Showing papers on "Seedling published in 1972"

Seed Weight in Relation to Environmental Conditions in California

Abstract: Analyses of the California flora involving nearly 2,500 taxa are presented which show that there are correlations between the weights of individual seeds and environmental conditions in which their producers normally grow. These differences in seed weight appear to be adaptive and result from compromises between increased nutrition of the seedling which would result from larger food reserves in heavier seeds and increased dispersibility and increased reproductive output which are provided when smaller seeds are produced in larger numbers. Literature and experiments show a general positive correlation between seed weights and rates of shoot and root growth, at least within species. Herbs (annual and perennial), shrubs and trees are necessarily treated separately in the calculations in this paper (for seed weights increase progressively in a series from annual herb to tree when to California flora or any particular community type within it are considered). Raw seed weights are reduced to a series of classes (on a logarithmic basis) before means for floras or community types are calculated. Generalizations arrived at from considerations of "native" species in "natural" plant communities are confirmed by their applicability to "introduced" species now forming various kinds of "weed" communities in California. Finally, species lists from actual stand analyses, including both "native" and "introduced" species, are utilized to provide the data for more precise analyses. For herbaceous plants, seed weights are higher, on the average, for taxa whose seedlings are exposed to the risk of drought soon after establishment (giving faster root—development). Such a relationship can be demonstrated for species of a single genus or, on a combination basis, for community types as a whole and can be put on a quantitative basis by subjectively ordinating community types (in relation to the likelihood of drought stress hitting the seedlings) and making rank correlations with mean seed weight for each community type. The relation holds even for desert communities (where large—seeded perennials produce large root—systems but small—seeded ephemerals complete at least their seedling development in temporarily mesic conditions). In coastal communities, the importance of wind—dispersal of the seeds of species whose seedlings become established in rock crevices outweighs any droughtiness of the habitat in favoring smaller seeds than typify the community types generally. Correlations of herb seed—weight with likelihood of seedlings becoming established in shade or in conditions of severe competition are less marked for California than Salisbury found them to be in England. For shrubs, shading and competitive stress appear to be more influential factors in promoting increased mean seed weight but for trees moisture availability again appears to be most important. Another kind of correlation is established; between mean seed weight and altitude at which the plants occur. With decreasing length of the growing season as Californian mountains are ascended the mean seed weight (whether measured on a subspecies, species or community type basis) also decreases. This appears to represent the selection of a strategy in which a reduction in the availability of photosynthate is reflected in smaller seeds rather than in reduced output as found in Ranunculus by Johnson and Cook. Although taxa introduced to California have fitted with the rules holding for native plants, they tend to have slightly heavier seeds than native species growing in climatically similar habitat types. This difference may be particularly related to human influence in making such habitats somewhat more xeric. Improved methods of analysis are suggested and further correlations which might be sought are discussed.

Germination and Seedling Development of Common Milkweed and Other Species

Abstract: Common milkweed (Asclepias syriaca L.) seed did not survive storage in water for 1, 2, and 12 months at 40, 30, and 5 C, respectively; but under dry storage seed viability was destroyed only at 40 C for 5 months. Stratifying common milkweed seed in water at 5 C was more effective in breaking dormancy than at 22 C. Mechanical scarification also caused a significant increase in germination. Exogenous 6-furfurylamino purine (kinetin) and gibberellic acid-3 (GA) increased germination while indole-3-acetic acid (IAA) had no effect. The optimum germination temperature scheme for common milkweed was an alternating 20 to 30 C, the maximum between 35 and 40 C, and the minimum between 15 and 20 C. Common milkweed seedlings were more susceptible to moisture stress than kochia [Kochia scoparia (L.) Schrad.] but less susceptible than hemp dogbane (Apocynum cannabinum L.) and sunflower (Helianthus annuus L.). In a greenhouse study common milkweed was less drought tolerant than eight other weed species. Common milkweed seedlings tolerated wider pH ranges than honeyvine milkweed [Ampelamus albidus (Nutt.) Britt.], kochia, and sunflower. Common milkweed seedlings were less tolerant to salt solutions than four other species. Common milkweed emerged from 6-cm depths in Sharpsburg silty clay loam (sicl) at 20 or 30 C but only from the 3-cm depth at an alternating 20 to 30 C. Results from root box studies showed that common and honeyvine milkweed produced less shoot and root weight than kochia and sunflower and had a lower growth rate index of roots than sunflower. Common milkweed seedlings resprouted 21 days after planting when clipped at ground level. As days from planting to clipping increased, sprouting activity increased.

