A Reappraisal of the Growth and Development of Peach Fruit

Both the fresh weight and dry weigh increase of peach fruit [Prunus persica (L.) Batsch. cv. Golden Queen] have a double-sigmoid pattern. However, the lag period of slow fresh weight increase (fresh- weight-stage II) began and finished 1 month earlier than the start and finish respectively of the lag period of dry weight increase (dry-weight-stage II). Similarly, after the fruit had matured the rate of fresh weight increase declined 1 week before the rate of dry weight increase declined. The stone increased in dry weight rapidly in fresh-weight-stage II and this was accompanied by a compensating decline in the rate of dry weight increase of the flesh. There was no rapid increase in the dry weight of the seed until the rate of dry weight increase of the stone declined at the beginning of dry-weight-stage II. Although the decrease in the growth rate of the stone was accompanied by a marked increase in soluble sugar in the flesh, there was no compensating increase in growth rate of the flesh. While the second rapid stage of fresh weight increase (fresh-weight-stage III) was not accompanied by other apparent physiological changes, the second rapid stage of dry weight increase began at the same time as ripening commenced. The rate of natural abscission and the rate at which chlorophyll was degraded, both of which are known to indicate the level of ethylene present in the tissue, were high in dry-weight-stage I and dry-weight-stage III and low in dry-weight-stage II. The rate of growth of the fruit and its parts during different stages, the growth of the seed, the rate of abscission and chlorophyll degradation and the level of the major metabolites present in the fruit were all intricately interrelated. We have discussed the physiological significance of these observations and the way in which they may relate to earlier studies of peach fruit growth.