The biology of Butomus umbellatus in shallow waters with fluctuating water level

Butomus umbellatus L. is a plant species typical of littoral communities of river and stream shores. It can form continuous stands in shallow reservoirs with fluctuating water level. Their expansion is promoted by: (a) intensive vegetative reproduction of plants, (b) crowded sprouting from rhizome fragments on emerged pond bottom, (c) shallow water layer in the year following summer drainage. Expansion of B. umbellatus depends on ploidy level: two cytotypes were found in the Czech and Slovak Republics, differing in their reproductive ability. Seed production of triploids is strongly limited (they are self-incompatible within clones), while diploids can be fully fertile. Nevertheless, even in diploids, the efficiency of seed reproduction under natural conditions is low. Triploids spread by intensive vegetative reproduction, which is decisive for clonal growth of populations and their regeneration after scraping of bottom surface. During seasonal development, maximum of aboveground biomass is produced in early summer, while underground biomass increases till autumn. Growth of the plants is limited by cutting before maximum underground biomass is attained, or by duck grazing.     

Ecology of two cytotypes ofButomus umbellatus III. Distribution and habitat differentiation in the Czech and Slovak Republics

The distribution, total frequency of occurrence, regional differences and habitat conditions of diploid and triploidButomus umbellatus L. were studied in the Czech and Slovak Republics. Triploids are more frequent than diploids, with numerous localities in warm lowland regions in river floodplains. Diploids were found primarily in the South Bohemian T?eboň basin, outside the warm regions. The two cytotypes do not differ in dependence on water depth. Triploids occur more in habitats with more alkaline and base-rich soils. Considering the total distribution of both cytotypes in the area studied, triploidB. umbellatus appears to be more successful than its diploid progenitor, owing to its wider habitat range and superiority in vegetative reproduction.     

Vertically transmitted fungal endophytes: different responses of host-parasite systems to environmental conditions

The relationship between vertically transmitted asexual fungal grass endophytes and their hosts is considered to be mutualistic. Results from agronomic field support this line of reasoning but recent studies have shown more variable results in natural systems. We investigated how high and low nutrient and water treatments affected biomass allocation patterns of endophyte‐infected and uninfected Festuca pratensis and F. rubra in greenhouse experiments over two growing seasons. Irrespective of infection status, both grass species showed improved performance on highly fertilized and watered soils. However, infected F. pratensis plants produced larger tillers than endophyte‐free plants on soil low in nutrients and water in the first growing season, although they (E+) otherwise showed decreased performance on nutrient‐poor soil. In low nutrient and water conditions, endophyte‐infected plants produced less tillers and had lower total biomass compared to uninfected plants, and displayed a negative phenotypic correlation between seed production and vegetative growth. The latter indicates costs of reproduction when the plant shares common resources with the fungal endophyte. However, endophyte infection status (E+, E?) interacted significantly with the soil fertilisation in terms of plant growth, having a stronger positive effect on growth in infected F. pratensis plants. In F. rubra, endophyte‐infected plants showed higher vegetative growth in fertilized and watered soils compared to uninfected plants. However, infected plants tended to produce fewer inflorescences. This had no effect on seed production, perhaps because seed production was partly replaced by asexual pseudovivipary. Contrary to the general assumption in the literature that fungal endophytes are plant mutualists, these findings suggest that the costs of endophytes may outweigh their benefits in resource limited conditions. However, the costs of endophyte infections appear to differ among the grass species studied; costs of endophytes were mainly detected in F. pratensis under low nutrient conditions. We propose that differences in response to endophyte infection in these species may depend on the differences in life‐history strategies and environmental requirements of these two fescue and fungal species and may change during the life span of the plant.     

