Showing papers on "Seedling published in 1973"

Accelerated Germination by Osmotic Seed Treatment

Abstract: CROP seeds sown in cold soil are notoriously slow to emerge and it would obviously be desirable to shorten the time from sowing to seedling emergence and the time between the emergence of the first and the last seedling. This has occasionally been achieved by the pre-sowing seed treatment sometimes referred to as ‘hardening’1–3 or ‘advancing’4 involving repeated cycles of imbibition of a carefully controlled quantity of water, followed by drying back the seeds before the radicles emerge but results have not been consistent. There have been some successful attempts to replace this method by imbibition of seeds in salt solutions5–7; tomato seeds thus treated for 6 d exhibit a much higher level of RNA production during germination than untreated seeds8.

Patterns in the evolution of amentiferous fruits

Abstract: The diversity of fruit types within the Amentiferae appears to be the result of different seed dispersal and seedling establishment strategies that have evolved independently in the amentiferous families within the confines imposed by the wind-pollination syndrome. Dispersal of unadorned fruits and seeds by wind (e.g.,Betula, Rhoiptelea, Casuarina) has preceded the development of more efficient air-borne devices (e.g.,Ostrya, Carpinus, Engelhardia). Animal dispersal is the most advanced strategy, relying rarely on drupes, as in the shrubby Myricaceae, or on nuts, as inCorylus, Quercus, Carya, Juglans, Alfaroa, etc. The pattern of seedling establishment shows a structural-functional relationship to the seeddispersal strategy. Epigeal germination predominates in plants of open habitats. Those species with small fruits rely on wind dispersal, and their seeds have a relatively short germination time, whereas species with medium-sized fruits are often animal-dispersed with seeds that may have protracted germination times. In either case the reserve food supply for the young seedling is limited, and light is needed to spark photosynthesis. Hypogeal germination has evolved independently in several amentiferous families (e.g., Betulaceae, Fagaceae, Juglandaceae). This pattern is associated with closed habitats and plants with large seeds that have the capability of establishing vigorous seedlings in microhabitats of reduced light intensity where photosynthesis is impaired. The subterranean protection afforded the cotyledons and axillary meristems is a correlative feature that may have considerable importance in seedling survival where desiccation and predation are intense.

Endosperm Protein of Wheat Seed as a Determinant of Seedling Growth

Abstract: Seed of a Mexican semidwarf wheat (Triticum aestivum L. cv. Inia 66), was obtained from a nitrogen fertilizer field trial grown in Mexico. A high positive correlation was obtained between seed protein content and seedling dry weight after 3 weeks growth (r = +0.92**). The seedling dry weight was positively related to the protein content of the aleurone layer and endosperm, but not to the embryo. Small, 35 milligrams, high protein seeds (4.7 milligrams protein per seed) produced larger seedlings than large, 45 milligrams, low protein seeds (4.3 milligram protein per seed). There was no difference in the weight or protein content of embryos from low and high protein seeds and their growth was similar. Composite seeds of the two protein levels were produced by transferring embryos from one endosperm type to the other. After 4 weeks, there was no difference between the different embryo types grown on the same endosperm type. High protein endosperm produced more vigorous seedlings regardless of the embryo type grown on it, indicating that the factor(s) responsible for the greater growth of high protein seed is in the endosperm.

Seed germination in relation to salt concentration in three populations of Prosopis farcta.

Abstract: Prosopis farcta (Banks et Sol.) Eig., is a widespread perennial shrub in a variety of habitats over a large geographic area in the Middle East. In iraq it occurs in non-saline deserts of the west and saline agricultural lands of the Mesopotamian Plain. The species is economically important as fuel for a sizable segment of the population in rural areas. Seeds were collected in three environmentally distinct habitats, with regard to annual precipitation and soil salt content. The seeds were germinated in various concentrations of sodium chloride and their germination, seedling radicle growth, and dark respiration studied. The results indicate that the three populations differend in their response to NaCl with the northern population being generally more sensitive than the other two populations. The three populations represent “salt ecotypes” of this very widely distributed shrub. The salt ecotypes seem to be of somewhat recent origin and apparently have been further spread by improper agricultural land-use which created vast saline areas.

