Morphological and physiological parameters related to flower quality in apricot

Apricot (Prunus armeniaca L.) is particularly prone to erratic fruit set. Several reasons, such as adverse weather conditions at flowering or pollination failure, can explain this behaviour in some circumstances. However, there are a good number of instances where poor fruit set is produced without apparent cause. The term "flower quality" is used to express something inherent to the flower that is reflected in the subsequent fruit set. However, information is elusive regarding an explanation of what determines a good-quality flower. In an attempt to gain insight into the characters that shape flower quality, we have studied, in apricot 'Moniqui', several morphological and physiological flower parameters, such as stigmatic area, number of pollen grains and pollen tubes and presence of starch reserves, and related them to the subsequent fruit set. A good relationship between stigmatic area, evaluated with the help of an image-analysis system, and the subsequent fruit set was obtained, since flowers with a large stigmatic area have a better probability of setting a fruit than flowers with a small stigmatic area. Likewise, the number of pollen grains germinated at the stigma and the number of pollen tubes growing along the style and the presence of starch reserves at the base of the style show a good relationship with the probability that the flower becomes a fruit. The results are discussed in terms of the implications for flower quality and fruit set