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35.2:

ืžื—ื–ื•ืจ ื”ื—ื™ื™ื ืฉืœ ืžื›ื•ืกื™ ื–ืจืข

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JoVE Core Biology
The Angiosperm Life Cycle

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ื‘ืขืœื™ ืคืจื—ื™ื ืงื‘ื•ืฆืช ื”ืฆืžื—ื™ื ื”ืžื’ื•ื•ื ืช ื‘ื™ื•ืชืจ ืขืœ ืคื ื™ ื›ื“ื•ืจ ื”ืืจืฅ ื›ื•ืœืœืช ืขืฆื™ื ืคื•ืจื—ื™ื ื•ืคื™ืจื•ืช, ืขืฉื‘ื™ื, ื™ืจืงื•ืช ื•ืฆืžื—ื™ื ืคื•ืจื—ื™ื ืื—ืจื™ื ืžื—ื–ื•ืจ ื”ื—ื™ื™ื ืฉืœ ื‘ืขืœื™ ืคืจื—ื™ื ื ืฉืœื˜ ืขืœ ื™ื“ื™ ืฉืœื‘ ื”ืกืคื•ืจื•ืคื™ื˜ ื”ืžื™ื™ืฆืจ ื ื‘ื’ื™ื, ื•ืœื ืฉืœื‘ ื”ื’ืžื˜ื•ืคื™ื˜ื™ื ื”ืžื™ื ื™ื™ื. ื›ืžื• ืžื—ื˜ื ืื™ื, ื‘ืขืœื™ ืคืจื—ื™ื ืžื™ื™ืฆืจื™ื ืฉื ื™ ืกื•ื’ื™ื ืฉืœ ื ื‘ื’ื™ื. ื’ืžื˜ื•ืช ื–ื›ืจื™ื•ืช ื•ื ืงื‘ื™ื•ืช ืืœื” ืžื™ื•ืฆืจื•ืช ื‘ืื™ื‘ืจื™ ืคืจื—ื™ื ืจื‘ื™ื™ื” ืžื•ื‘ื—ื ื™ื.ืžื’ื” ื ื’ื‘ื™ื ืžื™ื•ืฆืจื™ื ื‘ืขืœื” ืฉื—ืœื”. ืขืœื” ืฉื—ืœื” ื›ื•ืœืœ ืฉื—ืœื” ื•ื‘ื™ืฆื™ื•ืชื™ื•. ื›ืœ ื‘ื™ืฆื™ืช ืžื›ื™ืœื” ืžื’ื” ืžื ื’ื‘, ื‘ื• ืžื™ื™ืฆืจื™ื ืžื’ื” ื ื’ื‘ื™ื ื‘ืชื•ืš ื›ืœ ืžื’ื” ืžื ื’ื‘ ื ืžืฆื ืžื’ืกืคื•ืจื•ืฆื™ื˜ ืชื ืื ืฉืœ ืžื’ื” ื ื’ื‘.ืžื’ืกืคื•ืจื•ืฆื™ื˜ ืžื™ื™ืฆืจ ืืจื‘ืข ืžื’ื” ืžื’ื” ื ื’ื‘ื™ื ื‘ืืžืฆืขื•ืช ืžื™ื•ื–ื”;ืื—ื“ ืฉื•ืจื“ ื•ืžืชืคืชื— ืœืฉืง ืขื•ื‘ืจ ื”ืžื•ืจื›ื‘ ืžื‘ื™ืฆื™ืช ื•ืžืกืคืจ ืงื˜ืŸ ืฉืœ ืชืื™ื ืื—ืจื™ื. ืžืงื•ืจื ืฉืœ ื”ืžื™ืงืจื•-ื ื’ื‘ื™ื ื‘ืžืื‘ืง ื”ืคืจื—ื™ื ื‘ืงืฆื•ืช ื”ืื‘ืงื ื™ื. ื‘ืชื•ืš ื”ืžืื‘ืงื™ื ื ืžืฆืื™ื ืžื™ืงืจื•-ืžื ื’ื‘ ื”ืžื›ื™ืœื™ื ืžื™ืงืจื•ืกืคื•ืจื•ืฆื™ื˜ื™ื.