Trade-off between seed number and weight: Influence of a grass–endophyte symbiosis

Plant fitness is enhanced by resource allocation to seed number (offspring number) or weight (offspring survival). Besides, there is a well known trade-off in resource allocation between both traits. Symbiotic interactions can influence plant resource allocation to reproduction, yet little research has been performed in this direction. We studied the consequences of a grass–fungus symbiosis on the trade-off between seed number and weight, using Lolium multiflorum and the endophyte Neotyphodium occultans as our study system. In ecological terms, we experimentally removed N. occultans from L. multiflorum plants, and compared reproductive allocation to seed number and weight in endophyte-symbiotic vs. non-symbiotic plants at different levels of nutrient availability (small pots vs. large pots). In evolutionary terms, we compared reproductive allocation between symbiotic vs. non-symbiotic plants for different host genotypes. All plants showed a negative association between seed number and weight, once standardized for total reproductive biomass. Under high nutrient availability, endophyte-symbiotic plants showed higher seed weight than non-symbiotic plants for any seed number. However, no differences were observed under low nutrient availability. Endophyte influence also varied according to L. multiflorum genotype; specifically, endophyte-symbiotic plants showed a lower slope in the relationship between seed number and weight than non-symbiotic plants for the ‘Marshall’ genotype but no endophyte influence was found for the “Pampean” genotype. The results implied a higher plasticity in seed weight and lower plasticity in seed number for symbiotic plants. Indeed, endophyte-symbiotic plants showed an overall lower slope in the association between seed number and total reproductive biomass than non-symbiotic plants. Our results suggest that N. occultans induces heavier seeds in L. multiflorum plants under environmental conditions favorable to plant growth or for certain plant genotypes. We propose that symbiotic interactions may influence the evolution of seed number and weight trade-off.     

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.     

Biology of the polyploid geophyte Allium oleraceum (Amaryllidaceae): Variation in size,sexual and asexual reproduction and germination within and between tetra-, penta- and hexaploid cytotypes

It has been proposed that plant species cytotypes commonly exhibit altered morphology, reproduction, geographic and ecological distributions. We studied phenotypic variation in height, sexual (flowers, seeds) and asexual (aerial bulbils) reproduction in natural populations and in the conditions of a common garden of three cytotypes (2n = 4x, 5x, 6x) of the bulbous geophyte Allium oleraceum in the Czech Republic. Additionally, we compared the germination and dormancy of seeds and bulbils to determine whether propagules have different ecological roles. The pattern of morphological differentiation observed between cytotypes under natural conditions was similar to that observed under common garden conditions, suggesting that variability in morphological characteristics appears to be associated with ploidy levels. We revealed differences in size and sexual and asexual production between A. oleraceum cytotypes, but with wide overlap among cytotypes, suggesting a limited possibility of the studied traits to reliably distinguish between cytotypes. Tetraploids and pentaploids were rather similar; they were taller and produced more flowers than hexaploids, which were mostly flowerless (mean <0.7 flower/plant). All cytotypes were able to produce viable seeds, but their numbers were extremely low, usually less than 3 seeds per inflorescence; clonal reproduction via aerial bulbils dominates in all cytotypes (flower:bulbil ratio <0.5), with tetraploids producing more but lighter bulbils than other cytotypes. The seed: ovule ratio was low (<0.1) in all cytotypes, although hexaploids reached higher values than other cytotypes. Bulbils germinated better (means >80%) than seeds in all cytotypes, with pentaploid bulbils showing the highest germination (mean 90.5%). The cytotypes did not differ in seed germination (range of means 73.4%–76.3%). About 6% of seeds did not germinate but were still viable at the end of the experiment, while all non-germinated bulbils of all cytotypes had rotten away. Seeds, but not bulbils, can likely form a short-term persistent propagule soil bank. We found no evidence of a phenotypic trade-off between the production of flowers (seeds) and the production of bulbils within the inflorescence of all studied cytotypes. Together, inter-cytotypic differences in fitness-related traits cannot completely explain the different geographic and ecological distributions of cytotypes in the Czech Republic found by previous research.     

