Showing papers on "Seedling published in 1977"

Seed germination in response to diurnal fluctuations of temperature.

Abstract: Diurnal fluctuations in temperature may initiate or accelerate germination in certain flowering plants, and the effectiveness of the stimulus varies according to the amplitude of fluctuation and the presence or absence of light. Attempts to assess the adaptive significance of the phenomenon, however, have been limited by the scarcity of data for species of contrasted ecology. We report here an investigation of germination responses to fluctuating temperatures, conducted on seeds of herbaceous species collected from native populations near Sheffield. The results suggest that requirements for diurnal fluctuations in temperature are characteristic of the germination of species from particular types of habitat and provide mechanisms which cause seeds to germinate at times and in places favourable for seedling establishment.

Seed Production, Seed Populations in Soil, and Seedling Production After Fire for Two Congeneric Pairs of Sprouting and Nonsprouting Chaparal Shrubs

Abstract: A study of seed production, seed storage in the soil, and seedling production after fire was undertaken for a sprouting and a nonsprouting congeneric pair of species of Ceanothus and Arctostaphylos. All species exhibited large fluctuations in annual seed production. There was a signifi- cant correlation between fruit production and precipitation in the previous year. It is hypothesized that high carbon gain in years of high precipitation results in high numbers of floral primordia which, in these species, remain dormant until the following year. It was also noted that high fruit production was not dependent upon high precipitation the same year; suggesting that the fruits were utilizing carbon stored from the previous year. All 4 species were capable of producing more seeds in a single season than were stored in the soil. Apparently the soil seed pools do not represent a steady accumulation of seeds in the soil but rather are the result of dynamic fluctuations in seed inputs and outputs. Each species also had more seeds in the soil, by several orders of magnitude, than seedlings after fire in an adjacent burned stand. The sprouting and seeding reproductive strategies are quite different in the two genera. The infor- mation from this study coupled with that from other studies indicate 4 reproductive modes: sprouting and seedling production (C. leucodermis), abundant seedling production (C. greggii), low seedling production but better "equipped" seedlings (A. glauca), and predominantly sprouting (A. glandulosa).

Observations on the genetic structure and mating system of ponderosa pine in the Colorado front range.

Abstract: Variation of peroxidase enzymes is analyzed both in mature needle tissue and in open-pollinated seedling families of ponderosa pine, Pinus ponderosa, and is identified as being controlled by a single Mendelian locus. Variation at this locus, analyzed in 1, 386 individuals, is used in the analysis of population differentiation and the mating system. Significant variation of gene frequencies is detected over distances of several hundred meters, and is found to be associated with slopes of different aspects. Ponderosa pine is wind-pollinated, and an analysis of the mating system indicates that the level of outcrossing is greater than 90 %. Selection specific for different environments is evidently strong enough to overcome the homogenizing force of migration and produce population fissuring in ponderosa pine.

Viable seed populations by soil depth and potential site recolonization after disturbance

Abstract: Seedling emergence from organic and mineral soil layers was measured for nine study sites at the Acadia Forest Experiment Station near Fredericton, New Brunswick. The number of viable seeds showed ...

High soil fertility decreases sucrose content and susceptibility of loblolly pine roots to ectomycorrhizal infection by Pisolithus tinctorius

Abstract: Pinus taeda seedlings were grown for 10 weeks without ectomycorrhizae under low and high rates of complete soil fertility, as well as these rates minus N, P, K, or Ca. Seedling growth, inorganic chemical content of needles, and soluble-carbohydrate content of short roots were significantly affected by soil fertility, especially the high rates of N and P. Number and length of lateral and short roots were not affected by soil fertility. Sucrose and fructose contents of short roots were lowest at high levels of N and P; glucose was not detected. Seedlings from each of the 10 fertility combinations were inoculated with vegetative inoculum of Pisolithus tinctorius and incubated for 19 to 21 days at a moderate level of complete soil fertility. Significantly more ectomycorrhizae were formed on seedlings from the complete low fertility rate than on those from the high rates of N and P. Ectomycorrhizal development on seedlings from the other fertility combinations were intermediate from these extremes. Sucrose con...

