The Determination Time of the Carpel Whorl Is Differentially Sensitive to Carbohydrate Supply in Pharbitis nil

Herbert, Rob, Durdan, S.F., Rogers, H.J. and Francis, D. (2000) The Determination Time of the Carpel Whorl Is Differentially Sensitive to Carbohydrate Supply in Pharbitis nil. Plant Physiology, 123. pp. 189-200. ISSN Print 0032-0889 Online 1532-2548

Abstract

A shoot apical meristem is florally determined if, following its removal from an induced plant, it flowers when cultured in non-inductive conditions. Determination times were measured in the short-day plant Pharbitis nil to examine whether floral whorls are determined simultaneously or sequentially. Shoot apices were excised at daily intervals following a 48-h dark-inductive treatment, cultured in non-inductive conditions for 4 weeks in continuous light, and the number of floral organs scored. The culture medium was White’s supplemented with sucrose, glucose (Glc), fructose (Fru), or 1:1 Glc:Fru at 2% (w/v), 4% (w/v), or 6% (w/v) or sugar-mannitol combinations of osmotic potentials equivalent to 4% (w/v) or 6% (w/v). The minimum whorl determination time was 1 d for sepals, petals, and stamens regardless of carbon supply. However, for carpels it varied remarkably from 5 d on sucrose, to 2 to 3 d on Fru or Glc:Fru, to 1 d for 2% (w/v) and 6% (w/v) Glc. Therefore, depending on the carbon supply, the carpel whorl was determined at the same time or after the outer whorls. Generally, these effects could not be reproduced on the sugar-mannitol treatments.

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