Trade-offs between sexual and asexual reproduction in a monoecious species Sagittaria pygmaea (Alismataceae): the effect of different nutrient levels

Available resources could influence the trade-offs among different reproductive components in plants. Here, we created three nutrient levels to test the nutrient effects on trade-offs among sexual reproduction, clonal propagation and vegetative growth in a monoecious clonal herb Sagittaria pygmaea. The results of this study showed that the plant exhibited different trade-off patterns among different nutrient levels. When the nutrient level was low, there were weak trade-offs between sexual reproduction and vegetative growth and between clonal propagation and vegetative growth; when the nutrient level was moderate, we found a strong trade-off between sexual reproduction and clonal propagation; but when the nutrient level was high, we found no trade-offs among these three different reproductive components. These results indicated that the plant could adjust its trade-off patterns to fit the nutrient variation and suggested that trade-offs are unlikely to constrain the evolution of reproductive strategy in this species.     

Compensation of seed production after severe injury in the short-lived herb Barbarea vulgaris

A pot experiment with the common ruderal herb Barbarea vulgaris (Brassicaceae) was set up to elucidate to what extent short-lived species sprouting from roots regenerate and compensate for seed production after damage. We tested if sprouting from roots ensures survival after severe aboveground biomass damage, but the number of seeds produced declines with increasing severity of injury, decreasing nutrient availability and progress in the life cycle at the time of injury.Plants of B. vulgaris were cultivated in a 3-year garden experiment at two nutrient levels (high vs. low). During the experiment, two levels of injury severity were applied: high (removal of all aboveground biomass) and low (removal of aboveground biomass leaving basal axillary buds intact). Damage was applied at four life-cycle phases: young rosette, overwintered rosette, flowering plant and fruiting plant. All injured plants survived and resprouted irrespective of life-cycle phase, severity of injury and nutrient availability. Injury significantly affected seed production and also the plants’ life cycle. Plants injured in the second year of their life (overwintered rosette, flowering plant and fruiting plant) postponed reproduction to the third season (in the case of high injury severity) or their seed production was lower than in intact plants (in the case of low injury severity). In plants injured in the first life year, seed production and life cycle were not influenced. Nutrient level only marginally affected resprouting after injury and seed production.The experiment showed that the ability to sprout from roots enables plants to survive a 100% loss of aboveground biomass, and to keep some seed production or even compensate it. The short-lived ruderal species B. vulgaris successfully copes with severe disturbance by resprouting and does not rely only on its seed bank.     

Effects of soil nitrogen on diploid advantage in fireweed,Chamerion angustifolium (Onagraceae)

In many ecosystems, plant growth and reproduction are nitrogen limited. Current and predicted increases of global reactive nitrogen could alter the ecological and evolutionary trajectories of plant populations. Nitrogen is a major component of nucleic acids and cell structures, and it has been predicted that organisms with larger genomes should require more nitrogen for growth and reproduction and be more negatively affected by nitrogen scarcities than organisms with smaller genomes. In a greenhouse experiment, we tested this hypothesis by examining whether the amount of soil nitrogen supplied differentially influenced the performance (fitness, growth, and resource allocation strategies) of diploid and autotetraploid fireweed (Chamerion angustifolium). We found that soil nitrogen levels differentially impacted cytotype performance, and in general, diploids were favored under low nitrogen conditions, but this diploid advantage disappeared under nitrogen enrichment. Specifically, when nitrogen was scarce, diploids produced more seeds and allocated more biomass toward seed production relative to investment in plant biomass or total plant nitrogen than did tetraploids. As nitrogen supplied increased, such discrepancies between cytotypes disappeared. We also found that cytotype resource allocation strategies were differentially dependent on soil nitrogen, and that whereas diploids adopted resource allocation strategies that favored current season reproduction when nitrogen was limiting and future reproduction when nitrogen was more plentiful, tetraploids adopted resource allocation strategies that favored current season reproduction under nitrogen enrichment. Together these results suggest nitrogen enrichment could differentially affect cytotype performance, which could have implications for cytotypes’ ecological and evolutionary dynamics under a globally changing climate.     

