scispace - formally typeset
Search or ask a question

Showing papers on "Germination published in 1978"


Journal ArticleDOI
TL;DR: Methods of artificially softening impermeable seeds include acid and solvent, soaking, mechanical scarification, pressure, percussion, freezing, heating, and radiation treatments that can result in a change in germination in some untreated species up to 90% or more in treated species.
Abstract: Viable seeds that do not imbibe water and thus fail to germinate in an apparently favorable environment are commonly termed impermeable or hard seed. This physical, exogenous dormancy is especially common in species of the Fabaceae. The ecological significance of hard seed includes the ability to rapidly recolonize burnt areas after fire and to withstand ingestion by animals and birds. Advantages and problems that hard seed cause in agriculture are discussed. Species from different families with impermeable seeds appear to have in common a layer of macrosclerid cells that form a palisade layer in the testa. The term strophiole and its contradictory use in botanical literature are discussed. Genetic factors and environmental conditions both affect the proportion of impermeable seeds produced. Methods of artificially softening impermeable seeds include acid and solvent, soaking, mechanical scarification, pressure, percussion, freezing, heating, and radiation treatments that can result in a change in germination from less than 20% in some untreated species up to 90% or more in treated species. Natural softening involves high temperatures and temperature fluctuations and the degree of desiccation of the seed. The mechanism of water impermeability is related to the testa and is thought to involve waterproofing substances including wax, lignin, tannin, suberin, pectin, and quinone derivatives. The hilum acts as a hygroscopic valve that prevents water uptake but allows water loss to occur at low relative humidities in some species. The strophiole is an area of weakness in the testa of some Papilionoideae while the chalaza region has been determined as an area of weakness inPisum andGossypium. The water impermeable status of some species is reversible at a seed moisture content greater than 10%. The hard seed of a species can be described both in terms of the amount and the degree of impermeability.

466 citations


Journal ArticleDOI
Irwin A. Ungar1

399 citations


Journal ArticleDOI
TL;DR: This review surveys briefly the responses of seeds held at different hydration levels, from normal germination in a free water supply to seed activation without germination under slight moisture stress, seed deterioration at greater moisture stress and the damage that can be caused to seeds in very dry conditions, as well as the responses to subsequent dehydration.
Abstract: Current interest in seed hydration treatments for the improvement of level, rate and uniformity of germination or field emergence has revealed how little is known of the physiology of germination control under water stress. This review surveys briefly the responses of seeds held at different hydration levels, from normal germination in a free water supply to seed activation without germination under slight moisture stress, seed deterioration at greater moisture stress and the damage that can be caused to seeds in very dry conditions, as well as the responses to subsequent dehydration. Inhibition of germination, though not of seed activation, at certain levels of water stress is likened to various forms of dormancy, and the mechanism governing the initiation of cell elongation is suggested as the possible key to control over germination. Several lines of evidence on cell membrane integrity and action, and their responses to external factors, point to the role that the membrane may play in cell elongation (and hence germination) control, and membrane integrity may also be associated with the transition between seed deterioration at one hydration level and seed activation and repair at slightly higher hydration levels. Seed activation without germination is also considered in an ecological context.

305 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that acetic acid accumulated in slurries of peat, loam and clay soils mixed with wheat (Triticum aestivum) straw and reduced the growth of young barley (Hordeum vulgare) plants.
Abstract: Acetic acid accumulated in slurries of peat, loam and clay soils mixed with wheat (Triticum aestivum) straw and reduced the growth of roots of young barley (Hordeum vulgare) plants. Straw from wheat, barley, oat (Avena sativa) and rape (Brassica napus) and decaying rhizomes of couch grass (Agropyron repens) mixed with slurries of the loam soil, had the same effect. The breakdown of acetic acid was slow in flooded soil and the maximum accumulation took place under these conditions; by contrast aeration of the soil prevented its accumulation. Solutions in which straw had fermented produced inhibitory effects on seed germination and the growth of seedlings in atmospheres containing between 3 and 21% O2. The phytotoxicity could be mitigated by dusting the seeds with powdered chalk.

