Number Of Viable Seeds Research Articles

Effect of Pollen Source on Fruit Characteristics of Low-chilling Highbush Type Blueberries

Abstract The effects of pollen source on fruit set, berry size, seed characteristics, and potential pollen fertility were evaluated for low-chilling highbush type blueberries (Vaccinium spp.) pollinated in the greenhouse. Self-pollination of each clone, except for US79 which has low pollen viability, resulted in fruit set equal to or better than any type of cross. Berry weight and number of viable seeds per berry were not significantly higher for fruit produced from half-sib crosses than selling. Outcrosses generally produced the greatest berry weight and seed number.

Seed Ecology of Selected Amazon Basin Successional Species

Two adjacent forest sites-a mixed forest on well-drained Oxisols and a caatinga forest on waterlogged Spodosols-were similar in the number of viable seeds m-2 in the seed bank: 180 for the mixedforest site, 200 for the caatinga site. Most germinated seeds were of successional pioneer tree species Seeds were entering the mixed-forest seed bank at a rate of ca 50 seeds m-2 yr-1. Agricultural and pasture sites tended to have larger seed banks (580-1,250 viable seeds m-2) composed almost entirely of grasses and forbs. The most common grass, forb, shrub, and pioneer tree species in the forest and disturbed-site seed banks (eight species in all) were tested for their ability to persist for 1 yr in open storage cans on the forest floor and for their response to a variety of germination triggers. Seeds of all species tested were still alive after 1 yr of incubation on the forest floor. In a lighted environment these species showed good germination under both moist and flooded conditions, but neither daily tempera...

Limitation of the Recruitment of the Shrub Haplopappus Squarrosus (Asteraceae) by Flower- and Seed-Feeding Insects

(1) The hypothesis, that flowerand seed-feeding insects limit the density of seedlings and the establishment of young plants, was tested experimentally under field conditions in California for the shrub Haplopappus squarrosus (Asteraceae). (2) Fortnightly application of insecticide during flower development and fruit maturation reduced the loss of fruits caused by tephritid flies, microlepidopteran moths, and chalcidoid wasps from 94% to 41%. (3) The experimental reduction in insect damage to flowers, developing ovules, and seeds had three major effects. The number of viable seeds (those which matured and remained undamaged) increased significantly; the density of seedlings increased significantly, and the number of young plants which were recruited after one year increased significantly. (4) The experimental results, combined with observations of density and mortality in subsequent stages of growth, suggest that flowerand seed-feeding insects are the proximate factor limiting the recruitment and abundance of Haplopappus squarrosus in this coastal environment.

Effect of a Weevil,Rhinocyllus conicus, on Musk Thistle (Carduus thoermeri) Seed Production

Three musk thistle (Carduus thoermeriWeinm.) sites that were infested with a weevil (Rhinocyllus conicusFroel.) and a fourth non-infested site were evaluated for numbers of insects and seeds per seed head. At four successive weekly intervals, seed heads were sampled just after flowering. Initial sampling was in 1978 and was repeated in 1979. Weevil incidence in heads blooming during the first week was 6.7/head in 1978 and 28.0 in 1979. At infested sites, production of fully developed seeds averaged 28% less than at the non-infested site in 1978 and 78% less in 1979. Heads that were in bloom during the fourth sampling week had an infestation rate less than one weevil/head in both years. Fully developed seeds germinated well (96 to 99%) and were not affected by date of bloom. Because many heads bloomed during the third and fourth weeks, a large number of viable seeds were still produced at infested sites.

