中国狗牙根(Cynodon dactylon)优良选系的RAPD分析

对采自中国不同地区的6份狗牙根〔Cynodondactylon(L.)Pers.〕优良选系进行了RAPD分子标记实验。选用15个引物共扩增出438条带,平均每个引物扩增出29条带,其中多态性带415条,多态性位点百分率达到59.02%～75.49%。各选系间遗传相似性系数差异较大(0.408～0.672),说明各选系间在DNA水平上存在着丰富的遗传多样性,与新品种C106(爬地青)相比,各选系还存在一定的改良空间。实验结果也表明,RAPD分子标记可成功地用于中国狗牙根优良选系遗传多样性的研究及品种鉴定。

A Study on the Protective Effect of Cynodon dactylon Leaves Extract in Diabetic Rats

Objective To investigate the antidiabetic, antioxidant and hypolipidemic efficacy of Cynodon dactylon in diabetic rats. Methods The experimental rats were randomly divided into three groups： Group I： control; Group II： Alloxan diabetic, untreated; and Group III： Alloxan diabetic treated with ethanolic extract of C. dactylon leaves （450 mg/kg bw）. Experimental diabetes was induced by alloxan in a single dose of 150 mg/kg bw. Results A Significant diminution of fasting blood sugar level was observed and also significant increase in HDL and decrease （P0.05） in cholesterol, triglyceride, LDL and VLDL were observed after 15 days of treatment. The investigation also revealed, the activities of AST, ALT, ALP, AP, LDH, and CPK （P0.05） were decreased in the extract‐supplemented group. The significant decrease in protein content and SOD, CAT, GPx, and GSH （P0.05） activity and increase in LPO in plasma were found to be ameliorated after treatment. Conclusion Our result supports the fact that administration of extract of C. dactylon leave is able to reduce hyperglycemia and hyperlipidemia risk and also reduced the oxidative stress in diabetic rats.

Micromorphology of Leaf Epidermal Cells of Different Species of Cynodon dactylon in Pastoral Soil

To identify suitable grass species for growth in the Jianghan Plain,the micromorphologies of the upper and lower epidermis of the leaves of 14 bermudagrass varieties of Cynodon dactylon were investigated,and the number,length,and width of long and short cells and stomata were measured.The results showed that the anticlinal wall of epidermal cells looked like waves and the stoma was distributed in the upper and lower epidermis.However,the various indicators of the leaf epidermis of different species of Cd were significantly different.The length and width of long cells and the length of short cells of Cd Mohawk,Cd Suncity,and wild type Cd were relatively large,which may improve their ability to adapt to the pastoral soil and make them suitable for the rainy environment of the Jianghan Plain.On the contrary,the results of all indicators of Cd Xinnong 1,Cd hulled,and Cd unhulled ranked at the bottom,which was not suitable for pastoral soil habitats,while the wild type Cd could adapt to both the pastoral soil and the vegetation concrete habitat.Moreover,the long cells and short cells of Cd Kashi were tightly arranged,and the stoma in Cd Pyramid and Cd hulled were more dense,which may improve their ability to adapt to an arid environment.

