Nectar: properties, floral aspects, and speculations on origin.
Trends Plant Sci
; 9(2): 65-9, 2004 Feb.
Article
em En
| MEDLINE
| ID: mdl-15102371
ABSTRACT
Although nectar is crucial for most pollinators, its evolutionary origin has received scant attention. Nectar is derived from the phloem solution. Both have high sugar concentrations (usually 10-30% solutes by fresh mass); the main solute in the phloem is sucrose, whereas nectar can also contain considerable amounts of fructose and glucose. The phloem, not the xylem, is the supplier of water to flowers and certain other organs. Therefore, a 'leaky phloem' hypothesis for the origin of nectar is presented based on the elevated hydrostatic pressure that can occur within the phloem and the structural weakness of developing phloem tissues. A 'sugar excretion' hypothesis is also presented that considers the solute accumulation resulting from the relatively high transpiration rates of flowers.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Pólen
/
Carboidratos
/
Flores
/
Evolução Biológica
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article