刈割与水淹对三峡库区消落带优势物种狗牙根存活及恢复生长的影响

三峡库区消落带蓄水期间植物腐烂分解释放的养分会增加库区的富营养化风险,水淹前刈割是消减水体污染风险的有效方式之一,但刈割对库区消落带适生植物恢复生长的影响尚不清楚。为探究三峡库区消落带适生植物对水淹和刈割胁迫的耐受情况,选取消落带适生植物狗牙根为研究对象,设置对照(CK)、浅淹(SF)、浅淹-对照(SFK)、全淹(TF)、全淹-对照(TFK)5种水淹处理和不刈割(NC)、留茬30 cm(S30)、留茬20 cm(S20)、留茬10 cm(S10)4个刈割强度,研究不同水淹和刈割处理对狗牙根存活、生长和光合特征的影响。结果表明：(1)狗牙根在不同水淹和刈割处理下整体可保持较高的存活率(≥83.3%)。(2)刈割和水淹处理对狗牙根的形态生长和生物量分配均存在显著影响。与对照相比,SF组狗牙根的根长、基径和生物量显著降低,TF组狗牙根的株高、基径、根长和生物量显著降低,但是SFK和TFK处理(脱离水淹胁迫)相比SF和TF组却显著增长。(3)刈割和水淹处理对狗牙根的光合速率影响显著,其中SF组狗牙根的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Ci)显著降低,TF处理叶片全部凋落无光合作用...     

Physiological,morphological, and growth responses ofPlatanus occidentalis seedlings to flooding

Summary Flooding ofPlatanus occidentalis L. seedlings for up to 40 days induced several changes including early stomatal closure, greatly accelerated ethylene production by stems, formation of hypertrophied lenticels and adventitious roots on submerged portions of stems, and marked growth inhibition. Poor adaptation ofPlatanus occidentalis seedlings to soil inundation was shown in stomatal closure during the entire flooding period, inhibition of root elongation and branching, and death of roots. Some adaptation to flooding was indicated by (1) production of hypertrophied lenticels which may assist in exchange of dissolved gases in flood water and in release of toxic compounds, and (2) production of adventitious roots on stems which may increase absorption of water. These adaptations appeared to be associated with greatly stimulated ethylene production in stems of flooded plants. The greater reduction of root growth over shoot growth in flooded seedlings will result in decreased drought tolerance after the flood waters recede. The generally low tolerance to flooding of seedlings of species that are widely rated as highly flood tolerant is emphasized.     

前期水淹对牛鞭草后期干旱胁迫光合生理响应的影响

水淹和干旱是限制植物生长的两种主要环境因子。三峡库区消落带由于其特殊的地形条件和人工水文节律,呈现以年度为周期的“水淹-落干”交替变化的水文变动特征,在消落带生长的植物因此受到水淹和干旱交替胁迫的双重影响。为了探究库区蓄水对消落带植被干旱耐受性的影响,以当年生牛鞭草扦插苗为试验对象,设置对照组(CK)、表土水淹组(SF)、全淹组(TF)、对照-干旱组(CD)、表土水淹-干旱组(SFD)、全淹-干旱组(TFD)6个处理组,研究不同水分处理对牛鞭草光合特性的影响。结果表明:(1)水淹和干旱胁迫均对牛鞭草光合特性造成显著影响;(2)水淹胁迫阶段,与CK组相比,牛鞭草SF和TF组净光合速率、气孔限制值和水分利用效率显著下降,胞间CO_2浓度显著上升;(3)干旱胁迫阶段,牛鞭草CD和SFD组净光合速率、气孔导度、胞间CO_2浓度和蒸腾速率等光合参数显著低于CK组,TFD组净光合速率、气孔导度、胞间CO_2浓度和蒸腾速率等指标与CK组无显著差异;(4)复水阶段,各处理组净光合速率、气孔导度、胞间CO_2浓度和蒸腾速率等指标均与CK组无显著差异。研究表明,前期水淹并未增加牛鞭草对后期干旱胁迫的敏感性,牛鞭草对水淹和干旱胁迫均具有较好的耐受性,有助于牛鞭草对库区消落带生境变化的适应性。     

