1、三種觀賞草對土壤干旱脅迫的生理響應        【中文摘要】 本試驗首先對國內(nèi)外10個觀賞草種的抗旱性做出了初步評價,并以此為依據(jù),選出抗旱性不同的三種草并對其在干旱脅迫下的生理特征進行了研究,探討其對干旱脅迫的適應機制,主要內(nèi)容和結果如下:1.以土壤最大田間持水量75-80%為對照(CK),以30-35%為水分脅迫處理(Treat),采用生長與生理指標相結合的方法,并通過隸屬函數(shù)分析,對其抗旱性作出初步評價， 10個觀賞草種的抗旱性由強到弱的順序為:蒲葦(白)、蒲葦(粉)、野青茅、柔穗狼尾草、橘草、狼尾草、黃背

2、草、小布尼狼尾草、知風草、彎葉畫眉草。選出抗旱性強、中、弱不同的三草種,分別為蒲葦(白)、狼尾草、彎葉畫眉草進行下一步的試驗。2.在干旱脅迫條件下,抗旱性最強的蒲葦酶促抗氧化系統(tǒng)SOD、POD、CAT、APX活性和抗氧化物質(zhì)ASA和Car含量均增加,但由于其POD基礎活性較低,推測POD不是蒲葦清除H2O2的主要酶。抗旱性最弱的彎葉畫眉草在嚴重干旱脅迫下保護酶活性(POD除外)和抗氧化物質(zhì)ASA和Car含量均明顯降低,標志著體內(nèi)活性氧代謝嚴重失調(diào)。在不同的干旱脅迫條件下,膜傷害度的順序依次為蒲葦<狼尾草<彎葉畫眉草。3.滲透調(diào)節(jié).更多能力與脅迫持續(xù)時間有關。抗旱性最強的蒲葦滲調(diào)能力

3、在脅迫早期較小,但隨著脅迫時間的延長,滲調(diào)能力持續(xù)增大;其中抗旱性最弱的彎葉畫眉草隨著干旱時間的延長,滲調(diào)能力降低;抗旱性中等的狼尾草滲調(diào)能力在干旱脅迫期均高于蒲葦,但是隨著脅迫程度的加劇和脅迫時間的延長,其滲調(diào)能力表現(xiàn)為下降,復水后滲調(diào)能力降低幅度最大。三種觀賞草積累的滲調(diào)物質(zhì)有所不同。對蒲葦而言,起滲調(diào)作用最大的是可溶性糖,其次是可溶性蛋白,游離氨基酸起的作用較小。對狼尾草和彎葉畫眉草來說,可溶性糖和游離氨基酸是其主要的有機滲調(diào)物質(zhì)。脯氨酸不作為三草種的滲調(diào)物質(zhì),更宜作為干旱脅迫敏感指標。K+、Na+、Ca2+、Mg2+都參與了觀賞草的滲透調(diào)節(jié),K+、Ca2+是其主要的滲調(diào)離子,K+含量最

4、大,Ca2+增幅最大。4.隨干旱脅迫的加強,三種觀賞草Pn、Gs、E值均有較大幅度的降低,抗旱性越強的草種Pn下降的幅度越小,且復水后恢復的好。狼尾草和彎葉畫眉草隨著脅迫水平的加劇, WUE呈下降趨勢。蒲葦WUE表現(xiàn)為先升后降。狼尾草和彎葉畫眉草自中度干旱脅迫開始就出現(xiàn)光合的非氣孔限制。蒲葦在嚴重干旱脅迫下,出現(xiàn)光合的非氣孔限制。受到干旱脅迫后,狼尾草和彎葉畫眉草Chla、Chlb、Chla+Chb和類胡蘿卜素含量均下降,但彎葉畫眉草葉中Chlb含量下降較小,處理間無顯著差異。而蒲葦葉中色素含量均上升。狼尾草葉中Car/Chl隨著干旱脅迫的加劇而增加,蒲葦和彎葉畫眉草葉中Car/Chl隨著土壤