Short-term effects of a simulated acid rain upon the growth and nutrient relations of Pinus strobus , L.

Abstract: Acidified precipitation may affect the productivity of forests by altering the availability of plant nutrients of by affecting the ability of trees to absorb and assimilate those nutrients. In this study, the short-term effects of simulated acid rain (pH range 5.6 - 2.3) upon the growth and nutrient relations of Eastern White Pine seedlings (Pinus strobus, L.) grown in a sandy loam soil were examined. Soil chemistry, soil leachate chemistry, seedling tissue chemistry, and seedling productivity were monitored. In spite of increased leaching of cations from the soil, resulting in near depletion of available K+1, Mg+2, and Ca+2 at pH 2.3, seedling productivity increased with acidity through the 20-week experimental period. Foliar nitrogen concentrations indicate that fertilization with NO3-1, added to the rain as HNO3, may have caused the growth increase. Implications of cation losses and NO3-1 fertilization are discussed.

Early Stages of Regeneration After Burning in Dry Sclerophyll Vegetation. II. Regeneration by Seed Germination

Abstract: Following experimental burns in three dry sclerophyll communities, all except the geophytic species regenerated from seedlings in the first year. The annual and perennial species in the shrub strata regenerated from surviving seeds in the soil and ash, and the eucalypts from seeds released from the trees after burning. Although many seeds were destroyed during the fires, the germination of most species was higher in burnt than in unburnt plots. Fire appeared to stimulate germination through direct heat effects on the seeds, and by removing inhibitors present in the unburnt vegetation. Seedling mortality was highest during the first year. Many seedlings died while in the cotyledon stage, the main observed causes of mortality being desiccation, fungal disease and predation by insects. Seedling survival was enhanced by burning, owing to the removal of the litter and other fire-induced changes which made conditions more favourable for seedling establishment and/or growth. Two years after burning, the relative positions of dominance of the three major species in the tall shrub stratum had changed compared with the pre-burn status of each. Evidence suggests that such shifts in dominance depend on a number of interacting factors which selectively promote or inhibit the recovery of each species.

Synergistic inhibitory effects ofp-coumaric and ferulic acids on germination and growth of grain sorghum

Abstract: The data support the hypothesis that there is a synergistic phytotoxic effect whenp-coumaric and ferulic acids are found together. Equimolar mixtures of both acids showed greater reduction in sorghum seed germination, shoot elongation, and total seedling growth than either phytotoxin caused when alone. Repeated experiments showed mixtures containing 5×10−3 Mp-coumaric and 5×10−3 M ferulic acids reduced germination to 34% of controls after 24 hr and 59% by 48 hr. The same concentration of either phenol-treated seeds alone showed 69 and 92% germination at comparable times. The phytotoxic action of the combination approximated the inhibitory effect on germination of 10−2 M ferulic acid and was a greater reduction than caused by 10−2 Mp-coumaric treatments. Sorghum seedling growth was more sensitive than germination, with an equimolar mixture of 2.5×10−4 Mp-coumaric and 2.5×10−4 M ferulic acids reducing seedling dry weight significantly below weights of seedlings treated separately with 2.5×10−4 Mp-coumaric or ferulic acids. Further dilutions showed a 1.25×10−4 M concentration of either phenol was stimulatory to seedling growth, whereas a mixture of these two produced inhibition.