Flooding tolerance of Tabebuia cassinoides: Metabolic, morphological and growth responses

Tabebuia cassinoides (Lam.) DC (Bignoniaceae) is a tree species that occurs in swampy areas of the coastal “restinga” in SE Brazil (a coastal sandy plains scrub and forest formation). To elucidate possible adaptive strategies that enable this species to occupy areas subjected to seasonal or perennial waterlogging, metabolic, morphological and growth responses of plants under flooding conditions were studied. The root system of T. cassinoides plants presented elevated amounts of ethanol (10.6 μmol g⁻¹ fresh wt) only in the first 5 d of soil water saturation. The two-fold increase in ethanol production under flooding was corroborated by an increase in ADH activity in the same period. Lactic acid concentrations did not change significantly during four months of flooding treatment. The decrease of alcoholic fermentation under hypoxia was associated with the appearing of new roots. The induction of aerenchyma formation in roots developed under flooding conditions, allowed oxygen transport from the shoot to these organs, thus maintaining an aerobic respiration. We conclude that this characteristic and the capacity to oxidize the rhizosphere are probably responsible for the survival and growth of plants while flooded and for their success in an environment, which restricts the presence of the majority of competing tree species.     

Germination responses of Diplotaxis harra to temperature and salinity

Diplotaxis harra (Forssk.) Boiss, an annual herb in the family of Brassicaceae, is widely distributed in many sandy and gypseous areas in southern Tunisia. Laboratory experiments were carried out to assess the effects of temperature and salinity on seed germination and recovery responses after seed transfer to distilled water. The germination responses of the seeds in complete darkness were determined over a wide range of temperatures (5, 10, 15, 20, 25 and 30 °C) and salinities (0, 50, 100, 150 and 200 mM NaCl). Germination was inhibited by either an increase or decrease in temperature from the optimal temperature (15 °C). Highest germination percentages were obtained under non-saline conditions and an increase in NaCl concentrations progressively inhibited seed germination. Rate of germination decreased with an increase in salinity at all temperatures but comparatively higher rates were obtained at 15 °C. Salt stress decreased both the percentage and the rate of germination. An interaction between salinity and temperature yielded no germination at 200 mM NaCl. Seeds were transferred from salt solution to distilled water after 20 days, and those from low salinities recovered at all temperatures. At NaCl concentration of 200 mM, the recovery of germination was completely inhibited.     

黄果龙葵幼苗对镉胁迫的生理生长响应

黄果龙葵（Solanum diphyllum）是茄科的小灌木,已有的研究对黄果龙葵的镉（Cd）响应知之甚少。该研究采用水培控制试验,在160μmol·L^-1 Cd胁迫下,测定了黄果龙葵幼苗在不同胁迫时间点（0、0.5、1、3、7、19 d）的生长、耐性系数（TI）、Cd富集特性、超氧化物歧化酶（SOD）活性、渗透调节物质和光合色素等指标。结果表明：（1）在胁迫0～3 d时Cd对黄果龙葵幼苗的生长无显著影响。胁迫3～19 d时表现为明显抑制,且毒害随胁迫时间延长而加重。与对照组相比,Cd胁迫使黄果龙葵幼苗的生物量降低13.28%～62.40%。（2）黄果龙葵幼苗的最大Cd积累量为60.14μg·plant^-1,其地上部份的Cd积累量占植株的15.46%～35.24%。（3）丙二醛（MDA）含量呈上升趋势,根的MDA含量最大增幅为对照组的5.25倍。SOD活性、游离脯氨酸、可溶性糖、叶绿素a、叶绿素b和类胡萝卜素的含量均呈先升后降的趋势。（4）黄果龙葵幼苗的耐性系数TI随胁迫时间延长而降低,最小值为0.64。综上结果认为,黄果龙葵是一种潜在的Cd...     

