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Showing papers on "Seedling published in 1985"


Journal ArticleDOI
01 Jun 1985-Ecology
TL;DR: The results demonstrate clear advantages to local seed dispersal for a tree of the rainforest canopy and suggest that dispersal of seeds > 20 m by large birds, such as guans and toucans, is more favorable for seedling survival than that of the smaller trogons and motmots, which regurgitate seeds under or near the tree crown.
Abstract: We examined the effects of distance from a fruiting conspecific, light environment, and initial seed size on survivorship using Virola surinamensis seeds and seedlings placed in concentric rings around fruiting Virola trees. Insects and mammals killed 99.2% of seeds and seedlings between fruit drop and exhaustion of parental endosperm at 12 wk after germination. During this time, survival was not influenced by either seed size or light environment, but up to a 44-fold advantage accrued to seeds dropped 45 m from a fruiting tree as compared with those underneath Virola crowns. Seeds that germinated under and near fruiting Virola trees suffered disproportionate attack from a curculionid weevil {Conotrachelus sp. nov.). Both large initial seed size and favorable light environments (assessed by canopy photographs) enhanced seedling vigor at 18 wk of age. Among those seedlings that escaped predation beyond the exhaustion of parental seed stores, a difference of as little as 1% in the amount of canopy open overhead distinguished seedlings with three leaves (3.5% open) from those with two leaves (2.3% open). Our results demonstrate clear advantages to local seed dispersal for a tree ofthe rainforest canopy. They further suggest that dispersal of seeds > 20 m by large birds, such as guans {Penelope purpurascens) and toucans {Ramphastos sulfuratus and R. swainsonii), is more favorable for seedling survival than that of the smaller trogons (Trogon massena) and motmots {Baryphthengus martii), which regurgitate seeds under or near the tree crown.

437 citations


Journal ArticleDOI
TL;DR: It is concluded that the beneficial effect of high Ca2+ concentrations on root growth of cotton seedlings in a saline environment may be due to maintenance of K/Na-selectivity and adequate Ca status in the root.
Abstract: . The effects of NaCl salinity on germination and early seedling growth of cotton were studied. Germination was both delayed and reduced by 200 mol m−3 NaCl in the presence of a complete nutrient medium. Seedlings, 7–9 d old, were greatly reduced in fresh weight by salinity. The addition of supplemental Ca2+ (10 mol m−3 as SO42− or Cl−) to the medium did not improve germination but, to a large degree, offset the reduction in root growth caused by NaCl. Roots growing in the high salt medium without supplemental Ca2+ appeared infected by microbes. The cation specificity of the beneficial Ca2+ effect on growth was ascertained by testing additions of MgSO4 or KCl to the NaCl treatments. The contents of K4 and Ca2+ were reduced in both roots and shoots by the NaCl treatments. Supplemental Ca2+ partially offset this effect for K4 in the roots and for Ca2+ in both roots and shoots. Sodium contents were not affected by the supplemental Ca2+. It is concluded that the beneficial effect of high Ca2+ concentrations on root growth of cotton seedlings in a saline environment may be due to maintenance of K/Na-selectivity and adequate Ca status in the root.

245 citations


Journal ArticleDOI
TL;DR: A reciprocaltransplant experiment demonstrated that, in a habitat with a high herbaceous cover, plants produced small seeds regardless of their origin, which is a phenotypically plastic characteristic in P. vulgaris.
Abstract: (1) The effects of seed size and microsite characteristics on seedling emergence were examined in two woodland and two old-field habitats of Prunella vulgaris. Seeds of known size were sown in the field and subsequent seedling emergence was monitored. Characteristics of the microsites in which seedlings emerged were also noted. (2) Both seed size and microsite characteristics affected seedling emergence. In general, large seeds had a higher percentage emergence. Litter and herbaceous cover inhibited seedling emergence in woodland habitats and herbaceous cover inhibited emergence in old-field habitats. In all habitats, larger seeds had less stringent requirements. (3) Within a habitat, the magnitude of the effect of seed size on seedling emergence may be influenced by the mean size of seeds produced and the abundance of microsites favourable for germination. (4) Seed size is a phenotypically plastic characteristic in P. vulgaris. A reciprocaltransplant experiment demonstrated that, in a habitat with a high herbaceous cover, plants produced small seeds regardless of their origin. Larger seeds were produced by both transplanted and native individuals in a habitat with a low herbaceous cover.

