角果藜的地上地下结果性与种子萌发行为

对角果藜(Ceratocarpus arenarius L.)的种子形态进行了观测,并进行了种子萌发实验,探讨了角果藜的地上地下结果特性.结果表明: 角果藜的地上果实和地下果实的颜色、大小、质量均存在差异;种子的异质性导致了地上种子、地下种子(果实)的不同萌发行为;角果藜地上种子、地下种子的萌发率均较低,分别为32%、27%(30 d)(5 ℃/25 ℃);划破种皮可显著提高地上种子和地下种子的萌发率(P＜0.05);延长储藏时间能显著提高地上种子的萌发率(P＜0.05),也能部分提高地下种子的萌发率,表明地上种子和地下种子均属于生理休眠,但地上种子的休眠程度浅;角果藜的地上地下结果性是对荒漠极端环境适应的一种特殊繁殖策略.     

角果藜的生长动态及其生殖配置

通过对角果藜(Ceratocarpus arenarius L.)的地上与地下部分生长动态以及生物量配置进行研究,结合其生活周期内土壤含水量变化规律,分析了角果藜的生态适应对策。结果表明:①角果藜植株高度生长速率随时间变化呈"增加—减缓—增加"的模式,而根的生长速率呈"逐渐减缓"的模式。角果藜株高、垂直根的生长速率变化同土壤水分的变化密切相关。②地上部分生物量在5月果实初形成时期和8月至9月的果实成熟期形成两个高峰值。地下部分生物量在3月至5月增长缓慢,随后以最大增长速率迅速达到地下生物量的最大值。角果藜地上、地下生物量的积累动态体现了其与季节变化相吻合的生长发育特点。③具有地上地下结果性的角果藜的生殖配置高达40%以上,高于一次结实的草本植物的生殖投入。这些特性是角果藜适应荒漠生境生长策略选择的综合表现。     

24种十字花科短命植物的扩散体特征与扩散对策

对准噶尔荒漠中24种十字花科短命植物的扩散体特征与扩散对策的观测结果表明:种间果实和种子的形态各异,角果开裂与否与其木质化程度有关。木质化程度较高的角果不开裂。其中长角果以果节为扩散单元自体扩散。而短角果有两种扩散单元,以果实为扩散单元的无辅助扩散结构或具翅或绵毛,分别进行自体或风媒扩散;以果序的一段为扩散单元的果实具坚硬呈勾状的喙,通过果序梗断裂或附在动物体表散布,兼具自体扩散和动物体外传播的二重性。木质化程度较低的角果开裂,以种子为单元扩散。其中微尘状种子无辅助扩散结构,在果皮开裂时产生的张力或风力的作用下散布;粘液种子以水媒为主,兼具风媒和动物传播的特点;粘液和翅并存的种子具有风媒和水媒扩散的二重性。果翅等辅助扩散结构有利于长距离散布,绵毛及种皮粘液使果实或种子与地表能更好地粘附,木质化结构及种皮粘液还具有保水和保护作用。从扩散的时空特征看,24种植物在扩散持续时间上有集中扩散和持续扩散两种方式,前者避免了种子干旱失水和被捕食,属逃逸对策;后者形成空气种子库逐批扩散,属保护对策。从空间上,异果芥(Diptychocarpus strictus)果序上、下部果实的开裂方式与时间、种子形态完全不同,导致其扩散时间与距离不同;离子芥(Chorispora tenella)等类群果实不同部位的果节非同步脱落以及爪花芥(Oreoloma sulfureum)果实上、下部木质化程度及开裂方式不同,导致其果节或种子的扩散时间不同。以上这些特征对于它们在荒漠环境中成功地扩散、定居,抵御干旱、逃避捕食,避免同胞种子间的竞争、保障物种延续并扩大种群等,具有重要的生态学意义。     

