内蒙古科尔沁沙地两种沙生植物冷蒿和差不嘎蒿竞争策略的生理生态学依据(英文)

Gas exchange, water relations and leaf chemical characteristics were examined of twodominant psammophytes: Artemisia frigida Willd and A halodendron Turcz. ex Bess in Horqin sandy land, NeiMongol, China under different water regimes. The measurements were conducted by submitting the plantsto five different irrigation levels. A. fTigida was characterized by lower photosynthetic rate (Pn), lowertranspiration rate ( TR and lower shoot water potential (ψuw) relative to A. halodendron. Foliage of A frigdahad higher values of relative water deficit (RWD), bound water content (BWC), ratio of bound water contentto free water content (BWC/FWC) and integrated drought-resistant index (DI than that of A. halodendron.Water relations differed significantly between two species in response to soil water availability. ψw, BWCand BWC/FWC ratio of A halodendron exhibited large variation with gradual decrease of soil moisture.However, in terms of these parameters, A. fRIGIDA was characterized by higher capacity of water holding anddrought tolerance relative to A halodendron. Proline and total soluble sugar contents of A frigida and Ahalodendron tended to increase with decrease of soil moisture and the former had a larger increaseamplitude than the latter. This shows that A frigida has a higher osmotic regulation ability than A halodendron.Under the extreme drought conditions, ψw, RWD, BWC and BWC/FWC of two species were approximate,but soluble proteins degraded largely. A large amount of accumulation of organic matter, proline and totalsoluble sugars were observed in both A halodendron and A frigida. The increase in proline and total solublesugar contents and soluble protein degradation of A frigida far exceeded those of A. halodendron. Webelieve that the accumulated materials at this moment are mostly of nutrient substances available for therecovery of plants after the drought. This is one of the reasons why A halodendron plants died while Afrigida plants survived under extremely drought condition. Our results suggest that these ecophysiologicalfeatures of A frigida are favorable to its growth in the fixed sandy land compared with A halodendron, whichoften lost its dominance due to weak competition for water sources under lower soil water availability andare major factors resulting in replacement of A. halodendron by A. frigida in the later stage of sandyvegetation succession in Horqin.     

科尔沁草原主要牧草冷蒿和差不嘎蒿的生理生态学特性与竞争机制

一日内冷蒿和差不嘎蒿的光合速率（Pn）、蒸腾速率（E）和水分利用效率（WUE）在早或晚出现了最高值,而其余时间则变化低缓,原因归结于沙地环境因子和植物内部因子的共同作用。冷蒿的Pn和WUE日均值高于差不嘎蒿,E的日均值却低于差不嘎蒿,说明冷蒿在干旱环境下具有较高的物质生产量和节约用水的能力。自然状态下冷蒿各生长季的水势（ψω）和充分膨胀时的渗透势（ψπ^100）远低于差不嘎蒿,水分相对亏缺（RWD）、束缚水含量（BWC)、缚水与自由水的比值（BWC／FWC）元高于差不嘎蒿,表明其具有更强的抗旱性;干旱和旱后复水条件下差不嘎蒿的RWD、BWC和BEW／FWC产生大幅度波动;长期极端干旱条件下两才RWD、EWC和ψω终极植相近;长期淹水对冷蒿生理过程的影响更大些。干旱使两种牧草蛋白质发生分解,脯氨酸和可溶性糖大量累,其中冷蒿的累积量远远超过差不嘎蒿,这种累积特征可能正是两种牧草竞争机制的本质所在。     

科尔沁沙地植被恢复中差不嘎蒿种群不同龄级个体的点格局分析

差不嘎蒿（Artemisia halodendron）主要分布在呼伦贝尔沙地和科尔沁沙地的流动和半固定沙丘上,是良好的乡土固沙半灌木,也是退化沙地固定和植被恢复过程中的建群种。点格局分析方法是20世纪末发展起来的多尺度空间格局分析方法。通过对差不嘎蒿种群的点格局分析,发现差不嘎蒿幼体的空间格局多为集群分布,在各个尺度上都极为显著,而随着差不嘎蒿龄级的增加,其空间分布也逐渐显现为随机分布。差不嘎蒿相邻龄级的空间关系差异不显著,而间隔龄级间则呈空间负相关。这与其幼体聚集,成体随机分布的空间格局相一致。     

