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Fruit Development Stages and Factors that Influence Size
- 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
- 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 FruitsReceptacle & 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 this or this 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
- 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 Cultivar or Leaf:Fruit Leaf Area Fruit Species Ratio (cm2 )/Fruit Volume (cm3 ) 10 171 131.4 20 372 167.4 Golden Delicious Apple 30 585 225.5 40 812 227.2 50 965 228.3 10 438 68.7 20 877 89.8 Elberta Peach 30 1316 90.7 40 1754 110.1 50 2199 119.4 75 3300 133.8
- 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 (GAx) 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
- 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
- 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