氮沉降对城市绿地植物及土壤养分的影响初探——以果岭草(Cynodon dactylon)为例

大气氮沉降是近年来全球变化研究的焦点问题之一,大量而持续的氮沉降对陆地生态系统造成了广泛的影响,但关于氮沉降对城市绿地生态系统的影响及其机制仍然缺少足够的研究。通过模拟氮沉降控制试验,以NH_4NO_3作为外加氮源,设置了N0、N1、N2和N3(分别相当于氮沉降0、5、10、15 g·m^(-2)·a^(-1))4个不同处理,历时12个月,探讨不同程度氮沉降增加对典型城市绿化物种果岭草(Cynodon dactylon)生长状况及土壤化学性质的影响。研究结果表明:(1)氮沉降量为5 g·m^(-2)·a^(-1)时,果岭草地上、地下生物量以及植株密度最大;氮沉降量为10 g·m^(-2)·a^(-1)时,株高最高;根冠比随着施氮量的增加呈减小趋势;适量氮沉降处理有利于植株的生长以及生物量的积累;同时,降水的季节变化可能影响植物对氮的吸收利用;(2)城市绿地土壤pH值随施氮量的增加呈减少趋势,低度适量的氮沉降作用于城市碱性土壤可以中和土壤酸碱度,调节土壤pH值;(3)施氮处理使得城市绿地土壤中的有效氮含量和城市绿地生产力得到一定程度提高。本研究结果证明氮沉降将对城市绿地植物及土壤理化性质产生持续的影响,同时一定程度的氮沉降对城市绿地植物生产力的提高具有促进作用。

Anti-chikungunya activity of luteolin and apigenin rich fraction from Cynodon dactylon

Objective:To obtain Iuteolin and apigenin rich fraction from the ethanolic extract of Cynodon dactylon(L.)(C.dactylon) Pers and evaluate the fraction's cytotoxicity and anti-Chikungunya potential using Vero cells.Methods:The ethanolic extract of C.dactylon was subjected to silica gel column chromatography to obtain anti-chikungunya virus(CHIKV) fraction.Reverse phase-HPLC and GC-MS studies were carried out to identily the major phytochemicals in the fraction using phylochemical standards.Cytotoxicity and the potential of the fraction against CHIKV were evaluated in vitro using Vero cells.Reduction in viral replication was assessed by reverse transcriptase-polymerase chain reaction(RT-PCR) after treating the viral infected Vero cells with the fraction.Results:Reverse Phase-HPLC and GC-MS studies confirmed the presence of flavonoids,luteolin and apigenin as major phytochemicals in the anti-CHIKV ethanolic fraction of C.dactylon- The fraction was found to exhibit potent viral inhibitory activity(about 98%) at the concentration of 50 μg/mL as observed by reduction in cytopathic effect,and the cytotoxic concentration of the fraction was found to be 250 μg/mL.RT-PCR analyses indicated that the reduction in viral mRNA synthesis in fraction treated infected cells was much higher than the viral infected control cells.Conclusions:Luteolin and apigenin rich ethanolic fraction from C.dactylon can be utilized as a potential therapeutic agent against CHIKV infection as the fraction does not show cytotoxicity while inhibiting the virus.

Cynodon dactylon extract ameliorates cognitive functions and cerebellar oxidative stress in whole body irradiated mice

Objective: To explore the effect of hydroalcoholic extract of Cynodon dactylon on the whole body radiation-induced oxidative status of the cerebellum and cognitive impairments in mice. Methods: Swiss albino mice were randomly divided into the control group, radiation control group, low dose and high dose Cynodon dactylon extract treated groups and pre-treated with Cynodon dactylon extract before irradiation. Cynodon dactylon extract was administered for 7 d daily in low dose(0.25 g/kg) and high dose(1 g/kg). On day 7, mice were irradiated with a sublethal dose of 5 Gy gamma rays. Motor coordination was assessed by elevated rotarod test and spatial memory was studied by water maze test. Subsequently, biochemical markers(glutathione, lipid peroxidation and nitric oxide levels) in the cerebellum were evaluated. Results: The gamma irradiated group showed significant impairment in motor coordination and spatial memory compared to normal mice. Mice treated by Cynodon dactylon extract prior to gamma radiation showed good improvement in both paradigms compared to the radiation control group. Moreover, glutathione level was increased, while lipid peroxidation and nitric oxide levels were significantly reduced in mice receiving low dose and high dose of Cynodon dactylon extract compared to the radiation control group. Conclusions: The present study suggests the neuroprotective role of Cynodon dactylon against radiation-induced cognitive impairment and oxidative stress on the cerebellum of mice.

