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Showing papers on "Seedling published in 1975"


Journal ArticleDOI
TL;DR: Environmental factors affecting germination and growth in the understory of mature stands of Adenostoma fasciculatum H. & A. were examined in the Santa Ynez Mountains near Santa Barbara, California, and none of the seedlings exposed to animal grazing survived.
Abstract: Environmental factors affecting germination and growth in the understory of mature stands of Adenostoma fasciculatum H. & A. were examined in the Santa Ynez Mountains near Santa Barbara, California. Nomenclature follows Munz and Keck (1959). Using a multifactor plot design, the effects of animal grazing, soil heating and soil fertility were examined under the shrub cover. Seed germination was greatly stimulated in several species by heat. Seedling growth was enhanced by nutrient enrichment similar to that observed in burned chaparral. Animal grazing had drastic effects on seedling survival. None of the seedlings exposed to animal grazing survived. Growth under the shrub cover was apparently suppressed, even in fertilized plots, by shrubderived toxins and decreased light levels. No single factor can, by itself, account for the entire pattern of germination and growth of all species beneath Adenostoma. The environmental complex under the shrub cover is such that the probability of survival of any single seedling is very low. These selective forces have resulted in the evolution of very efficient seed dormancy mechanisms in several species.

107 citations



Journal ArticleDOI
TL;DR: Control experiments on post-emergence damping-off, using small populations of garden cress seedlings inoculated with Pythium irregulare demonstrate that planting density of the host population plays an important role in determining the rate of multiplication and the rates of advance of the disease.
Abstract: SUMMARY Controlled experiments on post-emergence damping-off, using small populations of garden cress seedlings (Lepidium sativum) inoculated with Pythium irregulare, demonstrate that planting density of the host population plays an important role in determining the rate of multiplication and the rate of advance of the disease. At high seedling densities the disease is transmitted readily between host plants, but at lower densities the greater distance between adjacent plants reduces the probability of successful transmissions, and this is reflected in the parameters of multiplication and advance. A simple negative relationship was found between the mean distance separating adjacent plants and both rate of advance of disease front and rate of multiplication of disease in a randomly inoculated seedling stand.

75 citations



Journal ArticleDOI
15 Dec 1975-Botany
TL;DR: In the crowded parts of patches of Hieracium floribundum Wimm.
Abstract: In the crowded parts of patches of Hieracium floribundum Wimm and Grab, which were established for at least a decade in an ungrazed pasture, 7–10% of the population (3700 individuals/m2) flowered Of the plants that flowered, 94% were alive a year later, but only 5% of these flowered Abortion of flower heads was common; one half of all those which were initiated in early June had aborted by flowering time in early July Freshly dispersed seed had a viability of 57%, which was reduced to 17% a year later, after its storage close to the soil surface Less than 6% of the viable seed was innately dormant Dry, laboratory-stored seed retained its viability for the year but was slower to germinate than soil-stored seed In field conditions, germination was temperature inhibited during most of the growing season Maximum daytime microsite temperatures of less than 32 °C, which is necessary for germination, were found to occur only in early spring and late fall Successful seedling establishment accounts for 1

60 citations


Journal ArticleDOI
D. Gray1
TL;DR: In varieties with a high upper temperature limit for germination, seedling emergence was rapid even during periods of high soil temperate, apparently related to the prevailing soil temperatures and the upper temperature limits of each variety.
Abstract: SummaryThe response of seed germination to temperature, over the range 5-33°C, was studied for 22 varieties of the Crisp, Cos and Butterhead types of lettuce. The overall patterns of response were similar in all varieties, irrespective of the storage conditions or origin of the seed lot. The optimum temperature for germination in all varieties was between 15°C and 22°C, but there was a marked upper temperature limit for germination ranging from 25.7+0.9°C in cv Hilde to 32.8+0.9°C in cv Avoncrisp. In the main, the Crisp types germinated well at 30°C, which inhibited germination in the Butterhead types.In a field experiment where eighteen of these varieties were sown during a period of hot sunny weather, two distinct patterns of emergence were observed, apparently related to the prevailing soil temperatures and the upper temperature limits for germination of each variety. In varieties with a high upper temperature limit for germination, seedling emergence was rapid even during periods of high soil temperat...