四种一年生荒漠植物构件形态与生物量间的异速生长关系

1年生草本植物是古尔班通古特沙漠夏秋季节草本层片的主要组成部分。选择4种藜科1年生草本植物(刺沙蓬、沙蓬、角果藜和对节刺)作为研究对象,对比分析了各物种构件形态特征、生物量分配以及它们之间的异速生长关系。结果表明:沙蓬个体最大,其次为刺沙蓬,角果藜和对节刺个体最小;对节刺具有最大的根冠比(R/S),其次是刺沙蓬,沙蓬和角果藜R/S最小。4种植物构件形态与生物量间均呈显著正相关,表现出强烈的协同变化趋势。R/S与绝大部分指标间呈显著负相关,表明随个体增大地下生物量分配比例逐渐减小。4种植物各构件形态、地上及地下生物量间大部分呈指数1.0的异速生长关系,但各物种间的异速生长指数绝大部分无显著差异且具有共同的异速生长指数。研究表明:尽管物种不同、个体大小迥异,但4种1年生植物构件特征间多具有相同的生长速率和协同变化特征,体现了1年生植物这一生活型内的不同物种对干旱荒漠环境的趋同适应。     

增加降水对荒漠短命植物当年牧草生长及群落结构的影响

通过模拟降水增加试验研究了古尔班通古特荒漠常见短命植物盖度、密度及产量对水分输入量增加的响应.结果表明:尖喙牻牛儿苗、弯果胡卢巴、角果藜、琉苞菊、条叶庭芥及囊果苔草6种牧草生物量总和占总生物量的60%以上,是荒漠草原的优势牧草植物;供水量增加显著促进了角果藜、尖喙牻牛儿苗、弯果胡卢巴、条叶庭芥和琉苞菊5种牧草植物的个体生长;在自然降水的基础上,增加40mm和80mm供水使这5种植物生物产量比对照增加86%～230%.供水增加后,6种重要牧草对整个群落的生物贡献比例发生很大变化,只有角果藜和尖喙牻牛儿苗的贡献比例规律性增加,分别比对照增加了58%和11%,表明2种植物对供水增加的环境变化适应能力强;供水量增加促进了弯果胡芦巴、尖喙牻牛儿苗和角果藜3种植物N、P和K养分的吸收量;与此同时,供水量增加也显著提高了荒漠短命植物的密度和盖度.在降水增加的背景下,古尔班通古特沙漠南缘荒漠短命植物群落结构发生改变,植被盖度和群落净初级生产力提高,这对于防风固沙、稳定沙面,增加荒漠草原载畜能力有着积极的意义.     

生物结皮对5种不同形态的荒漠植物种子萌发的影响

生物结皮广泛分布于干旱、半干旱区, 强烈影响着土壤表层理化特性, 进而对种子散布、萌发和定居产生影响。目前关于生物结皮与植物种子萌发关系的研究结论存在争议。该文通过室内人工控制实验, 研究了生物结皮对古尔班通古特沙漠5种具不同种子形态特征的荒漠植物白梭梭(Haloxylon persicum)、蛇麻黄(Ephedra distachya)、角果藜(Ceratocarpus arenaarius)、涩芥(Malcolmia africana)和狭果鹤虱(Lappula semiglabra)的种子萌发的影响。结果表明, 在干燥和湿润两种条件下, 生物结皮对不同形态植物种子萌发均具有不同的作用。在干燥条件下, 生物结皮显著抑制了角果藜和涩芥种子的萌发(p<0.05), 对其它3种植物无显著影响; 而湿润条件下, 生物结皮显著抑制了白梭梭、角果藜和狭果鹤虱种子的萌发(p<0.05), 对蛇麻黄、涩芥则无显著影响。     

