The effect of plant size on vegetative reproduction in a pseudo-annual

The relationship between plant size and vegetative reproduction in clonal plants appears complex because vegetative expansion, growth, and reproduction are not clearly separable in such plants. In pseudo-annuals, which are clonal plants surviving the winter only as seeds and hibernacles produced by the rhizome apices, vegetative growth and reproduction are clearly separate processes so that the relationship between vegetative reproduction and plant size can be studied. We used the pseudo-annual Helianthus x laetiflorus Pers. to study the relationship between plant size and total rhizome biomass, rhizome (hibernacle) biomass, and number of hibernacles. We manipulated resource acquisition of the plants by reducing leaf area (leaf-clipping) and by fertilization, thus affecting plant size. Furthermore, we studied the success of thin and thick hibernacles in terms of future growth and reproduction in a separate experiment. The results showed that vegetative reproduction was positively related to plant size. The ratio between the number of hibernacles and mean hibernacle weight was affected by plant size in such a way that in small plants both number of hibernacles and mean hibernacle weight were reduced to the same extent as compared to those in large plants.However, the size distributions of plants of the next generation growing from thin and thick hibernacles did not differ. It remains unclear therefore why this pseudo-annual species produces thick hibernacles at all.     

Vegetative propagation and sexual reproduction in the woodland understorey pseudo-annual Circaea lutetiana L.

On the forest floor of deciduous woodlands, relative light intensity gradually declines during the early growing season. The woodland understorey pseudo-annual Circaea lutetiana L. completes its life-cycle at the end of summer. These pseudo-annuals are clonal plants which survive the winter only as seeds and as hibernacles produced by the rhizome apices. In this paper, we asked several questions related to the life-history of C. lutetiana. It was found that shoot formation in early spring did not exhaust the old hibernacle. A trade-off between rhizome + hibernacle number and weight might be expected when plants grow under resource limitation. It was hypothesised that both number and weight of rhizomes and hibernacles will be affected by light availability. Since the effect of resource supply on the size number trade-off will depend on the developmental pattern of the rhizome system, rhizome development was studied as well. Soon after the shoots emerged, 1st order rhizomes were formed in May on the nodes of the old hibernacle. First-order rhizomes branched in June and 2nd order rhizomes (side-branches) were continuously produced throughout the growing season. The phenology and developmental rate of plants growing in different light treatments were plastic. On average 30% of rhizome biomass was formed during the vegetative phase, and rhizome and fruit production were only partly separated in time. The ratio of total rhizome biomass to total fruit biomass was not affected by light. Also flower bud removal did not lead to an increase in rhizome production, which suggests that division of biomass to both reproductive modes is rather rigid. The number of 1st order rhizomes was not affected by the light treatments. Under light limitation, both rhizome number and weight of single rhizomes were reduced. In contrast, fruit number, but not weight of single fruits, was limited.     

Density-dependent reproductive and vegetative allocation in the aquatic plant Pistia stratiotes (Araceae)

Pistia stratiotes is an aquatic macrophyte that grows in temporary-ponds in the southern Pantanal, Brazil. It reproduces both sexually and asexually and is usually observed forming dense mats on the water surface, a condition favored by the plant's vegetative reproduction coupled with an ability for rapid growth. In this study we examined the effect of densely crowded conditions on the production of reproductive and vegetative structures. In addition, we verified whether there is a trade-off between clonal growth and investment in sexual reproductive structures, and whether there is an allocation pattern with plant size. Individual plant biomass and the number of the rosettes producing sexual reproductive structures and vegetative growth structures both increased with density. Increase in plant size resulted in increased proportional allocation to sexual reproductive structures and vegetative growth structures. Allocation of biomass to reproduction did not occur at the expense of clonal growth. Thus, the density response appears as a increase of rosettes producing sexual reproductive structures and vegetative growth structures. Therefore, long leaves and stolons may be adaptive under densely crowded conditions where competition for light is intense. An important aspect in the study of trade-offs is the size-dependency of the allocation patterns .Usually, larger plants produce more biomass. Therefore, larger plants can allocate more biomass to both vegetative and sexual reproduction than smaller plants and thus show a positive correlation between both traits rather than the expected negative one.     

