Variation In Seed Production Research Articles

Nitrogen Addition Affects Interannual Variation in Seed Production in a Tibetan Perennial Herb.

The variability observed in the annual seed production of perennial plants can be seen as an indication of changes in the allocation of resources between growth and reproduction, which can be attributed to fluctuations in the environment. However, a significant knowledge gap exists concerning the impacts of nitrogen addition on the interannual seed production patterns of perennial plants. We hypothesized that the addition of nitrogen would impact the annual variations in the seed production of perennial plants, ultimately affecting their overall reproductive efficiency. A multiyear field experiment was conducted to investigate the effects of varying nitrogen supply levels (e.g., 0, 4, and 8 kg N ha-1 yr-1 of N0, N4, and N8) on vegetative and floral traits, pollinator visitation rates, and seed traits over a period of four consecutive years. The results showed that the N0 treatment exhibited the highest levels of seed production and reproductive efficiency within the initial two years. In contrast, the N4 treatment displayed its highest level of performance in these metrics in the second and third years, whereas the N8 treatment showcased its most favorable outcomes in the third and fourth years. Similar patterns were found in the number of flowers per capitulum and the number of capitula per plant. There exists a positive correlation between aboveground biomass and several factors, including the number of flowers per capitulum, the number of capitula per plant, the volume of nectar per capitulum, and the seed production per plant. A positive correlation was found between pollinator visitation and the number of flowers per capitulum or the number of capitula per plant. This implies that the addition of N affected the maintenance of plant aboveground biomass, flower trait stability, pollinator visitation, and, subsequently, the frequency of seed production and reproductive efficiency. Our results suggest that augmenting the nitrogen content in the soil may have the capacity to modify the inherent variability in seed production that is observed across various years and enhance the effectiveness of reproductive processes. These findings have the potential to enhance our comprehension of the impact of nitrogen addition on the reproductive performance of perennial herbaceous plants and the underlying mechanisms of biodiversity in the context of global environmental changes.

Variation of Seed Production and Viability in a Full-Sib Trial of Melaleuca cajuputi sub sp. cajuputi in Gunungkidul Yogyakarta

Family variation of capsule production and the seed viability in the Paliyan full-sib trial of Melaleuca cajuputi subsp. cajuputi , at Gunungkidul, Yogyakarta, were observed. The full-sib trial was designed as Incomplete Block Design, consisting of 39 families; six individual as tree plot and replicated in eight blocks. Height and diameter at breast height were assessed to identify the correlation between capsule category and growth performance. The capsule production was assessed visually to one of the capsule categories: “0” for none; “1” for light; “2” for medium and “3” for heavy. Results showed that each family of M. cajuputi sub sp. c ajuputi equally contributed to the seed production. Progeny analysis showed that the seed productions were not strongly under genetic control (h2i) = 0.12. This study also found positive correlation between the flowering strength (the flower production levels) and the number of capsule (R 2 =0.279). However, there were no significant differences between the flowering levels and the viability of M. cajuputi sub sp. cajuputi . Mean seed viability was 31%, there were no significantly differences of capsules production between trees having high flowering intensity and low flowering intensity. Low seed viability was assumed due to the unsynchronicity of flowering, leading to the low levels of outcrossing rate. Therefore, selection of families with synchronicity of flowering was recommended to establish a seed orchard.

Factors Contributing to Variation in Seed Production among Remnant Populations of the Endangered Daisy Gerbera aurantiaca1