科尔沁沙地植被恢复中差不嘎蒿种群不同龄级个体的点格局分析

差不嘎蒿(Artemisia halodendron)主要分布在呼伦贝尔沙地和科尔沁沙地的流动和半固定沙丘上, 是良好的乡土固沙半灌木, 也是退化沙地固定和植被恢复过程中的建群种。点格局分析方法是20世纪末发展起来的多尺度空间格局分析方法。通过对差不嘎蒿种群的点格局分析, 发现差不嘎蒿幼体的空间格局多为集群分布, 在各个尺度上都极为显著, 而随着差不嘎蒿龄级的增加, 其空间分布也逐渐显现为随机分布。差不嘎蒿相邻龄级的空间关系差异不显著, 而间隔龄级间则呈空间负相关。这与其幼体聚集, 成体随机分布的空间格局相一致。     

两种生境条件下差不嘎蒿细根寿命

细根寿命对细根周转具有重要影响, 是生态系统C分配格局和养分循环研究的重要内容。该文利用微管法研究了流动沙地和固定沙地生长的差不嘎蒿(Artemisia halodendron)灌丛细根生长的动态过程, 通过Kaplan-Meier方法估计了细根存活率和中位值寿命, 并做存活曲线, 用对数轶检验比较了不同生境、不同土壤层次和不同月出生细根寿命的差异程度, 同时分析了不同样地细根寿命同土壤全氮、有机质、体积含水量和容重的相关关系。结果表明, 流动沙地和固定沙地差不嘎蒿细根具有相似的存活曲线, 但在各观测点, 流动沙地的细根累积存活率均高于固定沙地, 流动沙地细根中位值寿命(47 d)显著高于固定沙地(35 d)。细根寿命同各样地的土壤全氮和土壤容重呈显著的负相关关系, 同土壤水分呈显著的正相关关系, 但多元回归分析表明, 土壤水分是引起细根寿命变异的关键因素。土层深度对流动沙地细根寿命没有显著影响, 但两生境深层30~50 cm的细根寿命均显著高于上层(10~30 cm)。不同出生月的细根寿命显著不同, 流动沙地和固定沙地细根寿命具有相似的季节变化规律, 春季(4、5月)细根的寿命最长(71 d), 秋季(8、9月)次之(61 d), 夏季(6、7月)最短(39 d)。     

科尔沁沙地两种蒿属固沙半灌木的开花物候比较研究

对科尔沁沙地的乌丹蒿和差不嘎蒿的开花物候进行了调查研究;从头状花序、花序枝、个体以及群体水平比较两种植物的开花物候特性。结果表明：（1）乌丹蒿的群体始花期为6月18日;较差不嘎蒿的早9 d;持续时间为19 d;差不嘎蒿开放持续16 d;两种植物群体花期重叠约10 d。在个体水平上;乌丹蒿始花日期比差不嘎蒿早7 d;单株花期长2d;（2）乌丹蒿二级花序枝上头状花序数比差不嘎蒿的少;开放持续时间更长。两种植物开花频率均为单峰型;二级花序枝开放持续时间频率均以8 d为最高;其次为9 d;头状花序水平上两者开放持续时间频率较高的均为5 d、4 d、6 d;5 d频率最大;（3）差不嘎蒿二级花序枝上近基部的头状花序先开放;自基部向上的第2和第3个位置最先开放的频率相对为高;分别为12.7%和11.9%。而乌丹蒿则是顶端的头状花序先开放;最先开放的频率高达56.3%;（4）两种植物的开花振幅曲线均呈单峰曲线;其中乌丹蒿开花后第9 d开花量达到高峰;差不嘎蒿开花后第6 d开花量达到高峰。两种植物开花物候的相似性反映出它们的亲缘关系及对共同环境的适应性;不同点尤其是最先开放顺序的差异性;表明了两者长期进化的遗传差异。     

The effect of soil drought on water-use efficiency in a contrasting Great Basin desert and Sierran montane species

Abstract. The effect of soil drought on water-use efficiency (WUE) and water relations was examined for potted Artemisia tridentata Nutt. and Pinus ponderosa Laws., a dominant Great Basin desert shrub and a Sierran montane tree, respectively. Before the onset of drought, A. tridentata had slightly higher photosynthetic rates than P. ponderosa and A. tridentata maintained positive photosynthetic rates at substantially lower water potentials (Ψ). Complete stomatal closure and cessation of photosynthesis occurred at a Ψ of ca. −2.5 MPa for P. ponderosa and less than −5.0 MPa for A. tridentata. Repeated drought cycles caused a small increase in bulk modulus of elasticity for A. tridentata and neither species exhibited significant osmotic adjustment. WUE was similar at Ψ≥−1.0 MPa but as Ψ decreased P. ponderosa consistently maintained higher WUE than A. tridentata. The primary factor contributing to higher WUE for P. ponderosa was the rapid decrease in stomatal conductance with decreasing Ψ. Comparatively low WUE for A. tridentata , a drought tolerant species, suggests that efficient use of water is a conservative ecophysiological 'strategy' that can be detrimental in a competitive water-limited environment. The combination of profligate use of water and a high degree of drought tolerance may be a more successful combination of physiological characteristics in certain dry habitats.     