126 citations



Journal ArticleDOI
TL;DR: During germination, Streptomyces antibioticus arthrospores passed through stages: darkening, swelling and germ tube emergence, where the spores exhibited the highest cytochrome oxidase and catalase activities and respiratory quotient.
Abstract: During germination, Streptomyces antibioticus arthrospores passed through stages: darkening, swelling and germ tube emergence. The first stage, darkening, whose main features were a decrease in absorbance and a loss of refractility, only required exogenous divalent cations (Ca2+, Mg2+ or Fe2+) and energy that can be obtained from the spore reserves. This stage was blocked by agents that inhibit ATP formation but not by antibiotics that inhibit macromolecular synthesis. The second stage, swelling, needed an exogenous carbon source and was not blocked by mitomycin C. In this stage, the spores exhibited the highest cytochrome oxidase and catalase activities and respiratory quotient. The last stage, germ tube emergence, required additional carbon and nitrogen sources. Ammonium compounds were superior to nitrate. Dry weight remained constant during the stages of darkening and swelling, with a rapid increase from the moment of germ tube emergence. Optimum pH and temperature for germination were 8.0 and 45 degrees C, respectively. Heat treatment (55 degrees C for 10 min) had no effect on germination. The fine structure of the spore underwent important changes during germination. The wall of the swollen spore became stratified and the inner layer was continuous with the germ tube wall. Macromolecular synthesis occurred in the sequence RNA, protein and then DNA. Rifampicin, streptomycin and mitomycin C prevented synthesis when added at the start of incubation. The same effect was obtained if the addition was made during germination, except with mitomycin C which inhibited DNA, but not RNA and protein synthesis.

106 citations


Journal ArticleDOI
TL;DR: In this paper, a positive significant correlation coefficient was found between total P and phytate P in cooked beans and cotyledons, when the beans-to-water ratio was 1:4.
Abstract: Phytate phosphorus, calcium, magnesium, zinc and iron were determined in black gram (Phaseolus muizgo) seeds. Phytate phosphorus (P) represents 79%± 0.48 of the total P in black gram seeds. Fifty percent of phytate P had disappeared on the 10th day of germination with a simultaneous increase in the quantities of available inorganic P. After cooking for 45 min, whole seeds and cotyledons did not show any breakdown in the phytate P or losses of minerals after initial leaching, when the beans-to-water ratio was 1:4. A positive significant correlation coefficient was found between total P and phytate P in cooked beans and cotyledons. During germination a negative significant correlation coefficient was established between total P and phytate P.

105 citations



Journal ArticleDOI
Nils Fries1
TL;DR: Basidiospores from five randomly selected species of mycorrhiza-forming Hymenomycetes did not germinate on any agar media tested, nor did an addition of activated charcoal or a living Rhodotorula glutinis colony induce spore germination, but with these two supplements together on the same agar plate slight germination occurred in all five species.
Abstract: Basidiospores from five randomly selected species of mycorrhiza-forming Hymenomycetes, viz. Laccaria laccata, Amanita muscaria, Lactarius helvus, Paxillus involutus, and Leccinum scabrum, did not germinate on any agar media tested (except for very few and irregular germinations in A. muscaria), nor did an addition of activated charcoal or a living Rhodotorula glutinis colony induce spore germination. However, with these two supplements together on the same agar plate slight germination occurred in all five species. In P. involutus percentage germination was further increased by a volatile factor produced by the mycelium of P. involutus. In L. scabrum a non-volatile substance exuded from its own mycelium strongly promoted germ vesicle and germ tube formation in the presence of activated charcoal. In both of these mycelial germination-inducing factors a certain specificity was indicated.