Antidiabetic and antidiarrhoeal potentials of ethanolic extracts of aerial parts of Cynodon dactylon Pers

Objective: To explore the antidiabetic and the antidiarrhoeal effects of ethanolic extracts of Cynodon dactylon Pers. aerial parts(EECA) in Wistar rats.Methods: To assess the antidiabetic activity of EECA, oral glucose tolerance test(OGTT) model and alloxan induced diabetic test(AIDT) model were performed. The EECA was used at the doses of 2 g/kg, 1 g/kg and 500 mg/kg body weight in OGTT model and 1.5 g/kg was used for AIDT model. Castor oil-induced diarrhoeal model and gastrointestinal motility test with barium sulphate milk model were performed for evaluating the antidiarrhoeal effects at doses of 1 g/kg, 750 mg/kg respectively.Results: The dose 2 g/kg in OGTT and 1.5 g/kg in AIDT model blood glucose levels decreased significantly(P < 0.01) in Wistar rats that showed antidiabetic effect of EECA. After administration of EECA at the dose of 1 g/kg, the extract showed significant(P < 0.05) antidiarrhoeal activity in castor oil-induced diarrhoeal model. The results were also significant(P < 0.01) in barium sulphate milk model for the same dose by using above mentioned animals.Conclusions: It is concluded that EECA contains both antidiabetic and the antidiarrhoeal properties.

中国狗牙根〔Cynodondactylon(L.)Pers.〕耐寒性及其变化规律

将49份具有代表性的我国狗牙根〔Cynodondactylon(L.)Pers.〕种源的离体叶片进行模拟低温处理,用电导法测其电导率,将电导率拟合Logistic方程,计算出狗牙根各种源叶片的半致死温度(LT50)。回归分析的结果表明:各种源的LT50与其所在的经纬度呈显著的线性关系,线性回归方程分别为Y=-31.3797+0.1478X和Y=-10.7982-0.1420X。依据LT50的变化,可将这49份狗牙根种源分为3大类,即低温敏感型(LT50≥-10℃)、过渡型(-18℃<LT50<-10℃)和耐寒型(LT50≤-18℃),3类狗牙根的分布具有一定的规律性。对狗牙根的耐寒机理也进行了探讨。

Enhanced Cadmium Accumulation in Transgenic Tobacco Expressing the Phytochelatin Synthase Gene of Cynodon dactylon L

Bermudagrass （Cynodon dactylon L. cv. Goldensun） is highly resistant to and accumulates large amounts of cadmium （Cd）. A phytochelatin synthase （PCS） cDNA （CdPCS1） was isolated from this grass by rapid amplification of cDNA ends. The putative CdPCS1 protein shared a high homology with PCS from other plants, with 79% homology at the N-terminal and 47% homology at the C-terminah However, 16 Cys residues were found at the C-terminal of CdPCS1, and among these residues, three positions were different from other PCS proteins. Semiquantitative reverse transcription-polymerase chain reaction analysis showed that Cd stress induced CdPCS1 expression in both roots and leaves in Bermudagrass. We verified that CdPCS1 plays an important role in Cd tolerance in yeast cells by expressing the gene in ABDE1, a Cdsensitive mutant. CdPCS1 was then introduced into tobacco plants. The phytochelatin level in some transgenic tobacco lines increased 3.88-fold more than in wild type plants and Cd accumulation in these transgenic plants was enhanced 3.21-fold accordingly. The results suggested that CdPCS1 could be used as a gene element for phytoremediation in the future.