Effects of light and nutrient availability on chasmogamy and cleistogamy in an understory tropical herb,Calathea micans (Marantaceae)

The effects of light and nutrient availability on chasmogamous and cleistogamous flower and fruit production were investigated in an understory tropical herb, Calathea micans (Marantaceae). I censused chasmogamous and cleistogamous flower and fruit production at five permanently marked demographic study sites in Costa Rica, characterized by different successional stages. Using a transplant experiment, I examined whether an increase in light and/or nutrients would increase chasmogamous and/or cleistogamous flower production. In natural populations as well as in the experiment, chasmogamous reproduction increased with light; nutrient availability significantly increased chasmogamous reproduction in the transplant experiment. Field observations indicated that very few plants reproduced and low investment in reproduction might have been due to poor environmental conditions. Larger plants had a higher probability of reproducing, but plant size did not have an effect on the mode of reproduction, chasmogamy vs. cleistogamy. However, the production of new vegetative shoots increased the probability of producing chasmogamous inflorescences. Cleistogamy may allow the plant to reproduce even in conditions of poor habitat quality and assures some seed set even in conditions unfavorable to plant growth.     

薇甘菊不同时期的营养繁殖及其生物量分配特征

薇甘菊是世界热带、亚热带地区最具危险性的外来植物之一,较强的无性生长与繁殖是其种群快速建立和扩散的主要原因。该实验采用生长期(40d、30d、20d、10d)和养分(1倍Hoagland’s营养液、清水+土壤、清水)二因子设计,探讨薇甘菊根、茎、叶的营养生长与繁殖和生物量分配特征。结果显示:(1)生长期对薇甘菊茎的存活率和养分对薇甘菊茎的净增生物量比例具有极显著影响(P<0.01),但对其他指标影响均不显著(P>0.05);生长期和养分互作除对薇甘菊根的存活率和茎的分枝数影响不显著外,对其他指标影响均达到极显著(P<0.01)。(2)所有薇甘菊根处理中的存活率为0,茎的分枝数在各处理之间的差异不显著。(3)随着生长期和养分增加,薇甘菊茎和叶的存活率及其生物量逐渐提高,且茎的分枝长、叶的分枝长及其分枝数逐渐提高,但中等养分更有利于提高生长期较短的薇甘菊叶的存活率、分枝长、分枝数及生物量。研究表明,薇甘菊不同营养器官在不同生长期和养分条件具有不同的存活情况以及形态可塑性和生物量分配特征。     

Trade-offs between vegetative growth and acorn production in Quercus lobata during a mast year: the relevance of crop size and hierarchical level within the canopy

The concept of trade-offs between reproduction and other fitness traits is a fundamental principle of life history theory. For many plant species, the cost of sexual reproduction affects vegetative growth in years of high seed production through the allocation of resources to reproduction at different hierarchical levels of canopy organization. We have examined these tradeoffs at the shoot and branch level in an endemic California oak, Quercus lobata, during a mast year. To determine whether acorn production caused a reduction in vegetative growth, we studied trees that were high and low acorn producers, respectively. We observed that in both low and high acorn producers, shoots without acorns located adjacent to reproductive shoots showed reduced vegetative growth but that reduced branch-level growth on acorn-bearing branches occurred only in low acorn producers. The availability of local resources, measured as previous year growth, was the main factor determining acorn biomass. These findings show that the costs of reproduction varied among hierarchical levels, suggesting some degree of physiological autonomy of shoots in terms of acorn production. Costs also differed among trees with different acorn crops, suggesting that trees with large acorn crops had more available resources to allocate for growth and acorn production and to compensate for immediate local costs of seed production. These findings provide new insight into the proximate mechanisms for mast-seeding as a reproductive strategy.     

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.     