177 citations


Journal ArticleDOI
01 Dec 1985-Ecology
TL;DR: The effects of herbivory and apical meristem damage on seedlings of the tropical wet forest tree Dipteryx panamensis (Leguminosae: Papilionoideae) were evaluated for natural and trans- planted seedlings at the La Selva Biological Station, Costa Rica.
Abstract: The effects of herbivory and apical meristem damage on seedlings of the tropical wet forest tree Dipteryx panamensis (Leguminosae: Papilionoideae) were evaluated for natural and trans- planted seedlings at the La Selva Biological Station, Costa Rica. Original seedling leaves were long lived, up to 21 mo, and new leaf production was slow. Damage to the original leaves was gradual and continued to accumulate well after the leaves matured. The amount of leaf area lost was serially correlated between census periods for individual seedlings. Seedling longevity was highly correlated with the percentage of original leaf area present at 1 mo after germination, and with the number of leaves present at 7 mo of age. Leaf damage and terminal meristem damage were positively related to seedling density. Onset of herbivory was earlier for seedlings in a dense natural population than for seedlings transplanted to sites with no nonspecific seedlings within 10 m. In a 1-ha population, the number of leaves on 7-mo- old seedlings was negatively correlated with the number of seedling neighbors within 10 m. Incidence of terminal meristem damage was positively correlated with seedling density. Leaf number and mer- istem damage were also correlated with distance from the nearest Dipteryx adult. Only 19% of the seedlings survived the 1 st yr without losing at least 1 apical meristem. Meristem damage was highly correlated with amount of rainfall in the preceding 60 d. We detected no effect of meristem damage on seedling survivorship. Processes acting on very young seedlings can have major effects on tree regeneration. Herbivory on the first seedling leaves may be one such important process.

174 citations


Journal ArticleDOI
TL;DR: Study of seed banks, field seedling emergence, and survival of macrophytes in four zones along transects perpendicular to a stream channel in a freshwater tidal wetland showed that many species are widely distributed and importance of a species relative to the rest of the vegetation may change with time.
Abstract: A B S T R A C T Study of seed banks, field seedling emergence, and survival of macrophytes in four zones (steep bank-SB; gentle bank-GB; midbank-MB; high marsh-HM) along transects perpendicular to a stream channel in a freshwater tidal wetland showed that many species are widely distributed. Ofthe 35 species in the seed bank, 50% were common to all zones; ofthe 20 species emerging in the field, 77% were observed in all zones. Density of seeds, seedlings, and mature plants of most species, however, varied significantly with habitat. The seed bank of each zone reflected the dominant vegetation of that zone. Most species, even those with high potential for water dispersal, were not evenly distributed. Reciprocal transplants and survival persistence data of dominants corresponded with their habitat preferences. Seed bank densities differed from zone to zone (SB 1,717 m-2; GB 1,645; MB 2,730; HM 3,620). In all zones the maximum field seedling density was less than the comparable seed bank one (SB 38% less; GB 33%; MB 46%; and HM 10%). These data, coupled with the higher proportion of the total seed bank and total field seedlings occurring in the HM, suggest that the stream channel sites were more stressful early in the growing season than the HM. Because of differential establishment and survival, importance of a species relative to the rest ofthe vegetation may change with time and occurrence of a species in the vegetation may greatly outweigh its importance in the seed bank or even the seedling stage. Although seeds of annual species were numerous with seven species making up 85% of the seed bank, annual species comprised only about half of the species recorded in the seed bank of each zone. It is not possible at our present level of understanding of seed banks in the freshwater tidal marsh to predict vegetation change. Various combinations of species attributes contribute to the zonation patterns observed in the freshwater tidal wetland.

169 citations


Journal ArticleDOI
TL;DR: Genetic variation for seed size has been maintained in this population of wild radish, suggesting that selection favoring large seeds during the seedling stage may be counteracted by selection for large numbers of seeds.
Abstract: To determine the role of seed size in creating adult plants of different reproductive success, individual seedlings were marked and periodically censused in a natural stand of wild radish (Raphanus raphanistrum L.) in Hamden, Connecticut. Maximum cotyledon witdth is a useful field estimator of seed weight in this species, although dramatic variation in the availability of water can modify this relationship. Using maximum cotyledon width as a linear estimate of seed weight showed that an increase in seed weight gives rise to a disproportionately large increase in an individual's total reproductive output. Analysis of covariance demonstrated that reproductive output is influenced more heavily by seed weight (maximum cotyledon width) than by emergence time. Genetic variation for seed size has been maintained in this population, suggesting that selection favoring large seeds during the seedling stage may be counteracted by selection for large numbers of seeds.

159 citations


Journal ArticleDOI
TL;DR: The predictions that decreasing size may increase dispersal ability, but also decrease the probability of seedling success, of wind-dispersed seeds are tested and substantial variation in seed morphology both among clones and among pods within clones is found.
Abstract: Using the propagules of common milkweed (Asclepias syriaca L.) we tested the predictions that decreasing size may increase dispersal ability, but also decrease the probability of seedling success, of wind-dispersed seeds. In 1982 and 1983 we released seeds from four milkweed clones at two heights in an open field and measured their dispersal distances. In the laboratory we measured falling times in a dead air space, seed mass and area, and coma mass and length of the same seeds. The seeds were later planted in a greenhouse and germination, mortality, and seedling dry mass were recorded.Seed mass was negatively correlated with dispersal distance in 1982, but not in 1983 under highly variable wind conditions. Coma mass/seed mass ratio was positively correlated with dispersal distance in 1982. During both years seed mass and coma mass/seed mass ratio were highly significantly correlated with falling time in dead air space. However, heavy seeds had superior germination, survivorship, and seedling mass at harvest, and seeds that germinated fell faster in dead air than those that did not. We found substantial variation in seed morphology both among clones and among pods within clones. Propagule falling times in dead air and (in 1982) dispersal distances in the field also differed significantly among clones and pods. The potential therefore exists for differential dispersal and establishment of milkweed genotypes.