石林地质公园不同群落类型植物果实组成与种子散布特征

喀斯特植物群落果实类型和种子散布特征的研究, 对于理解喀斯特植物群落更新与拓展特征, 进而揭示喀斯特石漠化地区恢复植被的自然扩展机制及制定植被恢复规划具有重要意义。该研究以石林地质公园不同群落类型为对象, 研究不同群落的果实类型谱与种子散布谱, 以揭示果实类型与种子散布方式对恢复植被的影响。采用石林地质公园不同群落各1 hm ²样地记名计数法调查的维管束物种名录, 依据Flora of China对物种果实的描述确定其果实类型; 根据文献、数据库以及果实、种子形态性状确定种子散布方式。结果表明: (1)石林地质公园282种维管束植物共16种果实类型(含孢子), 其中瘦果、蒴果、浆果和核果的物种比例均大于10%。木本植物、草本植物、藤本植物的优势果实类型分别为核果、瘦果和浆果。石林地质公园各群落的木本植物、草本植物和藤本植物的果实类型谱差异不显著。在原生林、次生林、灌丛、灌草丛和人工辅助云南松林不同群落中, 浆果和核果的物种比例减少, 瘦果、颖果和蒴果的物种比例增加。(2)石林地质公园植物种子以动物传播为主, 其次为风传播。在原生林、次生林、灌丛、灌草丛和人工辅助云南松林不同群落中, 风传播的物种比例增加了73%-87%, 动物传播(包括鸟类传播)减少了31%-36%。(3)物种的种子散布方式直接影响到植被恢复物种和恢复策略的选择。基于恢复目标, 选择自然传播能力强的乡土物种或地带性植被关键种, 辅以传播廊道, 有助于喀斯特的植被恢复。     

Fruit types and seed dispersal modes of plants in different communities in Shilin Geopark,Yunnan, China

喀斯特植物群落果实类型和种子散布特征的研究, 对于理解喀斯特植物群落更新与拓展特征, 进而揭示喀斯特石漠化地区恢复植被的自然扩展机制及制定植被恢复规划具有重要意义。该研究以石林地质公园不同群落类型为对象, 研究不同群落的果实类型谱与种子散布谱, 以揭示果实类型与种子散布方式对恢复植被的影响。采用石林地质公园不同群落各1 hm ²样地记名计数法调查的维管束物种名录, 依据Flora of China对物种果实的描述确定其果实类型; 根据文献、数据库以及果实、种子形态性状确定种子散布方式。结果表明: (1)石林地质公园282种维管束植物共16种果实类型(含孢子), 其中瘦果、蒴果、浆果和核果的物种比例均大于10%。木本植物、草本植物、藤本植物的优势果实类型分别为核果、瘦果和浆果。石林地质公园各群落的木本植物、草本植物和藤本植物的果实类型谱差异不显著。在原生林、次生林、灌丛、灌草丛和人工辅助云南松林不同群落中, 浆果和核果的物种比例减少, 瘦果、颖果和蒴果的物种比例增加。(2)石林地质公园植物种子以动物传播为主, 其次为风传播。在原生林、次生林、灌丛、灌草丛和人工辅助云南松林不同群落中, 风传播的物种比例增加了73%-87%, 动物传播(包括鸟类传播)减少了31%-36%。(3)物种的种子散布方式直接影响到植被恢复物种和恢复策略的选择。基于恢复目标, 选择自然传播能力强的乡土物种或地带性植被关键种, 辅以传播廊道, 有助于喀斯特的植被恢复。     

传粉方式和果实类型对木本植物繁殖物候的影响

该研究利用谱系独立比较法(Phylogenetically Independent Contrasts,PIC)和Wilcoxon秩和检验法,分析中国科学院植物研究所植物园(39°54'N,116°12'E)中的84个物种170株个体的传粉方式和果实类型对木本开花时间和结实时间的影响,其中Wilcoxon秩和检验法检验的结果作为PIC检验结果的参考。结果表明:(1)传粉方式显著影响植物开花和结实时间,风媒花植物比虫媒花植物开花和结实早;(2)果实类型对结实时间的影响在考虑和不考虑物种间系统发育关系时表现不同,当不考虑物种间系统发育关系时,肉质果实植物结实时间比非肉质果实植物早;(3)不同的传粉方式间以及不同的果实类型间植物的花果间隙期无显著差异,但本研究结果显示肉质果实植物结实时间比非肉质果实植物大约早20d。由此推论:(1)植物固有属性,如传粉方式和果实类型,会影响植物繁殖物候,且不同的属性影响强度不同;(2)与某一特定物候期或繁殖器官相关性大的属性对该物候期的影响可能更大,如传粉方式对开花时间的影响可能大于其对结实时间的影响,而果实类型对结实物候期的影响更大。     