52 citations


Journal ArticleDOI
TL;DR: Growth of isolated seedlings in sterile culture was not responsive to inhibition by abscisic acid or to stimulation by benzyl adenine, and these hormones had no effect on incorporation of 'H-amino acids into protein or of 'h-uridine into RNA.
Abstract: A B S T R A C T Fruits of Rhizophora mangle were collected at various stages of development, separated into fruit wall, testa, and embryo or seedling. Wet weight, dry weight, and percent water content was determined for each. All parts of the fruit showed a similar growth pattern with a period of rapid exponential growth during the first 100 days, followed by a period of slower growth after the radicle-hypocotyl axis emerged through the fruit wall. In the final 45 days of seedling attachment the fruit wall and testa did not grow, and seedling growth rate was further reduced. Water content of the fruit wall was constant at 65 % throughout development; that of the testa decreased uniformly from 60 to 54%; embryo water content was uniformly 80 %. In the germinated seedling, water content declined progressively to 58 % by the time detachment occurred. Growth of isolated seedlings in sterile culture was not responsive to inhibition by abscisic acid or to stimulation by benzyl adenine, and these hormones had no effect on incorporation of 'H-amino acids into protein or of 'H-uridine into RNA. These results are interpreted in relation to a theory which proposes that development of water stress in the seed is the signal for the inception of dormancy.

46 citations


Journal ArticleDOI
TL;DR: UV-B radiation from filtered and unfiltered FS-40 fluorescent sunlamps on germination and early seedling growth was examined for a range of vegetables and field crops, finding typical responses were short, stubby roots, bronzing of the cotyledons, increased pigmentation, and abnormal curvature of the shoots.
Abstract: The influence of UV-B radiation (280–320 nm) from filtered and unfiltered FS-40 fluorescent sunlamps on germination and early seedling growth was examined for a range of vegetables (tomato, radish, cucumber, lettuce, and bean) and field crops (wheat, cotton, soybean, and millet). Continuous exposure of seeds for 3 days to 26.9 × 10−2 W × m−2 UV-B radiation (280–320 nm) at 25°C, had a slight effect on fresh weight of seedlings but no appreciable influence on germination percentage, or dry weight of seedlings. Extending the time of exposure to 6 days, however, resulted in abnormal seedling growth in all species but wheat. Typical responses were short, stubby roots, bronzing of the cotyledons, increased pigmentation, and abnormal curvature of the shoots.

45 citations


Journal ArticleDOI
TL;DR: In this paper, Douglas fir seedlings were grown in a series of 7 sub-irrigated sand culture experiments in which N was supplied from either a nitrate or an ammonium source.
Abstract: Douglas-fir (Pseudotsuga menziesii Mirb. Franco) seedlings were grown in a series of 7 sub-irrigated sand culture experiments in which N was supplied from either a nitrate or an ammonium source. The first five experiments were designed to identify factors that influence seedling growth response to N source; the last two were concerned with N uptake from the two different sources under sterile conditions. In the five non-sterile cultures, seedling growth was generally greater on ammonium than on nitrate-N. In nonsterile cultures, the level of N supply affected response to N source, but greater growth occurred on the ammonium source at all levels despite this interaction. P accumulated in roots and was relatively low in shoots of nitrate seedlings. Different levels of P supply did not affect response to N source. Ca concentration of nitrate-fed seedlings was high compared with ammonium-fed seedlings, and increase in Ca supply caused a small increase in seedling growth on nitrate-N, but not on ammonium-N. Seedling growth response to N source was unaffected by light intensity, but frequency of sub-irrigation had a marked effect. Irrigation once in two days or once a day resulted in greater growth occurring on nitrate-N, whereas irrigation eight times a day or four times a day resulted in greater growth of ammonium-fed seedlings. In sterile cultures, which were sub-irrigated once a day, seedling growth was greater on nitrate-N than on ammonium-N. Aseptically grown seedlings of three different Douglas-fir provenances accumulated up to seven times the initial seed N content during 12 weeks of growth on nitrate-N. The conclusion was that Douglas-fir seedlings can grow satisfactorily on nitrate-N sources without the intervention of any other organism, and thus must be capable of nitrate reduction. re]19740805