秋华柳和枫杨幼苗对镉的积累和耐受性

以秋华柳和枫杨当年实生幼苗为研究对象,采用向土壤添加外源镉(CdCl₂ · 2.5H₂O)的形式设置了0(对照组)、10 、20 、50、100 mg/kg 5个处理,研究了镉胁迫下秋华柳和枫杨幼苗的生长、生物量变化和根茎叶镉含量,并评价了两树种的耐性指数(Ti)、转移系数(Tf)和生物富集系数(BCF)。结果表明:(1)在镉含量为10 mg/kg时,秋华柳和枫杨幼苗基于生长和生物量参数的耐性指数(Ti)分别为91.72和91.62,与对照组相比无显著变化,其余各组(20、50、100 mg/kg)则显著低于对照植株(P<0.05);(2) 土壤镉浓度小于20mg/kg时,秋华柳植株茎、叶镉积累量分别高达61.73 mg/kg、163.04 mg/kg,根镉积累量为91.05 mg/kg;枫杨植株茎、叶镉积累量最高分别为7.9 mg/kg、5.25 mg/kg,仅为秋华柳茎、叶的12.8%和3.2%,根镉积累量高达190.68 mg/kg;(3) 除对照外,秋华柳幼苗各部分镉含量为叶＞根＞茎,转移系数(Tf)介于0.789-1.513之间,枫杨幼苗各部分镉含量为根＞茎＞叶,转移系数(Tf)介于0.037-0.044之间,远远小于秋华柳Tf;(4)秋华柳和枫杨幼苗在土壤镉浓度为10 mg/kg时具有很高的生长适应性和耐性,秋华柳根吸收的镉向地上部分转移能力、地上部分积累镉的能力都远远大于枫杨,生物富集系数(BCF)进一步证实了这一特性。研究证明,秋华柳植株具有很高的镉耐性、镉转移能力及地上部分积累镉的能力,适合于镉污染严重区域的植物修复。     

不同土壤水盐条件下多枝柽柳(Tamarix ramosissima)对胡杨(Populus euphratica)幼苗的影响

目前胡杨更新困难,种群处于退化阶段,而与其生态位高度重叠的多枝柽柳却在扩张。为探讨多枝柽柳对胡杨生长的影响,本研究设置了3个水平的水分、盐分梯度,对胡杨进行了单种和混种的盆栽控制实验,通过测定胡杨幼苗的生长和存活状况,分析不同水、盐梯度下多枝柽柳如何影响胡杨生长。结果表明：（1）多枝柽柳伴生降低当年生胡杨幼苗的存活率,随着水分条件改善,胡杨存活率提高,而盐分对存活率没有显著的影响。（2）水分、盐分和伴生模式几个因子对胡杨的生长特征的影响存在显著的交互作用（P<0.05）。各水盐条件下,多枝柽柳会不同程度降低胡杨幼苗的株高、主根长和地上地下生物量,而根冠比增大。混种条件下,胡杨幼苗对水盐的响应更为敏感。（3）相对竞争强度对水盐环境有明显的响应（P<0.05）,随水分条件改善,地上、地下相对竞争强度降低。多枝柽柳对胡杨的生长产生不良影响的机制是通过快速消耗土壤的水分,从而导致胡杨幼苗水分亏缺。土壤水分条件是胡杨和多枝柽柳幼苗共存的关键因素,在水分供给不足的情况下,对水分偏好的差异导致胡杨无法通过实生苗进行有效的更新从而加剧胡杨种群的衰退,而多枝柽柳更为耐旱的特性使其逐步占据河岸的生境。我们的研究结果强调了两个树种对环境因子的适应性差异决定了河岸带植被发育过程中植物-土壤的相互作用导致胡杨在演替过程中表现出的衰退现象。     

