No abstract

No abstract

No abstract

Seeds of the Virginia botanical type (9) of peanut are dormant for a variable period after harvest. That is, they fail to germinate under conditions normally favorable for germination. Although dormancy is an inherent property of Virginia type peanut seeds (11, 24) comparatively little is known about the nature of the dormancy.Hull (10) \When seeds were to be shelled the day after digging, pods were superficially dried overnight by spreading them in a thin layer on the laboratory floor in front of a fan to facilitate shelling.Immediately after shelling, seedls were graded. placed in folds of moistened cheese cloth to prevent drying, and then planted as quickly as possible. Seeds were gracled according to maturity largely on basis of texture and color of seed coat. Numbers were assigned to degrees of maturity (table I). As the peanut seed matures the fleshy outer layer of the coat graclually loses turgidity and becomes thinner. At full maturity the seed coat is papery thin.Well-developed pods of the 1955 and 1956 crops were selected and seeds of maturities 1 to 3, inclusive, were used from a random sampling. With one exception, only 2-seeded pods of 1957-59 crops were usedl. Seeds in the apical (distal) and basal (proximal) positions within pods were kept separate. Except where noted, seeds were of maturities 2 to 3. Maturity 1 was frequently excluded in tests involving early diggings because too few were available.Except as noted, seeds were germinated at 250 in large plastic boxes (fig 1). These boxes were placed in a germination chamber, or for the gas studies in a growth room, 1 meter from ten F72T8/ CW fluorescent tubes. Seeds were placed with the radicle end down between grooves (2 cm high) of wet corrugated paper toweling. The

Fully imbibed, viable seeds of many plants may fail to germinate. One limitation on germination may be a light requirement which can be removed by the correct poising of a reversible photoreaction (1,2, 8). This reaction which can be repeatedly reversed by alternate exposures to red and far-red radiation also controls photoperiodic flowering responses, etiolation, bulbing, and a number of other growth responses (5). That the photocontrol is ubiquitous in all higher plants is shown by the etiolation response of seedlings (6).The temperature, too, must be in a favorable range for seed germination which, for many kinds of seeds, is well below that best suited for subsequent growth of the seedling. A change in temperature is often effective in promoting germination. For limited periods, the temperature may greatly exceed the favorable constant range. A response to a change in temperature is also evident in vernalization, tillering, and dormancies of plant buds (9) as well as in diapause of animals. It is a phenomenon with broad significance.Germination requirements are examined here with reference to the results of a few simple physiological experiments involving the effects of light and temperature conditions and to some extent the effects of nitrate solutions. The results suggest a pattern for the control of the germination process as well as for the growth of all organisms that must follow the temperature of the environment. from 2 to 5 days after the final experimental variable was introduced. Seeds with emerged radicles were counted as germinated. MATERIALS AND METHODSRadiation sources were incandescent and standard cool white fluorescent lamps. The incandescent-filament lamp, with a filter of two layers of red and two layers of dark-blue cellophane, either with or without a supplemental water filter, was an effective source of far-red radiant energy in the region of wavelengths greater than 7000 A for inhibiting germination. When provided with a two-layer red cellophane filter to eliminate the blue part of the visible spectrum the fluorescent lamp, because of its relatively low emission between 7000 and 8500 A, was an adequate source of red radiant energy in the region of 5800 to 7000 A for promotion of germination. The sources used each gave about 0.3 milliwatts/cm2 power in the wavelength regions of maximum effectiveness. Blue cellophane filters have been found to fade when subjected to the full intensity of 300-watt flood lamps at a distance of a foot or 18 inches, but only after several hundred hours of use. Care was accordingly exercised to replace them before significant change in transmission occurred.During germination tests in seed germination cabinets, temperatures were usually controlled within + 10 C. Some of the experiments involved several different constant temperatures; others made use of daily temperature alternations, an 8-hour period at one temperature being followed by 16 hours at a lower temperature. In still other experiments, a single change was made from the temperature employed during ...