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Structural and Metabolic After-Effects of Soaking Seeds of Phaseolus

William Marshall Bailey
Botanical Gazette
Vol. 94, No. 4 (Jun., 1933), pp. 688-713
Stable URL: http://www.jstor.org/stable/2471307
Page Count: 26
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Structural and Metabolic After-Effects of Soaking Seeds of Phaseolus
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Abstract

1. Soaking seeds of dwarf bean in distilled water with aeration resulted in a considerable decrease in the rate of germination (appearance of the seedlings at the surface of the soil) for periods of soaking as short as 8 hours. Practically a complete failure of germination resulted from soaking periods of 7 to 9 days. 2. The soaking treatment resulted in a still further reduction in the number of mature plants produced, as some of the seedlings from the treated seeds were unable to reach maturity. 3. The soaking treatment resulted in a progressive decrease in growth and weight of the plants produced and an increase in the time required for the plants to reach maturity. 4. The seed treatment resulted in general in a modification of the leaf structure, the leaf blades of plants from treated seeds generally being thinner and more compact in structure than those of plants from untreated seeds. 5. The greater average thickness of the phloem and higher ratio of the phloem to the xylem in the stems of the plants from soaked seeds is probably correlated with the relatively higher carbohydrate and lower nitrogen content of these plants. 6. The addition of calcium nitrate in very dilute solution to the water in which the seeds were soaked did not prevent the deleterious influence of soaking on germination and growth. 7. Soaking the seeds resulted in a marked relative increase in reducing sugars, starch and total carbohydrates, and solid matter, and in a relative decrease in total nitrogen, organic nitrogen, amino-acid nitrogen, and proteins in the mature plants produced from the soaked seeds. A correlation may be seen in the decreased nitrogen associated with decreased moisture and increased carbohydrates. 8. It seems probable that the greater relative accumulation of carbohydrates and deficiency of nitrogen compounds in the plants from the soaked seeds are due to a decrease in the ability of these plants to form the nitrogen compounds from the carbohydrates. The reduction in growth is probably due to the reduction in nitrogen compounds. 9. There was an increase in the rate of production of respiratory carbon dioxide in the sprouted seeds soaked before sprouting in comparison with those sprouted without previous soaking. This increase was probably due to the fact that the treated seeds contained considerably more water than untreated ones. The higher water content was favorable to a more rapid rate of respiration. The reduction in growth, of course, was not connected with any decrease in the rate of respiration. 10. Soaking the seeds without aeration resulted in a regular decrease in the catalase activity. Soaking with aeration resulted at first in a small decrease in catalase activity, but this was soon followed by a considerable increase. This modification of the result is evidently due to the fact that the seeds when soaked with aeration pass through the early stages of germination, and consequently there is an increase in catalase activity characteristic of seed germination.

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