Internal recycling of respiratory CO2 in pods of chickpea (Cicer arietinum L.):: the role of pod wall, seed coat, and embryo
Internal recycling of respiratory CO2 in pods of chickpea (Cicer arietinum L.):: the role of pod wall, seed coat, and embryo
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DOI：
10.1093/jxb/erh190
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发表时间：
2004-08-01
影响因子：
6.9
通讯作者：
Turner, NC
中科院分区：
文献类型：
--
作者：
Furbank, RT;White, R;Turner, NC
此前有人提出，豆类籽粒中胚胎释放的呼吸二氧化碳是由豆荚内壁上的一层细胞重新固定的。在鹰嘴豆中，这种重新固定的过程被认为对种子碳收支具有重要意义，特别是在干旱情况下。在这项研究中，报道了鹰嘴豆的离体胚、种皮和角果壁都具有光合作用，但只有角豆壁能够在呼吸作用之外净释放O-2。对同位素标记的二氧化碳的固定测量支持了吊舱壁在重新固定中的主要作用，这表明当提供到吊舱内部时，超过80%的二氧化碳被该组织固定。幼龄豆荚的胚芽、种皮和角果壁组织的叶绿素含量在面积和鲜重上都是相同的量级，但在结荚后12-30天随着发育而不同程度地下降。豆荚壁叶绿素分布的成像表明，只有不到15%的叶绿体位于被认为是重新固定豆类中二氧化碳的细胞的内层；这将足以重新固定不到40%的呼吸二氧化碳。结论是，虽然豆荚的所有组织都能够重新固定呼吸碳，但整个豆荚壁负责这一过程的大部分，而不是内表皮上的一层专门的细胞层。这种固定碳在豆荚中重新分配给种子的作用被讨论了。
It has previously been proposed that respiratory CO2 released from the embryo in grain legume pods is refixed by a layer of cells on the inner pod wall. In chickpea this refixation process is thought to be of significance to the seed carbon budget, particularly under drought. In this study it is reported that the excised embryo, seed coat, and pod wall in chickpea are all photosynthetically competent, but the pod wall alone is capable of net O-2 evolution over and above respiration. The predominant role of the pod wall in refixation is supported by measurements of fixation of isotopically labelled CO2, which show that more than 80% Of CO2 is fixed by this tissue when provided to the pod interior. Chlorophyll concentrations are of the same order for embryo, seed coat, and pod wall tissues in younger pods on both an area and a fresh weight basis, but decline differentially with development from 12-30 d after podding. Imaging of chlorophyll distribution in the pod wall suggests that less than 15% of chloroplasts are located in the inner layer of cells thought to refix CO2 in legumes; this would be sufficient to refix less than 40% of respired CO2. It is concluded that while all tissues of the pod are capable of refixing respiratory carbon, the entire pod wall is responsible for the majority of this process, rather than a specialized layer of cells on the inner epidermis. The role of this fixed carbon in the pod for reallocation to the seed is discussed.