Research On Reproductive Ecology And The Adaptability Mechanism On Two Clonal Plants Of Puccinellia In Alkalized Meadow In Northeast China

Plants have developed diverse reproductive characteristics during the course of evolution. Many plants, especially perennial grass can reproduce through sexual reproduction and vegetative reproduction. It is a hot science problem that how plants choose these two ways to reproduction according to the changing environment and the growth processes as well as how to allocate the biomass.The main plants of the alkaline grasslands in northeastern China are Puccinellia chinampoensis and Puccinellia tenuiflora which are perennial clonal grass of bunch types and have strong ability of sexual reproduction and vegetative reproduction. This paper takes these two plants as objects of study, studying the choice of the reproduction adaptive convergence mechanism in different basification environment and growth period through the perspective of asexual growth and reproduction, life history pattern of populations, allocation of sexual reproduction, size hierarchy, counterplan through sexual reproduction and so on. The main results and conclusions are as follows:1. Clonal growth includes the change of the size of tufts and the number of modules. During different growth periods of three successions community series, the clonal tufts of P. chinampoensis and P. tenuiflora were all the biggest in the monodominant community(PC1), the quantitative variation degree of modules during clonal growth was higher than that of tufts, the quantitative variation degree and the weight of inflorescence universally varied a lot while the weight of tillers varied a little. The clonal reproductive allocation(RAâ… , RAâ…¡, RAâ…¢) of P. chinampoensis during different growth periods in the three communities were similar to each other.Among different community series and different growth period, the clonal tufts of P. chinampoensis in monodominant community were all much bigger than that of P. tenuiflora(P<0.01). There existed large divergence on the number of ramets and quantitative characteristics of production for the two Puccinellias in the interspecific crossing, so did the reproductive tillers modules level and clonal level in the reproductive allocation. During different growth periods, the total number of clonal ramets, reproductive tillers, the total weight of plants and the weight of reproductive tillers of Puccinellia chinampoensis and Puccinellia tenuiflora all increase remarkably according to the growth of tufts in the form of linear function(P<0.05 or P<0.01). Apart from several communities, the clonal reproductive tillers, the weight of reproductive tillers, the total weight of plants and the weight of inflorescence of Puccinellia chinampoensis and Puccinellia tenuiflora all increase remarkably according to the growth of the total number of plants in the form of linear function(P<0.05 or P<0.01) during different growth periods; the number of reproductive tillers, the weight of reproductive tillers, the weight of inflorescence all increase remarkably according to the growth of the total weight of plants in the form of linear function(P<0.05 or P<0.01).2. The life history of P. chinampoensis and P. tenuiflora consisted of two cycles complementary to each other and held together the change and continuity of the population. There were sexual reproduction: seedsâ†'seedlingsâ†'nutrition tillersâ†'reproductive tillersâ†'seeds, and vegetative reproduction: winterness seedlings of tillers/springness seedlings of tillers and budsâ†'-nutrition tillersâ†'winterness seedlings of tillers/springness seedlings of tillers and buds. Different parts of the plant made different contributions to the growth. During the period of seedling establishment, winterness seedlings of tillers which were produced through vegetative reproduction and survived the winter made the most contribution, with P. chinampoensis being 83.7%-86.4% and P. tenuiflora being 85.0%-86.4%; During the periods of flowering and ripening, nutrition tillers took the biggest percent, with P. chinampoensis being 60.6%-68.4% and P. tenuiflora being 48.0%-51.7%; During the period of dormancy, they turned into winterness seedlings of tillers and buds, accounting for 97.9%-99.0% in all, which made full preparations for the update of the population. There was convergence in the pattern of life history, contribution of each part and the cycle in the interspecific crossing.During the periods of flowering and ripening, different populations of two Puccinellia plants shared similar variation trends in the ability of vegetative reproduction, biomass and productivity. In a reproductive allocation(RAâ… ) those of P. chinampoensis were higher than those of P. tenuiflora. In another reproductive allocation(RAâ…¢) those of P. tenuiflora were higher than those of P. chinampoensis. The rotation rate of nutrition tillers and reproductive tillers took opposite variation trends, meaning that of P. chinampoensis was higher than P. tenuiflora in terms of nutrition tillers but was lower in terms of reproductive tillers.3. The number of reproductive tillers of two Puccinellia plants during different growth periods both had strong phenotypic plasticity, especially the variable coefficient of the weight of inflorescence, with P. chinampoensis being 39.3%-89.0%, and P. tenuiflora being 37.7%-64.4%. The reproductive allocation of P.chinampoensis during the early period of growing was generally high, for example, that during beginning stage of heading and heading stage was 1.7 times and 1.4 times as that of P. tenuiflora. But when it comes to the period of flowering, the difference was unnoticeable and the period of ripening, convergent. There was a positively linear correlation between the characteristics of the growth and reproduction of P. tenuiflora and its height, but that of P. chinampoensis was exponential positive correlation. The phenotypic plasticity of the growth and allocation of the two plants and the regularity possessed both convergence and divergence in the interspecific crossing.4. No matter when two Puccinellia plants eared and bloomed, all the reproductive tillers ripened at a relatively concentrated time. The quantitative characteristics of the two plants during the whole generative growth period both showed strong phenotypic plasticity. When the length of prolonged reproductive growth was 16 days, the quantitative characteristics of P. chinampoensis showed apparent increase: with the height being 30.04%, the length of inflorescence being 41.54%, the weight of inflorescence being 2.24 times, the weight being 1.37 times, the weight of ripened seeds being 2.57 times and the weight of one thousand this kind of seeds being 50.6%. When the length of prolonged reproductive growth was 19 days, the quantitative characteristics of P. tenuiflora also showed apparent increase: with the height being 24.09%, the length of inflorescence being 75.23%, the weight of inflorescence being 3.68 times, the weight being 1.66 times, the weight of ripened seeds being 5.29 times and the weight of one thousand this kind of seeds being 1.11 times. The size hierarchy of reproductive tillers and the time of ear and bloom had close connection. In the regression analysis of linear function, power function and exponential function, with the extending of the reproductive growth, the coefficient of determination(R2) of the quantitative characteristics of P. chinampoensis was the biggest in a linear pattern and the coefficient of determination(R2) of the quantitative characteristics of P. tenuiflora was the biggest in an exponential pattern. When the earing and flowering periods were prolonged. The phenotypic plasticity of the growth and allocation showed convergence in the two Puccinellia plants, but the change rule showed divergence in the interspecific crossing according to the time periods.