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Flowers & Fruits Rosaceae-1

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We will use the Rose Family to explore some important variations in flower structure and relate these to fruit types. This family is one of the most important fruit-producing taxa, and most of its commercial fruits are well known. The most common examples of this taxon do not grow in the tropics. However, some ornamental roses can be grown in Hawaii. Oriental Hawthorn is a common ornamental that grows here as well.

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Oriental Hawthorn (Raphiolepsis umbellatus)

The Genus Rubus includes blackberries and raspberries. There is a native Rubus species that is being displaced by an alien race and this is an area of concern for Conservation Biologists.

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A] This Rubus flower has Five Petals, Many Stamens & Many Simple Carpels in its Apocarpous Gynoecium

B]  Close-up showing the Androecium & GynoeciumRubudAndroGynoLab.jpg (67145 bytes)

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C] Another species with relatively large Carpels. The Stigma is readily visible for each Carpel. Note the Green Sepals.RubusBudMicroLSLab.jpg (73868 bytes)
D] Microscopic Image of a Rubus Flower Bud. Relate this to all of the macrophotos to the Right! WB01570_.gif (184 bytes)

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E] Rubus flower post pollination. The Ovary of each Carpel is swollen due to successful fertilization. Note the withered Stigmas & Styles.

 

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F] Long Section through a Fragaria (Strawberry) flower: Compare with the Image to the Left
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G] Rubus, the Finished Product
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H] A closer inspection reveals the fact that the fruit is composed of many fruitlets that developed from each simple carpel. This is an Aggregate Fruit.
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Strawberry is in the genus Frageria. The flower structure is nearly identical to Rubus at the outset. However, it is the Receptacle of Frageria which becomes fleshy and is regarded as the "fruit". The carpels become tiny dry indehiscent fruits called Achenes.

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Long section through a  Frageria Flower

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Long section through a flower bud

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High magnification showing part of the Gynoecium

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Strawberry Fruits: The bulk of this Accessory Fruit is derived from the swollen Receptacle. The true fruits are the tiny, seed-like achenes on the surface.

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Close-up of a Strawberry Fruit

This is a type of "Accessory Fruit" because other Tissues besides those of the Ovary wall are part of the fruit.

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