Phytochemical analysis and antifertility potential of Cynodon dactylon in female Wistar rats:A herbal approach towards contraception

Objective:The objective of the present study was to evaluate the antifertility activity of ether(ErCD),chloroform(CeCD)and ethyl alcohol(EyCD)extracts of the whole plant of Cynodon dactylon in female Wistar albino rats.Methods:Acute oral toxicity and an antifertility study were performed in female Wistar rats with two dose levels(200 and 400 mg/kg,orally)of EyCD.The estrogenic and progestogenic effects of EyCD were further observed by administering it to immature Wistar rats by investigations of vaginal cornification,hormonal level,uterus weight,biochemical parameters,histopathology of the uterus and deciduoma formation,respectively.Isolation of EyCD was carried out by Flash Chromatography and isolated fraction was estimated by HPLC.Results:No toxicity with any of the extract was found up to the dose of 2000 mg/kg body weight.EyCD treated rats exhibited maximum reduction in pregnancy(83.33%).Estimation of EyCD on vaginal cornification,estrogen-induced uterotrophic assay and deciduoma model demonstrated vaginal cornification,significant(P<0.01)increase in uterine weight and uterine proliferation in histopathology and reduced deciduoma formation respectively.Hormonal and biochemical parameters confirmed the above findings indicating estrogenic potential and antiprogestogenic potential of EyCD that might be attributed to the presence of phytoestrogen(apigenin)in EyCD.Conclusion:The results suggested that extracts of C.dactylon possess significant antifertility activity,which is consistent with the literature reported in folk medicine of this plant in fertility regulation.

NaCl胁迫下pH值和氮素形态对狗牙根生长及钠钾离子调控的影响

以狗牙根〔Cynodon dactylon(Linn.)Pers.〕品种‘阳江’(‘Yangjiang’)为实验材料、2-(N-吗啡啉)乙磺酸(MES)为pH缓冲剂,采用水培法研究NaCl胁迫下pH值和氮素形态(铵态氮和硝态氮)对狗牙根生长和钠钾离子调控的影响。结果表明:处理1周后,若不添加MES,铵态氮处理组培养液的pH值下降到pH 4.0左右,而硝态氮处理组培养液的pH值则上升到pH 9.0左右;添加20 mmol·L^(-1)MES的铵态氮处理组培养液的pH值也下降到pH 4.0左右,而硝态氮处理组培养液的pH值则接近pH 7.0。与0 mmol·L^(-1)NaCl处理组相比,300 mmol·L^(-1)NaCl处理组狗牙根的枝条长度和枝条干质量显著(P<0.05)下降,而根长度、根干质量、根和叶中Na^(+)含量和Na^(+)/K^(+)比、钠钾选择性转运系数、叶Na^(+)和K^(+)的分泌量及分泌物Na^(+)/K^(+)比总体上显著升高。300 mmol·L^(-1)NaCl胁迫下,硝态氮处理组狗牙根的枝条长度、根长度、根干质量、根冠比、根中Na^(+)含量总体上显著高于铵态氮处理组,而叶中Na^(+)和K^(+)含量及Na^(+)/K^(+)比、叶Na^(+)和K^(+)的分泌量明显低于铵态氮处理组。300 mmol·L^(-1)NaCl胁迫下,20 mmol·L^(-1)MES处理组狗牙根的多数生长指标显著高于0 mmol·L^(-1)MES处理组,而根和叶中Na^(+)和K^(+)含量及Na^(+)/K^(+)比、钠钾选择性转运系数在0和20 mmol·L^(-1)MES处理组间的差异不显著。三因素方差分析结果表明:3个因子的单一和交互作用对多数生长指标、叶中Na^(+)含量和泌盐量相关指标的影响具有统计学意义。研究结果显示:硝态氮能缓解NaCl胁迫对狗牙根的伤害,而用MES缓冲根际酸碱环境对NaCl胁迫下狗牙根生长有一定的促进作用,因此,施用硝态氮或添加MES均有利于提高狗牙根的抗盐性。

