Effect of Alternate Moistening and Drying on Germination of Seeds of Western Range Plants

The seeds used in this study comprise 9 grass, 26 weed, and 7 woody species of Utah range plants. Twenty-three of the 42 species studied gave little or no germination at temperatures of 22⚬ to 29⚬C. Other conditions must be used for them before the effect of alternate moistening and drying can satisfactorily be determined. 2. The effect of alternate moistening and drying on the germination of seeds varies with the individual species. Of the 19 species which germinated at 22⚬ to 29⚬C., alternate moistening and drying had little effect upon the germination of Bromus polyanthus. It increased the germination of Stipa lettermani, Artemisia incompta, Lepidium densiflorum, and Plantago tweedyi. It decreased the germination of Geranium viscosissimum, Pseudocymopterus montanus, Chrysothamnus lanceolatus, and Stipa columbiana (slightly). 3. Rapid drying had little effect upon the germination of Poa interior, P. secunda, and Chenopodium album, but increased the germination of Achillea lanulosa, Androsace diffusa, Pentslemon rydbergii, and Rumex mexicanus; in all of these species slow drying decreased the percentage of germination. Rapid drying decreased the germination of Bromus anomalus, Lupinus parviflorus, and Rudbeckia occidentalis, while slow drying increased the germination of Rudbeckia but had little effect upon Bromus anomalus and Lupinus. 4. Increased germination was usually accompanied by a hastening of the germinative process and decreased germination was accompanied by a retardation. In five species, however, Poa secunda no. 1, Androsace, Plantago, Rudbeckia, and Rumex, retardation was followed by increased germination. 5. Some seeds after they have absorbed water will withstand short periods of alternate drying and moistening, and some will withstand a long period of drying without injury. The time at which drying begins in relation to the stage of development of the germinating seed is a very important factor in determining whether drying is harmful or beneficial. The effect of drying is also influenced by the rate at which drying takes place.