Chap 38

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Angiosperm reproduction. The dominant sporophyte produces spores that develop within flowers into male gametophytes (pollen grains) and female gametophytes (embryo sacs).

A complete flower haa all four basic floral organs. A perfect flower contains both male and female structures.

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Double fertilization. Each ovule develops into a seed enclosed by a protective seed coat derived from the integument. The ovary develops into a fruit enclosing the seed(s).
In many dicots, the food reserves of the endosperm are completely exported to the cotyledons.

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The development of a eudicot plant embryo. By the time the ovule becomes a mature seed and the integuments harden and thicken to form the seed coat, the zygote has given rise to an embryonic plant with rudimentary organs.

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Developmental origin of fruits.

Simple fruit. A simple fruit develops from a single carpel (or several fused carpels) of one flower (examples: pea, lemon, peanut). Aggregate fruit. An aggregate fruit develops from many separate carpels of one flower (examples: raspberry, blackberry, strawberry). Multiple fruit. A multiple fruit develops from many carpels of many flowers (examples: pineapple, fig).

Developmental origin of fruits.
Simple fruit. A simple fruit develops from a single carpel (or several fused carpels) of one flower (examples: pea, lemon, peanut).		Aggregate fruit. An aggregate fruit develops from many separate carpels of one flower (examples: raspberry, blackberry, strawberry).		Multiple fruit. A multiple fruit develops from many carpels of many flowers (examples: pineapple, fig).

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Gametophyte Development and Pollination.

A microsporocyte in a microsporangium umdergoes meiosis to priduce 4 haploid microspores, which mature into pollen grains each containing a generative cell and a tube cell.
A megasporocyte in an ovule umdergoes meiosis to priduce 4 haploid cells, one of which survives as the megaspore, which matures into a multicellular embryo sac contaning one egg cell and two polar nuclei.

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Dicot germination. The radicle (embryonic root) is the first organ to emerge from the germinating seed.
A hook forms in the hypocotyl, and growth pushes the hook with the attached cotyledons and epicotyl above ground. This action protects the delicate shoot tip as it emerges from the soil.

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Monocot germination. The coleoptile, which protects the young leaves, pushes upward through the soil and into the air.

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Growth of the pollen tube.
A tube cell in the pollen grain produces a pollen tube.
Two sperm produced by the generative cell travel down the pollen tube into the ovary.

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Rafflesia arnoldii, “monster flower” of Indonesia. The world's largest flower (the size of an automobile tire) takes several months to develop the bud while the parasitic plant obtains nutrients within the woody tissue of a Tetrastigma vine. <~-- A single female flower may produce up to 4 million seeds. --> The flower attracts carrion flies as pollinators with an odor reminiscent of a decaying corpse.

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Seed structure.

Eudicots have two cotyledons (seed leaves).

The radicle is the embryonic root.
The epicotyl consists of the shoot tip with a pair of miniature leaves.
The hypocotyl lies underneath, and will pull the cotyledons out of the soil during germination.

Monocots in the grass family have a thin cotyledon called a scutellum.

Monocots also have a coleoptile to protect the shoot, and a coleorhiza to protect the root.

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“Pin” and “thrum” flower types reduce self-fertilization. Some species produce two types of flowers: “pins,” which have long styles and short stamens, and “thrums,” which have short styles and long stamens. An insect foraging for nectar would collect pollen on different parts of its body; pin pollen would be deposited on thrum stigmas, and vice versa.

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Variations in floral structure.

Symmetry. In bilateral symmetry, the flower can be divided into two equal parts by a single imaginary plane. In radial symmetry, the floral organs radiate out from a center. Ovary Position. A superior ovary is located above the stamens, petals, and sepals; an inferior ovary is located below them. Floral Distribution. Some flowers are clustered into an inflorescence. A sunflower is a composite flower composed of many disk and ray flowers.

Variations in floral structure.
Symmetry. In bilateral symmetry, the flower can be divided into two equal parts by a single imaginary plane. In radial symmetry, the floral organs radiate out from a center.	Ovary Position. A superior ovary is located above the stamens, petals, and sepals; an inferior ovary is located below them.	Floral Distribution. Some flowers are clustered into an inflorescence. A sunflower is a composite flower composed of many disk and ray flowers.

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Variations in reproduction. FLowers that have only functional stamens are staminate; those with only functional carpels are carpellate (or pistillate - a pistil consists of one or more carpels). A dioecious plant has staminate and carpellate flowers on separate plants. A monoecious plant has both reproductive structures on the same individual.