Physiology Forum

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Physiology Forum

• Phillip Joy
• Kathy Pickle

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Effects of Delayed Fruit Harvest on Pn, E, and
Nutrient Remobilization of Apple Leaves

• Tartachnyk, I.I. and Blanke, M.M.
• New Phytologist 2004
• Vol. 164 441-450

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Apple Physiology

• Dominant sinks for photoassimilates are the fruit
• Enhancement of Pn E by fruit load
• After harvest
• Trees remobilize C N from leaves to woody parts
• Stored over winter and may affect flowering and
  fruit set in subsequent year

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Research Hypothesis
Fruit left on trees may enhance photosynthesis
(Pn) and transpiration (E) under possibly
restricting environmental conditions in autumn
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Research Methodology

• Trees with similar shape and fruit load used
• Two treatments
• Commercial harvest of Oct 14
• Delayed harvest by six weeks
• Measurements taken
• Pn
• E
• Chlorophyll fluorescence
• Leaf coloration
• Nutrient remobilization

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Research Results

• Pn decreased
• 44 in still-fruiting trees
• 66 in harvested trees
• Indicates that fruit presence on tress enhance
  apple leaf PN
• E unaffected by fruit presence
• Indicates that the promoting effect of fruit on
  Pn is non-stomatal enhancement.

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Research Results

• 2 week delay in chlorophyll degradation of still
  fruiting trees
• Decrease in total chlorophyll (a b)
• Anthocyanin absent from still fruiting trees
• Earlier start of leaf senescence of harvested
  trees

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Nutrient Remobilization

• Total leaf carbohydrate increased after harvest
• May indicate slower translocation of C from
  leaves to roots
• Delayed translocation of N, P, K in trees with
  fruit present
• Leaf Ca Mg not affected

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Research Conclusion

• Presence of fruit
• Increased
• Pn
• RUBISCO activity
• Photochemical efficiency
• Leaf longevity
• Decreased
• Leaf chlorophyll degradation
• Translocation of N, P, K
• Senescence

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