96 citations


Journal ArticleDOI
TL;DR: Although seeds of all species were not adapted to germina- tion under moisture stress, the existence of sharply pointed calluses and hygroscopically active awns on the seeds ensured that they would be buried below the moisture extremes of the immediate soil surface.
Abstract: The dormancy and germination requirements of five native grass species (Themeda australis, Chrysopogon fallax, C. latifolius, Sorghum plumosum, S. stipoideum) from the savannah woodlands of the Northern Territory were studied under controlled conditions. Results were related to the ecology of these species in the native grasslands of the region. All species were dormant at seed fall, and dormancy was found to be broken by exposure to dry heat. Gibberellic acid was also found to have a stimulatory effect on germination of dormant seed but there was no effect on stratification. In the field, temperatures existent at the soil surface during the dry season ensure that dormancy was broken before the heavy rainfall of the following wet season. Seeds of all species studied germinated over a similar range of temperatures with optimum germination at high temperature (c. 30°C). Although seeds of all species were not adapted to germina- tion under moisture stress, the existence of sharply pointed calluses and hygroscopically active awns on the seeds ensured that they would be buried below the moisture extremes of the immediate soil surface.

94 citations



Journal ArticleDOI
TL;DR: A combination of vanillic and p-hydroxybenzoic acid was shown to inhibit radish and grain sorghum growth in a synergistic manner by combinations of 5 × 10−3 M vanichic andp-hydroxyphenol (p-HB) acids.
Abstract: Radish and grain sorghum germination and sorghum growth were inhibited in a synergistic manner by combinations of vanillic andp-hydroxybenzoic acids. At threshold inhibition levels, 2.5 × 10−3 M vanillic acid-treated radish seeds had 71 % of control germination after 24 hr and 2.5 × 10−3 Mp-hydroxybenzoic acid-treated radish yielded 95% germination. A mixture of 2.5 × 10−3 M of each of these two phytotoxins showed 52% germination after 24 hr. Equimolar mixtures of 5 × 10−3 M vanillic andp-hydroxybenzoic acids allowed sorghum germination of 60% of untreated seeds after 24 hr, whereas separate treatments of individual phenols had 93% and 96% of control seed germination. Sorghum root and shoot elongation and total seedling growth were more sensitive than germination to vanillic andp-hydroxybenzoic acid treatments, and synergistic effects also were apparent. A combination of 5 × 10−3 M vanillic with 5 × 10−3 Mp-hydroxybenzoic reduced root length more than either did individually, and a mixture of 5 × 10−4 M vanillic with 5 × 10−4 Mp-hydroxybenzoic acid reduced sorghum seedling growth to approximately that resulting from a 10−3 M concentration of either phenol alone. Phytotoxin levels inhibitory to sorghum growth caused small increases in lower leaf surface diffusive resistance, but did not close stomates, and this effect was not judged to be the cause of reduced sorghum growth.

Journal ArticleDOI
TL;DR: Carbon dioxide at atmospheric pressure inhibited the spore germination of B. cereus spores but strongly enhanced the germination rate of those of the clostridia, which was generally higher at pH 6.7 than at 5.2–6.0.
Abstract: The influence of carbon dioxide at 1–55 atm on the germination of Clostridium sporogenes, Clostridium perfringens and Bacillus cereus spores in a complex medium was studied. The germination studies at atmospheric pressure were done in the pH range 5.2–6.7. Controls at the same pH were done in 100% nitrogen. Carbon dioxide at atmospheric pressure (1 atm) inhibited the spore germination of B. cereus spores but strongly enhanced the germination rate of those of the clostridia. Spore germination of Cl. sporogenes and Cl. perfringens was inhibited completely at 10 atm and at 25 atm, respectively. The germination rate in carbon dioxide or nitrogen was generally higher at pH 6.7 than at 5.2–6.0.


Journal ArticleDOI
TL;DR: In this paper, the authors found that germination of barley and ryegrass seeds appeared to be inhibited by the presence of sewage sludge, and that the effect was more closely related to the organic matter (OM) content of sludge-soil mixtures on which seeds were incubated.

