Stomatal and Chlorophyll Distribution of Cox's Orange Pippin Apple Flowers Relative to Other Cluster Parts

Surface area, chlorophyll concentration and stomatal size and density were measured for all green components of floral clusters on Cox's Orange Pippin apple trees to assess their relative potential for photosynthesis. Before flower opening, sepals and receptacles had chlorophyll concentrations similar to those found in the laminae of rosette leaves. But, whereas the concentration in rosette leaves continued to increased until fruit set, those in the sepals and receptacles decreased. Sepals had a greater mature stomatal density than leaf laminae shortly after bud burst; although both densities increased, that on the laminae later exceeded that on sepals. Flowers contributed significantly to the green surface are (40%), chlorophyll content (30%) and mature stomatal number (25%) of floral clusters at the green cluster stage, but these contributions then decreased. Cox apple flowers appear to have the potential for contributing significantly to their carbohydrate requirement at a time when the rosette leaves are not thought to be exporters of photosynthate.