| Root is the core link of water cycle and carbon cycle of the entire ecosystem,also it is a vital organ of the plant to communicate with the outside world about material and information. After a long period of exploration, scientists have a deeper understanding about the role and function of plant root already. By the way, research about the phenomenon and mechanism of plant species recognition through root has attracted much attention in recent years. However, only very few experiments have been done to study the gender recognition of dioecious plant. In this study, the hydroponic Populus cathayana seedlings were used as experiment materials to study the effect of opposite sexual neighbour on the root growth, physiology, component of root exudates and the secreting rate of female and male P. cathayana seedlings.The purpose of the study is aimed at revealing the effect of a heterosexual neighbour on root performance, explores the potential mechanism about the root identification between dioecious gender. The main results were as follows:1. Effect of opposite sexual neighbour on the root morphology of female and male P. cathayana seedlingsThe results showed that the morphologic characteristics of share plants were significantly higher than that of owners. Average diameter of males of share mode increase 24% significantly compared to male owners. Female of share mode raised it’s total tips, total length, total surface area and total volume of root by 96%,34%,48% and 97%. Compared with the owner mode, males in share had no significant change. Female of share mode raised it’s fine root length, coarse root length, fine root surface area, coarse root surface area, fine root volume and coarse root volume by 33%,218%,44%,252%,61% and 285%, but there are no significant changes in male of share mode. The results showed that male neighbour significantly promote the root morphology of female seedlings.2. Effect of opposite sexual neighbour on the root biomass concentration and allocation of female and male P. cathayana seedlingsThe results showed that fine root dry mass, coarse root dry mass, total root dry mass of female of share mode are significantly promoted by 55%, 200% and 95%compared to the owner female. While, males in share had no significant change. In addition, root weight ratio of share plants are significantly promoted, 38% of female and 30% of male compared to the owners. Specific root length and specific root areahave inapparent change between different mode and different sexes. The results showed that male neighbour significantly influenced the biomass allocation of female seedlings, make the roots biomass allocation of female seedlings transfer to underground part, and the coarse root and fine root biomass of the female seedlings significantly higher than seedlings that have no adjacent plant. In addition, higher coarse/total root ratio and lower fine/total root ratio of share female and male resulted in biomass of P. cathayana seedlings transfer to coarse root.3. Effect of opposite sexual neighbour on the root nutritional elements concentration of female and male P. cathayana seedlingsThe results showed that effect of opposite sexual neighbour on the organic carbon concentration of fine root and coarse root of male and female P. cathayana seedlings under different planting mode are not significant, and total root organic carbon accumulation of share female increased 107% compared with owner female,but the change of share male are non-significant. Under the mode of share plants,total nitrogen concentration of male and female coarse root didn’t change significantly, but total nitrogen concentration of fine root of male and female significantly descended(16% of female and 9% of male), total nitrogen accumulation of total root in share female are significantly increased by 57%. Under the mode of share plants, total phosphorus concentration of male coarse root significantly descended by 18%, but not changed of female. Phosphorus concentration of male and female fine root in share plants all descended significantly(20% of female and24% of male), and phosphorus accumulation of female total root in share plants are significantly increased by 49%. Potassium concentration of male and female seedlings in share plants all descended significantly(13% of female and 14% of male), and male fine roots descended by 47%, female fine roots increased by 27%,and potassium accumulation of female total root in share plants are significantly increased by 112%, but decreased 44% in share male. Calcium concentration of male coarse and fine root in share plants all increased(20% of coarse root and 16% of fine root), but there are no change of females in different mode. Magnesium concentration of male coarse and fine root in share plants all descended significantly(26% of coarse root and 12% of fine root). Calcium and magnesium accumulation of female total root in share plants are significantly increased by 92% and 91%. The results showed that the effect of opposite sexual neighbour in coarse and fine root of P. cathayana female and male seedlings are different, total root elementaccumulation in share female are significant increased, and except potassium accumulation there are non-significant change in nutritional elements accumulation of share male.4. Effect of opposite sexual neighbour on the root vigor and secreting rate of exudates of male and female P. cathayana seedlingsThe results showed that root vigor of male and female seedlings don’t change in different planting mode. Organic carbon concentration of share mode root exudates is higher than male owners, but there is no significant difference with female owners.Total nitrogen concentration in share plants are significant lower than in own plants.The exudates TOC rate of root weight in share plants have decreasing trend, but it’s not significant. The exudates TN rate of root weight in share are significant less than in male owner. These results showed that organic carbon concentration in roots exudates increased when grow with opposite sexual neighbour, and total nitrogen concentration decrease, but organic carbon concentration showed little change,absorption rate of total nitrogen decreased.5. Effect of opposite sexual neighbour on the root component of male and female P. cathayana seedlingsThe results showed that hydroponic P. cathayana seedlings have more kinds of exudates when grow with opposite sexual neighbour, and commom components of share mode are more than in owner mode. Exudates components of P. cathayana seedlings are hydro carbons(4 kinds), alcohol(3 kinds), phenols(1 kinds), esters(3kinds) and amide(1 kind), among them the alcohol have the biggest relative content about 42%, and the phenols are lowest about 7%. In addition, some independent exudates components occur in share mode such as amide(1 kind), alkane(3 kinds),esters(2 kinds). And the amide(N,N-diethyl-formamide) have the highest percent of42%, secondly the esters including 14% of octanoic acid, 2-butyl ester and 13%pentanoic acid, 2-methyl-, butyl ester. |
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