ABSTRACTThe species‐rich mist‐belt grasslands of southern Africa have been severely reduced in extent as a result of commercial afforestation, thus confining many endemic plants and animals to small populations in habitat fragments. We investigated the influence of various environmental factors on seed production and seedling recruitment in remnant populations of the endangered grassland herb Gerbera aurantiaca (Asteraceae). Experiments with color traps showed that Eriesthis beetles, which appear to be the primary pollinators of G. aurantiaca, were most abundant in the two largest y extant populations. Seeds are produced in a very small proportion (typically <10%) of the ca 80 female florets in a capitulum. The mean number of seeds produced in undamaged capitula was found to be significantly lower in small than in large populations. Pollen limitation was evident from a significant overall increase in seed set after supplementalpollination in three populations over two seasons. The proportion of capitula containing seed predators did not differ markedly among populations or years, but lepidopteran larvae, which destroy all of the seeds in a capitulum, weremost abundant in the two largest populations in 2003. The presence of juvenile plants varied markedly amongpopulations, but this could not be linked firmly to estimates of seed production. Clonal growth is likely to contribute to the persistence of small isolated populations of G. aurantiaca, even when seed production is severely compromised by pollen limitation and predation.

Factors Contributing to Variation in Seed Production among Remnant Populations of the Endangered Daisy Gerbera aurantiaca1

The species-rich mist-belt grasslands of southern Africa have been severely reduced in extent as a result of commercial afforestation, thus confining many endemic plants and animals to small populations in habitat fragments. We investigated the influence of various environmental factors on seed production and seedling recruitment in remnant populations of the endangered grassland herb Gerbera aurantiaca (Asteraceae). Experiments with color traps showed that Eriesthis beetles, which appear to be the primary pollinators of G. aurantiaca, were most abundant in the two largest extant populations. Seeds are produced in a very small proportion (typically <10%) of the ca 80 female florets in a capitulum. The mean number of seeds produced in undamaged capitula was found to be significantly lower in small than in large populations. Pollen limitation was evident from a significant overall increase in seed set after supplemental pollination in three populations over two seasons. The proportion of capitula containing seed predators did not differ markedly among populations or years, but lepidopteran larvae, which destroy all of the seeds in a capitulum, were most abundant in the two largest populations in 2003. The presence of juvenile plants varied markedly among populations, but this could not be linked firmly to estimates of seed production. Clonal growth is likely to contribute to the persistence of small isolated populations of G. aurantiaca, even when seed production is severely compromised by pollen limitation and predation.

Relationships between age and biomass of individual plants and seed production in two grazed tropical legumes. 1. Derivation of relationships

The distributions of individual plant age and biomass of Chamaecrista rotundifolia cv. Wynn and a mix of Stylosanthes scabra cvv. Seca and Fitzroy in grazed grass–legume pastures were examined to determine their effect on seed production. The effects of enhanced soil water conditions and severe defoliation on seed production were assessed in ungrazed plots. These experiments were part of a larger study to develop a demographic model of perennial forage legumes. The distribution of individual plant age and biomass was highly skewed towards a large number of young/small plants, with fewer old/large plants. Lack of seed set when stem length was less than approximately 200 mm, and in most small plants (&lt;2 g), resulted in older/larger plants contributing far more to seed production and, to a lesser extent, legume biomass, than they did to legume plant numbers. C. rotundifolia seed production was linearly related to individual plant biomass but was highly varaiable and was greatly reduced in swards containing &gt;3000 kg/ha of grass. Using log-transformed data, plant biomass accounted for 74% of the variation in seed production (SP), but together with grass biomass accounted for 91% of the variation [ln(SP) = 6.01 + 0.91*ln(BIOMASS) – 0.28*ln(GRASS BIOMASS), P &lt; 0.001]. Total legume biomass accounted for only 44% of the variation in seed production. S. scabra herbage allowance (kg legume/head) had a major impact on seed production. Total legume biomass and individual plant biomass alone accounted for less than 40% of the variation in seed production. Using herbage allowance (HA) as well as individual plant biomass improved the prediction of seed production (SP) to account for 74% of the variation [ln(SP) = 0.11 + 1.14*ln(BIOMASS) + 0.24*ln(HA), P &lt; 0.001]. Enhanced soil water conditions increased the biomass of individual plants of both species and increased the seed production per gram of plant in S. scabra but not in C. rotundifolia. Severe defoliation in early summer or autumn can greatly reduce or even eliminate seed production by some plants by removal of flowers, reducing individual plant biomass, or allowing insufficient time for plants to reach minimum stem lengths. The different factors affecting seed production in the 2 species highlight the complexity of legume seed set in grazed pasture systems, and some implications for grazing management and modelling are discussed.

