Portal de Periódicos da CAPES

The Control of Food Mobilization in Seeds of Cucumis sativus L. VI. The Production of Starch

1985; Oxford University Press; Volume: 55; Issue: 1 Linguagem: Inglês

10.1093/oxfordjournals.aob.a086874

1095-8290

John Chapman, Luciano Galleschi,

Lipid metabolism and biosynthesis

During germination and early seedling growth of cucumber, cotyledonary lipid and protein reserve material mobilization is controlled through a cotyledon/axis, source/sink relationship. Earlier work has shown that some cotyledonary lipid breakdown is able to occur even in the absence of the embryonic axis. This study shows that such breakdown is probably a consequence of the formation of a transitory starch store. Excised cucumber cotyledons accumulate large amounts of starch following the accumulation of reserve breakdown products which can no longer be utilized in the absence of the axis and represents a mechanism in the issue to regulate the concentration of osmotically active substances such as sucrose and glucose. The starch content of both attached and excised cotyledons increased during the experimental period. In the former case, however, the increase was very small and starch levels fell subsequently, while in the later instance the increase continued, reaching a maximum at day 8 after which it stabilized at this elevated level. The increase in starch content is most closely correlated with an increase in the activity of bound ADPG-starch synthase although soluble ADPG-starch synthase activity also increases during the experimental period.