147 citations


Journal ArticleDOI
TL;DR: The effects of maternal treatments on seed weight, percentage germination, and an index of germination rate were detectable in a second generation of Plantago lanceolata families.
Abstract: (1) The importance of temperature experienced during seed maturation (maternal environment) and during germination and seedling growth (progeny environment) on seed and seedling characters was examined in four maternal half-sib families of Plantago lanceolata. (2) High maternal temperatures decreased seed weight and increased the percentage germination and an index of germination rate. (3) Families of P. lanceolata responded to the maternal and progeny environments in different ways. (4) The effects of maternal treatments on seed weight, percentage germination, and an index of germination rate were detectable in a second generation.

137 citations


Journal ArticleDOI
TL;DR: One hundred experimental inbreds of sunflower (Helianthus annuus L) have been tested for their ability to produce adventitious shoots from cultured leaves as discussed by the authors, and significant genotypic variation was observed.

137 citations


Journal ArticleDOI
TL;DR: The results suggest that with the future increase in atmospheric CO2 concentration, sweetgum seedlings should “tolerate” longer exposure to low soil moisture, resulting in greater first year survival of seedlings on drier sites of abandoned fields in the North Carolina piedmont.
Abstract: The effects of CO2 enrichment and water stress on gas exchange of Liquidambar styraciflua L. (sweetgum) and Pinus taeda L. (loblolly pine) seedlings were examined for individuals grown from seed under high (1000 μmol·m-2·s-1) and low (250 μmol·m-2·s-1) photosynthetic photon flux density at 350, 675 and 1000 μl·l-1 CO2. At 8 weeks of age, half the seedlings in each CO2-irradiance treatment were subjected to a drying cycle which reduced plant water potential to about -2.5 MPa in the most stressed plants, while control plants remained well-watered (water potentials of -0.3 and -0.7 MPa for sweetgum and loblolly pine, respectively). During this stress cycle, whole seedling net photosynthesis, transpiration and stomatal conductance of plants from each CO2-irradiance-water treatment were measured under respective growth conditions.

121 citations


Journal ArticleDOI
01 Mar 1985-Oikos
TL;DR: It is suggested that mast seeding in trees is more effective in reducing seed predation by insects than by vertebrates.
Abstract: Patterns of beech seed production, seedling establishment, sapling densities, and sapling mortalities were studied in several forests dominated by different tree species. In a beech dominated forest, seed production and seedling establishment were negatively correlated in space. Seedlings became established mainly where there was least canopy coverage of mature beeches. Vertebrate seed predation was low in a year with an abundant seed crop but relatively higher in a year with a moderate crop. In the latter year predispersal insect seed predation was about 39%. I suggest that mast seeding in trees is more effective in reducing seed predation by insects than by vertebrates. Data in the literature support this prediction. The mortality rates of saplings and small trees of beech and oak were higher below mature trees of their own species than below trees of other species. In a spruce forest without mature oaks and beeches there was a high density and low mortality of saplings and small trees of the latter two species. Evidence suggests that the jay Garrulus glandarius had dug down the acorns and beech nuts. The jay appears to store beech mast only when no acorns are available. This situation occurred in the study area in 3 out of 13 years. The jay seems to be one of the species that could have dispersed the beech northwards during the Holocene.

Journal ArticleDOI
TL;DR: In this article, the authors used path analysis to summarize the interactions among the continuous variables and to disentangle direct from indirect causal effects, concluding that seed weight enhanced performance primarily through its effects on emergence date and cotyledon area.
Abstract: Summary In 1978 and 1980 I planted 660 and 900 seeds of Impatiens capensis Meerb. at four densities in the greenhouse to examine how variation in plant performance is generated. I noted seed weight, seed type (cleistogamous or chasmogamous), maternal parent, and population of origin, and monitored emergence date, cotyledon area, the biomass of competitors within the same flat, and the final size reached by the seedlings after 63 to 80 d of growth. Larger seeds tended to germinate sooner, as did seeds derived from chasmogamous flowers. Seeds from northern populations took longer to germinate. Seeds from different maternal parents also germinated at different rates. Cotyledon area strongly depended on seed weight, and, to a lesser extent, germination date. Maternal parent and seed type significantly affected cotyledon area in 1980. Plant density and cotyledon area influenced final size the most, but almost every factor proved to be statistically significant. As expected, earlier emerging seedlings with larger cotyledons growing at the lowest density grew into the largest plants. I applied path analysis to summarize the interactions among the continuous variables and to disentangle direct from indirect causal effects. This technique revealed that seed weight enhanced performance primarily through its effects on emergence date and cotyledon area. Chasmogamous seedlings outperformed cleistogamous seedlings, and their advantage was expressed during most phases of growth. Together, the predictor variables accounted for over four-fifths of the total variation in final size. The inequality of plant sizes, as measured by the Gini coefficient, increased appreciably during the course of the experiment. There was no simple relation to density, however, suggesting that both intrinsic differences in growth rate, and competitive dominance and supression fuel the establishment of size hierarchies.