不同光环境对海南龙血树幼苗表型可塑性及生存策略的影响

为了解光照对海南龙血树(Dracaena cambodiana)幼苗生长的影响,研究了不同光照环境下海南龙血树幼苗形态、生理特性和生物量分配的变化,并分析了其生态适应性。结果表明,海南龙血树幼苗的形态、生理和生物量分配指标在不同光照强度间存在显著差异,各指标的可塑性指数为0.08~0.86,其中根茎叶及总生物量的可塑性指数普遍较高(0.67~0.86),表明海南龙血树幼苗有较好的光照适应性,其策略主要是通过调整根茎叶生物量的分配来适应光照的变化。随着光照强度的降低,海南龙血树幼苗的比叶面积、叶根比呈现显著增大趋势,表明幼苗可通过增加单株叶面积比例,扩大光合作用面积,有效调节自身生物量配置。37.3%自然光照(L2)是海南龙血树幼苗生长的最佳光照强度。现存海南龙血树生境改变,生境缺少林荫以致光照强度过大,不利于幼苗根系生长,难以度过干旱季节,可能是海南龙血树自然更新失败的重要原因之一。     

长期水陆周期性变化条件下香根草形态性状和生物量分配的可塑性

香根草是能够长期适应三峡水库消落带生境的少数物种之一。虽然国内对香根草的引种栽培和研究已有几十年的历史,但是对香根草在三峡库区消落带长期水陆周期性变化条件下的生态适应对策还知之甚少。为此,以2008年在三峡水库巫山段消落带建立的香根草引种栽培试验示范基地为研究平台,在2016年对海拔166—169 m、169—172 m和172—175 m区段的香根草的形态性状、生物量及其分配特征进行了研究。结果表明：(1)海拔166—169 m香根草的分蘖株数、平均株高、节间数量、节间长度、叶片数/分蘖株、叶片数/丛、叶片长等各指标值均低于海拔169—172 m和海拔172—175 m,海拔166—169 m与其它海拔区段的节间数量差异显著(P<0.05);(2)海拔166—169 m香根草的根系数量最少,但根系长度最长;(3)海拔166—169 m无节间的香根草株数最多,且与海拔172—175 m和海拔169—172 m差异显著(P<0.05);(4)不同海拔区段香根草的总生物量大小表现为海拔172—175 m>海拔169—172 m>海拔166—169 m,且海拔166—...     

三峡库区消落带野生狗牙根对水淹适生性的转录组分析

为探究狗牙根对水淹环境的适生性机制,取长势一致的狗牙根分为未水淹对照组(A1)和30 cm沉水处理组(A2),A2水淹15 d后两组同时采样,提取样本总RNA作转录组测序。A1和A2测序数据经de novo组装分别获得128031和83363条高质量Unigene;A1和A2对比发现28844条差异表达基因(differentially expressed genes, DEGs),其中11858条DEGs上调表达,16986条DEGs下调表达;功能注释显示,这些DEGs主要集中在转录、翻译、碳水化合物代谢和环境适应等途径;信号通路富集显示,包括植物对病原体的防御、物质代谢、光合作用、形态发育和抗氧化等过程的103个信号通路与狗牙根对水淹生境的适生性有关;随机挑选4个DEGs作qRT-PCR分析,荧光定量结果与测序数据基本一致,说明基于转录组分析DEGs的表达情况较为可靠。该工作或可为进一步挖掘与狗牙根水淹适生性相关的调控基因和功能基因提供基础。     

Leaf gas exchange, chlorophyll fluorescence and growth responses of Genipa americana seedlings to soil flooding

