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Causes and effects of changes in xylem functionality in apple fruit
Lazar Drazeta1, Alexander Lang, Alistair J Hall
1HortResearch, Palmerston North Research Centre, Private Bag 11 030, Palmerston North, New Zealand.
Annals of Botany
|February 28, 2004
Summary
Xylem failure in apples (Malus domestica) increases with fruit development, leading to reduced mineral uptake. This breakdown, caused by flesh expansion, is linked to bitter pit disorder, especially in susceptible cultivars.
Area of Science:
- Plant Physiology
- Horticultural Science
- Fruit Development Biology
Background:
- Xylem in developing fruits often becomes dysfunctional, reducing nutrient inflow.
- This dysfunction can impact fruit mineral balance, potentially causing disorders like bitter pit.
- Apple (Malus domestica) bitter pit is a calcium-related disorder linked to xylem function.
Purpose of the Study:
- To investigate the dynamics and nature of xylem failure in developing apples.
- To compare xylem dysfunction in apple cultivars with differing bitter pit susceptibilities.
Main Methods:
- Dye infusion technique used to visualize and assess xylem functionality in 'Braeburn' and 'Granny Smith' apples.
- Quantification of vascular bundle staining intensity throughout fruit development.
- Microscopic examination of dysfunctional xylem tissue.
Main Results:
- Increasing proportion of vascular bundles showed dysfunction as the season progressed, particularly in primary bundles and further from the stalk.
- Xylem dysfunction occurred earlier in 'Braeburn' apples compared to 'Granny Smith'.
- Microscopy revealed physical disruption of xylem due to flesh expansion as the cause of dysfunction.
Conclusions:
- Progressive xylem breakdown, caused by growth-induced damage, leads to relative calcium deficiency in apple fruit.
- Earlier xylem dysfunction in susceptible cultivars suggests fruit growth dynamics influence calcium-related disorders.
- Understanding xylem failure mechanisms is crucial for managing bitter pit in apples.
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