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Short Video: Flowering Plant Life Cycle

by Pearson
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This video shows the growth and reproduction of a mustard plant, Brassica rapa, sped up 12,000 times. The seeds of flowering plants contain a young embryo and stored food to fuel the early stages of growth. In Brassica rapa seeds, the food is stored in two cotyledons, or "seed leaves," which emerge first from the ground and quickly become photosynthetic. As growth progresses, the stem elongates and more leaves are produced. The appearance of flower buds signifies that the plant is about to engage in sexual reproduction. Meiosis produces two types of spores within the flower: microspores are produced in the anther sacs, and megaspores are formed in structures called ovules. Ovules are found inside the base of the carpel in a region called the ovary. Both the microspores and megaspores undergo mitotic cell divisions to produce small, multicellular organisms called gametophytes. The microspores develop into pollen grains, each containing a male gametophyte, whereas the megaspores develop into female gametophytes. At maturity the male gametophyte produces two sperm cells, and the female gametophyte produces one egg cell. Pollination occurs when some agent moves pollen grains from the anther to the stigma. In this video, a small black brush is the pollinator. Now the sperm from a pollen grain can reach the egg cell through a pollen tube that is produced by the pollen grain, allowing double fertilization to occur. One sperm combines with two nuclei called the polar nuclei in the female gametophyte, forming a triploid nucleus that gives rise to a transient storage tissue in the seed called the endosperm. In Brassica rapa, the developing embryo of the maturing seed consumes nearly all of the energy stored in the endosperm. The other sperm combines with the egg cell of the female gametophyte, forming a zygote that in turn will form the seed embryo by mitosis. As the seeds develop, the ovary enlarges to form a fruit that protects the developing seeds. During fruit enlargement, the petals fall off and the stamens wither. In annual plants, such as Brassica rapa, the energy of the entire plant is diverted to the developing fruits and seeds, and the plant turns brown. After the fruits turn brown and dry out, they split open and release the seeds. Credit: Courtesy of Graham R. Kent and Rebecca L. Turner, Smith College.
This video shows the growth and reproduction of a mustard plant, Brassica rapa, sped up 12,000 times. The seeds of flowering plants contain a young embryo and stored food to fuel the early stages of growth. In Brassica rapa seeds, the food is stored in two cotyledons, or "seed leaves," which emerge first from the ground and quickly become photosynthetic. As growth progresses, the stem elongates and more leaves are produced. The appearance of flower buds signifies that the plant is about to engage in sexual reproduction. Meiosis produces two types of spores within the flower: microspores are produced in the anther sacs, and megaspores are formed in structures called ovules. Ovules are found inside the base of the carpel in a region called the ovary. Both the microspores and megaspores undergo mitotic cell divisions to produce small, multicellular organisms called gametophytes. The microspores develop into pollen grains, each containing a male gametophyte, whereas the megaspores develop into female gametophytes. At maturity the male gametophyte produces two sperm cells, and the female gametophyte produces one egg cell. Pollination occurs when some agent moves pollen grains from the anther to the stigma. In this video, a small black brush is the pollinator. Now the sperm from a pollen grain can reach the egg cell through a pollen tube that is produced by the pollen grain, allowing double fertilization to occur. One sperm combines with two nuclei called the polar nuclei in the female gametophyte, forming a triploid nucleus that gives rise to a transient storage tissue in the seed called the endosperm. In Brassica rapa, the developing embryo of the maturing seed consumes nearly all of the energy stored in the endosperm. The other sperm combines with the egg cell of the female gametophyte, forming a zygote that in turn will form the seed embryo by mitosis. As the seeds develop, the ovary enlarges to form a fruit that protects the developing seeds. During fruit enlargement, the petals fall off and the stamens wither. In annual plants, such as Brassica rapa, the energy of the entire plant is diverted to the developing fruits and seeds, and the plant turns brown. After the fruits turn brown and dry out, they split open and release the seeds. Credit: Courtesy of Graham R. Kent and Rebecca L. Turner, Smith College.