Effects of soil flooding on photosynthesis and growth of Genipa americana L. seedlings, a neotropical fruit-tree species used in gallery forest restoration programs, were studied under glasshouse conditions. Despite the high survival rate and wide distribution in flood-prone habitats of the neotropics, previous studies demonstrated that growth of G. americana is reduced under soil flooding. Using leaf gas exchange and chlorophyll fluorescence measurements, we tested the hypothesis that stomatal limitation of photosynthesis is the main factor that reduces carbon uptake and growth rates of G. americana seedlings. Throughout a 63-day flooding period, the survival rates were 100%. The maximum values of the net photosynthetic rate (A) and stomatal conductance to water vapor (g_s) of control seedlings were 9.86 μmol CO₂ m⁻² s⁻¹ and 0.525 mol H₂O m⁻² s⁻¹, respectively. The earliest effects of flooding were significant decreases in g_s and A, development of hypertrophied lenticels and decrease in the dry weight of roots. A strong effect of the leaf-to-air vapor pressure deficit (LAVPD) on g_s and A were observed that was enhanced under flooded conditions. Between 14 and 63 days after flooding, significant reductions in g_s (31.7% of control) and A (52.9% of control) were observed followed by significant increments in non-photochemical quenching (q_N) (187.5% of control). During the same period, there were no differences among treatments for the ratio between variable to initial fluorescence (F_v/F₀), the maximum quantum efficiency of the photosystem II (F_v/F_m) and photochemical quenching (q_P), indicating that there was no damage to the photosynthetic apparatus. Based on the results, we conclude that decreases in stomatal opening and stomatal limitation of photosynthesis, followed by decrease in individual leaf area are the main causes of reductions in carbon uptake and whole plant biomass of flooded seedlings.     

中华蚊母树在干旱-水淹交叉胁迫下形态和活性氧代谢的适应机制

为阐明中华蚊母树(Distylium chinense)在消落带干旱-水淹交叉胁迫下的形态和活性氧(ROS)代谢适应机制,通过控制实验模拟了三峡水库消落带的水文节律,研究了干旱-水淹交叉胁迫及恢复过程施加不同外源物质对中华蚊母树形态学和ROS清除的变化。结果表明：(1)前期干旱胁迫增强了中华蚊母树对后期水淹胁迫的适应,主要表现在叶片脱落、大量不定根的形成及茎基部膨大等形态学的变化;(2)干旱或水淹单一胁迫下,中华蚊母树·OH、■等ROS水平明显高于对照,表现出氧化应激反应,其超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)等抗氧化系统酶活性及脯氨酸(Pro)等抗氧化系统小分子含量也均显著高于对照,表现出一定的抗氧化防御作用机制,且在复合胁迫下,SOD、CAT、APX酶活性及Pro含量显著高于单一胁迫;(3)恢复阶段,相关性分析表明,中华蚊母树清除ROS(·OH、■的酶促(SOD、CAT、APX)及非酶促(Pro)系统具有一定的协同性。同时,恢复阶段施加脱落酸(ABA),内源Pro显著高于正常水平;施加Pro, SOD、CAT等抗氧化酶活性显著高于对照;施加可...     

Effect of flooding and temperature regime on growth and stomatal resistance ofBetula platyphylla var.japonica seedlings

Summary Both flooding and low temperature reduced height and stem diameter growth; leaf initiation; growth of leaves, stems, and roots; and lowered root-shoot ratios of 112-dayoldBetula platyphylla var.japonica seedlings. Flooding also induced leaf scorching and abscission. Growth was reduced much more by flooding than by low temperature. Interactive effects of flooding and temperature were shown on height growth, leaf initiation and expansion, and dry weight increment of leaves, stems and roots. The amount of growth reduction by flooding and low temperature was greater when based on analysis of dry weight increment of leaves, stems, and roots, than on their relative growth rates. The greater reduction of growth by flooding than by low temperature was associated with fewer and smaller leaves, more leaf injury, more stomatal closure, and greater decay of roots in flooded plants. Flooding and low temperature appeared to reduce growth by somewhat different physiological mechanisms. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI, USA and by Yamagata University, Tsuruoka, Japan. McIntyre-Stennis Project 2599.     