5、含水量的下降而降低。三草種PSII反應中心最大光能轉換效率(Fv/Fm)、PSII潛在光化學活性(Fv/Fo)、光化學猝滅系數(shù)(qP)、PSII實際光化學效率(PS)隨著干旱脅迫的加劇而降低。抗旱性越強的草種下降幅度越小,復水后恢復至正常狀態(tài)的能力強;抗旱性弱的草種則相反。非光化學猝滅系數(shù)(NPQ)值總體呈上升趨勢,但抗旱性強的蒲葦NPQ值最低。相關分析表明,當用葉綠素熒光參數(shù)對干旱脅迫下觀賞草的光合作用做出評價時,Fv/Fm、qP、PS是較為重要的指標。5.干旱脅迫下,三種觀賞草ABA含量整體呈上升趨勢,抗旱性強的蒲葦在干旱脅迫下ABA升高幅度最小,抗旱性最弱的彎葉畫眉草ABA升高幅度最大。

6、三種觀賞草葉片IAA含量均降低,抗旱性較弱的狼尾草和彎葉畫眉草IAA降幅顯著高于抗旱性強的蒲葦,但二者相差不大。蒲葦葉中GA含量表現(xiàn)為先升后降,狼尾草GA含量表現(xiàn)為先降后升。彎葉畫眉草GA含量隨著水分脅迫而持續(xù)下降,中度脅迫下降低幅度較小,嚴重脅迫下明顯下降。觀賞草葉片中ZR的含量隨著干旱脅迫程度的增加均呈下降趨勢。脅迫程度越大,下降幅度越大,抗旱性越弱的草種,ZR含量下降幅度越大。干旱脅迫下三種觀賞草四種激素之間協(xié)調(diào)的總趨勢均是向著氣孔關閉,抑制生長的方向進行的。蒲葦ABA/ (IAA+GA+ZR)值在不同的水分脅迫下增加幅度較小,且在中度和嚴重脅迫下,變化不大,表明干旱脅迫對蒲葦?shù)纳L抑制

7、較小。在中度水分脅迫下,對狼尾草生長抑制較大;在嚴重水分脅迫下,對彎葉畫眉草的生長抑制較大。6.干旱脅迫下,3種觀賞草Spm、Spd和多胺總量均增加,但Put含量下降。Spd的積累是多胺類物質(zhì)增強觀賞草抗旱性的主要因素。3種觀賞草(Spd+Spm)/Put比值均增加,抗旱性越強的草種,該比值越大。  【英文摘要】 The drought resistance of 10 ornamentral grass species collecting from both at home and abroad was evaluated preliminarily in the experim

8、ent, on the basis of the results,three ornamentral grass species were selected as strong droughtresistance,medium droughtresistance and weak droughtresistance experiment materials to study the physiological characteristics under different drought stress in order to esplore their adaptation mechanism

9、 to drought stress.The main results and conclusions were followed:1. The drought resistance of 10 ornamentral grass species was evaluated preliminarily with subordinate function analysis according to growth indexes and physiological indexes.The drought resistance,s order of ornamentral grass from be

10、tter to worse is Cortaderia selloanaWhite, Cortaderia selloanaRosea, Deyeuxia arundinacea, Pennisetum alopecuroidesCaudatum, Cymbopogon goeringii, Pennlseturn alopecuroides, Themeda japonica, Pennisetum alopecuroidesLittle Bunny, Eragrostis ferruginea,.Eragrostis curvula. Strong drought-resistance (

11、Cortaderia selloanaWhite), medium drought-resistance (Pennlseturn alopecuroides) and weak drought-resistance (Eragrostis curvula) were chosen for the further study.2. The antioxidation enzyme activity such as SOD,POD,CAT,APX and the contents of antioxidation substance such as ASA and Car increased i

12、n the leaves of strong drought-resistance(Cortaderia selloana) under drought stress.The lower basic activity of POD indicated that the POD was,t the main enzyme eliminating H2O2 in Cortaderia selloana leaves. Compared with strong drought-resistance species, the activity of SOD,CAT,APX and the conten

13、ts of ASA and Car decreased significantly in the leaves of Eragrostis curvula,which showed the metabolize of active oxygen was out of balance severely. The descending order of membrane damaging degree in 3 grass species could be listed as followed: Eragrostis curvul is highest, Pennisetum alopecuroi