44 citations



Journal ArticleDOI
TL;DR: Leaf expansion, dry matter accumulation, and mobilization of 65Zn from the cotyledons was severely impaired in the young developing shoot under unfiltered UV-B radiation, and a significant stress response was observed in seedlings exposed to this radiation.
Abstract: The influence of UV-B radiation from filtered or unfiltered fluorescent sunlamps on early seedling growth and translocation of 65Zn from cotyledons to the shoot was examined in two cultivars of cotton, Acala and Gregg Ten-day-old seedlings which had been irradiated in the greenhouse for 6 h continuously each day for 14 days with 081 or 161 W × m-2 UV-B radiation under two unfiltered FS-40 sunlamps, showed pronounced phytotoxic damage This was characterized at first by bronzing and glazing of the cotyledons and later by upward curling of the leaves and abscission Leaf expansion, dry matter accumulation, and mobilization of 65Zn from the cotyledons was severely impaired in the young developing shoot under unfiltered UV-B radiation A significant stress response also was observed in seedlings exposed to 061 W × m-2 UV-B radiation through a polystyrene filter and 073 W × m-2 UV-B radiation through a cellulose-acetate filter This stress response was characterized by the formation of a red pigment in the petioles of the cotyledons, reduced leaf expansion, and reduced transport of 65Zn Control seedlings exposed to 003 W × m-2 UV-B radiation through a mylar filter were green, had maximum leaf size and dry-matter accumulation, and had the greatest percentage of 65Zn translocated from the cotyledons

Journal ArticleDOI
TL;DR: Greater germination and survival at the surface supports the evidence for ragweed's dependence on soil disturbance for germination, and the induction of secondary dormancy explains why ragweed does not constitute a dominant part of the vegetation when disturbance occurs after the soil warms to a critical point in the summer.
Abstract: Common ragweed (Ambrosia artemisiifolia) seeds were stored under natural environmental conditions by placing them at three soil levels (surface, 5 cm, and 15 cm) in the field on November 1, 1972. Germination tests at 4-week intervals indicated that dormancy was broken by the end of January. Germination was initially greater at high temperatures, but this difference decreased with increasing time in the field. Secondary dormancy was evident in surface seeds by March 21 but not until April 18 at 5 cm and June 13 at 15 cm. Germination in the field was greatest at the surface but was observed at all soil levels by March 21. Seedling survival was 68 % at the surface and 0% at 5 and 15 cm on June 13. Maximum and minimum soil temperatures were recorded at each soil level during the experiment and were correlated with the results. Greater germination and survival at the surface supports the evidence for ragweed's dependence on soil disturbance for germination, and the induction of secondary dormancy explains why ragweed does not constitute a dominant part of the vegetation when disturbance occurs after the soil warms to a critical point in the summer. SEED DORMANCY and germination are very important in determining the success of a species as an invader after soil disturbance. Estimates of the number of seeds (Brenchley and Warington, 1930) and viability of seeds (Crocker, 1938; Toole and Brown, 1946; Darlington and Steinbauer, 1961) in arable soil confirms the maintenance of large populations of seeds for long periods of time. After soil disturbance and subsequent exposure to light, these seeds may give rise to weedy species found in cultivated fields or weedy primary invaders of secondary succession (Saur and Struick, 1964; Wesson and Wareing, 1967, 1969). Germination of the exposed seed after disturbance depends on the existing environmental conditions and the dormancy state of the seed. Seeds of many weedy species under field conditions exhibit cyclic changes in dormancy which follow a seasonal pattern (Courtney, 1968; Taylorson, 1970, 1972; Stoller and Wax, 1974). Secondary dormancy is usually induced during early summer and is broken during the winter, resulting in nondormant seeds in the spring, and if germination doesn't occur the cycle is repeated. Laboratory germination studies have provided some information regarding the success of common ragweed (Ambrosia artemisiifolia) as a primary invader after soil disturbance (Bazzaz, 1968, 1970; Willemsen and Rice, 1972; Willem1 Received for publication 16 July 1974. Supported by a grant from The Research Council, Rutgers University. I am grateful to Mr. Ralph H. Hofmann, officer in charge of the USDA, Cereal Division Seed Branch, Federal Seed Laboratory in New Brunswick, New Jersey, for his cooperation in the use of this agency's seed germination facilities. sen, in press). However, observations on seed germination and dormancy under field conditions would be complementary to these laboratory investigations and would provide a better understanding of this species' natural behavior. MATERIALS AND METHODS-Ragweed plants bearing mature seeds were collected on October 11, 1972, from a one-year abandoned field on the William L. Hutcheson Memorial Forest property on the Piedmont of New Jersey. Fruits were removed from the plants after 4 days of air drying at 20-25 C. The seed was winnowed and stored in the dark in an air-conditioned laboratory (1824 C) until burial on November 1, 1972. For burial, 500 seeds were placed in individual 10 x 10 cm fiberglass screen envelopes (mesh size 6/cm). These envelopes were then placed on the soil surface and 5 cm and 15 cm below soil surface. Every four weeks four envelopes were collected from each soil level and cleaned under running tap water. The number of seeds which had germinated and the number of seedlings present were counted. The remaining seeds were placed on germination paper in sandwich boxes (11 x 11 x 2.5 cm) and 12 ml distilled water was added. Small quantities of water were subsequently added if drying became evident. Percent germination (as indicated by root emergence) was determined in continuous darkness and light (8 hr photoperiod) at 5/15, 10/20, 15/25, and 20/ 30 C (? 1 C). The higher temperature of each alternating temperature regime was present during the 8-hr light period. The same alternating temperature regimes were maintained in constant darkness. Ihe seeds placed in constant dark were