Sexual and vegetative reproduction in the aboveground part of a dioecious clonal plant, <Emphasis Type="Italic">Dioscorea japonica</Emphasis> (Dioscoreaceae)

In dioecious clonal plants, the reproductive effort required to set seeds will be responsible for the larger investment in sexual reproduction by females. If there will be a trade-off in resource allocation between sexual and clonal reproduction, this differential sexual reproduction will lead to sexual differentiation in the relative amount of clonal reproduction. To test this prediction, we studied differences between the sexes in their phenologies and investments in sexual and vegetative reproduction (clonal reproduction by means of bulbils) with respect to ramet size in a dioecious clonal plant, Dioscorea japonica Thunb. The period of bulbil production overlapped the period during which infructescences developed. Females flowered later, produced heavier inflorescences, and fewer flowers per inflorescence than did males. Regression analysis using the size of the individual plants demonstrated that large females made smaller investments in inflorescences and larger investments in sexual reproduction than did large males. In contrast, females invested fewer resources in vegetative reproduction than did males. However, the total investments in sexual and vegetative reproduction did not differ between the sexes. These results supported our hypothesis on the sexual differentiation in sexual and clonal reproduction.     

Mineral allocation to reproduction in Sorhum bicolor and Sorghum halepense in relation to parental nutrient supply

Summary This experiment investigated the effect of parental nutrient shortage on the allocation of five nutrients to seeds and rhizomes in Sorghum halepense, a perennial, noxious weed, and to seeds in Sorghum bicolor, an annual, cultivated species. Plants from both species were grown from seeds and supplied with fertilizer at three concentrations. The allocation of biomass and nutrients (N, P, K, Ca and Mg) to reproductive and vegetative parts was determined. Relative biomass allocation to reproduction (either sexual or vegetative) remained constant in S. halepense in spite of large differences in total plant weight. In S. bicolor, however, biomass allocation to sexual reproductive structures decreased significantly with decreasing nutrient supply. Individual seed weight was not modified by parental nutrient supply in S. halepense, but it increased with decreasing nutrient availability in S. bicolor. Important differences in mineral allocation to seeds were found between the two species. While S. bicolor seeds were largely buffered from the differences in parental nutrient status, concentration of nutrients in S. halepense seeds decreased significantly with decreasing supply for all the nutrients analyzed except Ca. However, mineral nutrient concentration in S. halepense rhizomes remained remarkably constant despite differences in the external supply, evincing the priority given to vegetative reproduction at the expense of sexual reproduction. Overall, the pattern of nutrient allocation in S. bicolor seeds under different nutrient supply resembled the pattern observed in S. halepense rhizomes, but it had little resemblance to the pattern of nutrient allocation in S. halepense seeds. The results are discussed in terms of differences and similarities in the reproductive strategy of these two species.     

