The cellular pathway of sucrose transport in developing cotyledons ofVicia faba L. andPhaseolus vulgaris L.: a physiological assessment

Abstract

The cellular pathway of sugar uptake in developing cotyledons ofVicia faba L. andPhaseolus vulgaris L. seed was evaluated using a physiological approach. The cotyledon interface with the seed coat is characterised by a specialised dermal cell complex. In the case ofVicia faba cotyledons, the epidermal component of the dermal cell complex is composed of transfer cells. Sucrose is the major sugar presented to the outer surface of both cotyledons and it is taken up from the apoplasm unaltered. Estimated sucrose concentrations within the apparent free space ofVicia andPhaseolus cotyledons were 105 and 113 mM respectively. Rates of in-vitro uptake of [14C]sucrose by cotyledon segments or by whole cotyledons following physical removal or porter inactivation of the outer cells demonstrated that, for bothVicia andPhaseolus cotyledons, the dermal cell complexes are the most intense sites of sucrose uptake. Accumulation of [14C]sucrose in the storage parenchyma of whole cotyledons was directly affected by experimental manipulation of uptake by the outer cell layers and plasmolytic disruption of the interconnecting plasmodesmata. These findings indicated that sucrose accumulated by the dermal cell complexes is transported symplasmically to the storage parenchyma. Overall, it is concluded that the dermal cell complexes of the developing legume embryo, irrespective of the presence or absence of wall ingrowths, are the major sites for the uptake of sucrose released from the maternal tissues to the seed apoplasm. Thereafter, the accumulated sucrose is transported radially inward through the symplast to the storage parenchyma.

DOI: 10.1007/BF01106758

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@article{McDonald2004TheCP, title={The cellular pathway of sucrose transport in developing cotyledons ofVicia faba L. andPhaseolus vulgaris L.: a physiological assessment}, author={Roseanne McDonald and Hatti L Wang and John W Patrick and Christina E Offler}, journal={Planta}, year={2004}, volume={196}, pages={659-667} }