Eco-physiology of apple trees: dry matter production and partitioning by young Golden Delicious trees in France and England.
Young Golden Delicious trees were grown at Bristol for 1 year then, in January 1975, half the batch were moved to Montpellier; in January 1976, 6 trees were returned to Bristol and a further 6 sent to Montpellier. Over the growing period in 1975, Montpellier received 18% more radiant energy than Bristol; in 1976 it received 24% more. Spring temperatures were higher and dew points generally lower at Montpellier than Bristol. Full bloom was reached about mid-April in France and early to mid-May in England. Fruit numbers/flower cluster were 2 to 3 times higher in England than in France. Shoot growth started about 3 weeks earlier in France and leaf area/tree was always higher. Up to the time of crop harvest in 1975, dry matter production by the trees in England, which had more fruits than the trees in France, was greater than in France, but over the whole season dry matter production was 12% greater in France. In 1976, fruit loads were approximately the same at the 2 sites and differences in dry matter production were proportional to leaf area duration and total radiant energy received; dry matter production in France was greater than in England up to crop harvest and 25% greater overall. Fruit number/unit area was the main determinant of the partitioning of assimilates.