Analysis of seed growth, fruit growth and composition and PEPCK occurrence in apricot (Prunus armeniaca L.).

In 2011, in central Italy, a study was carried out in order to acquire new information on the growth of the fruit and seed of apricot, the changes in the contents of sugar and organic acid and the occurrence of phosphoenolpyruvate carboxykinase (PEPCK) in the mesocarp + epicarp. The maximum relative growth rate (RGR) of the different parts of the fruit an seed occurred at different times during the development of the whole fruit. The endocarp possessed the maximum RGR during stage I of fruit development, the seed (embryo + endosperm) during stage II and, together the mesocarp + epicarp, during stage III. Throughout development, the increase in diameter of the fruit was higher than its increase in length, and the fruit became more spherical. In unripe fruit glucose was the most abundant soluble sugar. In ripe fruit sucrose was the most abundant soluble sugar, followed by glucose and then by fructose and sorbitol. Starch was only detected in the first part of fruit growth and the amounts were very low. During fruit development, the absolute contents (mg fruit-1) of malate and citrate increased up to the first half of ripening period and net dissimilation was only observed in the second part of it. PEPCK was present in the edible parts of the fruit both when there was a net dissimilation of organic acids and when there was not, and this suggests that it functions in other processes besides an involvement in the net dissimilation of organic acids.