The 2012 ASHS Annual Conference

The size of floral organs is important for pollinator attraction in many plants. Filament length in particular plays a role in the efficacy of self-pollination, and style length is a key element of effective pollination period (EPP). As part of a broader effort investigating causes for variable fruit set among sweet cherry genotypes, we studied the role of temperature on floral organs in cultivars exhibiting high fruit set (‘Sweetheart’ and ‘Rainier’) and low fruit set (‘Benton’ and ‘Tieton’).  Two-year-old limbs were collected at ‘tight cluster’ flower stage and distributed randomly among three controlled environment chambers programmed to mimic high, moderate and low field temperatures according to climate data from the past 20 years. Entire flowers were sampled and dissected at ‘tight cluster’, ‘first white’, ‘half white’, ‘first open’ and ‘full open’ stages. The areas of individual sepals and petals was determined by scanning and image analysis using MATLAB. The dimensions of filaments, styles, pedicels and ovaries, were assessed by digital calipers. We found no relation between perianth organ size and cultivar productivity. ‘Tieton’ floral organs were significantly larger than other cultivars with the exception of the length of the filament, style, and pedicel. Interestingly, stylar length was not significantly different among cultivars nor influenced by temperature.  This indicates that pollen tube growth and/or ovule viability may be more important in determining EPP. Across all cultivars, style length increased linearly from ‘tight cluster’ to ‘full open’ by ca. 90%. Only filament and pedicel length were influenced by temperature – both being shorter under cold conditions.  Pedicel length was about 15% shorter comparing high and low temperature regimes and increased by 71% between ‘tight cluster’ and ‘full open’. Filament length increased linearly throughout sampling stages, increasing by ca. 3.5-fold between the earliest and latest stages.