Showing papers on "Germination published in 1982"

The germination of seeds

Abstract: Provides a comprehensive overview of the physiology, biochemistry and ecology of the process of seed germination. This revised edition includes extended coverage of the influence of molecular biology on seed science and a new chapter on seed technology and propagation.

The Effects of Low Temperature on Zea mays

Abstract: Publisher Summary This chapter describes various physiological effects of low temperature on maize and evaluates their significance for maize growing and breeding. A distinction has been made between low-temperature damage and the effects of suboptimal temperatures above the injury threshold on growth rate and the processes underlying it. Maize is sensitive to frost in all phases of its growth cycle except as dry seed. Freezing injury depends on the temperature, the duration of freezing, the water status of the plant, and the stability of supercooled water. Temperatures below and around the minimum temperature for germination and growth cause various types of physiological damage in maize. These low-temperature effects are referred to as chilling injury. Low-temperature chlorosis occurs at temperatures above the chilling range. Seeds and seedlings are sensitive to various types of injury. Soil fungi cause seed rot and seedling blight. Several types of physiological damage may occur, such as freezing injury, chilling injury, and low-temperature chlorosis. Low temperatures not only retard germination, emergence, and vegetative growth, but also affect morphogenesis. The chapter presents evidence showing that seedling growth at suboptimal temperatures is limited by leaf and root extension rather than by photosynthesis or the uptake of water and mineral nutrients.

Phytochrome control of seed germination in the tropical rain forest pioneer trees cecropia obtusifolia and piper auritum and its ecological significance

Abstract: SUMMARY The tropical forest pioneer trees Cecropia obtusifolia and Piper auritum germinate and become established in large light gaps of the forest canopy in the rain forest of south-eastern Mexico. Germination of the seeds of both species is under photocontrol and is triggered when the red: far-red ratio (R: FR) of the incident light increases due to a reduction of the green canopy density. Exposure to simulated light canopies retarded and reduced germination. The light environment inside the forest inhibits germination totally. Experiments with alternate R and FR light treatments indicate the need for long periods of exposure to R light for germination, and demonstrate a strong reversibility of the R light stimulation by FR light in both species. This property of the seeds may be related to the detection of light gap size and its differentiation from the normal sunflecks of the forest.

The effects of propagule size on germination and seedling growth in Mirabilis hirsuta

Abstract: Mirabilis hirsuta, a fugitive prairie plant species, occurs only on disturbances (mounds) resulting from the foraging activity of badgers on the Cayler Prairie Preserve in northwestern Iowa, U.S.A. Seedling survivorship and later competitive success are predicated upon the root's rapid extension to and occupation of a moisture-retentive layer of buried vegetation which forms the base of these disturbances. Seed size, which varies from 6 mg, is a predictor of the likelihood of establishment success through effects upon germination and seedling vigor. Regressions indicated that germination increased by 10.2% per milligram increase in seed weight, leaf area of 30-day-old seedlings increased by 47.8 mm2/mg seed weight, and dry weight biomass of these seedlings increased 40.2 mg/mg seed weight. Germination also occurred more rapidly with heavier seeds. Differences in seedling growth with increases in seed size are largely due to the capital provided by initial food reserves. The instantaneous rate of in...

Germination ecology of halophytes

Abstract: Germination is an important stage in the life cycle of species growing in saline environments because it determines the soil conditions later stages in the life cycle will be exposed to. Laboratory investigations of seed germination indicate that seeds of most halophytic species reach their maximum germination in distilled water (Seneca, 1969; Onnis and Bellettato, 1972; Breen et al. 1977; Okusanya, 1977; Ungar, 1977a, 1978a; Zid and Boukhris, 1977; Dietert and Shontz, 1978). Seed germination in saline environments ordinarily occurs during the spring or in a season with high precipitation, when soil salinity levels are usually reduced (Ward, 1967; Chapman, 1974; McMahon and Ungar, 1978). Several studies have shown that seeds of many halophytes remain dormant when exposed to low water potentials (Ungar, 1962, 1974a, b, 1975, 1978a; Williams and Ungar, 1972).

