DRY MATTER AND NUTRIENT PARTITIONING, SEASONAL WATER CONSUMPTION AND GAS-EXCHANGE OF PACLOBUTRAZOL GROWTH-CONTROLLED APPLE TREES

One-year-old, potted apple trees cv.
Golden Delicious growing under strict moisture control were treated with paclobutrazol.
The dose rates were: 100 mg/plant applied as soil drench in May, and 50 + 50 mg/plant and 25 + 25 mg/plant both applied as foliar spray in May and June.
Results showed that season-long growth control of shoots was correlated with leaf area, water input and CO₂ uptake.
The overall water intake per plant was found to be lower in the treated plants but higher on a dry matter basis, especially for the soil-drench treated plants in which shoot growth was completely arrested.

Leaf transpiration and CO₂ uptake were higher in the treated plants in the first part of the growing season and dropped to the level of control about 50 days following application.
This was probably due to the early leaf senescence of the arrested shoots, as stomatal resistance was higher in the soil-drench plant.

The apparently higher efficiency of the treated plants in general was offset by a lower water efficiency and by a depletion of stored starch in the two-year-old branches.
At the end of the season, the leaf contents of Ca and Mg were especially high in the soil-drench plants.

VI International Symposium on Growth Regulators in Fruit Production

R. Bonomo, D. Neri, S. Sansavini

https://doi.org/10.17660/ActaHortic.1989.239.21