林木根系衰老研究方法与机制

根系衰老研究方法主要有根窗直接观测和挖根取样间接观测。在整株水平上,树木同化碳的能力,碳在不同器官间的分配,尤其是在地上部分和地下部分间的分配比例,对根的萌生和衰老起着重要作用;地上部分的生长过程和健康状况也对根系的生长和寿命有很大影响;当树木的生长环境受到某种胁迫时,树木的抵抗力下降,容易招致病原菌的危害,造成根系衰老和死亡。在生态系统水平上,干旱洪涝、干扰等胁迫和树木一土壤间的养分循环都会引起树木生长环境的改变,对根系的衰老过程发生作用;季节变化使树木的地上部分和地下部分的生理活动处于不同的旺盛期,从而使碳的分配方式有些改变,影响到根系的生长;土壤中养分的存在形式,某些离子的浓度也直接影响到根的寿命;病原菌对根系的危害与土壤中养分含量变化有关。所以,衰老过程受环境条件的影响,伴随着代谢,RNA和蛋白质合成速率的下降和(或)膜与细胞器结构的改变。

Research methods and mechanism of senescence of tree root: A review

Methods of root senescence study involve observation window and/or collecting roots by sequential core sampling. At whole tree level, root turnover and senescence is mainly concerned with the capacity of carbon fixation and carbon allocation among various organs, especially the ratio between above- and below ground systems; growth stages and healthy state of aboveground parts are closely related to root growth and longevity; when living surroundings of trees are in some stress, tree resistance gets weak and is easily attacked by pathogens resulting out root aging and mortality. While at ecosystem level, stress such as drought, flooding, dis- turbance and nutrient cycling between tree and soil will cause living conditions variation and root senescence; seasonal change de- termines different metabolism modal among above- and below ground systems, and causes carbon allocation patterns altering, which affect root development and growth; different nutrient elements and contents of some ions in soil also response to root turnover and aging; existence of Rhizobium nodules and mycirrhizae can improve microsite environment of root tips and helps it span life; patho- gens damage on roots is related to soil nutrition and has vital influence on root longevity. Thus root senescence is a complex proce- dure, involved with environmental factors, metabolism, RNA and protein synthesis rate decrease as well as membrane and/or cell structure reconstruction.