狗牙根覆盖对三峡库区消落带波浪作用力和侵蚀的影响

波浪侵蚀是三峡库区消落带土壤侵蚀的主要类型,已严重威胁到库区经济发展和生态环境构建。植被修复可以实现水土保持和增强消落带稳定性目的,但关于在波浪作用于消落带上坡面时植物覆盖对波压力和孔隙水压力和侵蚀量的影响及关系尚不明确。为此,设置3个波高(4、6和8 cm)、3个坡面条件(裸坡对照、30%狗牙根覆盖和60%狗牙根覆盖),开展模拟波浪试验,分析不同植被盖度对消落带波浪作用力和侵蚀的影响。结果表明:裸坡时,随波高增加,波压力和孔隙水压力分别增加3.80%~48.62%和13.12%~50.44%,侵蚀量增加0.88%~8.08%。存在植被时,对比裸坡,随波高增加,波压力和孔隙水压力分别降低2.98%~220.17%和15.47%~75.64%,侵蚀量则降低29.31%~80.83%。植物可以通过地上部分和地下部分消散波压力和孔隙水压力,从而提高消落带受波浪作用的耐受性,进而有效降低波浪造成的侵蚀量。以上结果加深了在波浪作用于紫色土消落带坡面时狗牙根覆盖与波浪作用力与侵蚀量关系的理解,为库区消落带植被恢复和水土保持提供一定的参考。

铅胁迫下吲哚乙酸对狗牙根铅累积及生理特性的影响

为明确外源生长素对狗牙根在铅(Pb)胁迫下的作用与机制,本研究以Pb耐性植物狗牙根为对象,在盆栽试验条件下,对处于324.4 mg·kg^(-1)土壤Pb胁迫下的狗牙根叶面喷施不同浓度的(0、1、10、100 mg·L^(-1))吲哚乙酸(IAA)与5、10 mg·L^(-1)的生长素极性运输抑制剂(NPA),探究外源IAA对狗牙根的生长、生理特性及Pb积累的影响。结果表明:外源IAA使狗牙根IAA与细胞分裂素(CTK)含量升高,脱落酸(ABA)含量及吲哚乙酸氧化酶(IAAO)活性降低,促进了狗牙根在Pb胁迫下株高、根长、地上和地下部干重的增加。其中,喷施10 mg·L^(-1)IAA效果最好。与对照相比,10 mg·L^(-1)IAA叶面喷施处理使株高、根长及地上与地下部干重分别提高了32.4%、30.1%、32.2%和25.5%,叶绿素a、叶绿素b、胡萝卜素含量分别升高到对照组的1.35、1.36和1.21倍,叶与根中的Ca2+与可溶性蛋白含量显著上升。10 mg·L^(-1)IAA叶面喷施还改善了狗牙根体内的抗氧化指标,表现为丙二醛(MDA)含量相较于对照组显著下降,过氧化物酶(POD)活性显著升高。此外,10 mg·L^(-1)IAA叶面喷施促进了根对Pb的吸收和固定,同时抑制Pb的根-冠转移。但喷施NPA加重了Pb对狗牙根的生长抑制且该生长抑制具有对NPA的剂量依赖效应,10 mg·L^(-1)NPA的抑制效果最强,削弱了狗牙根内源激素对Pb的应激效应、降低了叶绿素荧光参数与光合色素含量、提高了狗牙根地上部分Pb含量、导致MDA含量升高。综合分析表明,本试验条件下狗牙根喷施10 mg·L^(-1)IAA效果最佳,通过增强狗牙根对Pb的激素应激反应、提高光合作用和抗氧化能力改善了植株生长;同时通过提升胞内Ca2+与可溶性蛋白含量抑制了Pb的根冠迁移,从而降低膜脂质过氧化水平,缓解了Pb胁迫下狗牙根的氧化损伤。本研究结果丰富了狗牙根耐Pb机制,并为应用外源IAA缓解植物Pb毒害提供了科学依据。