Journal ArticleDOI
TL;DR: A study of the population dynamics of yellow mallee, Eucalyptus incrassata, based upon the life-stage approach revealed, contrary to previous speculation, that the populations are not static under present conditions, and recruitment events are widely spaced in time, imparting a steady-state appearance to mallee populations.
Abstract: (1) A study of the population dynamics of yellow mallee, Eucalyptus incrassata, based upon the life-stage approach revealed, contrary to previous speculation, that the populations are not static under present conditions. Successful establishment of seedlings is rare and is restricted to recently-burnt stands. (2) Following a fire in December 1977, the rates of seedling recruitment were 7000 ha-'. Adjacent unburnt stands were devoid of seedlings at this time, but some germination occurred in these stands during the winter of 1980, resulting in densities of less than 100 ha-1. (3) In recently-burnt areas, seedling mortality (75% in 2 years) was density-dependent, greatest at higher positions on the dunes, and confined to summer. The mortality at sites of high seedling density was reduced by experimental increases in soil moisture and nutrients. (4) Fire caused an increase in the rates of mortality of adults (0.6% in 2 years in unburnt stands compared to 5.0% in 2 years after fire). The establishment of seedlings following fire may be facilitated by fire-mediated changes in resource availability as a result of the release of nutrients, from burnt wood and litter, reduction in evapotranspirational demands on soil moisture, and increased rates of adult mortality. (5) Seedling recruitment of mallee eucalypts is uncommon, even following fire. This phenomenon may result from the infrequent coincidence of fire and years favourable for germination and establishment. Recruitment events are thus widely spaced in time, imparting a steady-state appearance to mallee populations.

Journal ArticleDOI
TL;DR: Overall, high CO2 levels decreased seed weight, increased germination percentage and rate, and increased seedling size, which suggests the existence of genetic variability in P. lanceolata in response to CO2 enrichment.
Abstract: Four genotypes of P. lanceolata were grown to maturity at combinations of two levels of atmospheric CO2 concentrations and two temperature conditions. Seed weight was determined, and seed germination and seedling growth were measured for the progeny of each genotype under the same environmental conditions. Overall, high CO2 levels decreased seed weight, increased germination percentage and rate, and increased seedling size. Families differed in their response to CO2 enrichment, and to combinations of CO2 and temperature levels for several characters. These results suggest the existence of genetic variability in P. lanceolata in response to CO2 enrichment.

Journal ArticleDOI
TL;DR: Root-colonizing pseudomonads capable of inhibiting seedling winter wheat root growth in an agar seedling bioassay also significantly inhibited wheatroot growth in vermiculite, providing further evidence that a toxin, produced by these organisms, is involved in growth retardation.
Abstract: Root-colonizing pseudomonads capable of inhibiting seedling winter wheat (Triticum aestivum L.) root growth in an agar seedling bioassay also significantly inhibited wheat root growth in vermiculite; however, the inhibitory trait is quite labile in laboratory culturing. The extent of inhibition in both the agar and vermiculite medium depended on inoculum level. These pseudomonads were found to produce a toxin capable of inhibiting growth ofEscherichia coli C-la andBacillus subtilis. Field isolates that strongly inhibit growth of indicator bacteria also inhibited root growth. Toxin production by the bacteria appeared necessary for inhibition of root growth and indicator bacteria as toxin-negative (TOX−) mutants no longer inhibited either. Antibiosis towardsE. coli as well as wheat seedling root inhibition in agar was reversed by L-methionine, providing further evidence that a toxin, produced by these organisms, is involved in growth retardation.