新疆郁金香营养生长、个体大小和开花次序对繁殖分配的影响

植物有性繁殖与资源分配的关系研究对于揭示植物生活史特征及繁育系统进化具有重要意义。新疆郁金香(Tulipa sinkiangensis)是新疆天山北坡荒漠带特有的一种多年生早春短命植物。在自然生境中,该物种仅以有性繁殖产生后代,每株能产生1-8朵花,且不同植株上的花数及果实数以及花序不同位置上的花与果实大小明显不同。本文通过对新疆郁金香有性繁殖与营养生长及植株大小的关系以及花序中不同位置花及果实间的资源分配研究,旨在揭示营养生长、个体大小及开花次序对其繁殖分配的影响。结果表明:在开花和果实成熟阶段,新疆郁金香植株分配给营养器官(鳞茎和地上营养器官)与繁殖器官的资源间均存在极显著的负相关关系(P<0.01),说明其植株的营养生长与生殖生长间存在权衡关系。多花是新疆郁金香的一个稳定性状,其植株上花数目、花生物量、果实生物量和种子数量与植株生物量间均呈极显著的正相关关系(P<0.01),说明新疆郁金香植株的繁殖分配存在大小依赖性。在具2-5朵花的新疆郁金香植株中,花序内各花的生物量、花粉数和胚珠数、结实率、果实生物量、结籽数、结籽率及种子百粒重按其开花顺序依次递减,说明花序内各花和果实的资源分配符合资源竞争假说。植株通过减少晚发育的花或果实获得的资源来保障早发育的花或果实获得较多的资源,从而达到繁殖成功。     

根茎型植物扁秆荆三棱对光照强度和养分水平的生长响应及资源分配策略

自然界中光照和养分因子常存在时空变化,对植物造成选择压力。克隆植物可通过克隆生长和生物量分配的可塑性来适应环境变化。尽管一些研究关注了克隆植物对光照和养分因子的生长响应,但尚未深入全面了解克隆植物对光照和养分资源投资的分配策略。以根茎型草本克隆植物扁秆荆三棱(Bolboschoenus planiculmis)为研究对象,在温室实验中,将其独立分株种植于由2种光照强度(光照和遮阴)和4种养分水平(对照、低养分、中养分和高养分)交叉组成的8种处理组合中,研究了光照和养分对其生长繁殖及资源贮存策略的影响。结果表明,扁秆荆三棱的生长、无性繁殖及资源贮存性状均受到光照强度的显著影响,在遮阴条件下各生长繁殖性状指标被抑制。且构件的数目、长度等特征对养分差异的可塑性响应先于其生物量积累特征。在光照条件下,高养分处理的总生物量、叶片数、总根茎分株数、长根茎分株数、总根茎长、芽长度、芽数量等指标大于其他养分处理,而在遮阴条件下,其在不同养分处理间无显著差异,表明光照条件可影响养分对扁秆荆三棱可塑性的作用,且高营养水平不能补偿由于光照不足而导致的生长能力下降。光照强度显著影响了总根茎、总球茎及大、中、小球茎的生物量分配,遮阴条件下,总生物量减少了对地下部分根茎和球茎的分配,并将有限的生物量优先分配给小球茎。总根茎的生物量分配未对养分发生可塑性反应,而随着养分增加,总球茎分配下降,说明在养分受限的环境中球茎的贮存功能可缓冲资源缺乏对植物生长的影响。在相同条件下,根茎生物量对长根茎的分配显著大于短根茎,以保持较高的繁殖能力;而总球茎对有分株球茎的生物量分配小于无分株球茎,表明扁秆荆三棱总球茎对贮存功能的分配优先于繁殖功能。研究为进一步理解根茎型克隆植物对光强及基质养分环境变化的生态适应提供了依据。     

Life history trade-offs in Amphibromus scabrivalvis (Poaceae): allocation to clonal growth,storage, and cleistogamous reproduction