药用植物狗牙根的化学成分及其抗炎活性研究

综合采用正相、反相硅胶柱色谱、Sephadex LH-20凝胶柱色谱、半制备液相色谱等色谱方法进行化学成分分离纯化,运用核磁共振和质谱等波谱方法鉴定化合物的结构,对药用植物狗牙根[Cynodon dactylon(L.)Pers.]95%乙醇提取物进行化学成分研究,并对其中的黄酮类和蒽醌类进行抗炎活性研究.从狗牙根全草中分离得到16个化合物,分别鉴定为苜蓿素(1)、chrysoeriol(2)、isoliquiritigenin(3)、tricin 4′-O-(threo-β-guaiacyl-(7′′-O-methyl-9′′-O-acetyl)-glyceryl)ether(4)、木犀草素(5)、tricin 4′-O-(erythro-β-guaiacylglyceryl)ether(6)、calquiquelignan D(7)、calquiquelignan E(8)、5,5′-dihydroxy-2′,4′-dim-ethoxyflavone-7-O-β-D-(6′′-O-Zp-coumaroyl)-glucopyranoside(9)、4′-hydroxy-2,3-dihydroflavone-7-β-D-glucopyranoside(10)、tricin 4′-O-(threo-β-guaiacyl-(7′′-O-methyl)-glyceryl)ether(11)、ω-Hydroxyemodin(12)、phomarin(13)、aurantio-obtusin(14)、β-谷甾醇(15)、豆甾醇(16).除化合物5外,其他化合物均为首次从该植物中分离得到,其中化合物2、3和14显示显著抗炎活性,其IC50值分别为2.74、2.35、3.61μmol/L.

狗牙根根系抗拉性能对水淹时长的响应

为明确水淹胁迫下植物根系对水淹时长的响应特征,该研究以三峡库区消落带优势植物狗牙根根系为研究对象,以未水淹为对照,分析不同水淹时长下(0,15,30,60,90,120,150和180 d)狗牙根根重密度、根系活力及抗拉性能的变化规律,明确根系抗拉性能对水淹时长的响应规律。结果表明:随着时间的增加,对照组根重密度和根系活力基本无明显变化,而淹没组根重密度与根系活力均随水淹时长增加呈先急剧减小后缓慢减小的变化规律,水淹初期(15 d)减小量分别占根重密度和根系活力总减小量的65.15%和75.86%。水淹环境会明显降低狗牙根根系抗拉性能,根系最大抗拉力和抗拉强度均随水淹时长的增加而下降,180 d水淹分别造成根系抗拉系数和抗拉强度系数减小了59.46%和59.48%。不同直径根系对水淹的响应程度有所不同,根系最大抗拉力下降程度随其直径的增加而增加,0.6~0.7 mm直径狗牙根根系最大抗拉力下降幅度最大,达7.56 N,抗拉强度下降程度则随根系直径的减小而增加,0.1~0.2 mm直径狗牙根根系抗拉强度下降幅度最大,达36.42MPa。因此,水淹显著降低狗牙根根重密度、根系活力和抗拉性能(P<0.05),根系活力能够较好的解释其抗拉性能的变化。研究结果对进一步探究水淹胁迫下根系固土机理具有重要科学意义。

‘桂南’狗牙根的选育

中国野生狗牙根(Cynodon dactylon)种质资源非常丰富,但育成品种较少。为选育更多优良狗牙根新品种以供草坪建植应用,中国热带农业科学院热带作物品种资源研究所自2000年起开展了狗牙根新品种的选育研究,从国内外收集的狗牙根种质资源中筛选出坪用性状优良的种质,经过连续多次单株选择和扩繁、坪用价值系统评价、品种比较试验、区域试验及生产性试验,选育出坪用性状优良的狗牙根新品种‘桂南’狗牙根,于2020年审定通过。‘桂南’狗牙根具有质地细腻、草坪密度大、均一性好、绿色期长、成坪速度快等特点。适于在我国长江中下游及以南地区作为景观绿化和水土保持草坪建植。本研究对‘桂南’狗牙根的选育过程、品种特征特性、栽培技术要点等进行总结,为‘桂南’狗牙根新品种的推广利用提供科学依据。

