Study The Pollination Ecology Of Four Stipa Species In Inner Mongolia Steppe

Breeding ecology is an important field of ecological research.Stipa is the main dominant species and excellent forage of grassland ecosystem in China,but there is a great controversy about the pollination mode of sexual reproduction.In this paper,the dominant species of Stipa grandis and S.krylovii were selected from the typical steppe of Inner Mongolia,the dominant species of S.breviflora and S.gobica were selected from the desert steppe of Inner Mongolia.The differences in the breeding system and the pollination characteristics of four species of Stipa were determined by analyzing the diameter of little flower,the total number of pollen,pollen viability,outcrossing index(OCI),pollen/ovule(P/O)value and other indicators.Based on grazing control experimental platform and regional sampling,the paper analysis region differences of Stipa pollination characteristics and its response to grazing disturbance.The study is of certain significance to the pollination ecology theory and grazing ecosystem management.The main conclusions are as follows:1.Significant interspecific differences between the dominant species of typical steppe:S.grandis and the S.krylovii and the dominant species of desert steppe:S.gobica and S.breviflora.The order is:S.grandis(d=0.94 mm)>S.gobica(d=0.80 mm)>S.krylovii(d=0.68 mm)>S.breviflora(d?0.56 mm).The outcrossing index(OCI)is 1 or 2,according to the index,we judge the breeding system is specialized sexual intercourse or facultative selfing.2.There were some interspecific differences of four Stipa species in the total number of pollen.The order is:S.grandis(n=1243)>S.gobica(n=887)>S.krylovii(n=443)? S.breviflora(n=316);the value of pollen/ovule(P/O)range from 316 to 1243.According to the classification standard of Cruden,Stipa grandis,S.krylovii and S.gobica are facultative outcrossing(P/0=244.7?2588),but S.breviflora is facultative selfing(P/0=31.9-396)or facultative outcrossing.3.There were some differences in the vitality of four kinds of Stipa:S.breviflora(v=75.93%)>S.gobica(v=69.74%)>S.grandis(v=51.76%)? S.krylovii(v=51.13%);they have similar performance of effective seed setting rate:S.krylovii(v=65.57%)? S.grandis(v=64.91%)? S.breviflora(v=63.65%)? S.gobica(v=63.53%).4.Grazing disturbance had no significant effect on the small pollen diameter of Stipa,which had a certain effect on the total number of pollen,but the performance was complex,which was related to species,grazing intensity and grazing season.5.There were no significant regional differences in little flower diameter of S.gobica,but the total number of pollen and pollen vitality have slight differences.There were no significant regional differences in little flower diameter and pollen vitality of S.breviflora,but the total number of pollen shows a certain slightly regional differences.