林隙对香樟和枫香幼苗早期生长阶段功能性状的影响

探究林隙对不同需光性树种早期生长特征和功能性状的影响,对揭示林隙微生境影响次生林内幼苗更新机制具有重要意义。以亚热带次生林中耐荫常绿树种香樟和阳性落叶树种枫香幼苗为试验对象,研究大林隙(D/H介于1.5—2.0)、中林隙(D/H介于1.0—1.5)和小林隙(D/H介于0.5—1.0)对不同需光树种幼苗早期(1—3年生)生长特征和功能性状的影响。结果表明：(1)林隙大小对两种幼苗的生长均有显著影响。其中,中林隙可显著促进香樟2—3年生幼苗的生长,大林隙对枫香1—3年生幼苗的生长均具有显著促进作用。(2)对林隙环境因子与幼苗功能性状的关系进行冗余分析表明,香樟幼苗功能性状的变化与林隙土壤有机质含量、水解性氮含量、酸碱度和有效磷含量密切相关,而枫香幼苗功能性状则主要受林隙土壤酸碱度、有机质含量、水解性氮含量、土壤含水率、冠层透光率和土壤有效磷含量的影响。(3)维持较高的根重比、细根比根长、叶碳氮比和叶碳磷比是幼苗应对林隙环境影响的重要生理生态调节机制。     

Importance of adventitious roots to growth of floodedPlatanus occidentalis seedlings

Summary Flooding of soil with standing water for 50 or 110 days drastically reduced growth of 178-day-oldPlatanus occidentalis seedlings, with growth inhibited more as the duration of flooding was increased. Flooding reduced the rate of height and diameter growth, leaf initiation and expansion, and dry weight increment and relative growth rates of leaves, stems, and roots. Flooding also induced leaf epinasty, leaf necrosis, and formation of hypertrophied lenticels and many adventitious roots on submerged portions of stems. Severing of adventitious roots after 50 and 95 days from the submerged portions of stems of continuously flooded seedlings reduced several growth parameters including height and stem diameter growth and relative growth rates of leaves and roots. Evidence for the physiological importance of flood induced adventitious roots is discussed.Research supported by College of Agricultural and Life Sciences, University of Wisconsin, Madison and by Yamagata University, Tsuruoka, Japan. The technical assistance of John Shanklin is appreciated.     

香附子光合生理对三峡库区消落带陆生环境的响应

植物在消落带水淹结束后的陆生环境中能否合成和储存足够的碳水化合物,对其在消落带长期定居、存活和扩散具有重要影响。香附子是能够适应三峡库区消落带生境的少数多年生草本植物之一。该试验通过对消落带水淹结束后生长在深水(22~27m)、浅水(2~7m)和未淹区段香附子光合生理的定期观测,研究其在陆生环境下的光合生理变化及其形成机制。结果表明:(1)生长在深水区段香附子的净光合速率(P_n)显著高于浅水区段与未淹区段。(2)随着香附子在陆生环境中生活时间的延长,其P_n、气孔导度、表观水分利用效率、表观光能利用效率、表观CO_2利用效率增加。(3)与未淹区段相比,浅水淹没区段香附子的光饱和点显著升高,而光补偿点显著降低。研究发现,淹水胁迫后积极的自我调节能力和光合补偿机制是香附子能够适生于三峡库区消落带的重要原因。     

Pollination of the red-hot poker Kniphofia laxiflora (Asphodelaceae) by sunbirds

Most of the species in the large African genus Kniphofia have floral traits that conform to the bird pollination syndrome, however there has been very little empirical work to confirm that birds are effective pollinators of Kniphofia species. From selective exclusion experiments, behavioural observations and pollen load analyses, we identified Amethyst Sunbirds (Chalcomitra amethystina) and Malachite Sunbirds (Nectarinia famosa) as the primary pollinators in two populations of Kniphofia laxiflora, with bees playing a smaller role. Bird visitors obtain moderate volumes (∼ 9 µl) of relatively concentrated (∼ 15%) hexose-rich nectar in the flowers. This species is shown to be genetically self-incompatible, and thus reliant on pollinator visits for seed set. Although mountain pride butterflies (Aeropetes tulbaghia) have been identified as important pollinators of this species at two other populations, they did not occur at the two populations we studied.     

