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Physiological Development of Lehmann Lovegrass Seeds During the Initial Hours of Imbibition¹

Data from both field and laboratory studies have suggested germination of Lehmann lovegrass (Eragrostis lehmanniana Nees.) caryopses (seeds) can be improved by various pre-sowing seed treatments. Some of these treatments include moistening and drying, oven-drying, scarification, and pre-chilling on a moist substrate.

The objective of this study was to determine if exposure of dry Lehmann lovegrass seeds to high humidity conditions, or to moisture under low temperature could effect rapid and detectable changes in their metabolic state. Seeds were (a) imbibed in cold water at 10 C (Treatment low), (b) exposed to a water saturated atmosphere at 24 C (Treatment 24v), or (c) imbibed in water at 24 C (Treatment 24w). For studies on physiological development, samples were collected after 6, 18, 31, 48, and 60 hours of treatment. Seed moisture content, germination percentage, rate of respiration, and ATP, ADP, alcohol soluble sugars, and starch contents were measured at each collection interval. In addition, -amylase activity was determined in air dry seeds, 24w seeds after 18, 31, 48 and 60 hours, and 24v and 1Ow seeds after 60 hours of imbibition.

Physiological development of seeds was advanced in all treatments. Moisture content of the 24w, 24v, and 10w treated seeds increased 6.4, 3.0, and 5.1 fold, respectively. As the moisture content increased in the 24w seeds, the contents of ATP, ADP, and rate of respiration increased. The content of alcohol soluble sugars decreased from 1.88 to 1.20% during the initial 31 hours, but increased to 3.03% in the following 29 hours. This increase occurred with an increase in a-amylase activity and subsequent active hydrolysis of starch. The 24v and low environments were unsuitable for germination, but ATP levels rose and starch and alcohol soluble sugars decreased slightly during the imbibition period. However, respiratory activity did not develop.

Key Words: Germination • Water content • ATP • ADP • Respiration • Starch • Alcohol soluble sugars • -amylase

² Assistant professor, Texas Agric. Exp. Stn., Dep. of Range Science, Texas A&M Univ. (formerly graduate research associate, Dep. of Watershed Management, Univ. of Arizona), professor, range management, and associate professor, cell and developmental biology, Univ. of Arizona, Tucson.

Received for publication June 12, 1976.