Journal ArticleDOI
01 Mar 1975
TL;DR: The microenvironment was monitored and vegetation was intensively sampled to interpret complex responses of an annual rangeland community to chemical weed control and reseeding to answer questions about the dynamics of a plant community.
Abstract: Syntheses of microenvironments based on monitoring are needed for understanding complex phenomena of an ecosystem and for establishing benchmark or standard regimes of temperature, light, and soil moisture for laboratory experiments involving seed germination, seedling growth, and other plant responses. These studies, in turn, answer questions about the dynamics of a plant community. The microenvironment was monitored and vegetation was intensively sampled to interpret complex responses of an annual rangeland community to chemical weed control and reseeding. Yield and density of plants varied among years, with aspect, within seasons, and in response to paraquat (1,1?-dimethyl-4,4?-bipyridinium ion). Establishment of hardinggrass and perlagrass (Phalaris spp.) was related directly to paraquat treatment and reduction of competition from resident annuals. Species and aspect (north and south slope) differences were more important in establishment of annual clovers (Trifolium spp.), with reduction of competition not the overriding factor. Available soil moisture permitted seed germination, seedling emergence, and growth of plants in this community. Temperature controlled the general rate of growth, and also created detectable differences in plant response when it dropped low enough to affect germination of seeds or caryopses or rose high enough to stress plants directly, or indirectly by more rapid depletion of soil moisture. The overriding factor of competition which prevented establishment of hardinggrass and perlagrass was interception of light by the canopy of annual plants during the growing season. The shading effect was most severe at ground level. During crucial periods of emergence and growth of the seeded species, this shading was virtually restricted to 1 or 2 cm above the surface. Soil-moisture depletion mattered primarily at the end of the growing season, but in some restricted periods during the season it became an important factor.

Journal ArticleDOI
TL;DR: In this article, the authors compared the performance of two Pennisetum typhoides cultivars and a P. purpureum biotype at four temperatures from 33/28 to 15/10°C (day/night) under natural irradiances.
Abstract: Germination, establishment, dry weight accumulation and leaf development of seedlings of two Pennisetum typhoides cultivars and a P. typhoides × P. purpureum biotype were studied at four temperatures from 33/28 to 15/10°C (day/night) under natural irradiances. Percentage seedling germination was independent of temperature. However, rate of germination and emergence were fastest, the spread in populations of time to germination least, and seedling survival highest, at the temperature at which rates of leaf area expansion and dry weight accumulation were greatest, i.e. 33/28°C. Rates of dry weight accumulation differed between the three pennisetums, the ranking in early growth at temperatures below 33/28°C being the same as that for seed size, and in later growth at all temperatures being in the order interspecific hybrid > intra-specific hybrid > selected strain.

Journal ArticleDOI
TL;DR: Extracts prepared from resting seeds of Scots pine rapidly hydrolysed two peptides, Leu–Tyr and Ala–Gly, at pH 8.6 and 7.8, which indicates that they are due to two different peptidases.
Abstract: Extracts prepared from resting seeds of Scots pine, Pinus sylvestris L., rapidly hydrolysed two peptides, Leu–Tyr and Ala–Gly, at pH 8.6 and 7.8, respectively. In gel chromatography on Sephadex G-100 the two activities were eluted as separate peaks, which indicates that they are due to two different peptidases. The seeds were allowed to germinate at 20°C, the activities of the two enzymes were assayed separately on extracts from the endosperm and seedling tissues at different stages of germination, and compared with corresponding changes in dry weight and total nitrogen. Both enzyme activities were relatively high in the endosperm of resting seeds, and they increased about 2- and 3-fold during germination (expressed as enzyme units per seed), the increases coinciding with the time of rapid reserve protein mobilization. Both enzymes were also abundant in the embryos of resting seeds, and during germination their activities increased even more rapidly than those in the endosperm. The possible role of these two “alkaline peptidases” in reserve protein hydrolysis is discussed.

