Dark Seeds Research Articles

Germination of lettuce induced by inhibitors of protein synthesis

L-threo chloramphenicol and actinomycin D act like D-chloramphenicol in being able to promote germination of light-requiring seeds of Lactuca sativa in darkness. The two isomers of chloramphenicol at relatively low concentrations also prevent the development of skotodormancy. Protein synthesis, measured by the incorporation of tritiated leucine, occurs in dormant seeds in darkness; evidence suggests that this occurs most intensively in the endosperm. The stimulation of germination by chloramphenicol and actinomycin D is preceded by a marked reduction in protein synthesis. It is suggested that these substances act by arresting an inhibitory process which requires protein synthesis.

Ricerche Comparate Sulla Morfologia e Sulla Fisiologia diLarixe diPicea. Azione Dell'oscuritàg e Della Luce di Diversa Lunghezza D'onda Sulla Germinazione Dei Semi

Abstract Comparative researches on morphology and physiology of « Larix » and » Picea ». Action of darkness and light at various vawelengths on seed germination. Seed germination under different light conditions was studied in prosecution of our morphological and physiological studies of seeds and seedlings of « Larix » and « Picea ». From the comparison of germination rates of the seeds in darkness or in light (about 4.000 lux), the « Larix » seed proved to be photo-blastic while that of « Picea » aphotoblastic: i. e. at the 5th day from imbibition, seed germination was inhibited by darkness in the case of « Larix » (up to 70%) and by light in the case of « Picea » (up to 80%). Single five minutes treatments with red and far-red lights of seeds kept in darkness during imbibition stage and after light exposure, induced quite different responses at the 8th day: in « Larix » far red light inhibited more than 70% seed germination as compared with seed treated with red light; in « Picea » seeds no difference ...

SOME FACTORS AFFECTING THE GERMINATION OF SEED OF THE SAGUARO CACTUS (CARNEGIEA GIGANTEA)

Alcorn, Stanley M. (U. S. Dept. of Agric., Tucson, Ariz.), and Edwin B. Kurtz, Jr. Some factors affecting the germination of seed of the saguaro cactus (Carnegiea gigantea). Amer. Jour. Bot. 46(7): 526–529. 1959.—Germination of saguaro cactus seeds is stimulated by red light (approx. 6550 A) or daylight and far‐red light (approx. 7350 A) counteracts this effect. About 0.1% germinate in continuous darkness. A single exposure to red light was most effective when the seeds were imbibed 24 hr., but maximum germination resulted from multiple exposures to red light during a 72‐hr. imbibition period. The optimum temperature for germination was 25°C.; no germination occurred at 15°C. and only slight germination at 35°C. Imbibition of light‐treated seeds in 0.05 to 0.2% KNO3 increased germination. Germination of seeds in either light or dark was increased by imbibing the seeds in 500 to 1000 p.p.m. gibberellic acid.

Lucerne investigations: III. Effect of heat treatment on germination and field establishment of lucerne seed

1. Lucerne seed samples of known harvest history were treated by dry heat at various temperatures and durations; their germination capacity, emergence and establishment were tested by laboratory, greenhouse and field establishment tests on heavy Boil during 1952–6 at Cambridge.2. A successful and safe heat treatment was 42° C. for 5 days, increasing the germination by as much as 44% up to about 90% at the cost of hard seed.3. The establishment obtained on heavy soil from treated seed samples, although varying from season to season, was significantly higher (P > 0·001) at all seed rates than that obtained from untreated control samples.4. Significant differences were obtained in germination capacity and establishment between samples harvested at different conditions. High moisture content of seed and high percentage of dark brown seeds was associated with late harvest. Brown seeds had a significantly lower germination capacity than yellow seeds. Only samples with a high initial moisture and high percentage of brown seeds showed a substantial decrease in germination capacity during the storage period of 3 years.5. Although the mean number of plants established is significantly higher for higher seed rates the mean percentage of plants established decreases significantly with higher seed rates and the greatest wastage of seeds occurred at the high seed rate of 15 lb; per acre.6. The viability of seed and speed of germination and of emergence were the most important factors in determining the successful establishment of a crop on heavy soil.7. Hard seed is viable and could germinate and produce seedlings by the end of the season, but only a very small percentage of it could normally be established under field conditions. With untreated seed no significant correlations were established between laboratory germination and field establishment or between laboratory germination and greenhouse emergence, yet there were highly significant correlations in these cases for treated seed. With increased duration of laboratory germination test, corresponding to a decrease in the proportion of hard seed, values of r increased. Correlations between field establishment at three seed rates and greenhouse emergence were significant in the case of both untreated and treated seeds.8. When the hard seeds were added to germination or establishment the relationships between the results of these tests were very close and highly significant correlations were established for both lots of seed, untreated and treated. The high proportion of hard seeds was the main limiting factor preventing a close relation between tests for untreated seed.