Effects of environmental conditions on germination and early seedling development in Agropyron spicatum Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/m326m468f

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  • This research evaluated the germination and early seedling development response of two sources of bluebunch wheatgrass (Agropyron spicatum) to a wide range of environmental conditions. Seeds collected near John Day, Oregon and Secar seed obtained from the Soil Conservation Service were used in the investigations. Evaluation of the germination response to conditions of controlled temperature and moisture stress revealed similarities and differences between the two sources. Seed of both John Day and Secar germinated over the widest range of water potentials at 20 C. In all temperature regimes, rate of germination and total percent germination declined as moisture stress increased. As temperature moved away from the optimum 20 C, seeds were less able to germinate at increasing levels of moisture stress. Secar seed germinated better than John Day seed at higher levels of moisture stress when temperatures were favorable. At high temperatures (30 C), germination of Secar was suppressed at all levels of moisture stress, where John Day germinated well at 30 C and lower levels of moisture stress. The effects of several soil moisture regimes on seedling development of the two sources of bluebunch wheatgrass were studied in a greenhouse trial. Soil moisture conditions were the same for all treatments through the emergence period, and John Day seedlings emerged faster than Secar seedlings. Since moisture was adequate at the onset of the study, all seedlings had an opportunity for initial growth and to develop good seminal root systems. Since John Day seedlings emerged first, they had a longer period for growth which resulted in larger herbage and root biomass production than in Secar. As soil moisture decreased, however, the rate and amount of seedling growth for both sources was suppressed. When seedlings were in the three-leaf stage and exposed to surface soil moisture above field capacity, adventitious roots were initiated. Secar seedlings developed adventitious roots sooner than John Day seedlings and produced significantly more and longer adventitious roots than John Day seedlings. Subsurface soil moisture above field capacity provided a favorable environment for rapid extension of adventitious roots once initiation had occurred. Secar seedling development was also related to soil moisture and air temperature in a field study, and findings were similar to the results of the greenhouse study. Seedlings subjected to several weeks of dry soil conditions did not develop well. Most seedlings did not develop three leaves until the tenth week after planting when rainfall increased soil mositure to field capacity. This moisture also stimulated initiation of adventitious roots. However, at the end of the 10 week study adventitious root system length averaged only 5.6 cm, and at this depth these roots would be very susceptible to drying conditions.
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