Interactive effect of salt (NaCl) and nitrogen form on growth, water relations and photosynthetic capacity of sunflower (Helianthus annum L.)

The effects of the ammonium (NH₄⁺) and nitrate (NO₃^-) forms of nitrogen and NaCl on the growth, water relations and photosynthesis performance of sunflower (Helianthus annuus L.) were examined under glasshouse conditions. Eight-day-old plants of cv. Hisun 33 were subjected for 21 days to Hoagland's nutrient solution containing 8 mol m^-3N as NH₄⁺or NO₃^-, and salinised with 0, 60, or 120 mol m^-3NaCl. Fresh weights of shoots and roots, and leaf area of NO₃^-supplied non-salinised plants were significantly greater than those of NH₄⁺-supplied non-salinised plants. But addition of NaCl to the rooting medium of these plants had more inhibitory effect on the growth of NO₃^--supplied plants than on NH₄⁺-supplied plants. Both leaf water and osmotic potentials of plants grown with NH₄⁺were lower than those of plants given NO₃^-under both non-saline and saline conditions. Chlorophylls a and b concentrations were higher in plants grown with NH₄⁺than N0₃^--supplied plants at the lower two levels of salinisation. The rate of photosynthesis in plants was considerably higher in non-salinised plants grown with NO₃^-than with NH₄⁺, but with increase in salinisation the photosynthesis rate decreased in NO₃^--supplied plants, but not in those given NH₄⁺. The rate of transpiration was increased significantly by salinisation in NO₃^--supplied plants, but not consistently so in NH₄⁺-supplied plants. The stomatal conductances were much higher in plants given NO₃^-than with NH₄⁺when grown under non-saline conditions, but not when salinised. As a consequence, water-use efficiency in NO₃^--supplied control plants was better than in NH₄⁺-supplied under non-saline conditions, but worse under saline conditions. The different forms of nitrogen and the addition of NaCl to the growing medium did not affect the relative intercellular concentrations of CO₂ (C_i/C_a). Overall, the NH₄⁺form of nitrogen inhibited the growth of sunflowers under non-saline conditions, but NO₃^-and NaCl interacted to inhibit growth more than did NH₄⁺under saline conditions.     

Physiological and Anatomical Basis of Differential Tolerance to Soil Flooding of Lotus corniculatus L. and Lotus glaber Mill

Lotus corniculatus L. and Lotus glaber Mill. are warm-season legume species adapted to many kinds of environmental stress, including flooding conditions, whereas other popular forage legumes, like alfalfa or white clover, cannot thrive. This study evaluates the relationship between root aerenchyma, water relations and leaf gas exchange and the differential tolerance to soil flooding of L. corniculatus and L. glaber. Adult plants of these species, established independently in grasslands mesocosms, were subjected to 40 days of early spring flooding at a water depth of 6 cm. Both species presented constitutive aerenchyma tissue in the roots. Under flooding conditions, this parameter was 26.2% in L. glaber and 15.3% in L. corniculatus. In addition, flooded plants of L. glaber presented a leaf biomass 47.5% higher above water while L. corniculatus showed a leaf biomass 59.6% lower in the same layer, in comparison to control plants. Flooded plants of L. glaber maintained the stomatal conductance (g _s) and transpiration rate (E) for 25 days, although these parameters reduce slightly to 40–60% in comparison to controls after 40 days of flooding. In this species, a reduction in photosynthesis (A) in flooding conditions was detected only on the last day of measurement. In L. corniculatus, the same parameters (g _s, E and A) were affected by flooding since day 18 of treatment, and values reached 25–40% in comparison to control plants after 40 days of flooding. Flooding did not affect above-ground biomass in L. glaber; while in L. corniculatus, above-ground biomass was 35% lower than in control plants. Our results confirmed that L. glaber is more able to cope with flooding stress than L. corniculatus, even in the presence of natural competitors. On the whole, this experiment provides information that can aid in the identification of anatomical and physiological parameters associated with flood-tolerance in this forage legume species, with economic potential for the agricultural areas subject to periodic flooding.     