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。     

Evaluation of the population dynamics of the forage legume (Lotus corniculatus), using matrix population models

The population dynamics of perennial crop plants are influenced by numerous factors, including management practices. Conditions in the field vary from year to year, and matrix population models are useful for evaluating population behaviour in relation to environmental variability. In Missouri, the stand persistence of birdsfoot trefoil ( Lotus corniculatus ), a perennial legume, is often limited by disease and poor seed production. A stage-based, matrix population model was developed to evaluate the population dynamics of birdsfoot trefoil in relation to clipping treatment. The plant growth stages represented in the model were seeds, seedlings, mature vegetative and reproductive plants. Two phases of population growth were evaluated in clipped and unclipped stands. Establishment-phase populations were characterized by relatively high mortality and low reproduction. Elasticity analysis indicated that growth of these populations was most sensitive to the survival of vegetative plants. Mature vegetative plants and seeds comprised the majority of surviving individuals in clipped and unclipped populations, respectively; however, establishment-phase populations under both management treatments tended toward extinction. Populations in the post-establishment phase of growth were characterized by relatively low mortality and high reproduction. Population growth in this phase of growth was most sensitive to seed production, and most individuals in these populations were at the seed stage.     

SEED AND VEGETATIVE REPRODUCTION IN RELATION TO DENSITY IN FRAGARIA VIRGINIANA (ROSACEAE)

Transplants of Fragaria virginiana Duchesne, the wild strawberry, from field and woods sites, were studied under controlled laboratory conditions to determine their seed and vegetative reproduction responses under different density conditions. The following results were obtained: (1) Increased competition among high density grown plants resulted in lower total biomass when compared to low density grown plants; (2) Increased shading in high density plots resulted in a greater percentage of biomass in leaves; (3) The percentage of total biomass in reproductive organs (seed and vegetative) was higher in low density grown plants; (4) Vegetative “reproductive effort” was higher in low density plots than in high density plots while seed “reproductive effort” remained constant between the two density treatments; (5) No significant difference between plants from habitats of different successional maturity was observed under the experimental treatments. These results are discussed in relation to reproductive density response models.     

谷子的亲缘识别能力及其与种植密度和土壤养分水平的关系

为探明作物是否具有识别邻株身份的能力以及这种能力是否受到环境因子的调控,通过大田试验,研究邻株身份(亲缘株、非亲缘株和陌生株)、种植密度和土壤养分水平的交互效应对谷子(Setaria italica)地上部分生物量分配的影响。结果表明,谷子与亲缘株为邻时的净繁殖生物量分配和种子生物量分配,比与非亲缘株为邻时显著提高,且营养生物量分配显著降低(P<0.05)。在高种植密度条件下,亲缘组谷子的穗长、净繁殖生物量分配和种子生物量分配显著大于非亲缘组,而营养生物量分配显著小于非亲缘组(P<0.05)。随着土壤养分水平提高,亲缘组谷子的种子生物量分配显著增加,营养生物量分配显著减少(P<0.05)。由此推断,谷子具有对亲缘邻株的识别能力,且这种能力受种植密度和土壤养分水平的调控,在高种植密度和高土壤养分水平条件下,谷子的亲缘邻株识别能力较强。     

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.     

食虫植物光萼茅膏菜的生物学研究

通过２年野外观察和栽培实验,对光萼茅膏菜的生活史特征、种群动态以及食虫习性进行了初步研究。结果表明：光萼茅膏菜杰早春植物;该种以球茎行营养繁殖,虽然种子产量较大,但实生苗更新能力较低;花期植物捕虫率最高;食虫对植物生长和繁殖有一定益处。     

Effects of burial in sand on the growth and reproduction of Cakile edentula

Studies were conducted to examine the effects of sand burial on the growth and reproduction of Cakile edentula under controlled greenhouse conditions Sand burial enhanced both the vegetative growth and reproduction of plants Within one week after burial, plants showed a significant increase in the length of the internode just below the current sand surface This response was not mediated by the dark conditions imposed by sand burial About two weeks after burial, adventitious roots grew upwards into the deposited sand Plants buried in washed sand did not differ in their dry weight whereas those buried in unwashed sand were significantly taller, produced greater biomass and larger number of seeds per plant than control However, the mean mass per fruit and per seed were not altered The frequency distribution of fruit and seed was only slightly modified by the burial treatments