. Botany for agricultural students . Botany. 92 GERMINATION OF SEEDS: SEEDLINGS Oxygen Requirement. — Although seeds are in the optimum temperature and properly supplied with moisture, they will usu- ally not germinate unless oxygen is supplied, as is often demon- strated in the laboratory by the use of some substance to absorb the oxygen in the germinator or by replacing the air in the ger- minator with hydrogen, nitrogen, or some other substance, so that oxygen is excluded. {Fig. 91.) However, since the air is about one-fifth oxygen, seeds receive enough oxygen to germinate well if only air
. Botany for agricultural students . Botany. 92 GERMINATION OF SEEDS: SEEDLINGS Oxygen Requirement. — Although seeds are in the optimum temperature and properly supplied with moisture, they will usu- ally not germinate unless oxygen is supplied, as is often demon- strated in the laboratory by the use of some substance to absorb the oxygen in the germinator or by replacing the air in the ger- minator with hydrogen, nitrogen, or some other substance, so that oxygen is excluded. {Fig. 91.) However, since the air is about one-fifth oxygen, seeds receive enough oxygen to germinate well if only air is supplied, although germination is often hastened \ '^J\ -s- -. Fig. 91. — The two U-shaped tubes, which contain soaked seeds (s) on moist blotting paper at their stoppered ends, are alike except that in B the open end of the tube is in pyrogallate of potash, which absorbs the oxygen from the air in the tube, while in A the open end of the tube is in pure water, in which case the oxygen still remains in the air of the tube. The seeds ger- minate well in A but not in B. when the amount of oxygen is increased artificially. For exam- ple, in an experiment Wheat, requiring 4 to 5 days to germinate in the air, germinated in 3 days in pure oxygen. There are a few seeds, however, which begin to germinate without oxygen, but they soon die unless oxygen is supplied. For lack of oxygen seeds germinate poorly when planted in the soil so deeply that not enough air is accessible, or when planted in soils with their pores so full of water that the circulation of the air is Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Martin, John N. (John Nathan), b. 1875. New York : John Wiley & Sons, Inc.
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