Differences in hydraulic architecture account for near-isohydric and anisohydric behaviour of two field-grown Vitis vinifera L. cultivars during drought

A comparative study on stomatal control under water deficit was conducted on grapevines of the cultivars Grenache, of Mediterranean origin, and Syrah of mesic origin, grown near Montpellier, France and Geisenheim, Germany. Syrah maintained similar maximum stomatal conductance (g_max) and maximum leaf photosynthesis (A_max) values than Grenache at lower predawn leaf water potentials, Ψ_leaf, throughout the season. The Ψ_leaf of Syrah decreased strongly during the day and was lower in stressed than in watered plants, showing anisohydric stomatal behaviour. In contrast, Grenache showed isohydric stomatal behaviour in which Ψ_leaf did not drop significantly below the minimum Ψ_leaf of watered plants. When g was plotted versus leaf specific hydraulic conductance, K_l, incorporating leaf transpiration rate and whole‐plant water potential gradients, previous differences between varieties disappeared both on a seasonal and diurnal scale. This suggested that isohydric and anisohydric behaviour could be regulated by hydraulic conductance. Pressure‐flow measurements on excised organs from plants not previously stressed revealed that Grenache had a two‐ to three‐fold larger hydraulic conductance per unit path length (K_h) and a four‐ to six‐fold larger leaf area specific conductivity (LSC) in leaf petioles than Syrah. Differences between internodes were only apparent for LSC and were much smaller. Cavitation detected as ultrasound acoustic emissions on air‐dried shoots showed higher rates for Grenache than Syrah during the early phases of the dry‐down. It is hypothesized that the differences in water‐conducting capacity of stems and especially petioles may be at the origin of the near‐isohydric and anisohydric behaviour of g.     

基于功能性状的铁杆蒿对环境变化的响应与适应

以延河流域3个植被区(森林区、森林草原区及典型草原区)稳定的自然植物群落中的铁杆蒿为研究对象,测定铁杆蒿的比叶面积、叶组织密度、叶氮含量、叶磷含量、叶氮磷比、比根长、细根组织密度、细根氮含量、细根磷含量、细根氮磷比10项能够反映植物生存对策且易于测量的功能性状,研究了不同生境下铁杆蒿功能性状的种内差异,以及气象因子和地形因子对铁杆蒿植物功能性状的影响,并分析了各功能性状间的相关关系.结果表明： 铁杆蒿各功能性状中除了叶磷含量、叶氮磷比、比根长、根组织密度和根氮磷比在各植被带间的差异显著外,其他5个性状差异均不显著.各性状在坡度、坡向间的差异不显著.比叶面积与叶组织密度呈显著负相关,比根长与根组织密度和根氮磷比呈显著负相关,根组织密度与根氮含量和根氮磷比呈显著正相关,叶组织密度、叶氮含量和叶氮磷比与其他功能性状的相关性不显著.表明铁杆蒿对恶劣环境的适应是通过叶片和细根功能性状间的相互作用和调节实现的.不同环境因素在不同程度上对铁杆蒿功能性状产生影响,对铁杆蒿功能性状影响大小依次是年均降雨量、年均温和年均蒸发量.     

CAM variations in the leaf-succulent Delosperma tradescantioides (Mesembryanthemaceae), native to southern Africa

Drought responses of diurnal gas exchange, malic acid accumulation and water status were examined in Delosperma tradescantioides , a succulent that grows in drought-prone microenvironments in summer rainfall and all-year rainfall regions of southern Africa. When well-watered, this species exhibited Crassulacean acid metabolism (CAM)-cycling, but its carbon fixation pattern changed during the development of drought, shifting to either low-level CAM or to CAM-idling. The rate and pattern of this change depended on environmental conditions, duration of water stress and leaf age. At the onset of drought, diurnal malate fluctuation increased, but was strongly depressed (by ca 70%) as drought continued, and when leaf water content and water potential were low (ca 35 and 50% of the initial levels, respectively). When rewatered, rates of growth and photosynthesis, gas exchange and water status recovered fully to pre-stressed values within two days. Whole-shoot carbon uptake rates suggested that leaf growth had continued unabated during a short-term (∼ one week) drought. This emphasises that CAM-idling allows the maintenance of active metabolism with negligible gas exchange when soil water is limiting. It is possible that old or senescent leaves may provide water for the expansion of developing leaves during initial periods of drought. Regardless of the water regime and environmental conditions, leaf nocturnal malate accumulation and water content were positively correlated and increased with leaf age. Thus the gradual loss of water from older mature leaves may induce CAM-idling, which reduces water loss. An important ecological consequence of this combination of CAM modes is the potential to switch rapidly between fast growth via C₃ gas exchanges when well-watered to water-conserving CAM-idling during drought.