Effect of Hormone-Directed Presoaking on Emergence and Growth of Osmotically Stressed Wheat (Triticum aestivum L.) Seeds

Abstract: The water potential gradient between a planted seed and the surrounding soil largely controls water absorption by the seed. Salinity of soil water affects this balance, which in turn lowers germination and seedling growth. Overcoming the inhibition of water intake by presoaking and the use of auxins and gibberellins has been shown to be advantageous for certain crops,but studies with wheat are limited. This approach constitutes the objectives of this investigation. The effects of presoaking wheat seeds in 10, 20, 50, and 100 ppm each of GA, IB A, IAA, and NAA at O, 3, 6, and 9 atm osmotic pressure on seedling development were observed. Auxins had little influence on emergence at 0 atm but promoted emergence at 3, 6, and 9 atm. Three-indole acetic acid (IAA) and α — naphthalene acetic acid (NAA) at 50 ppm produced maximum shoot length, whereas gibberellic acid (GA) and three-indole-butyric acid (IBA) gave better results at 100 ppm. Increased concentrations of GA and NAA significantly reduced primary root length, whereas IAA increased root length. All hormones increased proliferation of lateral roots, but auxins produced more lateral roots at all salinity levels. Root/shoot ratio was decreased by NAA and GA. Water absorption was increased by all treatments. IAA and NAA at 50 ppm gave the better results. The data support the hypothesis that the beneficial effects of hormones may be the result of increased water absorption, which improves plant growth even under high salt concentrations hi the growth medium.

Effects of Aflatoxin on Seeding Growth and Ultrastructure in Plants

Abstract: Nineteen plants belonging to 11 species of the cruciferae were studied to determine the effects of aflatoxin B1 on seed germination and seedling development. Germination was not inhibited in any test organism at a concentration of 100 μg of aflatoxin per ml of agar substrate. Inhibition of elongation of the hypocotyls and roots in the species studied varied from 29 to 93% and from 22 to 91% in the respective tissues. Lepidium sativum was the most susceptible plant studied and exhibited the maximal inhibitory response noted above at concentrations of 8 μg of aflatoxin per ml. The ultrastructure of Lepidium root cells treated with crystalline aflatoxin B1 exhibited morphological changes characteristic of those found in aflatoxin-treated animal cells. In addition to changes in the cytoplasmic organelles, numerous ring-shaped nucleoli with prominent nucleolar caps were produced. The effect of aflatoxin on plant cells is compared with similar effects induced by actinomycin D. Seed germination and seedling development is discussed in relation to the effects of both compounds on deoxyribonucleic acid-dependent ribonucleic acid biosynthesis.

The Effect of Arsenate and Other Inhibitors on Early Events during the Germination of Lettuce Seeds (Lactuca sativa L.).

Abstract: The effect of arsenate, arsenite, 2,4-dinitrophenol, and anaerobiosis on early events in seed germination was investigated using both intact and punched seeds of lettuce (Lactuca sativa L.). It was found that punching the seed removes penetration barriers to the entrance of inhibitors without an undue loss of germination or light responses. The kinetics of the action of germination inhibitors were established by 2-hour pulse experiments. Arsenate and 2, 4-dinitrophenol have very different kinetics. The inhibition of germination in punched seeds by arsenate given in conjunction with phosphate compared with the lack of inhibition of arsenate plus phosphate on the growing seedling, suggest a distinct metabolic change in the germinating embryo at some time between the onset of germination and subsequent seedling growth.

Control of cambial activity in roots of turnip (Brassica rapa)

Abstract: The physiological control of cambium activity in seedling roots and isolated cultured root tips of turnip was investigated. In seedlings, excision of the root tip had no effect on root cambial activity while excision of the shoot (including cotyledons) resulted in a dramatic reduction in both cambial derivatives and secondary xylem elements. Removal of one or two cotyledons also reduced root cambial activity. An investigation of the control of cambial activation in cultured first-transfer root tips of turnip showed that a combination of an auxin, a cytokinin, sucrose, and myoinositol was necessary for maximum radial growth of these excised root tips. The deletion of any one of these substances resulted in a reduction in cambial activity. Likewise, root tips treated with any one of these growth regulators alone showed little cambial activation. The present results are compared to results obtained by earlier workers using other genera of plants, and it is shown that the control of cambial activity is simila...