Journal ArticleDOI
TL;DR: Heterotheca grandiflora Nutt.
Abstract: Heterotheca grandiflora Nutt. (Asteraceae, tribe Astereae) is one of the few native Californian plant species increasing its range as a weed. The production of dimorphic seed, together with flexible development in either the annual or biennial habit, may contribute to its range expansion. Well dispersed disc achenes germinate rapidly to high percentages while poorly dispersed ray achenes show considerable dormancy, germinating at a much lower rate to lower final percentages. Ray achenes appear more sensitive to environmental factors and have more specific germination requirements than do disc achenes. Thus, germination is distributed in space and time. Plants growing as annuals have one flowering period while those acting as biennials may flower up to three times, although seed production differs greatly among the stages. These factors aid in forming the "general purpose genotype" so frequently encountered in weedy species.

Journal ArticleDOI
TL;DR: Cyclic physiological changes thus occur in seeds of V,hederifolia present in the soil, with which consistent seasonal periodicity of seedling emergence is associated, and the capacity for germination progressively increased, but alter 12 months there was a sharp decline in germination at 4° C.
Abstract: Summary: Emergence of Veronica hederifolia seedlings began in mid-October and continued into spring; few appeared from June to September. Ripe seeds shed in June were dormant but wben buried in soil outdoors developed a capacity for germination initially at low temperatures (constant4 C; daily alternations of 4-10° and 4-1 5 C) and later at somewhat higher temperatures, with peak germination in September-November. During winter, spring and early summer thc germination capacity declined, to increase again in late summer and early autumn. Cyclic physiological changes thus occur in seeds of V,hederifolia present in the soil, with which lhe consistent seasonal periodicity of seedling emergence is associated. In dry storage ihe capacity for germination progressively increased, but alter 12 months there was a sharp decline in germination at 4° C. Few seeds germinated at 20° C, but moistening with GA 4/7; brought about complete germination at this temperature.

Journal ArticleDOI
15 Sep 1978-Botany
TL;DR: A period of 1 to 3 days imbibition followed by drying altered the subsequent germination responses of seeds of Rumex crispas, explaining why seedlings of R. crispas appear rapidly each summer following a droug...
Abstract: A period of 1 to 3 days imbibition followed by drying altered the subsequent germination responses of seeds of Rumex crispus L. When the imbibition took place under alternating light and temperature conditions subsequent germination was faster and more complete. In contrast, when the seeds imbibed at a constant temperature and in nearly continuous darkness subsequent germination was delayed and less complete. Subsidiary tests demonstrated that (a) within a 24-h drying period, the seeds lost virtually all water imbibed over 1 to 3 days; (b) a 3-day imbibition pretreatment was followed by faster, more complete germination in a 0.25 M mannitol solution; (c) the duration of the drying period (up to 29 days) had little effect on the outcome; and (d) seeds pretreated for 1 to 3 days under an alternating light and temperature regime germinated more rapidly than untreated seeds when sown in soil in a greenhouse. These results help to explain why seedlings of R. crispas appear rapidly each summer following a droug...

Journal ArticleDOI
TL;DR: In a reconstruction of the courses of development, the populations were shown to possess different strategies: Population W1 builds up a uniform seed stock, and population W2 a phenotypically diverse seed reserve.
Abstract: Population differentiation in Stellaria media was studied with regard to life-cycle strategy and germination ecology. Two populations were identified in the study area, growing side by side, W1 and W2. The life-span of population W1 is much shorter than that of population W2, especially under summer conditions: 1–2 months versus 4–6 months; the time to flowering differs accordingly. Germination properties of seed produced under summer, winter, and field conditions were studied. Fresh seeds produced at 20° C showed good germination (ca. 75%) over a broad range of temperatures in the case of population W1, but seeds of population W2 showed appreciable germination only at high temperatures (ca. 30%). Seeds produced at 7° C showed very little (population W2) or no germination at all (population W1). To simulate seasonal changes in temperature, a “comprehensive” germination scheme was developed which enabled the response of hydrated seeds to two temperature cycles (cold-warm-cold and warm-cold-warm) to be tested. The two populations reacted differently. At the end of the cycles, only a few seeds of population W1, but about half of the seeds of population W2, remained dormant. The data obtained were used to study the effects of differential germination ecology on the dynamics of the two populations. In a reconstruction of the courses of development, the populations were shown to possess different strategies. Population W1 builds up a uniform seed stock, and population W2 a phenotypically diverse seed reserve. The implications for population dynamics are discussed.