Seed Production and Spring Seedling Establishment of Diffuse and Spotted Knapweed

Annual seed production of diffuse (Centurea diffusa) and spotted knapweed (Centurea maculosa) is reduced in dry years by a reduction in the number of viable seeds per seed head and increases when above-normal precipitation occurs by increase in the number of heads/flower stem. Seed production was approximately l,OOOfold that needed to maintain observed levels of infestation. Seedlings emerging in April had a high rate of survival with most plants flowering the following season, while those emerging after May 15 had a very low survival rate and almost no flower stem production the following season. (Table 1). Each site was sampled annually the first week of August in 1973 through 1976. The number of flower stems per unit area was estimated by random counts of m* hoop. Each area was subsampled to determine the number of seed heads/flower stem and the number of mature achenes/flower head. Only seed heads that were in the maturity range of well-developed seed, but had bracts still tightly closed, were counted for the latter measurement. Location and general features of each site are shown in Table 1. Diffuse and spotted knapweed are short-lived perennials of the Centaurea genus that have become major weed problems on semiarid range and pasture lands of the Pacific Northwest. The problem of these weeds, which are continuing to spread into many prime grazing areas, was recently reviewed (Maddox 1979). Control of these species is possible by chemical means (Renney and Hughes 1969) but these measures are not always practical because of economics, terrain, or environmental considerations. Several biotic agents are under study [Maddox (1979); Watson and Renney (1974,] but at present have only a minor impact. Watson and Renney (1974) summarized observations related to the reproduction of these species. In general, they reported that these species under range conditions were capable of producing 400-900 seeds/plant that would germinate under a range of temperatures of 7 to 34O C when optimum moisture was supplied. Some post harvest and light-induced dormancy was measured. We have also observed viability greater than 80% of the seeds still retained in the seed heads of diffuse in April. These normally are fully dispersed by mid June. Both fall and spring seedling emergence is common with these species.

A reconstruction of the recent vegetational history of a prairie marsh, Eagle Lake, Iowa, from its seed bank

Substrate samples were collected at four depths (0–5, 10–15, 20–25, and 30–35 cm) from six vegetation types at Eagle Lake, Iowa. The number of viable seeds in a sample was estimated by placing samples in environments appropriate for seed germination and counting the number of seedlings. Quantitative and qualitative differences in the composition of the seed bank at different depths and locations revealed that the marsh has two distinct vegetation areas. In the northern area, the vegetation changes cyclically. These cycles involve a rotation of three vegetation types: submerged, mudflat, and emergent ( Scirpus validus Vahl./ Typha glauca Godr.). In the southern (shallower) area, the composition of the seed bank indicated that there have been no cyclical changes in vegetation. The presence, however, of Typha seed in 0–5 cm samples and in some 10–15 cm samples (in numbers exceeding those normally found in contemporary Typha communities) in vegetation types presently dominated by Sparganium eurycarpum Engelm., Scirpus fluviatilis (Torr.) Gray, and Carex atherodes Spreng. suggest that, in recent years, Typha has declined significantly in the southern area. Because of the failure of their seeds to germinate under assay conditions or because the dominant species annually produces very little seed, most shallow-water emergent community types could not be detected in the seed bank.

Buried viable propagules as a factor in postfire regeneration in northern Saskatchewan

Soils collected from seven sample plots in a burned mixed-wood area in northern Saskatchewan were held at optimum laboratory conditions to determine the number of viable seeds and latent underground buds. A total of 270 plants developed, representing a rate of emergence of 426 plants/m2 of which 372 plants (87%) originated from seed and 54 (13%) came from remnant roots or rhizomes. In addition, 19 birch seeds were extracted from the soil following the germination tests giving a total count of 456 propagules/m2. Tree species accounted for 42.9% of this total.

Influence of Seed Size and Density on Germination, Seedling Emergence, and Yield of Grain Sorghum1

AbstractSeed size is highly influential in determining germinability and seedling vigor of grain sorghum (Sorghum bicolor L. Moench), but whether this factor is predominate over seed density (i.e. specific gravity) has not been established. A 2‐year study was conducted to determine to what extent seed size and density influence germination and subsequent field performance. Large and small seed lots from the same genotype were compared to “more dense” and “less dense” seed lots which were separated using either urea‐phosphate or sucrose solutions. The results indicated that seed lots with larger and denser seeds had a higher percent germination. The data also supported the conclusion that a higher percentage of viable seeds could be selected from seed lots with low average germinability by using specific gravity separations. However, the establishment of seedlings, final stands, and grain yields were not a function of size or density when the same number of viable seeds were planted in the field.

