Sweet cherry floral organ size varies with genotype and temperature

Abstract

Floral organ attributes are important for pollinator attraction and pollination success in many plants. As part of a broader effort investigating causes for variable fruit set among sweet cherry (Prunus avium L.) genotypes, we have studied the role of temperature on floral organs in cultivars exhibiting high (‘Sweetheart’ and ‘Rainier’) or low fruit set (‘Benton’ and ‘Tieton’) in field conditions. In 2010 and 2011, two-year old sweet cherry limbs collected at ‘tight cluster’ flower stage were distributed randomly among three controlled environment chambers programmed to mimic a warm, moderate, or cool blooming period. Entire flowers were sampled and dissected at ‘tight cluster’, ‘first white’, ‘half white’, ‘first open’ and ‘full open’ stages. There was high year-to-year variability in size of all organs except stylar and filament lengths. ‘Tieton’ floral organs were significantly larger than other cultivars with the exception of filament, style and pedicel lengths. Between the earliest and the latest developmental stages petal area enlarged ca. 4.5 times, filament length increased ca. 3 times and styles doubled in length, across all cultivars. Irrespective of cultivar, the lengths of the styles and filaments were the most sensitive to temperature, being about 11% and 25% shorter in the low temperature environment compared to high temperature, respectively. This suggests that temperatures after the ‘tight cluster’ stage play an important role in the growth of styles and filaments. In addition, interestingly, our current results revealed that low productivity cultivars, i.e. ‘Tieton’ and ‘Benton’, have relative short styles to its petal size compared to the other two high productivity cultivars.