Effect of strength, tilth and heterogeneity of the soil surface on radicle-entry of surface-sown seeds

Abstract: Seeds of Medicago sativa, Trifolium subterraneum, Lolium perenne and Phalaris tuberosa were sown on different soil surfaces and the effects of strength, tilth and heterogeneity of the surface on the entry of the radicle into the soil were noted. On a level, finely structured soil surface prepared in the laboratory slight increases in soil strength markedly reduced percentage radicle-entry. At constant soil strength, radicle-entry was greater on coarse than on fine tilth; which helped to explain the higher percentage radicle-entry on heterogeneous soil surfaces taken from the field compared with the level, finely structured surface, prepared in the laboratory despite the lower soil strength of the latter. As conditions for radicle-entry hecame less favourable (stronger, smoother surface) the rate of radicle-entry became slower and there was a greater use of radicle-entry methods in which the radicle was more exposed to desiccation. The radicle-entry ability of the four species declined in the order: perennial ryegrass < phalaris < lucerne and subterranean clover. Factors considered to account for the superior radicle-entry of the grasses were better anchorage of the seedling, better angle of entry of the radicle and smaller radicle diameter.

Delayed germination in seeds of Phacelia dubia var. dubia

Abstract: Not all seeds of a particular seed crop of the winter annual Phacelia dubia var. dubia germinate the first autumn after their dispersal in spring, and germination of a given seed crop is spread over several years. Nondormant seeds that do not germinate in autumn are induced into secondary dormancy by low winter temperatures and must afterripen again during summer before they are capable of germinating. Seeds that do not afterripen the first summer after dispersal are prevented from doing so until at least the next summer because winter temperature conditions prevent afterripening. These responses of the seeds to the environment insure that germination will occur only in autumn, the only season of the year that is suitable for seedling establishment and eventual completion of the life cycle.

Activity of six fungicides against cereal foliage and root diseases

Abstract: SUMMARY During 1970 and 1971 six systemic fungicides were compared as seed dressings and sprays against foliage and root diseases of cereals. The fungicides differed greatly in effectiveness against mildew, loose smut, rusts and eyespot but none controlled take-all. Effects were also noted on germination, seedling growth and leaf-surface microflora.

An Analysis of Soil Water Movement towards Seedlings Prior to Emergence

Abstract: Water uptake by viable seeds initiates the metabolic processes which lead eventually to seedling emergence. There exists a discrepancy between germination percentage determined under laboratory conditions and the field performance of the same seed stock. Excluding pest damage, it seems that under field conditions the soil moisture in the surface layer is continuously depleted due to evaporation, causing the germinating seed to compete with the atmosphere evaporative demand for water, a competition which is more severe under dry-farming systems.

Effect of moisture stress on Red Maple seedlings from different seed sources

Abstract: Red maple (Acer rubrum L.) seedlings grown from half-sib seed collected from wet and dry sites were subjected to three levels of plant water stress. Transpiration on a per seedling and per unit leaf weight basis was greatest in seedlings from a swamplike site, at both high and low water potentials. Seedlings from the two wet sites came to temporary and permanent wilt sooner than seedlings from dry sites. However, at all levels of water stress, growth rates were greater for the seedlings from the wet sites than for those from the dry sites. At permanent wilt, the stem and leaf moisture content and the water potential values were highest in the seedlings from the swamplike site. At temporary wilt, the leaf water potential was lowest in seedlings from dry sites. Transpiration of seedlings from a swamplike site was double that of those from another wet site at the same leaf water potential.

Evaluation of Seedling Progeny of Soybeans Treated with 2,4-D, 2,4-DB, and Dicamba

Abstract: Seed were harvested from soybean [Glycine max (L.) Merr. ‘Cutler’] plants treated at flowering and pod filling with (2,4-dichlorophenoxy)acetic acid (2,4-D), 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB), and 3,6-dichloro-o-anisic acid (dicamba). Progeny of plants treated at flowering with 2,4-D and 2,4-DB or at pod filling with the lowest rate were normal. When higher rates were applied at pod filling, these phenoxy herbicides caused appreciable injury to the progeny in the form of reduced emergence and dry weight and malformed unifoliate leaves. Dicamba was much more injurious to the progeny of treated plants than 2,4-D and 2,4-DB. Even at low rates dicamba caused reduced germination, emergence, and dry weight and malformed first trifoliate leaves.