Journal ArticleDOI
01 Jan 1978-Flora
TL;DR: It is concluded that one of the possible causes of the mentioned difference between cultivated and wild plants is the agricultural selection for uniform and immediate germination.


Journal ArticleDOI
TL;DR: In this paper, the rate of biosynthesis of total polyamines, proteins, and RNA in the developing seeds follows similar profiles, reaching maxima 3 hours from germination, reaching a peak at 15 hours and polyamines and proteins peak 24 hours after germination.

Journal ArticleDOI
01 Jan 1978-Planta
TL;DR: Although the lipase in the glyoxysomes had the highest activity, it had to cooperate with lipases in other cellular compartments for the complete hydrolysis of reserve triglycerides.
Abstract: The castor-bean endosperm-the best-studied material of reserve lipid hydrolysis in seed germination-was previously shown to have an acid lipase and an alkaline lipase having reciprocal patterns of development during germination. We studied oil seeds from 7 species, namely castor bean (Ricinus communis L.), peanut (Arachis hypogaea L.), sunflower (Helianthus annus L.), cucumber (Cucumis sativus L.), cotton (Gossypisum hirsutum L.), corn (Zea mays. L.) and tomato (Lycopersicon esculentum Mill.). The storage tissues of all these oil seeds except castor bean contained only alkaline lipase activity which increased drastically during germination. The pattern of acid and alkaline lipases in castor bean does not seem to be common in other oil seeds. The alkaline lipase of peanut cotyledons was chosen for further study. On sucrose gradient centrifugation of cotyledon homogenate from 3-d-old seedlings, about 60% of the activity of the enzyme was found to be associated with the glyoxysomes, 15% with the mitochondria, and 25% with a membrane fraction at a density of 1.12 g cm-3. The glyoxysomal lipase was associated with the organelle membrane, and hydrolyzed only monoglyceride whereas the mitochondrial and membrane-fraction enzymes degraded mono-, di- and triglycerides equally well. Thus, although the lipase in the glyoxysomes had the highest activity, it had to cooperate with lipases in other cellular compartments for the complete hydrolysis of reserve triglycerides.

Journal ArticleDOI
01 Dec 1978
TL;DR: High germination of both subspecies of P. lanceolata and P. coronopus seedlings showed opposite mortality curves and Root penetration of the surface occurred sooner on substrates of large particles than on those of small ones, in relation to the age of dry-stored seeds.
Abstract: SUMMARY (a) The germination of Plantago lanceolata L., P. coronopus L., P. major L. ssp.major, P. major L. ssp. pleiosperma Pilger, P. media L., and P. maritima L. in relation to the age of dry-stored seeds was investigated under laboratory conditions. In general, higher percentages of radicle emergence were found with two- to five-year-old seed than with fresh seed. Only P. lanceolata and P. media seeds germinated in complete darkness. A feature of interest was the high germination of both subspecies of P. major in so-called green safelight. (b) The germination and early establishment were tested on various microsites, obtained with glass beads of various sizes. At increasing particle size, an increase in radicle emergence was found for large seeds (P. lanceolata and P. media). Root penetration of the surface occurred sooner on substrates of large particles than on those of small ones. The effects of size of the glass beads on germination and penetration were less in species with small seeds than in species with large seeds. (c) Sowing tests in the field resulted in relatively high numbers of established P. lanceolata and P. coronopus seedlings in open and dry habitats. P. lanceolata seedlings were able to establish themselves in tall dense vegetation layers. P. major ssp. major occurred most frequently on moist and open sites with a compact soil. On trodden paths P. major and P. coronopus seedlings showed opposite mortality curves.