14、des is medium, Cortaderia selloana is lowest under different drought stress.3. The results showed that the osmotic adjustment ability of these three ornamental grasses have something to do with stress duration. The osmotic adjustment ability of the drought sensitive variety Eragrostis curvula decrea

15、sed with the elongation of stress time. In contrast, which of strong drought -resistant variety Cortaderia selloana changed slightly at early stress stage and constantly increased with the elongation of stress time. The osmotic adjustment ability of moderate drought-resistant variety Pennisetum alop

16、ecuroides was higher than that of Cortaderia selloana during water stress, but decreased with the intensity of water stress and the elongation of stress time. Furtherly,its osmotic adjustment ability decreased mostly after rewatered. The main osmoregulation substance within the three grass species w

17、ere different from each other; the soluble suger contributed most to osmotic adjustment ability, the soluble protein was the second,while the role of the free amino acid was smaller as for Cortaderia selloana. But the soluble suger and free amino acid contributed more to osmotic adjustment ability a

18、s for Pennisetum alopecuroides and Eragrostis curvul. The proline was not osmoregulation substance but drought stress sensitivity index.Under water stress, the inorganic ion such as K+, Na+, Ca2+, Mg2+ participated in ornamental grass osmotic adjustment, but K+, Ca2+ played the main roles.4. The net

19、 photosynthetic rate, stomatal conductance and transpiration decreased dramatically in the leaves of ornamental grass with the enhancement of drought stress intensity.But the decreasing extent of Pn in strong drought -resistant variety Cortaderia selloana leaves was the smallest and its recovery lev

20、el was highest compared with the other two ornamental grass.The water utility efficiencies of Pennisetum alopecuroides and Eragrostis curvul decreased under drought stress.,while that of Cortaderia selloana increased at first then fell .The non-stomatal restriction had been the main factor of the Pn

21、,s decrease in the leaves of Pennisetum alopecuroides and Eragrostis curvul since moderate drought stress.Until severe drought stress was non-stomatal restriction the main factor of the Pn,s decrease in the leaves of Cortaderia selloana.The contents of chlorophylla, chlorophyll b, chlorophyll a+b, c

22、arotenoids in the leaves of Pennisetum alopecuroides and Eragrostis curvul were all decreased under drought stress,but the contents of chlorophyll b in the leaves of Eragrostis curvul decreased slightly with no remarkable difference among treatments. Compared with the other two species, the contents

23、 of those in the leaves of Cortaderia selloana all increased when treated with drought stress. The ratios of Car and Chl increased in the leaves of Pennisetum alopecuroides while that in the leaves of Cortaderia selloana and Eragrostis curvul decreased with the reduction of soil moisture content.The

24、 three ornamental grass,s Fv/Fm,Fv/Fo,qP andPSall decreased under drought stress .The decrease extent of above chlorophyll fluorescence parameter was lower in strong drought-resistance variety and its capability of recover to the normal level was higher than those of the other two grass species. How

25、ever, the weak drought-resistance variety was just the opposite.The non-photochemical Quenching (NPQ) in three ornamental grasses increased under drought stress,while the NPQ in strong drought-resistance variety Cortaderia selloana was the minimum. Correlation analysis showed that Fv/Fm, qP andPSII

26、were more important chlorophyll fluorescence parameteres used as to evaluate photosynthesis of ornamental grass under drought stress.5. The content of ABA in the leaves of ornamental grasses increased under drought stress. Furthermore, the increasing degree of strong drought-resistance variety Corta

27、deria selloana was lowest and that of weak drought-resistance variety Eragrostis curvul was highest. IAA in the leaves of ornamental grasses decreased,but the decreasing degrees of Eragrostis curvula and Pennlseturn alopecuroides with no obvious difference was significantly higher than that of Corta

28、deria selloana. The content of GA of Cortaderia selloana increased under moderate drought stress and decreased under severe drought stress and that of Pennlseturn alopecuroides showed the opposite trend. GA of Eragrostis curvula decreased during water stress and the decreasing degrees increased with the enhancement of drought stress intensity.ZR content in the leaves of ornamental grasses all decreased under drought str