Diurnal changes in storage carbohydrate metabolism in cotyledons of the tropical tree Hymenaea courbaril L. (Leguminosae)

Author(s)

Velho Do Amaral, Lourdes Isabel ; Santos, Henrique P. ; Rossatto, Davi Rodrigo ; Buckeridge, Marcos Silveira

• Document type: Journal article
• Source: Rev. bras. Bot.; v. 35, n. 4, p. 9-pg., 2012-10-01.

Abstract

(Diurnal changes in storage carbohydrate metabolism in cotyledons of the tropical tree Hymenaea courbaril L. (Leguminosae)). The cotyledons of Hymenaea courbaril store large amounts of xyloglucan, a cell wall polysaccharide that is believed to serve as storage for the period of seedling establishment. During storage mobilisation, xyloglucan seems to be degraded by a continuous process that starts right after radicle protrusion and follows up to the establishment of photosynthesis. Here we show evidence that events related to the hydrolases activities and production (alpha-xylosidase, beta-galactosidase, beta-glucosidase and xyloglucan endo-beta-transglucosilase) as well as auxin, showed changes that follow the diurnal cycle. The period of higher hydrolases activities was between 6pm and 6am, which is out of phase with photosynthesis. Among the enzymes, alpha-xilosidase seems to be more important than beta-glucosidase and beta-galactosidase in the xyloglucan disassembling mechanism. Likewise, the sugars related with sucrose metabolism followed the rhythm of the hydrolases, but starch levels were shown to be practically constant. A high level of auxin was observed during the night, what is compatible with the hypothesis that this hormone would be one of the regulators of the whole process. The probable biological meaning of the existence of such a complex control mechanism during storage mobilisation is likely to be related to a remarkably high level of efficiency of carbon usage by the growing seedling of Hymenaea courbaril, allowing the establishment of very vigorous seedlings in the tropical forest. (AU)

• FAPESP's process: 98/05124-8 - Conservation and sustainable use of the plant biodiversity from the cerrado and Atlantic Forest: the storage of carbohydrates and their role on the adaptation and maintainance of plants in their natural environment
• Grantee: Marcos Silveira Buckeridge
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants