THE INFLUENCE OF TEMPERATURE AND WATER-SUPPLY ON APPLE FRUIT-GROWTH AND THE DEVELOPMENT OF ORCHARD-GROWN TREES

The growth of 'Cox's Orange Pippin' apples in an orchard was studied i n relation to temperature and irrigation. Temperature around a number of trees was raised by the use of polythene tunnels from bloom in May until harvest in September. These trees within the polytunnels receive d irrigation, while for comparative purposes some trees outside did no t. Continuous measurements of the canopy environment, particularly tem perature, were made until harvest. Throughout the growing season fruit size was repeatedly measured, non-destructively, on a large number of selected fruit. Despite differences in mean temperature and accumulat ed day-degrees between trees inside and outside the polytunnels, there was no benefit to fruit size from raised temperatures. Supplemental i rrigation did have a number of effects; spur leaf area was enhanced wi thout significant change in total leaf area, while in the absence of i rrigation, final shoot length was greater. This greater shoot producti on was however associated with a smaller crop load per tree. The patte rn of the calculated fruit growth with time, for each treatment, was s imilar and reflected bulk measurements made at harvest. Differences in the growth curves appeared to be likely to be due to irrigation enhan cing the rate of fruit maturity. Fruit dry-matter content declined wit h supplemental irrigation and was increased by fruit thinning in June. The most marked effect of temperature on the fruit storage potential was a considerable reduction in nitrogen concentration.