Comparative Ecophysiological Seed Adaptation Of Three Barnyardgrass (Echinochwa Crus-Galli [L.] Beauv) Ecotypes.

Abstract

Experiments were conducted under laboratory and greenhouse conditions to determine the longevity and germination pattern from seed burial, temperature effect, temperature and nitrate, temperature and water potential, and seeding depths and ecotype interactive effects, on seed germination and emergence; including photoperiodic effect, on barnyardgrass ecotypes originating from California (CA), Maryland (MD) and Prince Edward Island (PEl). Results indicated that the CA seed exhumed during the initial four months of burial had either germinated, died or rotted in the field. The MD and PEl ecotypes showed a seasonal cyclic germination pattern, corresponding to soil temperature changes. The temperature studies showed that the CA ecotype had over 80% germination at 10 to 40°C, whereas the MD and PEl ecotypes displayed more than 80% germination at temperature between 15 and 20°C, and decreased germination below 15 and above 20 °C. Temperature and nitrate interactive results, at 10-40 °C and 5-30 mM KN03, indicated that the CA ecotype had above 75% germination either imbibed in water or in KN03, hence suggesting that KN03 was not a factor in its germination. The MD and PEl ecotype germination, however were enhanced by the addition of KN03• The temperature and water potential interactive results indicated that the ecotypes displayed more than 86 and 80% germination at zero and -2 MPa, and decreased germination from -4 to -10 MPa, at 20 and 30°C. The MD and PEl ecotype germination was affected more at 30°C from -6 to -10 MPa, whereas the CA ecotype appeared better adapted at decreasing water potential and increasing temperature. The shoot and root lengths at 30°C were generally longer than those at 20 "C. Seeding depth results indicated that highest percent emergence of more than 65% for all the ecotypes was obtained from 1 and 2.5 ern depths, and least percentages of less than 20% from 7.5 and 10 em, Overall, the CA ecotype showed ability to emerge from greater depths, compared to the MD and PEl ecotypes. The photoperiodic effect showed that all the ecotypes under LD had vigorous vegetative growth, greater heights, large leaf area and greater fresh and dry weights, whereas the MD and PEl ecotype growth were severely inhibited, and the CA ecotype less inhibited under SD. Generally, these ecotype responses to different environmental factors reflect their adaptive strategies to their respective areas of collection.