FAA) similar. The activity of nitrate reductase (NR) gradually decreased with decline of soil moisture, and the activity of glutamine synthetase (GS) was increased by 25.75% and 12.22% at LD and MD respectively, but reduced by 8.21% and 28.72% at SD and VD respectively, indicating that NR was the sensitive to soil drought and GS had an adaptive response to drought. LD did not increase the activities of asparagine enzyme (AE) and endopetidase (EP), but MD, SD and VD significantly increased their activities, indicating LD slightly affected the degradations of leaf soluble protein and amino acid, but greatly enhanced the degraded procedure with increasing soil drought. SD and VD significantly reduced the contents of total nucleic acid and RNA, implying the severe soil water stress restricted the synthetic metabolism of nuclei acid and provoked its degraded metabolism. Severe soil drought also increased the malondialdehyde (MDA) content, indicating thatcell membrane peroxidating was provoked.2. Responses and adaptations of Leymus chinensis to soil drought and rewateringThe growth of Leymus chinensis could enhance because of moderate term drought acclimation, but rewatering offseted the loses of biomass and leaf area due to long term soil drought. The leaf stomatal density of moderate term soil drought (Mtd) was the largest followed by the short term soil drought (Std), those of Mtd and Std were 14.90% and 3.61% greater than that of the Control, and stomatal index was the similar trend. Rewatering stimulated leaf net photosynthetic rate (A), stomatal conductance (gs) and transpiration rate (E), and the recently rewatering could increase their kind of effect. Rewatering did not significantly affect leaf respiration at night. The diurnal fluctuation water use efficiency (WUE) showed the "M" curve pattern, which Mtd had the greatest peak, and which cubic function could be simulated by the curve in 24 h of day and night. Leaf chlorophyll fluorescence kinetic analysis showed that rewatering, especially recently, could significantly enhance PS II capacity, chlorophyll a and b, and its ratio, strengthen carbonic anhydrase (CA) activity.Nitrogen content was the greatest in leaves (4.40%), the lowest (1.99%) in roots, ranged from 2.26% to 4.40% in litter leaves, stems and sheaths, and rhizomes. That of control was the lowest and that of Std greatest in all Leymus chinensis organs. The ratio of carbon and nitrogen was the greatest at control, but other soil water treatments had no effects, implying that Leymus chinensis could acquire the nitrogen metabolism capacity when subjected to water stress in moderate term. The plant total nitrogen amount at Std was the greatest, compared to control, the nitrogen amount was increased by 35.58 , 2

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