Journal ArticleDOI
TL;DR: Net photosynthesis, chlorophyll content, and chloroplast ultrastructure of leaves differentiated from these conditions were investigated and chlorophyll in seedlings and plantlets was significantly higher in low light-treated plants.
Abstract: Liquidambar styraciflua L. seedlings and tissue-cultured plantlets were grown under high, medium, or low (315, 155, or 50 microeinsteins per square meter per second photosynthetically active radiation) quantum flux densities. Net photosynthesis, chlorophyll content, and chloroplast ultrastructure of leaves differentiated from these conditions were investigated. Seedling photosynthetic rates at light saturation were positively related to light pretreatments, being 6.44, 4.73, and 2.75 milligrams CO2 per square decimeter per hour for high, medium, and low light, respectively. Cultured plantlets under all light conditions had appreciably higher photosynthetic rates than noncultured seedlings; corresponding rates were 12.14, 13.55, and 11.36 milligrams CO2 per square decimeter per hour. Chlorophyll in seedlings and plantlets was significantly higher in low light-treated plants. Seedling leaves had chloroplasts with abundant starch regardless of light pretreatment. In high light, starch granules were predominant and associated with disrupted granal structure. Low light seedling chloroplasts had smaller starch grains and well-formed grana. In contrast, tissue culture-differentiated leaves were devoid of starch; grana were well organized in higher quantum flux density treatments, but disorganized at low flux densities.

Journal ArticleDOI
TL;DR: The results suggest that imbalanced root/shoot ratios caused the development of internal water stress and the consequent reduction in stomatal aperture, culminating in leaf and whole plant senescence.
Abstract: Root restriction may be of importance for productivity in both forestry and agriculture. To study the physiological effects of root restriction in European alder (Alnus glutinosa Gaertn.), seedlings were grown in aerated liquid culture under one of four root volumes to induce the following levels of root restriction: 1.5, 6,16 and 500 ml. Root restriction for 96 days reduced shoot elongation, plant dry weight, leaf area and chlorophyll levels and increased leaf area/root dry weight ratio and correlative bud inhibition in seedlings. The initial reduction in root/shoot ratios of severely restricted seedlings was followed by a reduction in leaf water potential, the development of internal water deficits in the upper shoots, a reduction in stomatal opening and transpiration rates and, eventually, stomatal closure. Severe prolonged root restriction (1.5 ml root volume) resulted in a decline in seedling vigour and ultimately, senescence as determined by increased electrical impedance ratios, followed by visible leaf senescence and later, by whole plant senescence. Of the severely restricted seedlings, 40% were dead after 96 days of restriction. The results suggest that imbalanced root/shoot ratios caused the development of internal water stress and the consequent reduction in stomatal aperture, culminating in leaf and whole plant senescence.

Journal ArticleDOI
TL;DR: Observations on seed dispersal and predation and juvenile mortality and spatial distribution are combined to show how dispersal helps the tropical tree Aglaia sp.
Abstract: Black hornbills (Anthracoceros malayanus) appear to be the principal long-distance seed dispersers of Aglaia sp. (Meliaceae) at Pasoh Forest Reserve in Peninsular Malaysia. The squirrel Callosciurus prevostii removed some of the large seeds at least as far as adjacent crowns and sometimes dropped them after consuming only the orange, oily sarcotesta. It chased other squirrel species, which are probably seed predators, and hornbills out of the fruiting crown. Seeds on the ground beneath the parent crown were removed more rapidly than those farther away by rodent and (possibly) phasianid seed predators. Sitophilus sp. (Curculionidae) was also an Aglaia seed predator or parasite. Aglaia juveniles grew slowly under closed canopy, and small ones (<50 cm in height) had only 9.7 percent mortality per year during a 4-year period. Seedling survival was positively size dependent. For unknown reasons, small seedlings near the parent had a higher death rate than those at a greater distance; this was apparently a long-term pattern, because large seedlings and saplings did not occur within 10 and 35 m, respectively, of the parent tree's base. For this species an advantage of seed dispersal is avoidance of disproportionate seed and seedling mortality near the parent. Although Aglaia grows much faster in gaps than under closed canopy, it may require several episodes of growth in successive gaps before becoming reproductively mature. IN THEIR REVIEW OF SEED DISPERSAL, Howe and Smallwood (1982) remarked that little is known about its ecological and evolutionary advantages to the plant. Here we combine observations on seed dispersal and predation and juvenile mortality and spatial distribution to show how dispersal helps the tropical tree Aglaia sp. (Meliaceae) avoid seed and seedling mortality that is greater near the parent than farther away. Webb et al. (1967), Janzen (1970), and Connell (1971) suggested that such a mortality pattern, generated by seed predators, herbivores, or allelopathy, would promote the maintenance of high tree species richness in tropical forests. More recently, Connell (1978, 1979) has withdrawn his support for this hypothesis because field studies have shown that seed and seedling mortality is not invariably higher near conspecific adults. However, Clark and Clark's (1984) review of 24 data sets on mostly neotropical, woody plants showed that most evidence indicates either densityor distance-dependence in progeny mortality, as originally predicted by Janzen and Connell. Hubbell (1979, 1980) challenged the Janzen-Connell hypothesis on empirical and theoretical grounds, daiming the latter to demonstrate that spacing between conspecific adults could contribute little to the maintenance of high species richness. His theoretical analysis has been questioned by Becker et al. (1985), who consider the issue unresolved for nonequilibrium