Journal ArticleDOI
TL;DR: The results indicated that the maintenance of a good grass cover coupled with a top removal agent such as fire or cutting at ground level will prevent encroachment of redberry juniper, a resprouting species, on grassland.
Abstract: Highlight: A relatively high moisture level (O to 4 atm) and a relatively low temperature (180C) were found to be most favorable for germination of redberry juniper (Juniperus pinchoti) seeds. Shallow planting depths (O to 2 cm) favored seedling emergence. Seed germination was not affected appreciably by passage through animals. Cutting of seedling tops above the axils of the cotyledons allowed 58%o survival, while cutting 1to 12-year-old plants at ground line, which removed the meristematic stem tissue, produced 99%0 mortality. Moderate and heavy blue grama (Bouteloua gracilis) competition severely limited redberry juniper seedling growth compared to no competition. It severely reduced shoot length, root length, number of shoot and root branches, and plant dry weight. These results indicated that the maintenance of a good grass cover coupled with a top removal agent such as fire or cutting at ground level will prevent encroachment of redberry juniper, a resprouting species, on grassland.


Journal ArticleDOI
TL;DR: Exposure of gibberellic acid-treated seedlings of a monoecious cucumber cultivar ;Chipper' (Cucumis sativus L.) to ethylene caused thickening of the hypocotyl, inhibited longitudinal growth, and had no effect on fresh weight.
Abstract: Exposure of gibberellic acid-treated seedlings of a monoecious cucumber cultivar ;Chipper' (Cucumis sativus L.) to ethylene caused thickening of the hypocotyl, inhibited longitudinal growth, and had no effect on fresh weight. Downward curvature of cotyledons was increased by the presence of ethylene. A gynoecious breeding line, ;Gy 3,' had thicker hypocotyls and displayed its cotyledons in a more downward position than ;Chipper'. Excised hypocotyls of the gynoecious seedlings produced three times as much ethylene as did the monoecious Chipper hypocotyls. Thus, ethylene may play a role in the regulation of cucumber seedling morphology.

Journal ArticleDOI
TL;DR: It is suggested that the effect of day length on plant performance is mediated by the level of growth regelating substances within the plant and that the behaviour of seeds can be modified by the parental environment via the accumulation of different levels of certain growth factors in the seeds.
Abstract: Seedlings of the self-fertilizing species Lactuca scariola L. grown continuously in 8 h days did not flower even one year from sowing. Seedlings grown in 16 h days uatil flower buds appeared 96 days after germination were either transferred to 8 h days or treated weekly with gibberellic acid (GA3), abscisic acid (ABA) or chlormequat (CCC) and retained, together with untreated control plants, in 16 h days. Each growth regulator caused characteristic morphological changes in the treated plants. All these plants flowered and produced seeds but the seeds showed distinct differences in weight, in their time to germination and in the seedlings which they produced. Germination and seedling characters depended on the light regime during germination as well as on the chemical applied to the parent plant and the rate of application. The parental treatment also affected the shape and size of the seedlings on a given day after germination, and certain treatments of the parent plant (transfer from long to short days and treatment with CCC in long days) advanced the flowering date of the seedlings. The gibberellin level in the seeds was raised, in increasing order, by treatment of the parent plant with 100 mg/1 GA3, transfer from long to short days, 10 mg/1 GA3, and 5000 mg/l CCC. It is suggested that the effect of day length on plant performance is mediated by the level of growth regelating substances within the plant and that the behaviour of seeds can be modified by the parental environment via the accumulation of different levels of certain growth factors in the seeds. A rise of one growth substance in the parent plant can result in the accumulation of a different one in the seeds.

Journal ArticleDOI
TL;DR: Investigating the effect of gamma radiation on dormant seeds of Avena fatua L. A. (wild oats) found higher radiation doses promoted seed germination but they also caused a reduction of seedling growth.

