Aspen Bibliography

Germination of Populus Grandidentata and P. Tremuloides, with Particular Reference to Oxygen Consumption

Document Type

Article

Journal/Book Title/Conference

Botanical Gazette

Volume

97

First Page

808

Last Page

821

Publication Date

1936

Abstract

1. Populus tremuloides and P. grandidentata produce seeds in great abundance in central and eastern United States. The former seeds mature approximately three days earlier than the latter. From six to ten weeks elapse between anthesis and maturation of the seeds. 2. Seeds collected when a light straw color and dried at once retain their viability the longest. 3. The best length of time for drying is from three to eight days in a room of uniform temperature of about 24⚬ to 25⚬C. Seeds dried only one day lose viability in thirteen weeks, even when placed at 5⚬C. 4. Small seeds do not germinate so readily nor retain their viability so long as large ones. This applies to individuals within the species. 5. Seeds showed the highest percentage of germination in media of pH 7.0 to 8.5. 6. Except when the viability is low, fifty seeds are sufficient for showing accurate percentages of germination. 7. A constant low temperature (approximately 5⚬C.) was found best for prolonging viability. 8. Seeds have been found to retain 100% viability for as long as thirteen weeks when placed in corked bottles in the laboratory and for five weeks in open dishes. Most of these lose their viability after eighteen weeks but occasionally show 1% at twenty-two weeks. 9. Seeds germinate whenever there is sufficient moisture (even when submerged) between temperatures of o⚬ and 35⚬C. Freezing for several weeks does not appear to injure the seeds when they are thawed at 5⚬C. 10. The largest percentage of germination is obtained at 29⚬ and 32⚬C.; 35⚬ to 38⚬C. appears to be too high but may only retard germination. The sturdiest seedlings are from seeds germinated at temperatures from 5⚬ to 29⚬C. 11. The time for initial germination is usually five hours for seeds germinated at 29⚬ and 32⚬C. This increases as the seeds age. Short initial germination time is correlated with high viability. 12. The seeds of both species are fatty and contain some proteins. 13. Seeds lose moisture rapidly during the first two days of drying. After three days there is little loss. 14. Oxygen consumption was studied by means of a microrespirometer of the closed system so sensitive that a temperature constant to ±0.005⚬C. was necessary for accurate results. 15. The extreme sensitiveness of the apparatus makes it possible not only to measure the oxygen consumption of ten resting seeds at half-hour intervals, but also that of a single germinating seed at five-minute intervals. 16. Oxygen consumption is high when the seeds are viable and contain much water. This decreases with the decrease in water content of the seeds. 17. The very great amount of oxygen consumed when the germinating seed first absorbs water drops to a minimum two hours before the hypocotyl emerges from the seed coat. It then rises rather abruptly for an hour, drops slightly in the next two hours, after which the crown of root hairs emerges. There is again a rather abrupt rise for an hour and then it becomes comparatively uniform.

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