Carbon/Nitrogen Imbalance Associated with Drought-Induced Leaf Senescence in Sorghum bicolor.
Carbon/Nitrogen Imbalance Associated with Drought-Induced Leaf Senescence in Sorghum bicolor.
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DOI：
10.1371/journal.pone.0137026
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Deng X
中科院分区：
文献类型：
--
作者：
Chen D;Wang S;Xiong B;Cao B;Deng X
干旱胁迫引发成熟的叶片衰老，支持植物存活和养分的再动员；然而，叶片衰老也严重降低了干旱后的作物产量。干旱通常导致碳/氮失衡，这反映在成熟叶片中碳/氮(C：N)比值的增加，这已被证明参与了正常生长条件下诱导叶片衰老的过程。然而，碳/氮平衡在干旱诱导的叶片衰老调控中的作用尚不清楚。为了研究碳氮平衡在干旱诱导高粱衰老中的作用，对高粱幼苗进行了渐进式土壤干旱处理。在干旱过程中监测叶片衰老症状和C/N比，C/N比由非结构性碳水化合物与全N含量之比表示。在本研究中，叶片衰老发生在干旱处理后12天左右，表现为各种衰老症状，包括光合作用、光系统II光化学效率(Fv/Fm)和叶绿素含量的下降，以及衰老标记基因的差异表达。C/N比在干旱处理后10~12天显著提高。叶片衰老发生在C/N比较高的老(下)叶，而C/N比较低的年轻(上)叶不衰老。此外，通过离体叶测定，研究了碳氮素有效性对干旱诱导衰老的影响。外源过量糖配合有限氮肥促进了干旱诱导的叶片衰老。因此，我们的结果表明碳/氮平衡可能参与了干旱诱导的叶片衰老的调节。
Drought stress triggers mature leaf senescence, which supports plant survival and remobilization of nutrients; yet leaf senescence also critically decreases post-drought crop yield. Drought generally results in carbon/nitrogen imbalance, which is reflected in the increased carbon:nitrogen (C:N) ratio in mature leaves, and which has been shown to be involved in inducing leaf senescence under normal growth conditions. Yet the involvement of the carbon/nitrogen balance in regulation of drought-induced leaf senescence is unclear. To investigate the role of carbon/nitrogen balance in drought-induced senescence, sorghum seedlings were subjected to a gradual soil drought treatment. Leaf senescence symptoms and the C:N ratio, which was indicated by the ratio of non-structural carbohydrate to total N content, were monitored during drought progression. In this study, leaf senescence developed about 12 days after the start of drought treatment, as indicated by various senescence symptoms including decreasing photosynthesis, photosystem II photochemistry efficiency (Fv/Fm) and chlorophyll content, and by the differential expression of senescence marker genes. The C:N ratio was significantly enhanced 10 to 12 days into drought treatment. Leaf senescence occurred in the older (lower) leaves, which had higher C:N ratios, but not in the younger (upper) leaves, which had lower C:N ratios. In addition, a detached leaf assay was conducted to investigate the effect of carbon/nitrogen availability on drought-induced senescence. Exogenous application of excess sugar combined with limited nitrogen promoted drought-induced leaf senescence. Thus our results suggest that the carbon/nitrogen balance may be involved in the regulation of drought-induced leaf senescence.