Journal ArticleDOI
TL;DR: Observations appear to indicate that contrary to pea cotyledon proteases, serido bean protesaes are intimately associated with reserve protein degradation.
Abstract: Seedling growth, protein, soluble amino nitrogen, and proteolytic activity of serido beans (Vigna sinensis) were studied during the first 6 days of germination. Cotyledon dry weight decreased constantly with germination time, reaching at the 6th day 27% of the weight it had at day 0. Embryo-axis dry weight increased during the same period, amounting to 79% of the total weight of the seedling at the 6th day of germination. Cotyledon proteins increased slightly during the 1st day of germination and then decreased until the end of the experimental period. Cotyledonary soluble amino nitrogen stayed constant for the 1st day of germination, increased up to the 3rd day, and then fell steadily until the 5th day. Embryo-axis soluble amino nitrogen followed the same pattern as the embryo-axis proteins, that is, a slight increase during the first 3 days, a pronounced increase from the 3rd to the 5th, and a leveling off from this day on. Proteolytic activity was studied at pH 3.5 and pH 6.0. Both proteases increased in activity during the first 3 days of germination, at which point they reached their maximum activities. From this day on their activities fell continuously, reaching on the 6th day values slightly higher than those of day 0. These observations appear to indicate that contrary to pea cotyledon proteases, serido bean protesaes are intimately associated with reserve protein degradation.


Journal ArticleDOI
TL;DR: Ten Certified Seed lots of S23 perennial ryegrass produced in different counties in England during 1966 and 1972 were examined and it was concluded that late N applications to grass seed crops may affect seed quality.
Abstract: Ten Certified Seed lots of S23 perennial ryegrass produced in different counties in England during 1966, and ten lots produced in 1972, were examined for differences in characters affecting seed quality. The 1966 seed lots differed significantly in 1000–seed weight, germination rate, N content of the seed and seedling dry weight, and there was a significant correlation between seed N content and the seedling weight of the progeny. In both S23 and S24 perennial ryegrass N applied at inflorescence emergence or at anthesis increased N content of the seed and seedling dry weight. In S24 application of N at anthesis increased 1000–seed weight also. When plants of S23 perennial ryegrass were subjected to reduced moisture supplies their seed N content was increased. It is concluded that late N applications to grass seed crops may affect seed quality.

Journal ArticleDOI
TL;DR: In field experiments Onychiurus spp.
Abstract: SUMMARY In eastern England Onychiurus armatus (Tullb.) and 0. fimetarius (L.) were found associated with damaged sugar-beet seedling roots soon after sowing in mid-March, 1973, when the mean soil temperature ranged from 3 to 11 °C; observations confirmed that 0. armatus caused similar damage to seedlings und.er laboratory conditions. In field experiments Onychiurus spp. were always more numerous in the seedling root zone than between the seedling rows, but different seed spacings had no significant effect on the extent of aggregation around individual sugar-beet seedlings in the cotyledon or early rough-leaf stages.

Journal ArticleDOI
TL;DR: Winter wheat samples naturally infected by S. nodorum were sown in the field and in a cool glasshouse, where the number of diseased seedlings was closely correlated with the percentage seed infection found by plating on agar and pycnidial production was abundant but rare on the tips of coleoptiles.
Abstract: Winter wheat samples naturally infected by S. nodorum were sown in the field, in some cases after applying seed treatments. The number of diseased seedlings was closely correlated with the percentage seed infection found by plating on agar. Observations were made on the type of symptoms produced and on seedling emergence, which was reduced by deeper sowing. Pycnidial production was abundant but rare on the tips of coleoptiles, from which source spores could spread the disease. In a cool glasshouse similar numbers of diseased seedlings were produced but symptoms were more severe than in the field. Time of sowing had a marked effect on the number of diseased seedlings and on pycnidial production in the glasshouse. Ripe pycnidia were common on stubble and persisted until May or June; Leptosphaeria perithecia were also found.