Seed germination of a tropical rain forest pioneer tree (Heliocarpus donnell‐smithii) in response to diurnal fluctuation of temperature

Abstract: The tropical rain forest pioneer tree Heliocarpus donnell-smithii Rose establishes itself only in light gaps of the forest canopy. A series of experiments with fluctuating temperatures have shown that the germination is increased if the temperature rises above 31°C during a few hours each day. The laboratory experiments were complemented with determinations of the seed viability in the soil each month during one year, and with determinations of germination under the natural diurnal fluctuation of temperature in a forest gap. Germination increases under fluctuating temperatures, and the seeds can remain dormant when buried in the soil during several months. The diurnal heating of the soil of light gaps as contrasted with the almost constant temperature under undisturbed canopies may be a precise environmental indicator of appropriate conditions for germination and establishment of the pioneer heliophytes of the rain forest.

Adaptation of gray squirrel behavior to autumn germination by white oak acorns.

Abstract: The oaks (Quercus L.) are divided into two subgenera, the white oaks (Leucobalanus Engelmann) and the red oaks (Erythrobalanus Spach). Like most midlatitude plants, red oaks have dormant seeds which germinate in spring after being dispersed in autumn. Acorns of many species of white oaks germinate in autumn soon after they fall, producing a large taproot which stores much of the acorn's food reserves over winter. Live (evergreen) oaks are taxonomically regarded as red oaks (Williams, 1939), but resemble white oaks in many important seed and life history traits, including early germination (Sargent, 1905; Lewis, 1911; Trelease, 1924; USDA, 1974). Red oaks and white or live oaks typically occur together as associates and potential competitors throughout North America. They will be referred to collectively as WO and RO; WO by implication includes live oaks insofar as their seed biology is convergent with white oaks. Unabbreviated common names refer to single species for which the scientific name is given at least once. The seedling taproot of white oak (Q. alba L.), probably the most common WO of eastern North America, grows rapidly in autumn and perhaps also grows more slowly through the winter, drawing upon the food reserves of the cotyledons. The seedling taproot is remarkably thickened on seedlings of Q. alba and Q. virginiana Mill. (Fig. 1A; Lewis, 1911) and appears to serve as an overwinter storage organ. A white oak acorn in a sense buries itself, and the rapid germination and root engorgement may serve as an escape from various seed predators (D. H. Janzen, pers. comm.). This paper reinterprets autumn germination in the WO as a post-dispersal escape from tree squirrels, although the trait may have other adaptive values as well. It also reports that gray squirrels (Sciurus carolinensis Gmelin) kill acorns of WO before caching them, by cutting out (excising) the seed 'embryo' (Fig. 1B, C). The adaptive value suggested for this behavior is preventing 'escape' and loss of that fraction of the acorn which is transferred into the seedling taproot between the time an acorn is cached in autumn and the time when a squirrel returns to utilize the acorn in winter. A brief description of oak seed and seedling morphology will be helpful (see also USDA, 1974 p. 698). The mature acorn, technically a fruit but here called a seed, consists of a pericarp (shell) enclosing two seedling leaves (cotyledons) which are filled with food reserves and occupy most of the seed. The cotyledons are connected by petioles to the tiny seedling (hereafter improperly but less ambiguously called the embryo when referring to ungerminated acorns). The embryo is located very near the apex or pointed end of the acorn and is folded between the cotyledons. In germination the pericarp splits at the apex and the radicle (seedling root) emerges first. Later, the entire seedling is thrust out, as the cotyledonary petioles arch out and downwards and lengthen to 2-5 cm. The radicle grows into a stout taproot in autumn, but the epicotyl and hypocotyl (the presumptive leaves and stem) grow scarcely at all until spring.

Effects of seed size on the germination, growth and competitive ability of rumex crispus and rumex obtusifolius

Abstract: (1) Seed size has no effect on percentage germination of Rumex obtusifolius or on the heavier seeds of R. crispus but germination of small seeds of R. crispus is reduced. Germination rate of seeds of R. obtusifolius increases as seed size decreases. (2) Seed size has no effect on the subsequent growth of R. crispus. In R. obtusifolius initial growth is slower from smaller seeds, though no difference is detectable at the end of the growing season. (3) Intraspecific competition results in reduced growth of plants from 1.4 to 1.2 mm seeds compared with those from > 1.4 mm seeds, but there are no competitive interactions. (4) The results are interpreted in terms of the response of the Rumex species to grazing by the chrysomelid beetle, Gastrophysa viridula.

