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Fruits Development

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  • 1. Fruits - Fruit Development
  • 2. Objectives
    • To learn how fruits develop
    • Consider the factors that influence fruit growth
    • Consider how horticulturists influence the growth and development of fruits
    • Learn about “ripening” - final stage of fruit development
  • 3. What is a fruit?
    • Botanically, a fruit is :
      • one or more mature ovaries together with accessory tissues
    • Horticulturally, a fruit is:
      • one or more mature ovaries together with accessory tissues that is relatively high in sugar content and, functionally, is usually eaten during the dessert portion of a meal, or as a sweet salad or snack
  • 4. Flower structure that leads to fruit structure
    • Ovary Position
    • Multiple Separate Ovaries Per Flower
    • Multiple Flowers
  • 5. Ovary Position Grape Apple
  • 6.
    • Superior (above)
      • Example:
        • Grape
        • results in a berry fruit (primarily ovary tissue)
    Ovary Position
  • 7.
    • Inferior (below)
      • Example:
        • Apple
        • results in a pome fruit (primarily receptacle tissue)
    Ovary Position
  • 8. Multiple Ovaries per Flower Whole Flower Cross Section Of Flower Whole Fruit Multiple Ovaries
  • 9. Multiple Ovaries per Flower
    • Example:
      • Blackberry
      • results in an Aggregate Fruit
      • Includes receptacle tissue
      • (Raspberry does not include receptacle tissue)
  • 10. Multiple Flowers Pineapple Inflorescence Receptacle & ovaries develop into fruit Flowers
  • 11. Multiple Flowers
    • Example:
      • Pineapple
      • results in a Multiple Fruit (primarily ovary tissue fused together)
    Individual Berry-like Fruits Receptacle & ovaries develop into fruit
  • 12. Ovary Wall Structure
    • Pericarp
      • Exocarp (outer layer)
      • Mesocarp (middle layer)
      • Endocarp (inner layer)
    • Examples:
      • All 3 fleshy - berry
      • Endocarp stony - drupe
      • All 3 hard - nut
    Seed(s)
  • 13. Factors that affect fruit size
    • Number of cells per fruit
    • Number of leaves per fruit
    • Intra-plant competition for photosynthate
    • Seed formation
  • 14. Fruit Growth Stages (after pollination & fertilization)
    • Cell Division
      • (to increase the number of cells in the fruit)
    • Cell Expansion
      • (to increase the fruit to mature size)
    • Ripening
  • 15. Fruit Growth Pattern Fruit Fresh Weight Time Pollination/ Fertilization Cell Division Period Cell Expansion Period Ripening Period Maturity (Full sized fruit)
  • 16. Fruit Growth Pattern
    • Cell Division
      • Sets potential for ultimate size of fruit
    • Cell Expansion
      • Achieves mature size
    Fruit Fresh Weight Time Pollination/ Fertilization Cell Division Period Cell Expansion Period Ripening Period After this point, there will not be any more cells in this fruit
  • 17. Number of Cells per Fruit Cell Division 4 cells 9 cells Limits the Potential for Fruit Size 1 cell 1 cell Each cell can only get so big, so how many cells matters! Each single cell from mitosis Only has the potential to get to a specific maximum size this or this
  • 18. Factors that affect fruit size
    • Number of cells per fruit
    • Number of leaves per fruit
    • Intra-plant competition for photosynthate
    • Seed formation
  • 19. Number of Leaves per Fruit
    • Leaves are the sources of photosynthate (fixed carbon), developing fruits are the sinks for photosynthate
      • Source = supplier
      • Sink = user
    • More leaves per fruit means larger fruit (up to a point!)
  • 20. Leaves per Fruit Effect
  • 21. Factors that affect fruit size
    • Number of cells per fruit
    • Number of leaves per fruit
    • Intra-plant competition for photosynthate
    • Seed formation
  • 22. Intra-plant Competition
    • A whole-plant view of not enough leaves per fruit
    • Overall, too many fruits and too few leaves
    • Removing some fruits very early in their development can allow those that remain to increase in size
  • 23. How far can you go with reducing competition?