Resource allocation and reproduction in populations of amphicarpum purshii (gramineae)

Abstract: A B S T R A C T Five New Jersey populations of Amphicarpum purshii (an annual panicoid grass) were investigated as to total allocation of biomass to reproduction and its distribution between aerial chasmogamous and subterranean cleistogamous inflorescences Germination of both types of seed was documented, for the first time, in not only the field but under three laboratory temperature regimes Overall, approximately 29 % of the shoot biomass was allocated to reproduction On a population basis, subterranean inflorescences accounted for 37-100 % of the reproductive biomass, and these seed (5 x heavier but fewer in number) were the source of most surviving seedlings Subterranean spikelets contained caryopses significantly more frequently than aerial spikelets The ratio of the number of viable aerial seed to the number of viable subterranean seed increased from 0/4 to 4/2 with recentness and/or frequency of disturbance As a pioneer species in secondary succession, Amphicarpum purshii produces a larger subterranean propagule, with greater seedling vigor and a higher probability of local reproductive success, and also a smaller aerial propagule in larger numbers with potentially greater genetic variability

Influence of seed size, protein content and cultivar on early seedling vigor em wheat

Abstract: Four greenhouse experiments were conducted to study the influence of seed size, protein content and cultivar on seedling vigor of wheat measured as seedling dry weight at 20 days. The simple and partial correlation coefficients among the variables were all positive and significant. No significant interaction occurred between seed size and genotype. The genotypic differences in seedling vigor may lead to its use as a selection criterion in wheat breeding programs.

Plant Damage by Bank Voles (Clethrionomys glareolus [Schreber]) and Related Species in Europe1

Abstract: A survey of the ecological adaptations of the bank vole, Clethrionomys glareolus (Schreber), indicates that this species is a potential pest, particularly to forest tree seeds and bark. Observations from most parts of Europe show clear cases of damage to seeds, young shoots and buds and bark of young trees above the snow level. Worst losses appear in central and eastern Europe. The bank vole may also attack a few year old seedlings (either bark or complete consumption). Widespread seedling attacks, which are economically very important in some countries, have, however, not been definitely proven for this species. In northern Europe, the bank vole may also cause damage to hay in barns. Bank vole populations show greatest fluctuations in eastern and northern Europe. The cycle length is variable. Damage (except, possibly, seed consumption) appears mainly during or just after the appearance of peak populations. Baits with zinc phosphide seem to be the most efficient control method. A number of other preparations have been tried more or less successfully. In summary, knowledge of the economic importance of the bank vole is very restricted. Specific studies are suggested for improving such an evaluation.

Germination, Establishment, and Demography of Coastal Bush Lupine (Lupinus Arboreus) at Bodega Head, California

Abstract: Lupinus arboreus is a large, fast-growing, short-lived shrub dominant in the northern coastal scrub of California. The age structure of its stands and the factors which contribute to that age structure were examined at Bodega Head, a coastal peninsula in Sonoma County, 73 km north of San Francisco. No plants older than 7 yr were found. Major causes of mortality of established plants were herbivory by two species of insect larvae and summer drought. Most plants flower and fruit after the age of 2 yr. Nearly all seeds dropped under lupine canopies are taken by mice, and the absence of establishment there is not caused by allelopathic factors or competition for light or moisture. Estab- lishment in surrounding grassland is limited by competition with grasses for light and moisture and, again, allelopathy is not a factor. Germination was enhanced by seed burial and exposure to alternate heat and cold, wetting and drying, and salt spray. Following seedling establishment, increase in biomass is approximately exponential for the first 4 yr, then growth rate declines. The mosaic of scrub and grassland at Bodega Head appears to be approaching a steady state, following release from grazing by cattle and protection from other disturbance since 1961.

The capacity of chlorophyll-a biosynthesis in the mustard seedling cotyledons as modulated by phytochrome and circadian rhythmicity.

Abstract: Within the temporal pattern of “primary differentiation” the capacity of chlorophyll — a biosynthesis in the cotyledons ofSinapis alba L. seedlings is controlled by phytochrome (in continuous light) or by releasing the circadian rhythm either with lightdark cycles or by a light→dark transition. The sensor pigment for this process is phytochrome. It is very probable that in continuous light as well as under conditions under which the circadian rhythm plays the major part, the capacity of chlorophyll a biosynthesis is limited by the capacity of the biosynthetic step which produces 5-aminolaevulinate.

