ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
GAS EXCHANGE AND WATER RELATIONS IN 'FUJI' APPLE TREES GROWN UNDER DEFICIT IRRIGATION |
| Authors: | L. Lombardini, H.W. Caspari, D.C. Elfving, T.D. Auvil, J.R. McFerson |
| Keywords: | Malus x domestica, partial rootzone drying, regulated deficit irrigation, whole-canopy net gas exchange, leaf water potential, transpiration |
| DOI: | 10.17660/ActaHortic.2004.636.4 |
| Abstract:
The article describes the results from the first year (2001) of a study which was designed to investigate the effects of partial rootzone drying (PRD) and season-long deficit irrigation (DI) on growth and productivity of apple trees. Control trees were maintained at soil moisture close to field capacity. Both PRD and DI received 50% of the irrigation volume applied to the control but differed in placement of irrigation. With PRD, water was applied to only half the trees’ rootzones while the DI regime had the same wetted surface area as the control. By the end of the season, volumetric soil water content (θ) in the two deficit irrigation treatments was 0.10 m3·m-3 lower than in well-irrigated soil. Predawn and midday leaf water potential (ψ) and single leaf gas exchange were measured every 2-3 weeks. Differences among treatments in predawn ψ were statistically significant only 104 days after full bloom (DAFB), but on the other dates no significant differences were recorded. Significant differences in mean midday ψ data began to show 90 DAFB and continued throughout the season. Midday ψ in PRD trees was always 0.28-0.39 MPa lower than in control trees. Leaf net gas exchange in control trees was higher than in PRD trees 78, 109, and 120 DAFB. Whole-canopy net carbon exchange (NCER) was monitored three times throughout the season. In general, NCER data suggested that carbon assimilation in the DI and PRD treatments was lower than in well-irrigated trees. Fruit growth was not affected by DI, while it was reduced in PRD in late August and September. Fruit quality characteristics were not affected by the treatments, but fruit from trees grown under PRD irrigation were smaller than fruits from control and DI trees. | |
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