Root exudates of plants: IV. Differences in chemical composition of seed and seedlings exudates

Abstract: Comparisons have been made of the amount and composition of seed and seedling exudates in barley, wheat, cucumber, and bean. Except in the case of wheat a greater proportion of the total nitrogen content in the seed exudates was formed by protein and peptide nitrogen than by nitrogen of free amino acids. In contrast, the greater part of the total nitrogen in the exudates of seedlings was formed by free amino acid nitrogen, except in the case of barley. Peptides represented 8 to 26 per cent of the protein and peptide fraction in seed exudates, the highest amount being found in bean. On an equal weight basis, the spectrum of amino acids released from seeds and seedlings differed little between barley, wheat and cucumber ; greater differences were observed in bean exudates. Seedlings exuded reducing substances to a considerably greater extent than seeds. The spectrum of reducing sugars in seed and root exudates differed greatly, especially in the case of keto sugars. Differences in the organic acid spectra were small, except for bean plants, the seedling exudate of which contained more organic acids with a richer spectrum than seed exudate. Both seeds and seedlings of cucumber exuded a small quantity and a poor spectrum of organic acids.

Content of Adenosine Phosphates and Adenylate Energy Charge in Germinating Ponderosa Pine Seeds

Abstract: An average of 540 picomoles of total adenosine phosphates was found in the embryo of mature seeds of ponderosa pine (Pinus ponderosa Laws.) and 1140 picomoles in the gametophyte. Adenylate energy charges were 0.44 and 0.26, respectively. After stratification, total adenosine phosphates increased 7-fold and 6-fold in embryo and gametophyte, respectively, and energy charges rose to 0.85 and 0.75. During germination, total adenosine phosphates increased to a 20-fold peak on the 9th day in gametophytic tissue, parallel with the peak of reserve regradation and organellar synthesis, and then decreased. In embryo and seedling, total adenosine phosphates elevated 80-fold with two distinct oscillating increases of AMP and ADP. The oscillating increases occurred before the emergence of radicle and cotyledons during which the highest mitotic index prevailed in all tissues. Energy charges fluctuated between 0.65 at the rapid cell dividing stage to 0.85 at the fully differentiated stage of the seedling, while energy charges remained around 0.75 in the gametophyte. These data indicated that the content of adenosine phosphates of germinating seeds reflects growth, organogenesis, and morphogenesis, and that a compartmentalized energy metabolism must exist in dividing and growing plant cells.

Yellow Nutsedge Tuber Germination and Seedling Development

Abstract: Upon germination, one or more rhizomes grew from the apical end of each yellow nutsedge (Cyperus esculentus L.) tuber. Each rhizome developed a basal bulb upon exposure to light. No significant differences in germination percentages existed between four lots of tubers which differed about five- fold in weight. The weight of plant material produced corre- lated significantly with the fresh weight of the tuber from which it emanated. When tubers germinated three successive times, over 60% of the tuber dry weight, carbohydrate, oil, starch, and protein were consumed during the first germina- tion; but less than 10% of these constituents were uitlized during each of the next two germinations. Plants weighed significantly more after 43 and 91 days of growth with tubers attached throughout the period than when tubers were de-

Germination and seedling response of atlantic and gulf coasts populations of uniola paniculata

