Productivity of Peach Trees: Factors Affecting Dry-weight Distribution During Tree Growth

The distribution of d.wt in peach trees varies greatly withincreasing tree size or age. The growth of the fruit, rootsand tree frame is competitively inter-related throughout thelife of the tree while the growth of leaves and the annual shootsthat support them is independent and increases in direct proportionto tree size. The proportion of the annual increment of d.wtdirected into fruit growth increases from less than 30 per centin a young tree of about 16 cm butt-circumference to almost70 per cent in a mature tree of about 55 cm butt-circumference.Thereafter the proportion of d.wt allocated to fruit growthdid not increase, although the total yield of d.wt continuedto increase exponentially. Conversely the proportion of d.wtallocated to the frame and roots declined from just under 40and 20 per cent respectively to less than 10 and 1 per centrespectively. In these organs also, the proportions did notchange further for larger trees. The ratio of vegetative growth made by the top of the tree comparedto root growth increased from 1 in a young tree to 4 in theoldest trees but there was a strong allometric relation (r=0·99)between the growth of both systems. The physiological implicationsof these data and their relation to horticultural productivityare discussed.