Annual Variability in Seed Production by Woody Plants and the Masting Concept: Reassessment of Principles and Relationship to Pollination and Seed Dispersal

By analyzing 296 published and unpublished data sets describing annual variation in seed output by 144 species of woody plants, this article addresses the following questions. Do plant species naturally fall into distinct groups corresponding to masting and nonmasting habits? Do plant populations generally exhibit significant bimodality in annual seed output? Are there significant relationships between annual variability in seed production and pollination and seed dispersal modes, as predicted from economy of scale considerations? We failed to identify distinct groups of species with contrasting levels of annual variability in seed output but did find evidence that most polycarpic woody plants seem to adhere to alternating supra-annual schedules consisting of either high or low reproduction years. Seed production was weakly more variable among wind-pollinated taxa than animal-pollinated ones. Plants dispersed by mutualistic frugivores were less variable than those dispersed by either inanimate means or animals that predominantly behave as seed predators. We conclude that there are no objective reasons to perpetuate the concept of mast fruiting in the ecological literature as a shorthand to designate a distinct biological phenomenon. Associations between supra-annual variability in seed output and pollination and seed dispersal methods suggest the existence of important reproductive correlates that demand further investigation.

Population-Level Estimates of Interannual Variability in Seed Production: What Do They Actually Tell Us?

Population-Level Estimates of Interannual Variability in Seed Production: What Do They Actually Tell Us?

Annual Variability in Seed Production by Woody Plants and the Masting Concept: Reassessment of Principles and Relationship to Pollination and Seed Dispersal

By analyzing 296 published and unpublished data sets describing annual variation in seed output by 144 species of woody plants, this article addresses the following questions. Do plant species naturally fall into distinct groups corresponding to masting and nonmasting habits? Do plant populations generally exhibit significant bimodality in annual seed output? Are there significant relationships between annual variability in seed production and pollination and seed dispersal modes, as predicted from economy of scale considerations? We failed to identify distinct groups of species with contrasting levels of annual variability in seed output but did find evidence that most polycarpic woody plants seem to adhere to alternating supra‐annual schedules consisting of either high or low reproduction years. Seed production was weakly more variable among wind‐pollinated taxa than animal‐pollinated ones. Plants dispersed by mutualistic frugivores were less variable than those dispersed by either inanimate means or animals that predominantly behave as seed predators. We conclude that there are no objective reasons to perpetuate the concept of mast fruiting in the ecological literature as a shorthand to designate a distinct biological phenomenon. Associations between supra‐annual variabiity in seed output and pollination and seed dispersal methods suggest the existence of important reproductive correlates that demand further investigation.

Variation in Seed Production and Germination of Spartina Anglica Within a Zoned Saltmarsh

(1) The coastal saltmarsh at Southport, Merseyside, supported four zones of Spartina anglica sward which, from seaward to landward, were named pioneer, transitional, mature, and invaded zones, respectively. (2) The mean density of inflorescences varied from nearly 4 m-2 in the pioneer zone to more than 112 m-2 in the adjacent transitional zone. The upper reaches of the marsh had intermediate densities. (3) Inflorescences from the upper zones were large and bore at least twice as many spikelets as those from lower zones. However, the proportion of mature, filled seeds per inflorescence was inversely related to the number of spikelets borne on it resulting in a marked difference between zones in the production of viable seed. The zone of most vigorous vegetative growth and largest inflorescences thus produced the smallest proportion of viable seed. (4) Germination of seeds was accelerated by cool (5 IC), moist and brief (60 day) storage. The length of photoperiod had no significant effect on germination whereas salt water was inhibitory. There were significant interactions between factors. Overall production of viable seeds was low (<6%) and 77% of potentially viable seed was produced in 16% of the total marsh area examined.