Life history trade-offs among clonal growth, storage, and sexual reproduction were investigated in the perennial grass Amphibromus scabrivalvis in relation to soil nutrients. This species exhibits clonal growth by producing rhizomes and stores reserves in the form of basal corms; seeds are matured in cleistogamous spikelets on panicles enclosed within the leaf sheaths along each culm. Ten seed-derived genotypes (clones) were separated into 72 ramets and planted in the greenhouse. Control ramets received only water while the remainder received fertilizer applied every 2 wk. Twenty-four ramets were harvested per clone at 11, 20, and 26 wk. The dry mass of corms, rhizomes, roots, shoots, and seeds were recorded. Biomass partitioning to rhizomes provided a measure of carbon allocation to clonal growth, partitioning to corms provided a measure of allocation to storage, and partitioning to seeds provided a measure of allocation to sexual reproduction. Allocation to most organs was significantly influenced by clone identity; fertilizer significantly increased allocation to corms and seeds at 20 wk, but never affected rhizome allocation at any age. Corm allocation increased from 2% at 11 wk to 27% at 26 wk; rhizome allocation decreased from 10% at 11 wk to 3% at 26 wk. Significant negative relationships were detected for rhizome vs. seed and corm vs. rhizome allocation in fertilized clones at 20 wk. This suggests an age-dependent physiological life history trade-off between clonality and sexual reproduction and between clonality and storage. In contrast, a significant positive relationship was consistently noted for corm vs. seed allocation in fertilized and unfertilized clones at 20 and 26 wk. The absence of a trade-off between storage and sexual reproduction may indicate that these two processes are not necessarily mutually exclusive components of life history.     

Clonal plasticity in response to nutrient availability in the pseudoannual herb,Trientalis europaea L.

Trientalis europaea plants were subjected to four levels of nutrient availability to test two hypotheses: (1) Clonal morphology of pseudoannuals with short-lived rhizomes is responsive to nutrient availability in terms of spacer length (a negative correlation expected) and branching intensity (a positive correlation expected), and (2) the size of the hibernacles of T. europaea shows a positive correlation with nutrient availability. The results support the first hypothesis, since the primary spacers of T. europaea were longer at lower nutrient levels while the branching intensity of the primary rhizomes increased at increasing nutrient supply. The second hypothesis was not confirmed, however; the plants produced fewer, but bigger hibernacles at lower levels of nutrient availability. The ecological significance of the results is discussed in the context of foraging for essential resources and habitat-related effects of hibernacle size on survival and establishment chances of daughter ramets.     

增加水分与养分对克隆植物羊柴自然种群繁殖权衡的影响

 羊柴(Hedysarum laeve)是豆科多年生半灌木,在自然条件下可以同时进行有性繁殖和克隆繁殖。该文在野外条件下研究了不同水平的水分和养 分处理对羊柴种群的繁殖权衡的影响。结果表明,与对照相比,增加一定量的水分处理显著减少了花和荚果的生物量;显著增加了克隆分株枝 的生物量,显著减少了分株根茎的生物量, 但没有影响其它部分的生物量。增加一定量的水分会抑制有性繁殖,改变生物量对克隆繁殖分株各 部分的分配比例。与对照相比,增加一定量的养分能够促进有性繁殖,抑制克隆繁殖。     

Evolutionary increase in sexual and clonal reproductive capacity during biological invasion in an aquatic plant Butomus umbellatus (Butomaceae)

To test the hypothesis that increased allocation to reproduction is selected during biological invasion, we compared germination, survival, growth, and reproduction of native vs. introduced populations of the invasive aquatic plant Butomus umbellatus in a common greenhouse environment. Although seedling emergence and establishment did not differ consistently, survival thereafter was twice as high for eight introduced North American than eight native European populations. As predicted, introduced plants were more likely to produce sexual inflorescences and clonal asexual vegetative bulbils, and they invested much more biomass in both reproductive modes. Higher reproductive investment was due to higher proportional allocation of biomass rather than larger plant size. These results are consistent with selection for increased reproduction during range expansion. However, population genetic surveys indicate that recruitment from seed rarely occurs in introduced populations. Hence increased sexual allocation is not an adaptive response to invasion. Although increased clonal reproduction may be advantageous in expanding populations, genetic evidence from introduced populations of B. umbellatus suggests that increased clonal allocation may have arisen via stochastic processes during long-distance transport or a selective filter right at introduction, rather than incremental natural selection during range expansion.     