Purple Moonflower: Emergence, Growth, Reproduction

Abstract: Purple moonflower's (Ipomoea turbinata Lagasca y Segura) vegetative growth and seed maturation were characterized in noncompetitive field studies. Seedling emergence of 50% or greater of mature scarified seed occurred to a soil depth of 12 cm. At vegetative maturity a typical plant produced 11 primary, 50 secondary, 94 tertiary, and 7 quaternary runners having a total length of 185 m. The average number of leaves per plant was 1,120. Maximum seed size, seed wet weight, occurrence of first mottled seed, and first capacity to germinate occurred 20 days after anthesis in immature seed that were removed from the seed pod. Maximum germination occurred at 26 days after anthesis. Seed moisture content (dry weight basis) reached 8.5%, seed had formed an impermeable seed coat, and physiological maturity (defined as maximum dry weight) occurred 34 days after anthesis. The total number of purple moonflower seed produced per plant averaged 9350. The major mechanism of seed dormancy was impermeability of seed coats.

Morphological acclimation to light intensity in Douglas-fir seedlings

Abstract: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown outdoors under 9, 44, and 100% light intensity and were sampled periodically over their first growing season for stem, leaf, and root dry weights, and the data were analyzed allometrically. In addition, seedlings were assessed for number of needles per stem length, ratio leaf surface area: leaf dry weight, and maximum seedling dry weight. The experiment was repeated during a 2nd, warmer, year.Maximum growth occurred under partial shade and moderate temperatures. In the 1st year, seedlings allocated progressively more dry matter to shoot than to root growth as light intensity decreased. In the 2nd year, root growth was favored at the expense of shoot growth. In both years, shoot structural alterations were such as to favor enhanced photosynthesis under low light. Acclimative changes are explained in terms of an interaction between light, temperature, and seedling size.A second experiment showed that seedlings grown under low light set ...

Effects of soaking, seed moisture content, temperature and seed leakage on germination of faba beans (vicia faba) and peas (pisum sativum)

Abstract: Among four faba bean (Vicia faba L.) and four pea (Pisum sativum L.) cultivars, significant differences occurred in the amount of water imbibed by whole seeds and seeds with their seed coats removed. Furthermore, seed soaking significantly reduced germination and growth of seeds of cultivars within both species. Transverse cracking of the cotyledons (TVC) was a cultivar characteristic in faba beans that was negatively associated with germination, but was not a factor in the pea cultivars studied. Low seed moisture and low temperature during imbibition of water reduced seedling growth in faba beans and peas and reduced germination in faba beans. There were significant cultivar differences in both faba beans and peas in the amount of seed leakage after 24 h of soaking. In faba beans the cultivars with the greatest TVC showed the greatest leakage. Smooth-seeded peas leaked more than wrinkle-seeded peas used in the study.

Growth of The Legume Seedling

Abstract: Publisher Summary This chapter focuses on the factors affecting the development and growth of the forage legume seedling. The chapter reveals that the growth of a legume seedling depends on its inherent vigor and the environmental conditions present during seed germination, maturation, and growth. Environmental conditions during seed formation could influence seed size and subsequent progeny performance. Growth responses—which could be traced to environmental conditions at some stage of previous development—are designated as physiological predetermination to distinguish them from those, which are because of hereditary causes. The chapter enlists three conditions, which could affect the potentiality of the seed or the capacity of the resulting plant for growth and yield: (1) parental conditions; (2) conditions immediately preceding germination, during germination, or in the early stages of the seedling's growth; and (3) harvesting conditions. Three stages of development of a seedling—that is, heterotrophic, transitional, and autotrophic are described in the chapter.