水盐变化对荒漠植物功能多样性与物种多样性关系的影响

研究植物功能多样性与物种多样性关系对土壤水盐环境的响应规律,有助于掌握胁迫环境下植物多样性的维持机理.本研究分析了艾比湖高、低土壤水盐环境下荒漠植物功能多样性、物种多样性差异及二者间关系在不同水盐环境下的变化规律.结果表明:(1)高水盐环境下植物功能离散度显著低于低水盐环境(P<0.05),物种多样性指数Fish-α显著高于低水盐环境;(2)一元与多元回归分析均表明,高水盐环境下物种多样性对功能多样性RaoQ与FRic指数有显著促进作用,低水盐环境下物种多样性对功能多样性和均匀度有显著促进作用,但对功能离散度具有显著抑制作用(P<0.05);(3)物种多样性对功能多样性的影响在低水盐环境下更显著,预测力更强;(4)功能丰富度、离散度与均匀度能较敏感地反映出荒漠植物功能多样性对水盐变化的响应.本研究有助于理解荒漠植物群落构建机制,并为荒漠植物恢复与管理提供理论参考.     

Trade-offs between seed dispersal and dormancy in an amphi-basicarpic cold desert annual

Background and Aims

Several studies have demonstrated trade-offs between depth of seed dormancy and dispersal ability for diaspore-dimorphic species. However, relatively little is known about trade-offs between these two life history traits for a species that produces more than two diaspore morphs. The aim of this study was to investigate the relationship between seed dormancy and dispersal in Ceratocarpus arenarius, an amphi-basicarpic cold desert annual that produces a continuum of dispersal unit morphs.

Methods

A comparison was made of dispersal and dormancy breaking/germination responses of dispersal units from ground level (a), the middle of the plant canopy (c) and the top of the plant canopy (f). Various features of the morphology and mass of dispersal units and fruits (utricles) were measured. The role of bracteoles in diaspore dispersal by wind, settlement onto the soil surface and dormancy/germination was determined by comparing responses of intact dispersal units and fruits. Movement of dispersal units by wind and animals, seed after-ripening, germination phenology and the presence of water-soluble germination inhibitors in bracteoles were tested using standard procedures.

Key Results

Dispersal units a, c and f differed in morphology and mass; in the majority of cases, extremes were exhibited by a and f, with c being intermediate. Overall, relative dispersal ability was f > c > a, whereas relative intensity of dormancy was a > c > f. Bracteoles increased dispersal distance by wind, enhanced settlement of diaspores onto the soil surface and mechanically inhibited germination.

Conclusions

The results provide evidence for a model in which there is a continuous inverse-linear relationship between diaspore dispersal ability and depth of dormancy. Thus, dispersal unit heteromorphism of C. arenarius results in a continuum, from no dispersal ability/high dormancy (dispersal unit a) to high dispersal ability/low dormancy (unit f), which may be a bet-hedging strategy in the cold desert environment.     

Amphicarpic plants: definition,ecology, geographic distribution,systematics, life history,evolution and use in agriculture

Although most plants produce all of their fruits (seeds) aboveground, amphicarpic species produce fruits (seeds) both above‐ and belowground. Our primary aims were to determine the number of reported amphicarpic species and their taxonomic, geographic, life form and phylogenetic distribution, to evaluate differences in the life history of plants derived from aerial and subterranean seeds, to discuss the ecological and evolutionary significance of amphicarpy, to explore the use of amphicarpic plants in agriculture, and to suggest future research directions for studies on amphicarpy. Amphicarpy occurs in at least 67 herbaceous species (31 in Fabaceae) in 39 genera and 13 families of angiosperms distributed in various geographical regions of the world and in various habitats. Seeds from aerial and subterranean fruits differ in size/mass, degree of dormancy, dispersal and ability to form a persistent seed bank, with aerial seeds generally being smaller, more dormant and more likely to be dispersed and to form a seed bank than subterranean seeds. In addition, plants produced by aerial and subterranean seeds may differ in survival and growth, competitive ability and biomass allocation to reproduction. Amphicarpic plants may exhibit a high degree of plasticity during reproduction. Subterranean fruits are usually formed earlier than aerial ones, and plants may produce only subterranean propagules under stressful environmental conditions. Differences in the life histories of plants from aerial and subterranean seeds may be an adaptive bet‐hedging strategy.     