Vegetative reproduction by species with different adaptations to shallow-flooded habitats

In shallow flooded parts of rich fens Mentha aquatica might thrive in deeper water than Epilobium hirsutum but previous experiments have provided no clear indication that the flooding tolerance of these species differs. In this study we investigated, by measuring growth, biomass allocation and vegetative reproduction, whether the impact of water level on vegetative reproduction might produce different lower boundaries on water level gradients. There was a striking contrast between biomass production at high water levels and the field distribution of both species. After 18 wk, the mean biomass of E. hirsutum grown in waterlogged and flooded conditions was 82% and 54%, respectively, of the mean biomass production of drained plants. Biomass of waterlogged and flooded M. aquatica was reduced to 57% and 37% in drained conditions. Waterlogged and flooded E. hirsutum had swollen stem bases and invested a high proportion of biomass in adventitious roots. Stems of M. aquatica did not swell, formed few adventitious roots and maintained an equal proportion of below-ground roots at all water levels. The effect of water level on vegetative reproduction corresponded well with the lower hydrological boundaries of both species. When waterlogged and flooded, most rhizomes of E. hirsutum emerged from above-ground parts of the stem base and were oriented in an upward direction. Plants in flooded soil allocated less biomass to rhizomes and also reduced the number and size of rhizomes. Rhizome formation of M. aquatica on the other hand was not directly affected by water level and only depended on plant size. These differences in vegetative reproduction are discussed in relation to the different abilities of both species to oxygenate their below-ground roots. It was concluded that the mode of adaptation to soil flooding might also affect vegetative reproduction and, therefore, a species' ability for long-term persistence in soil-flooded habitats.     

Size-dependent resource allocation among vegetative propagules and male and female functions in the forest herb Laportea bulbifera

Reproductive resource investment among vegetative propagules and male and female sexual function and their size-dependence were investigated in a perennial forest herb, Laportea bulbifera . A theoretical model based on fitness gain curves predicts that optimal investments in three reproductive modes will increase with plant size if fitness returns in all three modes increase but become saturated with investment. In a field population, large plants of L. bulbifera produced both male and female inflorescences with propagules, while small plants produced only vegetative propagules. Biomass of propagules, male inflorescences, and infructescences with achenes were all positively correlated with plant size. The increase in investment with plant size was larger for propagule production than for sexual reproduction. The relationship between propagule biomass and plant size was constant irrespective of year, while the relationship between the biomass of sexual reproductive organs and plant size differed between two successive years. Annual change of individual sex expression was investigated for 25 transplanted plants. Although each plant changed its sex expression variously among male, female and bisexual from year to year, 23 out of 25 plants produced both male and female inflorescences in at least one year. The number of viable (germinated and survived) offspring from seeds was not significantly different from the number from propagules. The production cost of a propagule was higher than that of a seed. Resource allocation theory does not seem to be applicable to size-dependent resource allocation, especially the allocation between seeds and propagules in this species.     

The role of vegetative spread and seed dispersal for optimal life histories of clonal plants: a simulation study

Sexual and vegetative reproduction of clonal plants phenotypically differ in dispersal distance, in the phenology of offspring production and establishment, and in the success of establishment. We applied a combination of analytical and of spatially explicit individual-based simulation modelling to calculate long-term fitness. We predicted optimal clonal plant life histories in a parameter space spanned by stolon number, stolon internode length, and relative allocation to sexual and vegetative reproduction. For a given allocation to sexual reproduction and number of stolons, fitness was optimised for rather short internode lengths under small disturbances, and for the longest possible internodes under larger disturbances. A trade-off between length and number of vegetative spacers drew parameters away from their unrestricted optima. Now, intermediate length and number of spacers led to maximum fitness under large disturbances. Simultaneous trade-offs between sexual and vegetative reproduction and between the length and number of spacers could also lead to fitness optima at intermediate parameter values, depending on the success of seedling establishment. We demonstrated that spatial habitat structure (1) selects for an efficient use of available space either by optimum internode length or by investment into seeds, which disperse farther than vegetative spacers, and (2) leads to an interaction between trade-offs. We conclude, that dispersal distance, i.e. a spatial life-history component, and trade-offs must be included in considerations on adaptive evolution of clonal life histories.     