Bioassays for detection and quantification of Helminthosporium maydis race T-toxin: a comparison

Abstract: Sensitivities of seven commonly used bioassays for Helminthosporium maydis race T-toxin were determined. The most easily quantified and highly sensitive bioassays were based either on dark CO2 fixation by green leaves or on respiration rates of isolated mitochondria. These bioassays were 5 to 10 times more sensitive than was the semiquantitative seedling root growth bioassay. Bioassays based on the production of visible lesions on leaves did not provide reliable dosage-response relationships and were estimated to be 20 to 100 times less sensitive to toxin than dark CO2 fixation or mitochondrial respiration. Choice of bioassay depends on the objective of the experiment in which it is used.

Root Exudates From Eucalyptus calophylla R.Br. And Eucalyptus marginata Donn. ex Sm. Seedlings and Their Effect on Phytophthora cinnamomi Rands

Abstract: Root exudates from seedling eucalypts were collected aseptically, analysed for sugars, amino acids and organic acids and an examination made of their effect on zoospore chemotaxis, mycelium growth and chlamydospore germination of Phytophthora cinnamomi. Seedlings of root-rot susceptible Eucalyptus marginata produced greater concentrations of sugar and amino acid exudates than the root-rot resistant Eucalyptus calophylla at all sampling times. There was, however, little qualitative difference between the eucalypt root exudates. Both eucalypts attracted zoospores to roots in culture tubes. Infection of the roots followed encystment and germination of the zoospores. Germination of chlamydospores and mycelium growth of P.cinnamomi was significantly increased by the presence of root exudates and no differences were observed between exudates of the two species. Only amino acids and organic acids stimulated germination of chlamydospores. It was concluded that differences in root-rot susceptibility of eucalypts to P.cinnamomi are not attributable to differences in root exudate from eucalypt seedlings.

Characteristics of Root‐to‐Shoot Transport of Cytokinin 6‐Benzylaminopurine in Intact Seedlings of Citrus aurantium

Abstract: Transport of the cytokinin 6-benzylaminopurine-8-14C in the root and shoot of intact Citrus aurantium L. seedlings was studied by “replacing” the 0.5 cm root tip with the uptake solution. The cytokinin was transported basipetally in the root and was distributed in an acropetal direction in the stem and into the leaves. Kinetic analysis of the transport for periods of up to 96 h revealed a characteristic advancing front of the label along the axis of the seedling. The estimated velocity of transport of 6-benzylamino-purine-8-14C in various regions of the intact root was 2.6 to 5.1 mm/h. The transport of 6-benzylaminopurine was predominantly in the transpiration stream, in stelar tissues of the root. Conditions of high transpiration favored enhanced transport to the shoot and an overall greater accumulation of the label. The total accumulation of 6-benzylaminopurine in roots of intact seedlings after 48 h of transport was 354% of that in roots of shoot-less seedlings. Root girdling and treatment of the root with KCN did not reduce the basipetal transport of the label in the root and into the shoot. Radiochromalogram scanning of root extracts and analysis of the ethanol insoluble-NaOH soluble fraction revealed considerable metabolic changes in the translocated cytokinin. Only 51% of the radioactivity remained in the original 6-benzylaminopurine peak after 24 h of incubation. Two other, unidentified, metabolites were detected. It is suggested that all the factors that affect the ascent of sap are involved in the long-distance transport of cytokinins, and that the rate and mode of transport of cytokinins from the root system to the shoot may be a major factor in the expression of their physiological activity.

Establishment of Ptelea trifoliata on Lake Michigan Sand Dunes

Abstract: The microclimate to which a seed or small seedling on the sand dunes of Lake Michigan is subjected is characterized by high surface soil temperatures and low soil moisture during the summer. The survival of lst-year seedlings of Ptelea trifoliata was very low (10.5%). Second-year seedlings had a 50% survival rate. The mortality was attributed to two environmental factors: insufficient soil moisture and illegal vehicular traffic. The slow elongation of the root makes the soil moisture a very critical factor. Shaded habitats within a Ptelea stand provide physical protection for the seedlings from vehicular traffic and have higher soil moisture; consequently, seedling survival is greater in shaded habitats than in open habitats. Because of the high mortality rate of young seedlings, seed production must be large to maintain the present population size.