Journal ArticleDOI
15 Sep 1975-Botany
TL;DR: Net changes in weights of P, K, Ca, Mg, B, Fe, Mn, Zn, Cu, Na, Al, Ba, Sr, and Cr in cotyledons and seedling axes of Acer rubrum L., Fraxinus pennsylvanica Marsh.
Abstract: Net changes in weights of P, K, Ca, Mg, B, Fe, Mn, Zn, Cu, Na, Al, Ba, Sr, and Cr in cotyledons and seedling axes of Acer rubrum L., Fraxinus pennsylvanica Marsh., and Robinia pseudoacacia L. were investigated during early seedling growth. Amounts of elements in embryonic cotyledons varied in the following order: Robinia pseudoacacia > Acer rubrum > Fraxinus pennsylvanica. Embryonic F. pennsylvanica cotyledons were very small and were embedded in endosperm. When seedlings were grown in the light with no inhibition of photosynthesis, mineral elements were either steadily translocated from cotyledons, accumulated in cotyledons, or initially accumulated in cotyledons and finally exported during cotyledon senescence. Differences depended on specific elements and species. The effects of growing seedlings in the dark or treating seedlings with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) to inhibit cotyledon photosynthesis were similar in that mineral translocation from cotyledons or accumulation in them was ...


Journal ArticleDOI
TL;DR: The successful culture of germinated embryos and seedlings on a simple, chemically defined medium of mineral salts and sugar suggests that these nutrient components are the minimal external requirements for stimulation and support of normal seedling growth.
Abstract: In vivo, seeds of the obligate root parasite Alectra vogelii Benth. (Scrophulariaceae) germinate only after being soaked in water for a period of time (pretreatment) followed by stimulation by certain factors exuded from a host root. Germinated seedlings do not develop beyond radicle emergence, and finally die, unless their radicles make contact with and penetrate into a host root conductive system. In vitro, germinated embryos obtained by exposing sterilized and pretreated seeds to root exudate of Vigna unguiculata were aseptically cultured on Knop's, White's and Murashige and Skoog's media. The embryos grew into seedlings with shoots and roots on a medium containing mineral salts and sucrose, but not on mineral salts alone. Seedling performance was generally not improved when the mineral salts-sucrose media were supplemented with vitamins. Shoot extension growth was better on Murashige and Skoog's mineral salts-sucrose medium than on Knop's or White's medium. However, seedling development was greatly boosted when cultivated on White's minerals salts-sucrose medium supplemented with coconut milk. Seedlings turned green on transfer to light but did not flower. The successful culture of these embryos and seedlings on a simple, chemically defined medium of mineral salts and sugar suggests that these nutrient components are the minimal external requirements for stimulation and support of normal seedling growth. These may be obtained in vivo by the parasite's tapping of the host root conductive system.

Journal ArticleDOI
TL;DR: During the first 6 days of incubation under the optimal conditions the embryo grows within the endosperm, thus accounting for the minimum lag period of 6 days prior to emergence of the seedling from the pericarp.
Abstract: The optimal temperature range for germination of achenes of the De Caen type of cultivated A. coronaria L. was 10-20°C. Continuous irradiation with white light retarded germination, particularly at supraoptimal temperature. The retardation was caused by the far-red component of the light. Blue light was inactive by itself but synergized with far-red. Gibberellic acid (GA3) promoted gerrnin- ation only at supraoptimal temperature (25°C). Abscisic acid (ABA) inhibited germination more at 20 than at 15°C. Rinsing the achenes with water completely removed the inhibition caused by 40 p.p.m. ABA. GA3 at a concentration of 100 p.p.m. partly overcame the inhibition caused by ABA. The growth retardants (2-chloroethyl)trimethylammonium chloride and Amo-1618 [2'-isopropyl-4'- (trimethylammonium chloride)-5'-methylphenyl piperidine-1-carboxylate] inhibited germination more at 20 than at 15°C; Amo-1618 was more inhibitory. GA3 at concentrations of 10-1000 p.p.m. partly overcame the inhibition by 100 p.p.m. Amo-1618, but not that by 1000 p.p.m. Partial stripping or cutting of the pericarp enhanced germination whereas complete removal inhibited it. During the first 6 days of incubation under the optimal conditions the embryo grows within the endosperm, thus accounting for the minimum lag period of 6 days prior to emergence of the seedling from the pericarp.

Journal ArticleDOI
TL;DR: The seeds ofMerremia aegyptia are indifferent to light conditions for germination, but in M. dissecta the highest percentage was found in red light within the first 24 hrs, and the seedling growth of the two species was least in blue and red lights, respectively.
Abstract: The seeds ofMerremia aegyptia are indifferent to light conditions for germination, which becomes 100% in the first 24 hrs. On the contrary, inM. dissecta the highest percentage was found in red light within the first 24 hrs. This difference was lost later on except in far-red. The seedling growth of the two species was least in blue and red lights, respectively. However, the growth of hypocotyl in the former species was faster than the latter.