No evidence for nutrient foraging in root-sprouting clonal plants

Clonality is defined as vegetative reproduction via the production of ramets, which are, at least initially, connected by spacers. In general, there are three types of spacers of two origins. Whereas stolons are aboveground spacers, rhizomes are belowground spacers; however, both of stem origin. The third type of spacers are roots in root-sprouting plants. The possibility of foraging in clonal plants has attracted broad interest among ecologists but has been experimentally documented only for stoloniferous clonal plants foraging for light. Foraging for belowground resources has yet to be demonstrated, perhaps because tests of foraging have focused on clonal plants that spread laterally via stolons or rhizomes, i.e. stem organs. Lateral spread based on sprouting roots has not been considered even though, in addition to functioning as conduits between ramets, root spacers are able to sense and take up nutrients. We therefore hypothesized that root-sprouting clonal plants may be able to directly react to environmental heterogeneity and exhibit nutrient foraging. To test this hypothesis, we conducted two experiments with root-sprouters in nutrient-heterogeneous and -homogeneous environments. We found that plants produced more biomass when growing in a heterogeneous environment than in a homogeneous environment and that root biomass was greater in the nutrient-rich patches than in nutrient-poor patches. However, the number of ramets did not differ between patches in the heterogeneous environment. We conclude that plants whose clonality is based on roots, similarly as plants whose clonality is based on stolons or rhizomes, do not exhibit accumulation of ramets in nutrient-rich patches. Foraging at the organ level, i.e. by roots, seems to be more probable in this clonal group. To analyse how clonal plants with different clonal strategies perceive and react to environmental heterogeneity, researchers must account for the high variability in clonal growth forms and in scales of environmental heterogeneity.     

青藏高原东缘块茎堇菜鳞茎分配的个体大小依赖性

块茎堇菜(Viola tuberifera)为青藏高原特有两型闭锁花植物,属多年生草本,具独特的混和交配系统,既可通过早春开放花异花受精和夏季地上地下闭锁花自花受精有性繁殖,还可通过秋季新鳞茎无性繁殖产生后代。高山环境下,异花受精常因花粉限制而无法正常进行,自花受精和克隆繁殖成为保障植物种群正常繁衍的不二之选,而克隆繁殖更能在植株资源消耗最小的情况下保障子代的存活。该文以青藏高原东缘高寒草甸的混合繁育植物块茎堇菜为研究对象,探索其生长期内鳞茎分配的个体大小依赖性,以及植株如何权衡鳞茎的资源分配以适应个体大小的变化。结果表明：块茎堇菜生活史阶段的鳞茎分配具有个体大小依赖性,鳞茎分配与个体大小呈极显著负幂指数相关关系(P<0.01),个体越大,鳞茎分配越小;反之,个体越小,鳞茎分配越高。即块茎堇菜对鳞茎的资源投入受个体大小的制约,通过鳞茎分配比例的高低响应植株自身资源状况的变化,保障在高寒环境下植物种群的生存和繁衍。该研究结果为高山植物克隆繁殖的生活史进化提供了依据。     

Genetic variation, disequilibrium and natural selection on reproductive traits in Allium vineale

Bulbils and seeds collected from Allium vineale plants from natural populations were grown under uniform conditions. The bulbil-derived offspring represented the parental generation, whereas the seed-derived offspring represented the sexually produced offspring generation. Molecular markers were used to identify maternal genets. Variation in traits determining the allocation to sexual and asexual reproduction was partitioned among genets and ramet families in the parental and offspring generations. From observations of a release of genetic variation and slippage in the mean phenotype in the offspring generation, we inferred that there exists extensive genetic disequilibrium for reproductive traits in A. vineale populations, that most of the genetic variance is because of dominance effects, and that natural selection favours a reduced allocation to sexual reproduction. No genetic correlation between sexual and asexual allocation traits was found. We discuss the implications of these results with respect to the evolution of a mixed reproductive system in A. vineale.     