不同抗旱性狗牙根地上地下表型特征及内源激素对干旱胁迫的响应

为了研究干旱胁迫对不同抗旱性狗牙根形态建成及内源激素的影响,明确不同抗旱性狗牙根响应干旱的表型特征及内源激素差异,探讨狗牙根表型特征与内源激素的相关性,丰富狗牙根抗旱理论以及生产实践中利用外源激素调控其抗旱性提供参考。采用PVC管栽植狗牙根,控制不同水分达到预设梯度维持10 d,对其叶、根相对含水量、相对电导率、内源激素[吲哚乙酸(IAA)、脱落酸(ABA)、赤霉素(GA_(3))、玉米素核苷(ZR)、油菜素内酯(Br)]、叶部特征(叶长、叶宽、叶面积)、根部特征(总根长、根表面积、根体积、根平均直径、根干重、最长根长、根系活力)进行测定,分析干旱胁迫下不同抗旱性狗牙根叶、根内源激素比例变化及表型特征与激素的相关性。结果表明,随着干旱胁迫加剧,显著降低了2类狗牙根的叶长、叶宽、叶面积、根平均直径,促进了根部生长发育;提高了叶、根ABA含量,降低了IAA、GA_(3)、ZR、Br含量,且IAA/ABA、GA_(3)/IAA与叶部指标、根部指标呈相反相关性,这均从侧面表明狗牙根叶、根在干旱胁迫下选择了相反的生存策略,即促进地下部生长,抑制地上部生长。抗旱狗牙根通过本身具有较大叶面积或者更发达的根系系统,以及相同胁迫下较高的ZR/ABA、GA_(3)/ABA、IAA/ABA、Br/ABA来维持一定的生长以及减缓衰老来更好地适应干旱胁迫环境。

三峡消落带不同坡度狗牙根及实生土壤生态化学计量特征

三峡库区消落带反季节水位波动驱使下植物的养分适应策略和内稳态特征研究对消落带植被恢复及生态功能调控有重要意义。然而,三峡消落带范围广、地形复杂,不同生境下植物适应特征仍存在不确定性。本研究以三峡消落带广泛分布的优势植物狗牙根为研究对象,选取28个地形差异较大的样地进行采样分析,重点探讨不同坡度(0—5°、5—10°、10—15°、15—20°、>20°)狗牙根及其实生土壤生态化学计量特征的变异关系,揭示坡度对狗牙根养分适应及内稳态的影响机制。结果表明:(1)坡度对狗牙根实生土壤的养分及化学计量特征具有显著影响,土壤有机碳(SOC)、全氮(STN)、速效氮(SAN)、全磷(STP)、速效磷(SAP)含量均随坡度增加而降低,<10°的缓坡消落带土壤养分显著高于10°以上的样地;土壤碳氮比(C∶N)、碳磷比(C∶P)均随坡度增加而降低,而氮磷比(N∶P)比相对稳定,表明坡度增大,土壤营养物的流失具有同步性,且流失速度较有机碳慢;(2)随坡度增加,狗牙根各营养器官C含量呈增加趋势,而氮(N)、磷(P)则呈降低趋势,且坡度变化改变了狗牙根各营养器官间的养分分配;植物根、茎C∶N、C∶P随坡度增加而增加,N∶P随坡度增加而降低,而叶片均没有明显变化,表明在坡度改变了土壤养分供应水平的情况下,狗牙根优先稳定其叶片化学计量比以提高适应能力;(3)坡度与土壤中SOC、STN、SAN含量呈现显著负相关,而土壤STN与狗牙根植物养分及化学计量特征均有显著相关关系,由此可见,坡度变化导致土壤氮素流失增加是影响狗牙根生态化学计量特征分异的主要机制;(4)狗牙根与实生土壤的碳氮磷元素内稳性整体表现为C>P>N,化学计量比内稳性表现为C∶P>C∶N>N∶P,随着坡度增加,狗牙根N、P的内稳性呈增强趋势,而C∶N、N∶P呈显著降低,表明坡度变化导致狗牙根形成了不同的适生策略。研究表明,在三峡库区复杂的地形条件下,狗牙根能有效维持体内化学计量平衡以响应不同的坡度条件,并且内稳性较好,是三峡库区消落带植被恢复与保护的优势植物物种。