Abstract: A B S T R A C T Germination response following various periods of cold treatment and seedling response to temperature, daylength, and salinity were studied for several Atlantic and Gulf coasts populations of Uniola paniculata L. Results indicated that Atlantic coast Florida populations did not require cold treatment prior to germination at 95-65 F, but that populations from Virginia and North Carolina did. Gulf coast populations exhibited a germination response intermediate between those just mentioned. Seedling studies revealed that alternating diurnal thermoperiods with daytime temperatures of 80 F and above produced good vegetative growth in all populations with little preference for either short- or long-day conditions. Gulf coast populations produced the most biomass under -all treatment conditions. Seedlings from a North Carolina and a Florida population indicated no difference in substrate salt tolerance. Salt tolerance was reduced in the higher temperature thermoperiod for both populations. Seedlings from these two populations produced more biomass in a salt spray treatment than in substrate salinity treatments. THE PERENNIAL DUNE grass Uniola paniculata L.

Hormonal regulation of germination and early seedling development in Acer pseudoplatanus (L.)

Abstract: Dormancy of intact sycamore (Acer pseudoplatanus) seeds was broken by chilling (5°C) for several weeks in moist conditions. Treatment of unchilled seeds with kinetin induced some germination, but gibberellin was ineffective. This stimulation by kinetin was not suppressed by the added presence of abscisic acid during incubation.

Effect of soil temperature on seedling emergence in different crops

Abstract: Seedling emergence in different crops was studied in the soil temperature range of 5°C to 45°C. In peas and turnips seedling emergence stopped at a soil temperature of 35°C and in other crops at 45°C. The minimum temperature for seedling emergence was above 10°C in case of cotton, sorghum, rice, maize and musk melon and above 15°C in case of squash, bottle gourd and okra. Winter crops like wheat, gram, peas, and turnips emerged at 5°C but the percent emergence was low. The optimum range for seedling emergence was narrower for vegetable crops as compared with cereals.

Hypocotyl and Radicle Elongation of Cotton as Affected by Soil Environment1

Abstract: Cotton (Gossypium hirsutum L.) seedling growth during emergence was studied under controlled conditions to estimate the main and interacting effects of soil temperature, moisture, and physical impedance on hypocotyl and radicle elongation. This information additionally provided a data base for the development of an elongation model for an emerging cotton hypocotyl which is not included in this report. Soil temperature increasing from 15.6 to 32.2 C resulted in more rapid and greater total elongation of hypocotyls and radicles. Increasing physical impedance decreased elongation of both hypocotyls and radicles, with hypocotyls being the most sensitive. Decreased hypocotyl elongation was consistently noted with increasing soil moisture tension; however, radicle elongation tended to be greater at 3.0 bars than for .3 bar. A marked temperature-moisture interaction was evident for hypocotyl and radicle elongation at 37.8 C which is near the hot null temperature (40 C) for cotton. However, this interaction did not exist at 15.6 which is near the cold null (14 C). A relative slow-down in hypocotyl elongation rate between 2.5 and 5.0 cm occurred at 37.8 C and .3 bars soil moisture, and at 32.2 C and 3.0 bars.

Seedling response to salinity in four dune grasses from the outer banks of north carolina

