干旱胁迫和遮光对印楝幼苗生长及碳氮代谢的影响

以0.5年生印楝半同胞家系实生苗为材料,设置4个干旱胁迫水平与3个遮光水平共12个处理盆栽试验,测定分析印楝叶片主要碳氮代谢酶活性、终产物含量及生长指标,以揭示印楝碳氮代谢对光照及水分胁迫的响应规律,为进一步研究印楝的物质转换及代谢规律充实理论基础。结果显示:(1)在干旱胁迫条件下,印楝可通过调节碳代谢酶(SS、SPS)和氮代谢酶(NR、GS、GOGAT)活性及加快可溶性糖、可溶性蛋白质和游离脯氨酸的积累以维持苗高较小的变幅。(2)在遮光条件下,轻度遮光就会导致印楝叶片主要碳氮代谢酶活性及代谢产物含量急剧下降,严重抑制幼苗生长。(3)在干旱胁迫和遮光共同存在的条件下,遮光(或干旱)在一定程度上可以减缓干旱(或遮光)对印楝初生代谢及生长带来的不利影响。研究发现,印楝幼苗具有较强的干旱适应能力,适度干旱胁迫(土壤相对含水量大于35%)可促进细胞碳氮代谢,但不利于净光和产物的积累;同时,印楝幼苗对光照需求较高,轻度遮光会使初生代谢及生长受到严重抑制;在苗木培育过程中要尽可能提供充足的水分和光照,在水分匮缺时可以通过适当遮光来缓解干旱对苗木生长带来的负面影响,而在光照不足的条件下则需要适当控制水分。

Effect of Drought Stress and Shading on Growth and Carbon nitrogen Metabolism of Azadirachta indica Seedlings

The purpose of this study was to investigate the response mechanism of carbon-nitrogen metabolism on different drought and shading conditions for A.indica seedling,and enrich the theoretical basis for exploring the matter conversion and metabolic pattern of A.indica.In this work,twelve potted plants with four drought stress levels and three light levels were set up to determine the activities of major carbon-nitrogen metabolism enzymes,the contents of some metabolites,and index of growth.The results showed that:(1)under the condition of drought stress,A.indica can maintain a smaller variation in height and diameter by regulating the activities of carbon-nitrogen metabolism enzymes such as Sucro synthase(SS),Sucrose phosphate synthase(SPS),Nitrate reductase(NR),glutamine synthetase(GS),glutamate synthase(GOGAT),as well as accumulate of more soluble sugar,soluble proteins and free prolines.(2)Under the condition of shading,slight shading can lead to a sharp decline in the activities of the carbon-nitrogen metabolites and the contents of metabolites in A.indica leaves,which severely inhibits the growth of seeding.(3)Under the conditions of drought stress and shading,shading(drought stress)can alleviate the adverse effects of drought(shading)on the primary metabolism and growth of A.indica to some extent.Our research found that A.indica has a strong drought resistance,appropriate drought stress(SRWC>35%)can promote cell carbon-nitrogen metabolism,but not conducive to the accumulation of organic matter.Meanwhile,seedling has a high demand for light,and slight shading will affect its carbon-nitrogen metabolism and growth seriously.In the process of seedling cultivation in the future,we suggested that should provide as much water and light as possible.The negative effects of drought on seedling growth can be mitigated by shading,while insufficient light needs to properly control the water.