不同抗旱性狗牙根种质的抗旱生理响应差异分析

为揭示狗牙根抗旱生理机制,筛选不同干旱胁迫下影响其抗旱性的关键指标,探明不同抗旱性狗牙根对干旱胁迫的响应差异,以2种类型不同抗旱性狗牙根(Cynodon dactylon)种质(敏旱种质:C10和C32;抗旱种质:C118和C138)为供试材料,研究其在渐进式缓慢干旱胁迫下叶片相对含水量、相对电导率、光合色素含量、抗氧化酶活性及渗调物质含量等的变化规律。结果表明,随着土壤含水量降低、干旱胁迫加剧,供试狗牙根叶片的相对含水量不断下降,相对电导率及丙二醛、可溶性蛋白、脯氨酸含量呈升高趋势,光合色素含量及3种抗氧化酶活性呈现先升后降趋势。与敏旱材料相比,抗旱狗牙根种质在中、重度干旱胁迫下能够维持较高的抗氧化酶活性,积累更多的脯氨酸和可溶性蛋白,导致其相对电导率及丙二醛含量增加缓慢。即使同为抗旱类型,不同种质对干旱的响应机制也存在差异,C118具有较高的叶绿素含量,而C138维持较高的类胡萝卜素含量。灰色关联分析表明,中度干旱下,相对电导率、类胡萝卜素含量及超氧化物歧化酶活性受狗牙根的抗旱性影响较大;而重度干旱下,脯氨酸和可溶性蛋白含量与抗旱性的关联度更高。以上结果明确了不同抗旱性狗牙根种质的干旱生理响应机制,为选育耐旱草种及节水技术奠定基础。

狗牙根叶与根氮代谢对不同干旱胁迫的响应机制

干旱会影响植物氮代谢过程,从而制约其生长及品质。为了明确狗牙根在干旱胁迫下其叶与根氮代谢指标的变化,探讨狗牙根叶与根氮代谢对不同干旱胁迫的响应机制,筛选关键抗旱氮代谢指标,丰富狗牙根抗旱氮代谢理论,本试验将不同抗旱性狗牙根在不同干旱梯度处理下培养10 d,测定其叶及根有机氮化物(脯氨酸、可溶性蛋白、游离氨基酸)、无机氮化物(全氮、硝态氮、铵态氮)、氮代谢相关酶活性(硝酸还原酶、亚硝酸还原酶、谷氨酰胺合成酶、谷氨酸合成酶)等生理指标。结果表明:随着干旱胁迫加剧,各供试材料的叶及根全氮降低,有机氮化物增加,叶片硝态氮先降后升,根系硝态氮降低,叶、根铵态氮、氮代谢酶则呈先增后降趋势。抗旱材料在胁迫下因具有较高的氮代谢酶活性及无机氮化物含量,加速了氮代谢进程,致使抗旱材料叶、根的有机氮化物含量快速上升且显著高于敏旱材料。干旱下狗牙根通过对根系吸收的氮素进行转运再分配、同化,与其地上部分共同抵御干旱。冗余分析表明谷氨酸合成酶(GOGAT),谷氨酰胺合成酶(GS)与中度胁迫时抗旱材料叶、根的相关性较强,脯氨酸、游离氨基酸、可溶性蛋白与重度胁迫时抗旱材料有较强的相关性。通径分析得根系可溶性蛋白(决策系数为-0.739)、叶片(0.530)与根系游离氨基酸(0.498)与干旱下狗牙根抗旱性关联度高。本试验结果可丰富、补充狗牙根抗旱氮代谢响应研究,也可为其抗旱资源选育提供参考。