Synthesis and Dissolution of Starch labelled with14Carbon in Tobacco Leaf Tissue
| Autor: | R. V. Martin, I. F. Bird, H. K. Porter |
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| Rok vydání: | 1959 |
| Předmět: | |
| Zdroj: | Journal of Experimental Botany. 10:264-276 |
| ISSN: | 1460-2431 0022-0957 |
| DOI: | 10.1093/jxb/10.2.264 |
| Popis: | SUMMARY Tobacco leaves, depleted of starch, were detached and allowed to assimilate equal amounts of 14COii and 12COii in succession, and vice versa. Distribution of radioactivity in starch, and sugars was determined after assimilation and after disks cut from the leaves had been kept in darkness for times up to 40 hours. The amount and activity of the respiratory C02 was also determined. 14C and 12C were incorporated in equal amounts into starch independently of the order in which they were supplied. In contrast sucrose had high activity when 14C was given last, and hexose a low one. The reverse was true when l2C was given last. Activity of respiratory C02 was slightly higher when 14C was assimilated last as compared with 12C. In the dark only 14C or 12C was at first lost from starch, in accordance with the view that leaf starch grains are built up and degraded by apposition or removal of discrete layers. Analytical results show that starch is the main respiratory substrate and to account for the redistribution of radioactivity in passage to C02 it is concluded that sucrose occurs at two sites separated inter or intra-cellularly, one of which is in equilibrium with the system interconverting starch and C02, and at the other hexoses are produced by inversion. A starch-like polysaccharide is formed during assimilation which persists in the dark and there is a significant contribution to respiration of carbon from non-carbohydrate sources when leaf disks are kept in the dark. |
| Databáze: | OpenAIRE |
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