Journal ArticleDOI
TL;DR: It is suggested that the observed large interactions on plant growth of plant age and CO2 concentration account for the relatively small enhancement by CO2 enrichment of total plant biomass and economic yield that are reported in the literature.
Abstract: The growth of wheat seedlings in a closed environment was measured from day 10 to day 24 after germination, in 12 separate and sequential experiments, in which the imposed variable was the ambient CO2 concentration. CO2 levels between 200 and 800 volumes per million (vpm) and a daily irradiance of 6.5 MJ m-2 were used. The effects of CO2 concentration on various growth parameters strongly interacted with plant age. For instance, in the 10-day-old plants, relative growth rate and net assimilation rate were increased (by 35 and 55% respectively) by an increase in CO2 levels from 200 to 800 vpm, whereas these two growth parameters were reduced (by 44 and 16%) in 24-day-old plants over the same interval of CO2 concentration. Also, increasing CO2 levels reduced the leafiness (leaf area ratio) of the plant, and increased the dry matter in the leaves (specific leaf weight). It is suggested that the observed large interactions on plant growth of plant age and CO2 concentration account for the relatively small enhancement by CO2 enrichment of total plant biomass and economic yield that are reported in the literature.

Journal ArticleDOI
TL;DR: The day length to which the mother plants of Trigonella arabica, a desert annual, were exposed during the last 8–12 days of seed maturation, affected seed coat colour, structure, permeability to water and germination.

Journal ArticleDOI
TL;DR: The germination and early growth of seedlings is reported for 4 species of Alismataceae (including Limnocharitaceae) and 2 species of Hydrocharitidae and the seedlings are temporarily anchored by hypocotylar hairs which form soon after the hypocrotyl emerges.

Journal ArticleDOI
TL;DR: Seeds of the summer annual sedge Cyperus inflexus Muhl.
Abstract: Seeds of the summer annual sedge Cyperus inflexus Muhl. are innately dormant at maturity in autumn. Seeds afterripen in the field during winter and germinate in light over a wide range of temperatures in spring and early summer. Seeds that do not germinate during spring and summer are prevented from germinating in autumn and winter because they lose their ability to germinate at lower temperatures. During autumn and winter these seeds regain their ability to germinate at lower temperatures and may germinate the next spring or summer. This narrowing and widening of the temperature range for germination may continue for several years in ungerminated seeds, until light, temperature, and soil moisture all become favorable for germination at the same time. These seasonal changes in the germination responses of the seeds allow germination to occur in spring and summer, when plants can complete their life cycle, and they prevent germination in autumn and winter, when plants cannot complete their life cycle.

Book ChapterDOI
TL;DR: This chapter discusses the heat injury of bacterial spores, characterized by the inability of the injured spores, as a result of sublethal damage suffered during heating, to develop visible signs of growth under conditions suitable or even optimal for unheated spores.
Abstract: Publisher Summary This chapter discusses the heat injury of bacterial spores. Heat injury of bacterial spores, like injury of vegetative cells, is characterized by the inability of the injured spores, as a result of sublethal damage suffered during heating, to develop visible signs of growth under conditions suitable or even optimal for unheated spores. Unlike vegetative cells, spores must germinate and complete outgrow before the vegetative cell growth can begin. Germination and outgrowth are distinct developmental stages, each with unique biochemical processes and cultural requirements. It is not surprising that a number of types of injury have been reported for spores involving both germination and outgrowth systems. The first stage in the development of an actively growing vegetative cell from a dormant spore is germination. It is a degradative process involving the rapid depolymerization, and excretion of spore constituents resulting in a loss of about 30% of the spore dry weight. Spore germination generally does not occur spontaneously, but is mediated by a wide variety of agents. Germination in bacteriological media and foods is stimulated by the so-called “nutrient germination stimulants.”