箭竹是大熊猫主要的食料来源，也是亚高山针叶林下层优势种群，在水源涵养、水土保持、养分平衡等生态功能发挥中具有重要的作用。箭竹作为一种浅根系植物对水分需求高，对干旱十分敏感。在干旱年份常会遇到箭竹出笋少或不出笋以及竹叶脱落甚至提早开花死亡的现象。因此，干旱在严重影响箭竹生长发育的同时，更使国宝大熊猫面临缺食危机。为了适应干旱等不利的环境条件，植物在漫长的进化过程中形成了一整套完备的对于逆境的自我保护机制如碳氮等主要物质代谢发生改变。然而，在我国干旱频率和强度日益增加的今天，有关箭竹对干旱逆境响应机制的研究鲜见报道，因而值得深入研究。
中科院成都生物研究所地下生态学学科组潘开文研究员课题组刘成刚、王彦杰等人以大熊猫主食竹缺苞箭竹为研究材料，以干旱为逆境，从物质代谢角度对不同程度干旱胁迫下发笋期缺苞箭竹不同器官碳氮代谢耦合响应机制进行了研究。结果表明：干旱胁迫显著降低了发笋期缺苞箭竹植株特别是幼叶和根的生长，同时显著降低了幼叶中色素含量；干旱胁迫未破坏发笋期缺苞箭竹幼叶中碳代谢的平衡状态，然而却加速了幼叶中硝酸盐(NO3-)的还原和铵(NH4+)的同化，以缓解其生长限制；干旱胁迫增加了发笋期缺苞箭竹老叶中参与碳代谢过程中的一些关键酶活力，进而减少了老叶中碳水化合物的含量，只有重度干旱胁迫增加了老叶中NO3-的还原和NH4+的同化；此外，发笋期缺苞箭竹根部碳氮代谢在重度干旱胁迫时增加。因此，缺苞箭竹不同器官具有各种应对策略以更好地适应不同程度的干旱胁迫，确保其在整个植株水平上的正常生长。
研究结果对提高箭竹的抗旱性、产量及品质具有指导意义。该研究得到了国家自然科学基金的资助，相关结果在线发表于J Plant Growth Regul。（生物谷Bioon.com）
生物谷推荐的英文摘要
Journal Plant Growth Regulation doi:10.1007/s00344-013-9367-z
Carbon and Nitrogen metabolism in Leaves and Roots of Dwarf Bamboo (Fargesia denudata Yi) Subjected to Drought for Two Consecutive Years During Sprouting Period
Chenggang Liu， Yanjie Wang， Kaiwen Pan， Tingting Zhu， Wei Li， Lin Zhang
Dwarf bamboo is an ecologically and economically important forest resource that is widespread in mountainous regions of eastern Asia and southern America. Fargesia denudata， one of the most important dwarf bamboos， is a staple food of the giant panda， but our knowledge about how F. denudata copes with drought stress is very limited. The objective of this study was to determine the responses of carbon (C) and nitrogen (N) metabolism to drought in leaves and roots of F. denudata plants. Plants were subjected to three water treatments， well-watered [WW， 85 % relative soil water content (RSWC)]， moderate drought (MD， 50 % RSWC)， and severe drought (SD， 30 % RSWC)， for two consecutive years during the sprouting period. Plant growth parameters， levels of carbohydrates and N compounds， and activities of key enzymes involved in C and N metabolism were analyzed. In young leaves， C metabolism was in balance after drought stress， but nitrate (NO3？) reduction and ammonium (NH4+) assimilation were accelerated. In old leaves， drought stress decreased carbohydrate contents by spurring the activities of the main enzymes that participate in C metabolism， whereas N metabolism was enhanced only under SD. Roots showed unchanged C metabolism parameters under MD， together with stable NO3 reduction and the key enzymes related to NH4+ assimilation， whereas they were stimulated by SD. Hydrolysates of carbohydrates in old leaves could be transferred into roots， but only to meet MD. Meanwhile， roots could allocate more N nutrition to young leaves and less to old leaves. These changes regulated the overall metabolic balance of F. denudata. Consequently， the results indicate that different organs with various response strategies will be well adapted to different drought intensities for ensuring regular growth of F. denudata plants at the whole-plant level.