Optimal resource allocation to seeds and vegetative propagules under density-dependent regulation in Syneilesis palmata (Compositae)

Syneilesis palmata reproduces by both seeds and vegetative propagules (short rhizomes). The latter result in the production of new plants that are larger in size and hence have a higher survival probability and a higher growth rate than seeds. A previous study predicted that the optimal reproductive strategy, in terms of maximizing population growth rate (a fitness measure under no density regulations), was pure vegetative reproduction. However, high resource investment to vegetative propagules can cause local crowding resulting in reduced demographic performances of the plants, because the vegetative propagules of Syneilesis are produced close to one another. We examined, in this situation, the impact of allocating a certain proportion of reproductive resource to seeds with relatively greater capacity for dispersal. We simulated dynamics of hypothetical Syneilesis populations with various reproductive resource allocation balances (from pure seed to pure vegetative reproduction), using a density-dependent matrix model. In the model, it was assumed that plants from vegetative propagules experienced density-dependent reduction in their survival probabilities, but this was not the case for plants originating from seeds. Each allocation strategy was evaluated based on an equilibrium population density, a fitness measure under density-dependent regulations. The optimal reproductive strategy predicted was pure vegetative reproduction. Unrealistic conditions were required for seed reproduction to be favoured, such as the production of seeds one hundred times the normal number per unit resource investment. However, the conditions were fairly relaxed compared with those required in the model where no density effects were incorporated. This indicates that escape from local crowding is likely to be one of the roles of seed production in Syneilesis.     

Patterns of resource allocation in the dioecious alpine herb Aciphylla simplicifolia (Apiaceae)

Abstract Patterns of reproductive and vegetative biomass allocation were compared in male and female plants of the alpine herb Aciphylla simplicifolia. Male and female plants had similar vegetative biomass but differed in the pattern of resource allocation. Inflorescences of males and females were similar in weight at the time of flowering, but differed in biomass allocation to some structures within the inflorescences, particularly those associated with ovule production and pollinator attraction (number and size of flowers). At the time of fruit production, female inflorescences were 2.6 times heavier than at flowering with developing fruit six times heavier than flowers. In addition to the increase in biomass allocated to structures associated with the provisioning and dissemination of seed, support structures (main and side stalks) were also heavier. As a result of this additional investment of resources at the time of fruit production, the reproductive effort (RE) of female plants was much higher than that of males: 37% of above ground biomass compared with 21% for males. Differences in RE did not change with plant size; however, allocation to reproduction appeared to be a constant proportion of biomass over nearly all plant sizes sampled. These results show that sex‐specific resource allocation can be a complex of temporal and morphological patterns.     

Effects of light on the growth and clonal reproduction of Ligularia virgaurea

Ligularia virgaurea is a perennial herb that is widely distributed in the alpine meadow on the eastern Qinghai-Tibet plateau.We investigated the patterns of growth and reproduction of L.virgaurea under two contrasting levels of light conditions for two continuous growing seasons.Our results showed that the light affects on the maximum relative growth rate,the shoot weight ratio and the root weight ratio differed between the two growing seasons.L.virgaurea reproduced initially through rhizome in the second growing season,rather than sexual reproduction.The proportion of genets with clonal reproduction decreased under shaded conditions.A minimum genet size should be attained for clonal reproduction to begin under the shaded conditions.There was a positive linear relationship between clonal reproduction and genet size.Light level affected the allocation of total biomass to clonal structures,with less allocation under the full natural irradiance than under the shaded conditions.There seemed to be a trade-off between vegetative growth and clonal reproduction under the full natural irradiance,in terms of smaller relative growth rates of genets with clonal reproduction than those without clonal reproduction.L.virgaurea emphasized clonal reproduction under the full natural irradiance,while the plant emphasized vegetative growth under the shaded conditions.