Ethylene and the germination and early growth of barley

Abstract: Barley seeds have been germinated in gas mixtures containing ethylene (up to 20 vpm) and various amounts of oxygen (0.5–21.0 per cent). When oxygen was adequate, ethylene had no effect on germination but decreased root growth and increased top growth. Ethylene-treated roots were short, broad and curled. When inadequate oxygen slowed seedling growth, ethylene had no effect on roots but increased top growth. Effects of carbon dioxide concentration and of the residual effects of ethylene on seedling growth are also discussed.

Influence of plant-parasitic nematodes on longleaf pine seedlings.

Abstract: Seedlings of longleaf pine (Pinus palustris) were grown in 20-cm pots for 5 to 7 months in the greenhouse following inoculation with a high or low level of one of seven species of plant-parasitic nematodes. Belonolaimus longicaudatus and Helicotylenchus dihystera had no effect on seedling growth. High inoculum densities of Hoplolaimus galeatus and Tylenchorhynchus claytoni caused a significant reduction of fresh weight of seedling roots. Root and top weights of seedlings grown in soil infested with Meloidodera floridensis or Pratylenchus brachyurus were significantly less than those of seedlings in noninfested soil. Root growth of seedlings was stimulated by the higher inoculum density of Scutellonema brachyurum.

Control by Phytochrome of Glutathione Reductase Levels in the Mustard Seedling

Abstract: Abstract The time-courses of the level of glutathione reductase (GR; EC 1.6.4.2) were followed in cotyledons and hypocotyl of the developing mustard seedling in the dark and under the influence of light (phytochrome). Localization of GR on polyacrylamide disc electrophoresis columns indicate that 2 isoenzym es of GR are present in both organs under all experimental conditions. GR can be induced by light (phytochrome) in the cotyledons; however, there is no influence of light (phytochrome) on the time-course of the level of GR in the hypocotyl. While the actual lag-phase of the response in the cotyledons is less than 6 hours (onset of light at 48 hours) there is no detectable effect of light on apparent GR synthesis before approx. 42 hours after sowing. Irrespective of the onset of light (at 24 or 36 hours after sowing) the time-course of the enzyme level remains precisely the same. A red pulse given at 24 hours after sowing leads to an increase of the enzyme level as determined 60 hours later. T he effect of the red pulse is fully reversed by a far-red light pulse given at 24 hours but not 12 hours later. Facts of this kind have led to the concept of a stable inter mediate in the chain of regulatory events between phytochrome (P fr) and GR increase. No in d i cations of a coordinated, simultaneous induction by phytochrom e of GR and ascorbate oxidase (AO) could be found. This result does not support the concept that a respiratory chain exists in which AO functions as a terminal oxidase.

Development of Ascorbate Oxidase Activity and Its Iso‐enzyme Pattern in the Roots of Pea Seedlings

Abstract: Early in the germination of peas, ascorbate Oxidase activity increased markedly in the root and epicotyl, but not in the cotyledons. The activity in the root was suppressed by the administration of 6-methylpurine, thiouracil, cyclohexi-mide, thioproline, and phenylthiourea. Although enzyme development was inhibited by phenylthiourea and thioproline, root elongation was not affected by these reagents. As germination progressed, the ascorbate oxidase activity in the extract of the seedling's root could be separated into at least 3 to 7 isoenzymes.

Pre germination seed treatment

Abstract: A method treatment of seeds by soaking in an aqueous medium containing the metabolites produced by green algae is disclosed. The culture is harvested during the early logarithmic phases of growth of the algae but after a cell density of about 1 X 105 cells per milliliter is reached. Rice, corn, and other seeds such as lettuce and barley treated with the invention exhibit more rapid root initiation, faster root establishment and larger quantities of roots per seedling. Increases in shoot weight and length also are observed.