Journal ArticleDOI
TL;DR: The resulting data suggested that a number of ferulic acid microbial metabolic products, as well as two other phenolic acids observed in soils, can reduce seedling dry weight, leaf expansion, and water utilization of cucumber seedlings in a similar manner.
Abstract: Cucumber seedlings (Cucumis sativus cv. ‘Early Green Cluster’) ranging from 6 to 16 days of age were treated with various concentrations (0– 1 mM) of caffeic, ferulic,p-coumaric,p-hydroxybenzoic, protocatechuic, sinapic, syringic, and vanillic acids and mixtures of ferulic acid and one or two of the other phenolic acids. Seedlings were grown in full-strength Hoagland's solution which was changed every other day. Phenolic acid treatments were given with each nutrient solution change starting at day 6 or given once when seedlings were 13 or 14 days old. Leaf area, mean relative rates of leaf expansion, transpiration rates, water utilization, and the concentrations of the phenolic acids in nutrient solution were determined at one- or two-day intervals. Seedling dry weight was determined at final harvest. Seedling leaf area and dry weight were linearly related. Since leaf areas can be easily obtained without destructive sampling and leaf area expansion responds rapidly to phenolic acid treatments, it was utilized as the primary indicator of plant response. The resulting data suggested that a number of ferulic acid microbial metabolic products, as well as two other phenolic acids observed in soils (p-coumaric and syringic acid), can reduce seedling dry weight, leaf expansion, and water utilization of cucumber seedlings in a similar manner. The magnitude of impact of each of the phenolic acids, however, varied with phenolic acid and concentration. It appears that the inhibitory activity of these phenolic acids involved water relations of cucumber seedlings, since the phenolic acid treatments resulted in closure of stomata which then remained closed for several days after treatment. The data also demonstrated that the effects of mixtures of phenolic acids on cucumber seedlings may be synergistic, additive, or antagonistic. The type of response observed appeared to be related to the factor measured, the compounds in the nmixture, and the magnitued of inhibition associated with each compounds. The data also indicated that the effects of the various phenolic acids were reversible, since seedling leaf area increased rapidly once phenolic acids were removed from the root environment. Mean relative rates of leaf expansion recovered even in the presence of the various phenolic acids.

Journal ArticleDOI
TL;DR: The data suggest that populations of mistletoes are genetically differentiated such that early seedling development is greatest when there is corre, rather than when the source host and source host species were different.
Abstract: In order to test the hypothesis that mistletoes (Phoradendron tomentosum) are differentially adapted for the host species that they occur on, mistletoe seeds from the three most common hosts in central Texas (hackberry, Celtis occidentaliss elm, Ulmus crmsi.folia, and mesquite, Prosopsis glandalosa) were planted onto different individuals of each of the three hosts. Germination of seeds and formation of haustorial disks by seedlings were followed in the subsequent 17 months. Germination of seeds was very high for all nine combinations of maternal (sourc* and seed (experimental) hosts (range 82%-98%). There were no significant differences in seed germination between the two groups when source and experimental hosts were the same species and when they were different species. In contrast development of haustorial disks when source and experimental hosts were the same species was significantly greater than when experimental host and source host species were different. The data suggest that populations of mistletoes are genetically differentiated such that early seedling development is greatest when there is corre

Journal ArticleDOI
TL;DR: Germination of the polymorphic seeds and seedling growth of Atriplex triangularis under various salinity, gibberellic acid and kinetin treatments were determined.
Abstract: Germination of the polymorphic seeds and seedling growth of Atriplex triangularis under various salinity, gibberellic acid and kinetin treatments were determined. Gibberellic acid (GA3; 2.9 mM) promoted germination and growth at high NaCl concentrations (345 mM). Kinetin (4.7 μM) stimulated germination at all salinities and seed sizes tested. GA3 and kinetin generally increased seedling growth at all concentrations of salinity studied. Higher concentrations of kinetin were found to be inhibitory.

Journal ArticleDOI
TL;DR: Recovery of leaf expansion after ferulic acid treatments was faster for seedlings grown in an adequate nutrient environment than for seedling grown in a limited nutrient environment, and two microbial metabolic products of ferulic Acid were identified in nutrient solutions.
Abstract: Cucumber seeds and seedlings at various ages (7–19 days old) were treated with a single treatment or multiple treatments (at 2-day intervals) of ferulic acid in nutrient culture. Ferulic acid treatments of cucumber seeds during stages of germination and radicle growth did not significantly reduce subsequent seedling growth. Ferulic acid treatments to seedlings reduced leaf area, leaf expansion, and dry weight of cucumber seedlings. Pretreatment of seeds and seedlings with 0.1 or 0.2 mM ferulic acid did not modify the effects of a single 1 mM ferulic acid treatment on leaf expansion when a single treatment was given at various times to seedlings ranging from 7 to 19 days of age. Treatments of 1mM or greater induced rapid wilting of leaves, but visible recovery occurred within 24–48 hr and subsequent treatments did not cause wilting. Once seedlings were removed from ferulic acid treatments, leaf expansion resumed. The magnitude of recovery depended on the concentration of ferulic acid, frequency of ferulic acid application and age of the seedling. Mean relative rates of leaf expansion recovered rapidly even in the presence of ferulic acid. Recovery of leaf expansion after ferulic acid treatments was faster for seedlings grown in an adequate nutrient environment than for seedlings grown in a limited nutrient environment. Ferulic acid disappeared from nutrient solutions with time, and two microbial metabolic products of ferulic acid (i.e., vanillic and protocatechuic acid) were identified in nutrient solutions.

