Abstract
BACKGROUND AND AIMS: The xylem in fruit of a number of species becomes dysfunctional as the fruit develops, resulting in a reduction of xylem inflow to the fruit. Such a reduction may have consequential effects on the mineral balance of the fruit. The aim of this study was to elucidate the dynamics and nature of xylem failure in developing apples (Malus domestica) showing differing susceptibilities to bitter pit, a calcium-related disorder. METHODS: Developmental changes in xylem functionality of the fruit were investigated in "Braeburn" and "Granny Smith" apples by using a dye infusion technique, to stain the vasculature along the path of dye movement. The vascular bundles were clearly visible in transverse section when fruit were sectioned equatorially. The intensity of staining of the vascular bundles in the fruit was recorded at regular intervals throughout the season. Tissue containing dysfunctional bundles was fixed and embedded in wax for subsequent sectioning and examination. KEY RESULTS: As the season progressed, an increasing proportion of vascular bundles failed to show any staining, with the most marked change occurring in the primary bundles, and in nearly all bundles with increasing distance from the stalk end of the fruit. Decreased conductance in the primary bundles of "Braeburn" occurred earlier than in "Granny Smith". Microscopy revealed that the xylem in vascular bundles of the fruit suffered substantial damage, indicating that the mode of dysfunction was via the physical disruption of the xylem caused by expansion of the flesh. CONCLUSIONS: Results support the view that the relative calcium deficiency of apple fruit is due to a progressive breakdown of xylem conductance caused by growth-induced damage to the xylem strand in the bundle. The earlier onset of xylem dysfunction in the cultivar more susceptible to bitter pit suggests that the relative growth dynamics of the fruit may control the occurrence of calcium-related disorders.
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Claims 8
Claim · model-written summary
An increasing share of apple fruit vascular bundles failed to stain as the season progressed.
- Taxon
- Apple
Malus domesticat0 - Organ / stage
- vascular bundlese0
- Outcome
- proportion of vascular bundles failed to show any staininge0
- Direction
- increasinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple Fruit”
e0“As the season progressed, an increasing proportion of vascular bundles failed to show any staining”
Claim · model-written summary
The largest seasonal loss of staining occurred in primary bundles.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- primary bundlese0
- Outcome
- most marked changee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple Fruit”
e0“the most marked change occurring in the primary bundles”
Claim · model-written summary
Bundle failure increased with distance from the stalk end of apple fruit.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- bundlese0
- Outcome
- bundlese0
- Direction
- increasinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple Fruit”
e0“in nearly all bundles with increasing distance from the stalk end of the fruit”
Claim · model-written summary
Primary bundle conductance decreased earlier in Braeburn than Granny Smith apples.
- Taxon
- AppleMalus domesticat0
- Material
- "Braeburn"e0
- Organ / stage
- primary bundlese0
- Outcome
- conductancee0
- Direction
- Decreasede0
- Comparator
- "Granny Smith"e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple Fruit”
e0“Decreased conductance in the primary bundles of "Braeburn" occurred earlier than in "Granny Smith"”
Claim · model-written summary
Apple fruit vascular bundle xylem showed substantial damage.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- xylem in vascular bundlese0
- Outcome
- substantial damagee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple Fruit”
e0“the xylem in vascular bundles of the fruit suffered substantial damage”
Claim · model-written summary
The authors attribute xylem dysfunction to physical disruption caused by flesh expansion.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- xyleme0
- Outcome
- dysfunctione0
- Qualifier
- expansion of the fleshe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple Fruit”
e0“the mode of dysfunction was via the physical disruption of the xylem caused by expansion of the flesh”
Claim · model-written summary
The authors attribute relative apple fruit calcium deficiency to progressive xylem conductance breakdown caused by growth damage.
- Taxon
- appleMalus domesticae0
- Organ / stage
- xylem strand in the bundlee0
- Outcome
- relative calcium deficiencye0
- Qualifier
- growth-induced damagee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“relative calcium deficiency of apple fruit is due to a progressive breakdown of xylem conductance caused by growth-induced damage to the xylem strand in the bundle”
Claim · model-written summary
Earlier xylem dysfunction in the cultivar more prone to bitter pit suggests fruit growth dynamics may control calcium-related disorders.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- fruite0
- Outcome
- occurrence of calcium-related disorderse0
- Qualifier
- relative growth dynamicse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple Fruit”
e0“The earlier onset of xylem dysfunction in the cultivar more susceptible to bitter pit suggests that the relative growth dynamics of the fruit may control the occurrence of calcium-related disorders”