Morphological Grading Studies with 1-0 Slash Pine Seedlings

Abstract: SUMMARY Slash pine seedlings were graded on the basis of three morphological characters: (i) Shoot development—eight classes are recognised based on stem, foliage and. bud maturity. Classes 1 to 4 show increasing development of stem lignification, secondary foliage and terminal bud. Class 5 stock are mature and dormant. Class 6 are breaking dormancy. Class 7 are actively reshooting. Class 8 possess a maturing flush shoot; (ii) Root collar diameter and (iii) Shoot length. Subsequent field performance was monitored for up to five years after planting and all three parameters, but particularly shoot development and diameter, influenced seedling survival and height growth. They can be used in routine grading operations as reliable predictors of field behaviour. Optimum outplanting performance was associated with the following specifications: Shoot development: Classes 5 to 8 inclusive; Root collar diameter: 4 mm and over; Shoot length: 15 to 40cm. These are recommended for adoption in defining 1-0 slash pine ...

Developmental Biochemistry of Cottonseed Embryogenesis and Germination: VIII. Free Amino Acid Pool Composition during Cotyledon Development.

Abstract: The composition of the free amino acid pool in embryonic cotton (Gossypium hirsutum) cotyledons is quite distinct from that of endosperm, and that of germinated, greened cotyledons is quite distinct from that of leaves. During germination (including the precocious germination of immature seeds), the pool expands considerably showing a pronounced accumulation of asparagine. The high level of asparagine found in seedling roots and in the cotyledon vascular exudate indicates that this is the major transported amino acid in germination. There is no pool expansion in the presence of abscisic acid. In the presence of actinomycin D, the pool expands, but an enormous accumulation of glutamine takes place. The composition of the pool at any stage is not related to the composition of the isoacceptor transfer RNA pool, nor to the composition of the storage protein. Anaerobiosis leads to an accumulation of aspartate, alanine, and glycine at the expense of asparagine; however, desiccation does not result in an accumulation of proline. Conspicuously high levels of arginine are maintained through embryogenesis and germination. The levels of individual amino acids are presented as nanomol per cotyledon pair and as per cent of total pool.

Survival of annual ryegrass (Lolium rigidum Gaud.) in a Mediterranean type environment. 1. Effect of summer grazing by sheep on seed numbers and seed germination in autumn

Abstract: Annual ryegrass–subterranean clover pastures that produced about 5000 kg total dry weight per hectare and 23,500 ryegrass seed per sq metre in spring were grazed by sheep at different stocking rates during summer. Intensive stocking equivalent to about 3000 sheep days ha-1 reduced seed numbers by 20%. Under continuous grazing, about 70% of the seed produced in spring fell readily to the ground during summer. The remaining seed was firmly held in seed heads, and apparently sheep ate mainly this component. Less than 1% of the seed ingested was voided in the faeces. No significant changes in seed numbers over summer were observed in ungrazed pasture. Subsequently, at the break of season in autumn, germination of seeds was examined in situ near the soil surface. The summer grazing history of pastures influenced the percentage of seeds that germinated; more seeds germinated in heavily than in leniently grazed pastures. Whether the pasture was leniently or heavily grazed, there was little effect on germination of shed seeds. Seeds in seed heads were found to germinate more slowly than seeds shed to the soil surface. Seedling emergence in autumn was regulated mainly by the interrelationship between the germination rate of the seed population, depending on summer-early autumn rains, and the period for which favourable moisture conditions prevailed at the soil surface after rain began in autumn. In the field, temperature and light appeared to be unimportant in influencing germination at the break of season. Dynamics of seed and seedling numbers in annual ryegrass pastures in a Mediterranean type environment, particularly at the break of season, are discussed.