Journal ArticleDOI
Sayed Hi1
TL;DR: A collection of wheat germplasm screened at the seedling stage for tolerance to salinity concentrations having electrical conductivities of 0.8, 12.5, 18.5 and 25.0 dS/cm salinity showed a good potential for salt tolerance at early stages and was indicative of maturity tolerance.
Abstract: A collection (5,072 lines) of wheat germplasm was screened at the seedling stage for tolerance to salinity concentrations having electrical conductivities of 0.8 (control), 12.5, 18.75 and 25.0 dS/m. Surviving seedlings were expressed for each line as a percentage of the control value. The 442 lines with greater than 70% surviving seedlings were tested for whole-life cycle survival under each salinity condition. The data of the reactions to salinity at both the seedling stage and maturity were used to classify the collection according to: (1) country of origin (2) species and ploidy level. The data were then subjected to a diversity analysis using the Shannon-Weaver information index. Seedling stage tolerance to 12.5 dS/cm salinity was widely distributed in the collection (79% of lines), whereas only 9% were tolerant at 25.0 dS/m salinity. The seedling stage tolerance was indicative of maturity tolerance. At the seedling stage, entries from USA and Egypt showed the largest proportions of tolerant lines. In addition, USA, Mexico and Egypt entries exhibited the widest variability. Diversity among regions was greater than among countries within regions, while the diversity among species was greater than among ploidy levels. Tetraploids exceeded hexaploids and diploids in the proportion of tolerant lines and diversity. Wheat-rye derivatives showed a good potential for salt tolerance at early stages. Screening more germplasm from the arid and semi-arid regions especially from countries with salt affected soils was recommended.

Journal ArticleDOI
TL;DR: Basidiospores of seven species of hypogeous, ectomycorrhizal fungi were inoculated on four conifer species in a bare-root nursery and inoculated seedlings had significantly greater survival, stem height, root collar diameter, and biomass than noninoculated seedling.
Abstract: Basidiospores of seven species of hypogeous, ectomycorrhizal fungi were inoculated on four conifer species in a bare-root nursery. Inoculation with either Rhizopogonvinicolor Smith or Rhizopogoncolossus Smith succeeded with two provenances of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). For R. vinicolor, the high spore-application rate produced the most mycorrhizae on the greatest number of seedlings. For R. colossus, the high spore-application rate produced the most mycorrhizae on the greatest number of seedlings of seed source 062, whereas the medium rate did better with seed source 252. Stem height and root collar diameter of seedling did not differ significantly between treatments and controls. Douglas-fir seedlings inoculated or not inoculated with spores of R. vinicolor were outplanted in southwestern Oregon. After 2 years, inoculated seedlings had significantly greater survival, stem height, root collar diameter, and biomass than noninoculated seedlings. Although new feeder roots of both noni...

Journal ArticleDOI
01 Dec 1985-Botany
TL;DR: The movement of seeds into the different vegetation types indicated that seed ingress could be important when one considers potential vegetation change.
Abstract: Seed numbers and the species composition of seed banks (germinable seeds) from a marsh adjacent to the Great Salt Lake were compared among five vegetation types prior to a drawdown, during a drawdown, and prior to fire, after fire, and after restoration of normal water levels. Substrate samples were processed in the greenhouse under submersed and moist soil treatments to simulate the two germination conditions found in the field. After the fire, seed movement into the different vegetation types was also estimated. Numbers of germinable seeds were not depleted during the drawdown, possibly owing to increased salinity and the presence of standing vegetation. Fire had little effect on seed banks and subsequent seedling response. In general, seed banks were not affected by disturbance (e.g., burning, drawdown). The movement of seeds into the different vegetation types indicated that seed ingress could be important when one considers potential vegetation change. Seed banks of open water sites contained few ger...