Effect of Temperature and Depth of Burial on the Persistence of Seed of Avena fatua L. In Western Australia

Two wild species of Avena predominate in the temperate south-west region of Western Australia; A. fatua L. is a major weed of cereal crops, while A. barbata Pott ex Link is found mainly on vacant, undisturbed land and in pastures (Paterson 1976). These habitat preferences may be due largely to the differing seed germination characteristics of the two species (Paterson 1974). A. fatua has considerable seed dormancy; less than 4000 of each seed crop germinates with the following opening rains and a further 10-30% germinates later in the season. In contrast, almost complete germination of A. barbata occurs with the opening rains and pre-sowing cultivation virtually eliminates this species in a cereal crop. The dormancy of A. fatua seed is known to continue through the following growing season regardless of soil temperatures (Paterson 1974). Banting (1962) and Forbes (1963), in Canada and England respectively, stated that a minimum of five years of continuous pasture is required before the number of viable seeds in the soil falls to a level where resulting plants do not constitute a weed problem in a subsequent cereal crop. Thurston (1966) in England and Quail & Carter (1969) in Eastern Australia believe that a much shorter period, possibly only one to two years, is equally effective. This paper reports on a study of the long-term persistence of A. fatua in Western Australia and the effect of temperature and depth of seed burial on persistence.

<i>Petunia hybrida</i> のはい珠培養における鉄, ホウ酸, および糖が発芽種子数におよぼす影響

The present investigation deals with in vitro growth of ovules on a half of the placenta of Petunia hybrida, W166H×K146BH (each clone is self-incompatible), with special reference to the influence of iron, boric acid, and sugars. The culture medium of NITSCH (1951), modified by the addition of 500mg/l KNO3 and 80mg/l NH4NO3, was used as a basal medium.The optimal initial hydrogen-ion concentration was at pH of 4.5-5.0 in the basal medium and at pH of 6.0 in the basal medium with Fe-EDTA at an iron concentration of ca. 2.5ppm instead of ferric citrate.The number of viable seeds per ovary increased with an increasing concentration of ferric citrate from 10 to 40mg/l in the basal medium. Iron complex Fe-EDTA composed of 50mg/l FeSO4•7H2O and 40mg/l disodium ethylenediaminetetraacetate, dihydrate (Na2-EDTA) was also an effective compound and was favorable for the viable seed production.10mg/l or above boric acid should be added to the basal medium containing either ferric citrate or Fe-EDTA. Medium containing 50mg/l boric acid was superior for the viable seed production to those with any other concentration. The efficancy of boron was influenced by the organic forms of iron. The medium with Fe-EDTA at an iron concentration of ca. 2.5ppm was superior to that with 10mg/l ferric citrate.Basal medium containing 7.5 per cent sucrose or 5 per cent fructose produced the maximal viable seeds and that containing a mixture of sucrose and fructose or sucrose and glucose was inferior to the basal medium.From these results, experiments were conducted to clarify the interaction among three components, iron, boric acid, and sugars. About 5-6 normal seedlings with two cotyledons and roots per ovary were obtained in the medium containing ca. 10 ppm Fe as Fe-EDTA, 25mg/l boric acid, and 7.5 per cent sucrose. This was about six times as the number of seedlings produced in the basal medium.In the basal medium containing fructose instead of sucrose, however, the higher concentrations of boric acid and/or iron failed to bring about the noticeable effect.

Effects of time of nitrogen application on the yield and characteristics of the seed produced by Demeter fescue (Festuca arundinacea)

Ammonium nitrate, applied in winter and in spring (at head emergence) increased the seed yield of a commercial crop of Demeter fescue (Festuca arundinacea) by up to 54 per cent. The nitrogen treatments each involved a total of 90 lb nitrogen an acre, which was divided differently between the two times of application. The early nitrogen applications increased the number of fertile tillers, but not the yield per tiller, whereas late applications increased only the yield per tiller. The germination percentage of the seed was affected only transiently by nitrogen treatments, but seed size was increased by the late nitrogen application. Thus the number of viable seeds per unit weight of sample was reduced by late nitrogen. The greatest yield of viable seeds was produced by a combination of 60 lb nitrogen in early August and 30 lb nitrogen in late September at heading.

