2种大型丛生竹对氮输入的可塑性响应

Plasticity responses of two sympodial bamboo species to nitrogen levels

为全面了解半自然条件和造林条件下丛生竹氮输入与表型可塑性之间的关联性,对酒竹和绿竹扦插移栽植株在土壤氮素梯度变化条件下(N0～N160)的形态和生理适应性差异进行了研究。结果表明:与绿竹相比,酒竹具有较高的资源利用效率和较高的生产力,酒竹最优氮素施用更倾向于N120,而绿竹则为N80,酒竹对氮素利用有更大的饱和阈值;随着供氮水平的增加,酒竹和绿竹通过提高SLA、扩大冠幅和总叶面积以使光能吸收率和利用率达到最优化,并与根系数据(RGRr和根半径)相对应;酒竹和绿竹在纵向生长上也表现为通过开拓立体空间使株型更有利于摄取可利用的光资源;在中等氮肥供应(N80～N120处理)情况下能显著促进目标竹种光合生理参数如Pmax、LSP、LCP、Rd和φAQY的上升;而各项形态和生理参数在高氮素施用情况下均有所下降,但与对照相比均有显著提高;N40数据表明2种竹种在低氮施用下可塑性并不明显,但是根系和φAQY对低氮仍有一定的响应。

Summary Bamboo has very wide applications such as construction materials, fibre production, biological energy, food and traditional Chinese medicines, etc. Moreover, the area of bamboo forest will increase in future as a result of bamboo industry＇ s development into a pillar industry in rural areas of south China. The limitation of nitrogen supplements in plant growth and biomass is more sensitive than other nutrition elements. So addition of different nitrogen fertilizers will affect the growth procession. Although there are numerous studies focusing on monopodial bamboo species, these types of key researches are missing in sympodial bamboo research, which is negative to the bamboo industry. Investigating the plasticity and physioecology of sympodial bamboo is helpful to comprehend its adaptability under different cultivation and afforestation conditions. In order to understand the relationship between plasticity of sympodial bamboo and soil nitrogen input under the semi-natural and afforestation condition, the morphological and physiological adaptability variations of two sympodial bamboo seedlings, namely, Oxytenanthera braunii wine bamboo ） and Dendrocalamopsis oldharni, were studied. We set up 5 nitrogen fertilization CO（NHz ）2 levels, i.e. No （calculated by N content）, N40 N80, N120, N160 kg/hm2 after 52.7 kg/hm2 Ca（H2PO4 ）e and （K2SO4）K2O 56.3 kg/hm2 were applied into the soil. And 1 a later, we measured the morphological and photosynthesis characteristics. Results showed that wine bamboo had higher biomass and resource utilization efficiency compared with D. oldhami. And the optimal nitrogen fertilizer level for wine bamboo was about N120 while for D. oldhami was N80, so wine bamboo had higher utilization capacity. These two bamboos achieved their most optimized light utilization by elevating SLA, extending crown, increasing total leave areas and developing height. Meanwhile, the positive behavior was observed that the relative growth rate and root radius of wine bamboo and D. oldhami increased with the increase of nitrogen level. The nitrogen content of N160 was to high that it affected the optimal growth, but it was still better than N40 and the control treatment. Under the condition of medium nitrogen fertilizer supply （N80- N120 ）, the physiological traits such as P LSP, LCP, Rd and φAQY were improved. The data of lower nitrogen supply like N40 treatment implied that the plasticity responses were not significant except for the root and φAQy. The higher biomass and SLA of wine bamboo, representing the capacity of absorbing carbon dioxide, implied that it could possess better adaptation and stronger propagation ability in the mid-high mountains of Southwest China after being introduced and afforested. The result of this study indicated that sympodial bamboo such as wine bamboo and D. oldhami should be planted on fertile soils where its habitat is managed to decrease the weeds growth, increase the root radius, branch length and total leaves areas so as to extend the crown to elevate photosynthesis and propagation rate.