ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
KEY PROCESSES IN LEAF SENESCENCE OF FRUITING APPLE TREES |
| Authors: | I. Tartachnyk, M. Blanke |
| Keywords: | apple (Malus domestica Borkh.), carbohydrates, chlorophyll, minerals, nitrogen, photosynthesis, source-sink, stomata, transpiration |
| Abstract:
The aim of this work was to study key processes of autumnal leaf senescence of apple trees after commercial harvest date. Changes in source-sink relationships and environmental effects on leaf senescence were evaluated with the following results: 1)The photosynthetic potential of the senescing apple leaves remained high at 8-14 μmol CO2 m-2 s-1 after the commercial harvest date. 2) Delayed harvest enhanced autumn leaf photosynthesis due to larger in vivo RUBISCO activity in comparison with trees harvested at the commercial harvest date. Therein, transpiration was not affected by fruit harvest and stomata did not limit leaf photosynthesis. 3) Maximum photochemical efficiency Fv/Fm of PS II of senescing apple leaves also remained at the optimum level of 0.80 for the first few weeks after commercial harvest date. The subsequent decrease in the photochemical efficiency was delayed in trees still bearing fruit. 4) Chlorophyll degradation was delayed in apple leaves of trees where harvest was delayed for six weeks. 5) Nitrogen content declined more rapidly in the leaves of apple trees harvested at the commercial date, an indication of earlier onset of senescence and more rapid remobilization to the woody, perennial parts of the tree. In conclusion, the combined environmental factors and the time of fruit harvest determined the rate of autumnal leaf senescence in terms of photosynthetic activity, chlorophyll breakdown and nitrogen translocation. | |
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