A Study On Reproductive Characteristics And Ecological Adaptability Of Three Rhizomatous Grasses

In this paper three rhizomatous grasses were used including Pennisetum centrasiaticum, Leymus secalinus and Leymus chinensis, systematic comparison was studied on their sexual propagation characteristics, vegetative propagation characteristics and reproductive allocation. This thesis analyzed characteristics and ability of sexual propagation and vegetative propagation, renewal function and contribution of population multiply in three grasses, also discussed their strategy of reproductive adaptation. The results were listed as below:1. The seed-setting rate of Pennisetum centrasiaticum,Leymus secalinus and Leymus chinensis were 1.85%, 11.54% and 55.29% . Potential seed yield of three grasses were 622.40kg/hm~2, 527.37kg/hm~2 and 357.69kg/hm~2 , while their actual seed yield were 10.34kg/hm~2, 280.55kg/hm~2 and 38.13kg/hm~2 ,which were 1.67%, 3.37% and 10.67% of potential seed yield.2. The seed germination of Pennisetum centrasiaticum was the highest in three grasses, which was 64.70%, seed germinal speed was quick . The seed germination rates of Leymus secalinus and Leymus chinensis were extremely low ,which were 6.00% and 4.00% respectively, and their seed germinal speed was slow. The seedling vigour and drought resistance of Pennisetum centrasiaticum were higher than that of Leymus secalinus and Leymus chinensis.3. Three rhizome grasses all simultaneously had rhizome bud and tillering bud. Two vegetative forms both appeared during the entire growing season. Their peaks was on the nutrition time of post harvest. they also had two vegetative propagation ways. Vegetative propagation of three grasses were different: the rhizome buds and its mature plants of Pennisetum centrasiaticum took absolute advantage of the total number of buds and upland remets. The vegetative propagation ability of rhizome mainly by rhizome buds was higher than that of tillering bud mainly by tillering buds. The rhizome buds and their mature plants of Leymus secalinus took the more advantage of total number of buds and the upland ramets .The vegetative propagation ability of rhizome was higher than that of tillering bud .The number of rhizome buds of Leymus chinensis was higher than that of tillering buds.4. Three grasses all belonged to"shortstop plants"which could walk by rhizome. their expansion ability were stronger than bunchy grasses. Compared with three grasses, the clone configuration of Pennisetum centrasiaticum tended to be"crowded"and occupied the space by growing dense rhizome system nearby the base rhizome. Leymus secalinus and Leymus chinensis tended to be"shortstop"and good at laying ramets on farther place by expanding the rhizome. In different environment level, the clone configuration of three grasses expressed the certain plastic change on interval length and branching length, but the expression was not completely consistent. It was explained that research about clone configuration and its plasticity changes of relative characteristics could not reach at the general summary stage .5. Along with water stress strengthening, the terdency on the increase of the number of upland branch and the total bud were dropping., The number of pennisetum centrasiaticum's total buds was higher than that of Leymus secalinus and Leymus chinensis in the same moisture condition. The proportion of underground biomass in Pennisetum centrasisaticum was rising and that of Leymus secalinus and Leymus chinensis were dropping. In the drought condition, interval sub-length of three grasses were all increasing . In conclusion, three grasses formed the certain compatibility in drought condition. Pennisetum centrasiaticum had a stronger compatibility to water stress.6. Biomass for reproductive organ spikes of three grasses were extremely low, Leymus secalinus was the highest which was only 6.3% , that of Leymus chinenisis was 4.26%, that of Pennisetum centrasiaticum was the lowest which was only 3.06%. On the contrary, biomass allocations of vegetation organ of Leymus secalinus, Leymus chinensis and Pennisetum centrasiaticum were 96.94%, 93.7% and 95.74%, this material assignment strategy also proved that the seed reproduction ability of three grasses were weak and the ability of vegetative propagation were strong. The biomass disposition of underground in Pennisetum centrasiaticum were 50.01%, while the biomass disposition of upland in Leymus secalinus and Leymus chinensis were 19.49% and 29.27% respectively. The investment for underground in Pennisetum centrasiaticum was much higher than that of Leymus secalinus and Leymus chinensis. Three grasses all had stronger rhizome system , Pennisetum centrasiaticum's rhizome system was more developed .7. Sexual propagation abilities of three grasses were weak, the reasons were different. Sexual propagation of three grasses had less effects on their population's prospering. Vegetative propagation had dominant position. Three grasses realized population's multiplication and renewal by the way of vegetative propagation in natural vegetation, it was K- strategy which won by quality.