Arbuscular Mycorrhizal Fungi Promote the Growth of Ceratocarpus arenarius (Chenopodiaceae) with No Enhancement of Phosphorus Nutrition

The mycorrhizal status of plants in the Chenopodiaceae is not well studied with a few controversial reports. This study examined arbuscular mycorrhizal (AM) colonization and growth response of Ceratocarpus arenarius in the field and a greenhouse inoculation trial. The colonization rate of AM fungi in C. arenarius in in-growth field cores was low (around 15%). Vesicles and intraradical hyphae were present during all growth stages, but no arbuscules were observed. Sequencing analysis of the large ribosomal rDNA subunit detected four culturable Glomus species, G. intraradices, G. mosseae, G. etunicatum and G. microaggregatum together with eight unculturable species belong to the Glomeromycota in the root system of C. arenarius collected from the field. These results establish the mycotrophic status of C. arenarius. Both in the field and in the greenhouse inoculation trial, the growth of C. arenarius was stimulated by the indigenous AM fungal community and the inoculated AM fungal isolates, respectively, but the P uptake and concentration of the mycorrhizal plants did not increase significantly over the controls in both experiments. Furthermore, the AM fungi significantly increased seed production. Our results suggest that an alternative reciprocal benefit to carbon-phosphorus trade-off between AM fungi and the chenopod plant might exist in the extremely arid environment.     

Effects of kin-structured seed dispersal on the genetic structure of the clonal dioecious shrub ilex leucoclada

Nonrandom patterns of gene dispersal have been identified as possible causes of genetic structuring within populations. Attempts to model these patterns have generally focused solely on the effects of isolation by distance, but the processes involved are more complex than such modeling suggests. Here, we extend considerations of gene dispersal processes beyond simple isolation by distance effects by directly evaluating the effects of kin-structured gene dispersal mediated by the group dispersal of related seeds within fruits (i.e., kin-structured seed dispersal) by birds on genetic structure in Ilex leucoclada, a clonal dioecious shrub. To examine the genetic structure patterns, we established two 30x30 m plots (one with immature soils in old-growth forest and one in secondary forest, designated IM and SC, respectively) with different I. leucoclada stem densities. In these two plots 145 and 510 stems were found, representing 78 and 85 genets, respectively, identified by analyzing their genotypes at eight microsatellite loci. The clonal structure was stronger in the SC plot than in the IM plot. Correlograms of coancestry for genets in both plots exhibited significant, positive, high values in the shortest distance class, indicating the presence of strong genetic structure. However, Sp statistics revealed that the pattern of the genetic structure differed between the plots. In addition, to estimate the family structure within fruits, we sampled forty fruits, in total, from 15 randomly selected plants in the area around the IM and SC plots, and found that 80% of the fruits were multiseeded and 42-100% of the multiseeded fruits contained at least one pair of full sibs. Simulations based on these estimates demonstrated that the group dispersal of related seeds produced through correlated mating both within and across fruits, but not unstructured half-sib dispersal, could generate the observed magnitude and trends of genetic structure found in the IM plot. Furthermore, in addition to kin-structured seed dispersal, isolation by distance processes is also likely to promote genetic substructuring in the SC plot. After discussing possible ecological factors that may have contributed to the observed genetic structure, we contrast our results with those predicted by general isolation by distance models, and propose that kin-structured seed dispersal should promote some evolutionary phenomena, and thus should be incorporated, where appropriate, in models of gene dispersal in natural plant populations.     