Seed banks in five boreal forest stands originating between 1810 and 1963

Abstract: The viable seed content of soil samples from five coniferous forest stands in northern Sweden, aged 16–169 years, was determined by means of germination trials. The soil samples were separated into...

Allelopathic potential of wheat (Triticum aestivum) straw on selected weed species.

Abstract: The allelopathic potential of wheat (Triticum aestivum (L) 'Doublecrop') straw residue was evaluated on weed-seed germination and seedling growth The in- hibition of weed-seed germination and seedling growth was extract-, species-, and temperature-dependent The extracts prepared by agitating and soaking caused greater inhibition than those obtained by leaching The descending order of species susceptibility was ivyleaf morningglory (Ipomoea hederacea (L) Jacq), velvetleaf (Abutilon theophrasti Medic), pitted morningglory (Ipomoea lacunosa L), hemp sesbania (Sesbania exaltata (Raf) Cory), sicklepod (Cassia obtusifolia L), and Japanese barnyard millet (Echinochloa crus-galli var frumetaceae (Roxb) Link) Incubation at 35 C caused the greatest inhibition of germination and growth Additional index words Seed germination, germination temperature, phytotoxicity, seedling growth

Effect of Citrus Root Exudates on Germination of Chlamydospores of the Vesicular-Arbuscular Mycorrhizal Fungus, Glomus Epigaeum

Abstract: The effect of root exudates from Troyer citrange (Poncirus trifoliata x Citrus sinensis) on germination of surface-sterilized chlamydospores of the vesicular-arbuscular mycorrhizal (VAM) fungus, Glomus epigaeum, was examined on water agar. Optimum temperature for spore germination was 25 C. After 7 da exposure of spores to root exudates, germination was increased from less than 10% (distilled water control) to up to 27%. Germ tube length of exudate-treated spores was more than four times greater than that of untreated spores. Root exudates stimulated branching of germ tubes, whereas germ tubes of untreated spores branched infrequently. These results indicate that root exudates affect spore germination and germ tube growth of G. epigaeum and thereby could influence subsequent root colonization and VAM formation.

Germination of the dimorphic fruits of bidens pilosa l.

Abstract: SUMMARY Dimorphic fruits of Bidens pilosa were tested separately for differences in germinability and seedling development. The long achenes were found to germinate readily under a wide range of conditions while the short achenes showed fairly exacting germination requirements. Germination of the short achenes was found to be enhanced by red light treatment, scarification, applied hormones, leaching and increased oxygen tensions. Seedlings originating from short achenes showed lower survival rates and initially slower development than those originating from the long achenes. The implications of the morphological differences and differences in germination and development of the two achenes are discussed.

Microbial hazards associated with bean sprouting.

Abstract: The behaviour of microorganisms was studied in mung beans and alfalfa seeds before and after germination in modified, commercially available bean-sprouting kits. The microorganism were enumerated by the aerobic plate count (APC) and by total yeast and mold count procedures. Salmonella species were artificially inoculated into selected samples and were enumerated by the most probable number (MPN) method. After germination of the beans or seeds into mature sprouts, significant increases were noted in APCs and in MPN values of Salmonella species. Although counts of yeasts and molds did not increase significantly after germination, these samples show an increase in toxic Aspergillus flavus and potentially toxic Alternaria species. The presence of toxic Penicillium cyclopium molds also increase substantially in 5 samples of a single brand of mung beans. Analysis of selected sprout samples, however, showed no presence of aflatoxin.

Limits to Microbial Growth in Soil

Abstract: SUMMARY: More organic carbon was released into solution from soils that had been air-dried and rewetted than from the natural soils. Irradiation and autoclaving of a range of air-dried or field soils greatly increased the amount of carbon that was released into solution. The carbon released appeared to provide substrates for fungal spore germination and bacterial growth, thereby relieving microbiostasis. The percentage germination of Penicillium citrinum spores was at least doubled in sterilized soil and halved in untreated soil compared with spores germinating in the absence of soil. In general, a streptomycin-resistant strain of Agrobacterium radiobacter made significant growth only in sterilized soils.

