A Preliminary Study On Physiological And Biochemical Mechanisms Of Slow Development Of Switchgrass Seedlings

Switchgrass(Panicum virgatum) is a perennial cross-pollination C4 herbaceous plant, with self-incompatibility characteristic. Due to the feature of high biomass yield, drought resistance, adapted to poor nutrients environment and easy to manage, it has important application value in the aspects of production of fuel ethanol, maintain of water and soil, and desert greening. In recent years, it has been determined for developing bio-energy utilization patterns of crop. However, switchgrass seedlings grow very slowly after sowing. It is a weak competitor with many summer annual grasses in nutrition and light. The slow development of switchgrass seedlings is not conducive to seedling establishment, which been one of the important factors affecting the popularization and application of switchgrass. At present, though there are a few reports about switchgrass seedlings growing slow phenomenon, switchgrass seedlings slow development formation mechanism especially the analysis in physiological and biochemical level has not been studied. To investigate the mechanism for the slow growing rate at the physiological and biochemical levels, an experiment was conducted using seeds from two domesticated varieties(Ma and Mg) of the Alamo ecotype. After incubating for 16 days, fast growing seedlings and slow growing seedlings were chosen based on growing rates, then we determinated and analyzed the factors related to plant growing. The main results as followed:1. Fresh and dry weight of slow growing seedlings shoot and root were significantly less than the ones of fast growing seedlings. Slow growing seedlings had fewer and shorter root after seedling 16,24 and 32 d, while the value of root/shoot and root activity had no significant difference between the two kinds of seedlings.2. The contents of chlorophyll, starch, cellulose, soluble protein, total nitrogen, free amino acids, NR acitivity had no differences at every stage between slow growing seedlings and fast growing seedlings.3. GSH content in slow growing seedlings were lower in early stage, while the contents of MDA, hydrogen peroxide, superoxide anion and reduced ascorbic acid had no differences at every stage between slow growing seedlings and fast growing seedlings.4. Compared with fast growing seedlings, ABA content of slow growing seedlings was higher during the whole determined stages, GA content was lower at 24 days, and IAA/ZR value was lower at 32 days.5. There were significant differences in root length, GSH content at 16 days and IAA/ZR ratio at 32 days between seedlings of the same type in the two materials, and there was no significant difference between the root number, ABA content and GA content at 24These results indicated that slow growing seedlings had a poorly developed root system with low GSH content at early stage, high ABA content, low GA content and IAA/ZR value, which probably resulted in the slow developmental rate during the seedling stage.