Journal ArticleDOI
TL;DR: Increased leaf surface area yields a productive advantage to seedlings grown at concentrations of CO2 up to 2000 μL•L−1 even if no increase in net photosynthesis is assumed.
Abstract: Relatively little work has been done to evaluate the effects of chronically high levels of carbon dioxide on growth and physiology of woody plants. In this study, seedlings of lodgepole pine (Pinuscontorta Dougl. var. latifoliaEngelm.) were grown for 5-month periods at 330, 1000, or 2000 μL CO2•L−1. Height growth; leaf area production; biomass of leaves, stems, and roots; and photosynthetic responses to changing light, moisture, and CO2 concentration were measured. Significant differences between treatments were found in mean seedling height on all measurement dates. Seedlings grown at 1000 μL CO2•L−1 were tallest, with seedlings grown in 2000 μL•L−1 intermediate between the control (330 μL•L−1) and 1000 μL•L−1 treatments. The same relationship was found in production of total leaf surface area. Increased leaf surface area yields a productive advantage to seedlings grown at concentrations of CO2 up to 2000 μL•L−1 even if no increase in net photosynthesis is assumed. Biomass of stems, roots, and secondary ...

Book ChapterDOI
01 Jan 1985
TL;DR: Respiration, enzyme and organelle activity, and RNA and protein synthesis are fundamental cellular activities intimately involved in the completion of germination and the preparation for subsequent growth.
Abstract: Respiration, enzyme and organelle activity, and RNA and protein synthesis are fundamental cellular activities intimately involved in the completion of germination and the preparation for subsequent growth. It is not surprising, therefore, that most research into the biochemistry of germination and growth have concentrated on these events, to which we now turn our attention.

Journal ArticleDOI
TL;DR: The role of germination per se in seedling establishment of Gustavia superba (Kunth) Berg (Lecythidaceae), a tropical moist forest in Panama is discussed, it is concluded that G. superba is not a tropical species whose seeds germinate in response to a light gap but its seeds do germine successfully under a range of microsite conditions.
Abstract: This six-month study examined percent germination, days until germination, and early seedling survival of Gustavia superba (Lecythidaceae) through field experiments in a tropical moist forest in Panama. The study had three goals: (1) to examine whether germination is a factor determining density of seedlings at three forest sites with different ages; (2) to test whether burial of seeds affects germination; and (3) to test if microsite conditions associated with light gap, gap-edge, or forest understory influence germination. The experiment, which was designed to fit a three-way ANOVA model, used three study sites, three microsites, two burial treatments, four replicates and 25 seeds in each replicate (1800 seeds total). Although seedling densities of G. superba at the forest sites varied inversely with age of forest, there was no evidence that germination success contributes to this pattern. Results indicated that this species germinates readily under most conditions: the overall mean was 85.4 percent and only six of 72 plots had less than 70 percent germination. Germination percent was reduced and mean number of days until germination was increased in the largest light gap. However, percent germination and days until germination did not differ among sites when only seeds in the understory microsite were compared. Burial of seeds and microsite conditions had minor effects on germination. Seedling mortality occurring soon after germination was not large (5.7%). It is concluded that G. superba is not a tropical species whose seeds germinate in response to a light gap but its seeds do germinate successfully under a range of microsite conditions. ALTHOUGH PLANT POPULATION SIZES can be affected by mortality at many stages, the seed to seedling transition generally is considered to be one of the most vulnerable. Mortality agents include pathogens, insect and vertebrate predators of seeds, as well as abiotic factors affecting germination levels. All these factors are intertwined in affecting seedling establishment. As a result, controlled experiments are required to identify the separate contribution of each factor. The focus of this paper will be to discuss the role of germination per se in seedling establishment of Gustavia superba (Kunth) Berg (Lecythidaceae), a

Journal ArticleDOI
TL;DR: The absence of in situ germination of quiescent spores during growth of the crop under which the spores formed or during storage in the soils may have a role in survival of the fungi in agricultural or range land ecosystems, or in maintaining inoculum levels in pot culture systems.
Abstract: In situ germination of quiescent spores of Glomus caledonium, Gigaspora calospora and Acaulospora laevis was prevented in soils under crops or pastures, and in pot cultures of the fungi. Quiescent spores also failed to germinate during long-term storage in these soils when they were at temperatures and water potentials appropriate for germination. Germination was also prevented in other crop soils. Soil from a virgin forest did not prevent germination but did so after it had carried one subterranean clover crop to maturity. In all soils, prevention of germination was relieved by seed germination and seedling growth or by treatment of soils with heat or methyl bromide. Water-soluble, heat-labile compounds which prevented germination were extracted from the crop and pot culture soils which prevented germination, but not from soil from under a virgin forest. In addition to compounds in the bulk soil, self-inhibitors seemed to be involved in regulating germination. Bacteria from the spore surfaces promoted germination on sterile extracts of soils in which germination was blocked. A multiplicity of factors appeared to have a role in preventing germination, and these included mid to late stages of crop growth and associated changes in microbial activity. The absence of in situ germination of quiescent spores during growth of the crop under which the spores formed or during storage in the soils may have a role in survival of the fungi in agricultural or range land ecosystems, or in maintaining inoculum levels in pot culture systems.