The Effects Of Arbuscular Mycorrhizal Fungi On Intra-or Intersexual Competition In Male And Female Populus Cathayana Seedlings

Arbuscular mycorrhizal(AM)fungi are known to form mutualistic symbiotic associations with the roots of more than 80% of terrestrial plant species,it can enhance the growth of host plants,involve in interactions among plants,even alter the differences between two opposite sexes.In our study,male and female Populus cathayana seedlings growing with opposite(intersexual competition)or same sex individual(intrasexual competition)were chosen to inoculate with Funneliformis mosseae,and morphological characteristics,biomass accumulations,gas exchange,physiological traits of roots and element content were measured to reveal the effects of AM fungi on intra-or intersexual competition in male and female Populus cathayana seedlings.The main results are as follows:1.The effects of AM fungi on morphological characteristics and biomass accumulations in male and female P.cathayana seedlings.The presence of AM fungi significantly increased morphological characteristics and biomass accumulations in male and female plants,and enhanced the differences between male and female plants under intrasexual competition,but not significantly affected the differences between male and female plants under intersexual competition.After being inoculated with AM fungi,female plants under intrasexual competition showed significantly higher morphological characteristics and biomass accumulations than males,but no significant differences was found in non-inoculated group.In addition,male and female plants under intersexual competition showed significantly higher morphological characteristics and biomass accumulations than plants under intrasexual competition.Furthermore,the presence of AM fungi significantly decreased the root/shoot ratio and root/stem ratio in male and female plants.2.The effects of AM fungi on gas exchange and water use efficiency in male and female P.cathayana seedlings.After being inoculated with AM fungi,female plants under intrasexual competition showed significantly higher chlorophyll a content than males,while there was no significant differences in chlorophyll b and total chlorophyll content.More,the presence of AM fungi slightly increased Fv/Fm in female plants.Furthermore,inoculated-plants showed lower photosynthetic rate than plants under non-inoculated condition.Male plants showed higher photosynthetic rate,but lower ?13C than females under two conditions,and the presence of AM fungi significantly increased ?13C in twosexes,while there was no significant effect in intra-and intersexual competition.3.The effects of AM fungi on root physiology traits in male and female P.cathayana seedlings.Under inoculated condition,male plants showed higher nitrate reductase(NR)activate than females,while there was no significant difference between two sexes in inter-and intrasexual competition.In addition,plants in intersexual competition showed higher NR activate than that in intrasexual competition under inoculated condition.However,there was no significant difference in root activate between two sexes either in two competitions or under two conditions.After being inoculated with AM fungi,male plants showed higher colonization rate(Col)than females,and whether female or male plants in intrasexual competition showed higher Col than that in intersexual competition.4.The effects of AM fungi on element content in male and female P.cathayana seedlings.The presence of AM fungi slightly increased C content in leaves,while there was no significantly difference in C content in roots and stems.Under non-inoculated condition,female plants showed higher C content in roots than males in intrasexual competition,while lower in intersexual competition.And under inoculated condition,C content in roots in male and female plants had the same trend as in C content in roots under non-inoculated condition.Furthermore,the presence of AM fungi significantly decreased N content in roots and stems,and N content in leaves in intrasexual competition.Moreover,under non-inoculated condition,male plants showed higher N content in roots and stems in intersexual competition,while showed lower N content in leaves in intrasexual competition than females.The results indicated that the presence of AM fungi increased male and female plants growth,and enhanced the differences in morphological characteristics,biomass accumulations,and element content between two sexes in intrasexual competition,while there had no significant effects on morphological characteristics,biomass accumulations,and element content in intersexual competition.In addition,the growth of male and female plants was promoted in intersexual competition compare with that in intrasexual competition.And in two competition,female plants showed higher competitive capacity than male seedlings.