THE WATER RELATIONS OF ‘BRAEBURN’ APPLE FRUIT GROWN UNDER DEFICIT IRRIGATION

Three irrigation treatments were applied to ‘Braeburn’ apple trees, grown in lysimeters, to assess effects on fruit water relations and composition.
The treatments were: control (C) which was fully irrigated, early deficit (ED) which was deficit irrigated from 55 days after full bloom (DAFB) until re-watering at 100 DAFB, and late deficit (LD) which was deficit irrigated from 105 DAFB until 177 DAFB. Compared to C, the ED and LD trees had reduced leaf water potential (₁). Throughout the season fruit water potential (_fw), fruit osmotic potential (_fs), sugar composition, titratable acidity (TA), dry matter concentration and mineral concentrations were monitored.
The ED fruit showed a reduction in _fw, coupled with a similar reduction in _fs, during the stress period.
This resulted in the maintenance of turgor (_ft). Increased sugar concentration in the ED fruit during the stress period appeared to account for at least part of the reduction in _fs. Despite the maintenance of _ft, fruit weight was reduced in ED fruit during the stress period.
The LD fruit showed no change in fruit water relations compared to C. Fruit composition was similarly unaffected in LD. These data indicate that fruit water relations and composition are modified under an early-season but not a late-season water deficit.

II International Symposium on Irrigation of Horticultural Crops

T.M. Mills, B.E. Clothier, M.H. Behboudian

Fruit water relations, fruit composition, Malus domestica Borkh., sugars

https://doi.org/10.17660/ActaHortic.1997.449.54