Abstract: Tolerance to salt in the substratum was determined in seedlings of four perennial dune grasses: Ammophila breviligulata Fern., Panicum amarulum Hitch. & Chase., Spartina patens (Ait.) Muhl., and Uniola paniculata L. An inverse linear relationship existed between growth and increased salinity in A. breviligulata, S. patens, and U. paniculata. Panicum ama- rulum seedlings demonstrated a curvilinear response to; salinity. Seedlings of A. breviligulata and U. paniculata grew moderately well in salinities up to 1.0% NaCl, those of P. amarulum achieved even better growth in this salinity range, and some seedlings of S. patens survived the entire 28-day experimental period at 4.0% NaCl. Seedlings of S. patens collected from the field were more salt tolerant than those grown from seed collected from the field and germinated in the laboratory. In the other species the performance of field- and laboratory- grown seedlings did not differ. Based on seedling growth response, the order of decreasing salt tolerance for the four species is S. patens, P. amarulum, U. paniculata, and A. breviligu- lata. This pattern correlates well with performance in nature. ance to burial, sand-blasting, salt spray, drought, and flooding. Although mature plants of these grasses grow together in the dune system, seedlings of sev- eral different species occupy fairly distinct areas or microhabitats. Seedlings of all species are exposed to approximately equal intensities of most environ- mental factors with the exception of flooding with sea water, which is related to elevation. Substrate salinity can damage and kill plants when flooding by salt tides is not accompanied by rainfall in hot, dry weather. Thus, substrate salinity can act as a major selective force determining seedling establishment and survival in areas subject to flooding. The present study was designed to determine substrate salt toler- ance among seedlings of four perennial grasses, Am- mophila breviligulata Fern., Panicum amarulum Hitch. & Chase., Spartina patens (Ait.) Muhl., and Unio~a paniculata L., to see whether this response could be correlated with habitat conditions of seed- ling populations in nature.

The shoot apical ontogeny of the picea abies seedling. i. anatomy, apical dome diameter, and plastochron duration'

Abstract: A B S T R A C T Developing embryos in immature Picea abies seeds already have well-delineated shoot apical meristems with clearly evident cytohistological zonation. During early seedling development the zonation characteristic of gymnospermous apical meristems is attained. Seedling development is also accompanied by an approximately threefold increase in apical dome diameter. The latter approaches a steady state about 140 days after germination. Seedlings display a spiral phyllotaxis consisting of a contact parastichy system, usually of the primary Fibonacci series. As the seedlings age and apical domes enlarge, higher Fibonacci number-pairs characterize their phyllotaxis. Mathematical analysis of the relation between cumulative leaf number and age revealed that the length of the plastochronic time interval declines from about 18.5 hr to 5.7 hr as seedling age increases from 20 to 140 days. A MAJOR AREA of study in this laboratory con

Effects of environment on the relation between seed protein and seedling vigor in wheat

Abstract: Wheat seedlings grown from seeds of different protein levels, obtained from an N fertilizer field trial, showed significant differences in dry matter and a high positive correlation (r = 0.920**) between seed protein content and dry matter after 3 weeks’ growth. In further studies using low and high protein seeds (99 and 142 mg/g), dry matter differences were obtained at up to 40 days from sowing and in different temperature and light intensity environments with nutrient concentrations containing up to 24 mM nitrate. Maximum dry matter accumulation occurred at approximately 5 mM nitrate but no limit was reached in protein accumulation with up to 24 mM nitrate. Seedlings grown from high protein seeds were shown to be more advanced in morphological development than those seedlings grown from low protein seeds.

Some observations on oxygen transport in conifer seedlings

Abstract: Summary The diffusive flux of oxygen from the roots of intact conifer seedlings was measured by a polarographic technique. With an anaerobic solution bathing the roots maintained at 23° C and with their aerial parts in air, flux rates were appreciable from eight of the twenty-five seedlings tested. When the aerial parts were placed in oxygen, there was a large increase in flux from each pine seedling. While their general response was barely measurable, a significant but much smaller increase occurred from eight of the spruce. Oxygen transport through the plants appeared to be by diffusion chiefly in the gas phase and significant flux rates from the roots with aerial parts in air might indicate some capacity for wet soil tolerance in the seedlings concerned. When the external concentration of oxygen was increased five-fold there was a disproportionate increase in oxygen flux from pine roots indicating that respiration in the plants might be affecting the flux rates. By cooling the bathing medium to 30 C a further demonstration of the respiratory effect-a large increase in flux rate-was obtained. With respiration reduced by cooling, the flux rates from the pine seedlings increased approximately five-fold for a five-fold increase in the external oxygen concentration. Cooling did not induce any pronounced response from the spruce seedlings. Internal diffusional resistance and oxygen leakage from the sub-apical parts of the roots may account for the absence of high apical flux rates in the pines and the extremely low readings recorded for the spruce seedlings.