EMBRYOLOGY OF DIPLOID × DIPLOID AND DIPLOID × TETRAPLOID CROSSES IN POINSETTIA

Hybridization between diploid cultivars of poinsettia results in abundant seed production. However, with the diploid used as the maternal parent in crosses with tetraploids, less than 1% viable seedlings are realized. Cytological observations indicated a 2:3:2 chromosome number ratio of the embryo, endosperm and maternal tissue in diploid crosses with endosperm development completed in about 45 days after pollination. Embryo differentiation in diploid crosses occurred at 26 days and matured in approximately 54 days after pollination. The chromosome number ratio of the embryo, endosperm, and maternal tissue was not firmly established for the diploid × tetraploid cross due to the small number of viable seeds obtained, but the expected 3:4:2 ratio was frequently observed. Endosperm development in most of the ovules examined did not progress beyond the large fragile cell stage. This study suggests that the endosperm may be the determining factor in setting of seed in the diploid × tetraploid cross.

Buried, viable seeds in two California bunchgrass sites and their bearing on the definition of a flora

A complete description of a plant community must include the buried viable seeds in the soil. The plants occurring in this form are a part of the flora, which helps to determine the community, even though they are not readily evident. The importance of defining an ecosystem's flora is reviewed. When the soil's buried viable seed population is used to help determine the flora, various problems arise since perennial plants reproduce much less abundantly by seed than do annuals, laboratory germination conditions probably do not suit all species, and seeds are not distributed at random so sampling is made difficult. In an investigation of buried viable seeds in two grazed and ungrazed California bunchgrass sites poor correspondence between vegetation and soil seed populations was found. Numbers were 8000 to 12,000 seeds per m2. Figures of this order or magnitude are general in the periodical literature which describes the buried viable seed populations and the factors which influence them qualitatively and quantitatively in various kinds of arable, mesic pastured or mown, steppe, and forest plant communities. Not only are the plants evident above ground in a stand of vegetation part of the ecosystem which includes that vegetation, so also are the plant disseminules in the soil. This paper records a determination of the kinds and numbers of viable seeds in two stands ofStipa pulchra, bunchgrass vegetation in the eastern foothills of the central Coast Ranges of California. Such vegetation is variable from year to year, over a climatic cycle of years, and successionally (i.e.), it is seral and therefore changes with time, other habitat factors being constant (Heady 1958). By no means all the species which can occur in this vegetation over a period of several years are evident above ground at one time. We have attempted to use the soil content of buried, viable seeds in the two stands as a measure of this potential flora.

Ecological Studies on Alopeculus aequalis Sobol : 5. On the influence of light intensity upon growth of the weed, viability of seeds at various stages of maturity and seed production. : 6. On the compost and the methods of field management as agents in seed dissemination.

As a fundamental investigation of controlling Alopeculus aequalis, one of the dominant weeds in winter cropping on drained paddy fields, seed production and seed dissemination were studied. The results are as follows : 1. Continuous shading started half a month before or soon after heading time of the weed affected on the growth of the weed, viability of seeds at various stages of maturity and seed production (fig. 1-3). 50% shading of sunlight was less influential, except causing only slight decrease in the seed viability when shading was started half a month before heading. By 80% shading of sunlight which was much more influential on growth and seed production, number of viable seeds was decreased distinctly at various stages of maturity. It was caused by decreased number and low-ered viability of seeds as a result of decreased ear numbers and retarded ripenning respectively. 2. It was found that seeds of the weed lose easily their viability by storage in compost-high temperature treatment (fig. 4). Because the seeds were rapidly destroyed during fermentation process of the compost, the compost can not be the carrier for seed dissemination. It was also found that seed dissemination in fields takes place mainly with seeds shattered from weeds growing in field, and generally speaking, the following seeds are not so important (fig. 6): seeds produced last year which remain alive in soil, seeds shattered on field from weeds growing on footpath, and seeds carried by water from irrigation channel or neighbouring field.