Carbohydrate profiles during cotton floral bud (Square) development

Cotton (Gossypium hirsutum) flower's showy corolla expands rapidly, then senesces quickly. Efficient opening of corollas is important for self- and cross-pollination, and indirectly lint yield. Carbohydrate relations are integral to bud water relations and growth, although they are not well understood. Soluble sugars and starch in developing floral buds and flowers of field-grown cotton plants were analysed. Buds contained significantly more sugar than starch. Sucrose and its hydrolysis products strongly contributed to increased sugars during corolla expansion, and contributed -0.211 MPa to osmotic potential. Water concentration was constant throughout expansion at 860 g kg(-1) FW, suggesting sucrose import and hydrolysis are coordinated with other drivers of expansion. Floral sugar content declined sharply during senescence (69 % in 24 h). Although remobilization to other organs could partially explain this decline, we suggest the possibility that most sugar is broken down via respiration, resulting in the production of metabolic water and the significant 7 % increase in floral water concentration during senescence. In summary, imported sucrose and its hydrolysis products increased rapidly during cotton floral bud growth, and supported bud expansion by decreasing the water potential of bud tissue.