狭叶红景天幼苗对水分及遮阴的生长及生理生化响应

研究植物对水分和遮阴胁迫的响应及其生理机制对制定合理的栽培管理措施十分必要。以红景天属植物为研究对象,设置土壤含水量分别为田间持水量的80%(过湿水分)、70%(正常水分)、60%(轻度干旱)、40%(中度干旱)、20%(重度干旱)5个水分梯度;设置2个遮阴处理,以全光照(遮阴率为0)为对照、黑色遮阴网遮阴(遮阴率为85%),研究狭叶红景天生长及生理生化指标的变化特征。结果表明:在不同水分处理下,与对照相比,叶绿素含量、茎干重和茎重比(SMR)显著增加(P0.05),株高、总生物量、叶面积、叶干重、叶重比(LMR)、比叶面积(SLA)、叶面积比(LAR)和叶面积根干重比(LARMR)增加,根冠比和根重比(RMR)减少;随着干旱程度加剧,丙二醛(MDA)、脯氨酸(Pro)和可溶性糖(Ss)含量增加,超氧化物歧化酶(SOD)活性总体呈先增加后减小的趋势。在遮阴处理下,株高、SMR、SLA、LAR和LARMR显著增加(P0.05),叶绿素SPAD值和叶面积增加,总生物量、根干重、根冠比和LMR显著减少(P0.05),茎干重和叶干重减少,MDA含量显著增加,Pro含量略有下降,Ss含量减少。在水分胁迫下,狭叶红景天中度干旱时通过增加酶活性抵御伤害,重度干旱超过其阈值,SOD活性下降,植物体受到伤害,Ss可能是主要的渗透调节物质。在遮阴处理下,狭叶红景天通过增加SLA避免遮阴伤害。狭叶红景天在受到环境胁迫时会通过形态改变、调节MDA含量、抗氧化酶活性和渗透调节物质来保证自身正常的生长发育。     

不同水淹下狗牙根-牛鞭草混作对植株生物量的影响

了解狗牙根(Cynodon dactylon)和牛鞭草(Hemarthria altissima)在不同水淹地区较优的种植方式对退化湿地的植被修复具有重要意义。设置4种不同水分条件,即对照组(CK)、水淹与干旱交替组(FD)、土壤表面水淹组(FL)和全淹组(SM),4种不同的植株密度(每盆分别种植1,2,4株或12株)和2种不同的种植方式(单作和混作),研究两物种在不同水淹条件下以不同方式和密度种植时的生物量变化。结果表明,水分、种植密度和种植方式均显著影响两物种的地上生物量和总生物量(P0.05)。CK和FD条件下,以中、高密度混作的狗牙根地上生物量和总生物量与单作相比显著下降(P0.05),牛鞭草在混作方式下的生物量与单作相比有了一定提高,其中在高密度混作情况下其生物量得到显著提高(P0.05)。在FL条件下,与单作相比,中、低密度混作的狗牙根和牛鞭草生物量均具有一定的上升。全淹条件下以中、低密度混作对狗牙根地上生物量和总生物量具有显著的促进作用(P0.05),对牛鞭草无显著差异(P0.05),高密度混作方式则对两物种生物量均无显著影响(P0.05)。随着水淹程度的增加,混作对狗牙根产生的生长抑制影响逐渐减弱。在长期浅水淹的地区,采取中、低密度混作将更有利于牛鞭草和狗牙根的长期共存。在较低海拔的全淹地区,采取高密度的牛鞭草-狗牙根混作方式将是更为理想的选择。