Effects Of Lights And Temperatures On Seedlings Morphological Characteristics And Biomass Allocation Of Six Poa Species

The effects of light, habitat and cooling on morphological characteristics, biomass allocation and survival rate of seedlings among six species in Poa on the eastern Qinghai-Tibet Plateau were studied, which could provide research basis on growth strategies of alpine plants in different environmental conditions. Seedling were grown in light incubator with three light treatments(100%、50%、20%×1.2×104Lx), two temperature treatments(growth conditions were emulated as grassland covered by vegetation, 25℃/15℃;grow in bare land, 30℃/10℃) and cooling treatments. The results showed that:(1) The six species in this study showed significant morphological plasticity to the changeble environmental conditions, which had more shoot allocation to increase competition for light resources under low light treatment, more root allocation and higher biomass under high light treatment. It revealed that light availability play an important role on seedling biomass allocation and morphological plasticityof plants in the alpine meadow.(2) The seedlings of six species had more shoot allocation when growth conditions were emulated as grassland covered by vegetation and had more root allocation when plants were assumed to grow in bare area. The conditions of grassland covered by vegetation was more fitable for seedling growth than exposed condition.(3) The seedling encountered cooling had more shoot allocation, lower biomass and relative growth rate than normal seedlings.(4) There were some correlations among the growth parameters of the six species. The relative growth rate only significantly correlated to morphological parameters, but had no significant correlation with the biomass allocation parameters.(5) The seedlings of six species showed approximate phenotypic plasticity, average morphological plasticity index among species had no significant difference, and the plasticity of seedling biomass, shoot allocation, area of leaf morphological characters showed similar trends.(6) The seedling survival when growth conditions were emulated as grassland covered by vegetation was significantly higher than that grew in exposed condition, and seedling encountered cooling had higher survival rate than those grew in normal condition.(7) The species with slow germination speeding were widely distributed, had slower growth rate and lower survival, which might be the manifestation of their competitive disadvantage, and the slow germination speeding might be a strategy to share the risk of environment. The species with fast germination speeding had faster growth rate and higher survival, and were easy to establish monodominant community.