Variation and Adaptive Role of Seed Dormancy in Some Annual Grassland Species

Abstract: A total of 87 seed samples collected from various parts of central and northern California were tested for variability in seed germination behavior of five grass species (Avena fatua, A. barbata, Bromus mollis, B. rigidus, and B. rubens) and two legume species (Medicago polymorpha and Trifolium hirtum). Laboratory germination after nearly 6 and 12 wk of storage at 21 C showed; (1) Seed dormancy breaks down more rapidly in the five grass species than in the two legumes. (2) There is a great deal of interpopulational variation within each species. (3) Seasonal dormancy in Avena and Bromus was highly correlated with the patterns of a probable rainstorm at different sites during the summer months; this suggested a direct adaptive role of seed dormancy in the timing of germination such as to ensure continued moisture availability in the fall. (4) Estimates of genetic variation between families in A. barbata, B. mollis, and T. hirlum suggested dormancy to have low heritability in A. barbata and B. mollis but hi...

Low temperature seed germination of Lycopersicon species evaluated by survival analysis.

Abstract: Low temperature germination responses were evaluated for 18 high altitude accessions representing five wild Lycopersicon species and 19 accessions of L. esculentum which have reputed ability to germinate in the cold. Survival analysis indicated that one accession of L. chilense germinates better at 10°C than PI 120256, the fastest-germinating L. esculentum genotype, and that PI 120256 germinates as well as PI 126435 (L. peruvianum). Additional wild ecotypes exhibiting rapid germination at 10°C were identified from L. peruvianum and L. hirsutum. These ecotypes may possess genetic potential for introgressing cold germination ability into L. esculentum cultivars.

Spore germination and germ tube growth of a vesicular-arbuscular mycorrhizal fungus in vitro1

Abstract: The effects of mineral nutrients, thiamine, pH, and organic substrates on germination and germ tube growth of a vesicular-arbuscular mycorrhizal fungus were examined. Surfacesterilized azygospores of Gigaspora margarita were plated on 1% water agar containing different components and incubated at 28 C up to 30 da. Maximum germination and germ tube growth occurred when 20 mg 1-1 CaH2PO4 was used, whereas 24 mg 1-~ NH4NO3 did not affect germination and depressed germ tube growth by 55%. Potassium or concentrations of soluble nutrient salts as high as those used to grow seedlings axenically had no effect on spore germination or germ tube growth. Thiamine at 0.1 mg 1-1 increased germination, and maximum germ tube growth occurred at 0.01 mg 1-1. The interaction between medium pH and medium composition was significant. Spore germination was not enhanced by any of the organic substrates. Low concentrations (4 g 1-1) of sucrose favored germ tube growth. Relation of these results to nutrition and root-colonizing ability of VA mycorrhizal spores is discussed.

Water Relations in the Germination of Seeds

Abstract: In seeds, the term germination includes those processes that lead to the initiation of growth in the quiescent embryonic sporophyte which they contain. Growth is a measurable and irreversible increase in size that results from cell expansion, whether or not accompanied by cell division. Most seeds contain within their embryos, or in the adjacent endosperm, or perisperm, the substrates that are necessary to sustain the initial growth of the embryo, by which germination is expressed, as well as for the subsequent growth and establishment of their seedlings in their natural habitat. These substrates (polysaccharides, proteins, triglycerides, salts of phytic acid) must first be hydrolyzed from the condensed and insoluble forms in which they are stored. In the dry seed, the metabolic machinery for the hydrolyses, for the subsequent syntheses and for the production of energy is almost entirely absent, inactive, or disassembled. In order for germination to take place, various components of this metabolic machinery must be activated, assembled and synthesized de novo. These processes require energy, but respiratory activity of the dry seed is very low, frequently undetectable. The first requirement for germination is water for hydrolysis, as a medium for translocation by diffusion, for hydration of enzymes, cell membranes and organelles to their operational conformation, and finally to provide the driving force for cell expansion that is initiated by germination.