    • In apple, can you remove all but one fruit and grow that one remaining apple to be as big as, say, a watermelon?
  • 24. NO!
    • The basic genetics of the species will prevent it!
    • So, way too many leaves per fruit is a waste!
    • You reach a point of diminishing return!
  • 25. Factors that affect fruit size
    • Number of cells per fruit
    • Number of leaves per fruit
    • Intra-plant competition for photosynthate
    • Seed formation
  • 26. Seed Formation
    • Seed number & distribution (in multi-seeded fruits) affect fruit size.
    • Each developing seed sends a hormonal signal (auxin) that stimulates pericarp and/or receptacle development around or near it.
    • If few seeds develop, fruit will be mis-shapen; if too few develop, fruit will abort.
  • 27. Hormonal effect of seeds
    • In apple, each part of the ovary has two seeds. Their growth stimulates the receptacle and ovary tissue to develop. No seeds, little development
    Cross-section Longitudinal section Absence of seed development Absence of seed development Seed develop- ment Seed develop- ment
  • 28. Apple Seed No./Fruit Size
  • 29. Hormonal effect of seeds
    • In strawberry, each achene has one seed and stimulates the receptacle tissue to develop below it. Few achenes result in mis-shapen fruit!
    Normal, dozens of achenes One achene Three achenes
  • 30. The Exception!
    • Fruit can develop without any pollination or fertilization or seed development!
    • Called parthenocarpy
      • From: parthenos (Gr., maiden) carpic (Gr., fruit)
    • Examples: bananas, navel oranges, seedless grapes
  • 31. Other Hormone Effects
    • Fruit shape and size can be altered by application of hormones
      • Auxin or gibberellic acid (GA x )
    • Examples:
      • Thompson Seedless grapes (green) - larger
      • Red Delicious apples - more lobed
  • 32. A Horticultural Manipulation
    • Fruit thinning to increase fruit size
  • 33. Thinning the crop
    • Horticulturists thin (remove some young fruit) to increase leaf:fruit ratio and reduce intra-plant competition .
    • Timing of thinning is critical!
    • Thinning, to be effective, must be done early in the cell division phase of growth
    • After cell division is complete, the ultimate potential size of the fruit is set!
  • 34. When to thin, When its too late Fruit Fresh Weight Time Pollination/ Fertilization Cell Division Period Cell Expansion Period Ripening Period Maturity (Full sized fruit) THIN HERE TOO LATE but, WHY?
  • 35. Why thin before cell division?
    • Assume a branch of an apple tree with 10 flowers
    • Assume enough leaves on that branch to support cell division in the developing ovaries (fruits) to total10,000 cells on the branch
  • 36.
    • If all 10 fruits remain on the branch and go through cell division, each fruit will have 1000 cells
    • If fruit thinning (remove 5 apples = 1/2 of the fruit) occurs then (after cell division is done) the 5 remaining apples will each have only 1000 cells!
  • 37.
    • If the number of flowers begins at 10, but fruit number is thinned to 5 just as cell division begins, and then cell division procedes to its maximum of 10,000 cells total, each fruit will have 2000 cells!
    • So, Thinning:
      • after cell division: 5 fruits@1000 cells ea.
      • before cell division: 5 fruits@2000 cells ea.
  • 38. Number of Cells per Fruit Cell Division 4 cells 9 cells Limits the Potential for Fruit Size 1 cell 1 cell Each cell can only get so big, so how many cells matters! Each single cell from mitosis Only has the potential to get to a specific maximum size Or 1000 cells 2000 cells
  • 39. How is fruit thinning done?
    • Hormone sprays to trees shortly after “petal fall”
  • 40. Summary
    • Horticultural fruits are varied in structure.
    • Fruit development procedes in a definable pattern
    • Several factors in that development influence fruit size
    • Horticulturists use thinning in tree fruit crops to influence the final size of fruits