The effect of deceptive fruits on predispersal seed predation by birds in Pistacia lentiscus

Deceptive fruits (fruits containing empty seeds and seedless fruits) inthe dioecious shrub Pistacia lentiscus L. (Anacardiaceae)remain attached to the plant throughout the dispersal season. This studyaddresses the hypothesis that deceptive fruits may contribute to parentalfitness by reducing predispersal seed predation by granivorous birds becausethese fruits represent handling costs to predators and they prefer to forageselectively on shrubs with filled fruits. This study was run in two populationsof P. lentiscus and finds that deceptive fruits reduceseedpredation by granivorous birds but only in the population that presented higherP. lentiscus female density, and a higher variability inthe percentage of deceptive fruits among P. lentiscusfemales. Under this scenario, the benefits of flying to another female might behigher than those of remaining in the same female searching filled seeds. Bycontrast, the costs of flying to other females, when they are scarce and have asimilar percentage of deceptive fruits may be higher than the benefits.     

Scale and macroecological patterns in seed dispersal mutualisms

Although some studies of seed dispersal mutualisms have documented adaptive relationships between fruits and frugivores, others have shown that adaptive patterns are constrained by phylogenetic, historical or climatic effects. Variable results among studies have thwarted attempts to find a paradigm to unite the field and direct research. Two recent studies in Global Ecology and Biogeography exemplify this dichotomy. One paper reported adaptive relationships between abundances of birds and fruits, while the other study found that bird‐fruit abundance patterns were constrained by climatic effects. Almost paradoxically, both studies were conducted at the same locale. However, they focused on different spatio‐temporal scales. These results are surprisingly consistent with several other recent studies that have taken a macroecological approach. They also indicate that mutualistic relationships between fruits and frugivores are scale dependent. When viewed together, recent work suggests that the conflicting results of previous studies may result from spatio‐temporal variability of mutualistic relationships. This paper briefly reviews the emerging field of seed dispersal macroecology. A growing appreciation for scale appears to be leading the field in a new direction.     

Reproductive and vegetative morphology of Polyptera (Juglandaceae) from the Paleocene of Wyoming and Montana

The morphology, systematics, and ecology of the extinct juglandaceous genus Polyptera are interpreted on the basis of infructescences, fruits, staminate catkins, pollen, and compound leaves from the Paleocene of Wyoming and Montana. The elongate infructescences of Polyptera manningii bear numerous helically arranged sessile fruits. The fruit is a pyramidal nut with a vascularized husk and a multilobed disk-like wing adaptive for wind dispersal. Associated staminate catkins bear numerous helically arranged florets, each with six or more stamens. Pollen from the anthers is triporate and isopolar, with ultrastructure diagnostic of Juglandaceae, but with a pattern of exinous thinning characteristic of the extinct dispersed pollen type Maceopolipollenites anellus (Nichols et Ott) comb. nov. The correlated leaves, Juglandiphyllites glabra (Brown ex Watt) comb. nov., are deciduous, pinnately compound, and have five to seven petiolulate finely serrate leaflets. Systematically, Polyptera shows relationships both with the Hicorieae and the Juglandeae. Occurrences in the Torrejonian and Tiffanian stages of the Paleocene place Polyptera as the oldest unequivocal record of Juglandaceae. Polyptera manningii typically occurs in low-diversity assemblages of 8-15 species, and usually is a dominant or subdominant constituent of floodplain assemblages. It may have been an early-successional colonizer.     

果实(种子)化学防御与食果实动物的适应对策

种子植物在果实(种子)成熟后需要防御食果实动物捕食种子,同时要传播种子至适宜萌发的生境。很多植物依赖食果实动物传播种子,称动物传播植物。果实(种子)化学防御是抵御种子捕食者的重要手段。果实(种子)中次生物质包括各种生物碱、生氰糖苷、萜类和酚类等,种类繁多;次生物质的含量随果实成熟过程而变化。次生物质可以抵御动物的捕食,其毒性对种子传播者和种子捕食者没有选择性,即具泛毒性。果肉中的次生物质也可以起到轻泻剂的作用,缩短种子在动物消化道的滞留时间,以影响传播效率。果实(种子)次生物质的产生不受植物环境条件的影响,其产生与果实质量有关。在温带地区,通常SS型果实次生物质含量低,而FL型果实含量高。食果实动物可通过调整捕食行为、摄取环境中特殊物质和获得丰富营养等3个方面适应次生物质。果实(种子)中次生物质的研究对动植物相互作用、协同进化理论具有重要的意义。