Plastid differentiation and chlorophyll synthesis in cotyledons of Black Pine seedlings grown in the dark

Abstract: The earliest stage in the development of black pine seedlings have been viewed and assayed in the present correlative study, resulting in a morphological and biochemical description of several forms of plastids. With the exception of ungerminated embryo cotyledons, the plastids are recognized in five stages of seedling development. They progress from proplastids containing protochlorophyll which are located among protein and lipid bodies to the chlorophyll containing chloroplasts with well developed grana. The differentiation period was between the first and the forth day, when active metabolism started.

Phytochrome-mediated induction of ascorbate oxidase in different organs of a dicotyledonous seedling (Sinapis alba L.).

Abstract: The time courses of the level of ascorbate oxidase (AO; EC 1.10.3.3.) were followed in the different organs (cotyledons, hypocotyl, taproot) of the developing mustard seedling. Phytochrome (operationally, far-red light, cf. [20]) rapidly and strongly enhances the rate of apparent ascorbate oxidase (AO)1 synthesis in cotyledons and hypocotyl, while in the taproot the detectable amount of AO is only small. However, the relative increase of AO as mediated by continuous far-red light is the same in all organs. Far-red → dark kinetics indicate that the phytochrome-induced enzyme is much less stable in the hypocotyl than in the cotyledons, at least during the experimental period. It is concluded that the effect of phytochrome on enzyme induction is precisely the same in cotyledons and hypocotyl, while the processes of enzyme degradation are specific for the organ. Thus the time courses of enzyme levels can be determined by the “nature” of the particular organ, even if no isoenzymes are involved and the “mechanism” of the inductive process is the same in the different organs.

Seedling response to photoperiod and temperature by smooth cordgrass,Spartina alterniflora, from Oregon Inlet, North Carolina

Abstract: Seedlings ofSpartina alterniflora Loisel. from North Carolina were exposed to thermoperiods of 18–14, 22–18, 26–22, and 30–26 C under both short- and long-day photoperiods for a 14-week period. Seedling biomass increased under both photoperiods as temperatures of the thermoperiods increased, but was greater in each thermoperiod under long-day conditions. Seedlings grown under short-day conditions were shorter, contained less biomass, produced more culms and rhizomes, had less shoot moisture, and contained higher chlorophyll concentrations than those under long-day conditions at the same temperatures. Flowering occurred earlier under short-day conditions in the 26–22 and 30–26 C thermoperiods, but also occurred under long-day conditions in these thermoperiods and appeared to be related to height growth.

Dark Germination and Seedling Growth in Monocots and Dicots of Different Photosynthetic Efficiencies in 2% and 20.9% O2

Abstract: The stimulation of net photosynthesis by 1 to 4% 02 in socalled "inefficient" plants is well established and is believed to result from the suppression of photorespiration (16). Growth of Phaseolus vulgaris, Mimulus cardinalis, and the liverwort Marchantia polymorpha increased when aerial portions of the plants were maintained in low 02 compared with ambient air (1, 2). Photosynthesis in the leaves of efficient species is not enhanced by low 02 (4, 9) nor is growth stimulated (1, 2); this is not surprising since these species have either no photorespiration or show quite low rates (5, 14). The assumption is widely held that respiration suppressed by low 02 or stimulated by higher 02 concentrations is nonessential or wasteful in plants. We asked if this kind of respiration is characteristic of a species throughout development, e.g., during germination and early seedling growth. If this were true we could expect to deduce photosynthetic efficiency of seedlings soon after germination and thus improve the efficiency of screening for efficient plants. Alternatively, we might discover an associated respiration with the same oxygen requirement as photorespiration. Growth in darkness of the embryo of imbibed seeds can occur only if respiration releases energy and produces intermediates for synthesis of new tissue. We tested our hypotheses by observing growth in darkness soon after germination in 2% and 20.9% 02 of seedlings of 28 monocots and dicots classified as inefficient or efficient by photosynthetic characteristics.

Hemp Dogbane Growth and Control

Abstract: Hemp dogbane (Apocynum cannabinum L.) was investigated relative to seed germination, depth of seedling emergence, response to clipping, influence of soil type and fertility on vegetative growth, and herbicidal control. Seed germination in this study was influenced by light and scarifi- cation. Seedling emergence was influenced by the amount of soil cover. Soil type and fertility affected vegetative growth. In a greenhouse clipping study, hemp dogbane became peren- nial 41 days after emergence and by 65 days was producing more than one shoot per plant following clipping. Hemp dogbane was more completely controlled following September application of herbicide than from application made in June.

Myxobacteria exert partial control of damping-off and root disease in container-grown tree seedlings

Abstract: Many tree seedlings for reforestation are now being produced in small discreet containers. On these seedlings, losses and stunting from root pathogens occur widely and unpredictably. Some myxobacteria of the group Cytophaga which produce powerful extracellular proteolytic and chitinolytic enzymes were introduced into fumigated or non-fumigated peat before or after sowing seeds of four species of conifer. They actively colonized the rhizosphere of the developing seedlings without affecting seedling development. In subsequent inoculation tests with pathogenic fungi, there was significantly less mortality, chlorosis, and stunting, than in checks without myxobacteria.

Chondrilla juncea in Australia. 4. Root morphology and regeneration from root fragments

Abstract: The morphology of the root system of Chondrilla juncea and its response to changes in soil type near Wagga Wagga, New South Wales, is described. The root system is described as consisting of vigorous long roots capable of vegetative reproduction at any depth and short roots, apparently without secondary thickening, of limited life span. The long root system consists of a simple tap root and a number of surface laterals, which increase in frequency and extent of lateral spread as soil clay content decreases. The relationship between plant age, growth stage, and depth of origin, as well as depth of planting and soil type, on shoot production from root fragments also was studied. Root fragments from depths to 80 cm and more did not differ appreciably in regenerative capacity. But, whereas shoot buds formed on some seedling roots two to four weeks after germination, all such roots formed buds five weeks after germination. Soil type and depth of planting did not affect shoot production from root fragments per s e, but establishment of new plants fell as depth of planting increased. A comparison of vegetative and reproductive plant roots of similar age showed that regenerative capacity was minimal during the reproductive growth phase. The inhibition of shoot bud formation on the roots, however, was confined to the proximal 40 cm. It is suggested that weed control operations are likely to be more effective when carried out shortly after stem initiation than at other times.

The effect of seed size on seedling growth in subterranean clover (Trifolium subterraneum L.)

Abstract: The effect of seed size on seedling growth in a single population of Daliak subterranean clover was studied by growing individually weighed seeds to the third trifoliate leaf stage in three controlled environments. The environments were: 18°C at high light intensity (27,000 lux), 12° at high light intensity, and 18° at low light intensity (5400 lux). Plant weight at emergence exceeded the weight of embryo in the original seed, owing in part to the utilization of endosperm. At emergence the ratio of plant weight to seed weight increased with increasing seed size. Nevertheless, in all environments the smaller seeds ultimately produced relatively larger plants owing to a higher relative growth rate, particularly during the cotyledon and unifoliate leaf stage of growth. Higher relative growth rates in seedlings from smaller seeds were associated with higher leaf area ratios resulting from the production of relatively larger cotyledon and individual leaf areas in all environments. More rapid leaf expansion in seedlings from larger seeds progressively offset this advantage.