ืžื™ืงืจื•ืกืคื•ืจื•ืฆื™ื˜ื™ื ืžื™ื™ืฆืจื™ื ืžื™ืงืจื•-ื ื’ื‘ื™ื ื‘ืืžืฆืขื•ืช ืžื™ื•ื–ื”. ื”ืžื™ืงืจื•-ื ื’ื‘ ืžืชืคืชื— ืœื“ื’ืŸ ืื‘ืงื” ื”ืžื›ื™ืœ ืชื ืฆื™ื ื•ืจ ื•ืชื ื’ื ืจืื˜ื™ื‘ื™. ืœืื—ืจ ืฉื”ืื‘ืงื” ืžื’ื™ืขื” ืœืฆืœืงืช ื”ื—ืœืง ื”ืขืœื™ื•ืŸ ืฉืœ ืขืœื” ื’ื‘ื™ืข-ืชื ื”ืฆื™ื ื•ืจ ื”ื•ืคืš ืœืฆื™ื ื•ืจ ืื‘ืงื”.ืฆื™ื ื•ืจ ื”ืื‘ืงื” ืžืฉืชืจืข ืœืื•ืจืš ืขืœื” ื’ื‘ื™ืข ืืœ ื”ื‘ื™ืฆื™ืช, ื”ืžื›ื™ืœ ืืช ืฉืง ื”ืขื•ื‘ืจ. ื”ืชื ื”ื’ื ืจืื˜ื™ ืžืชื—ืœืง ืื– ื›ื“ื™ ืœื™ืฆื•ืจ ืฉื ื™ ืกื•ื’ื™ ื–ืจืข ื–ืจืข ืืœื” ืžืฉืชื—ืจืจื™ื ื™ื—ื“ ืœื‘ื™ืฆื™ืช ืื—ืช, ื‘ืคืขื•ืœื” ืฉืœ ื”ืคืจื™ื” ื›ืคื•ืœื”. ื”ืื—ื“ ืžืคืจื” ืืช ื”ื‘ื™ืฆื™ืช ื•ื”ืฉื ื™ ืžืคืจื” ืืช ื”ืชื ื”ืžืจื›ื–ื™ ืฉืœ ืฉืง ื”ืขื•ื‘ืจ.ืœืื—ืจ ืžื›ืŸ ื”ื‘ื™ืฆื™ืช ื”ืžื•ืคืจื™ืช ื™ื•ืฆืจืช ื–ื™ื’ื•ื˜ื” ืฉืชืชืคืชื— ืœืขื•ื‘ืจ. ื”ืชื ื”ืžืจื›ื–ื™ ื”ืžื•ืคืจื” ืžื”ื•ื•ื” ืืช ื”ืื ื“ื•ืกืคืจื ืžื‘ื ื” ืื’ื™ืจืช ื—ื•ืžืจื™ ืžื–ื•ืŸ. ื”ืขื•ื‘ืจ ื•ืื ื“ื•ืกืคืจื ื ืืจื–ื™ื ื‘ื–ืจืข.ื‘ืžืงืจื” ืฉืœ ื‘ืขืœื™ ืคืจื—ื™ื ืจื‘ื•ืช, ื”ืฉื—ืœื” ืžืชืคืชื—ืช ืœืคืจื™ ื”ืžื›ื™ืœ ื‘ื“ืจืš ื›ืœืœ ืจื™ื‘ื•ื™ ื–ืจืขื™ื, ืื• ื‘ื™ืฆื™ื•ืช ืžื•ืคืจื•ืช. ื”ืคืจื™ ืœื•ื‘ืฉ ืฆื•ืจื•ืช ืืคืฉืจื™ื•ืช ืจื‘ื•ืช, ื‘ื“ืจืš ื›ืœืœ ื‘ื”ืชืื ืœืžื™ืŸ ืœืขื™ืชื™ื ื ืจืื” ื“ื•ืžื” ืžืื•ื“ ืœืฉื—ืœื” ื”ืžืงื•ืจื™ืช ื•ื‘ืคืขืžื™ื ืื—ืจื•ืช ืžื’ื™ื™ืก ืจืงืžื•ืช ื ื•ืกืคื•ืช ืื• ืžื—ื‘ืจ ื™ื—ื“ ื›ืžื” ืžื‘ื ื™ื ืคื•ืจื—ื™ื ืœื™ืฆื™ืจืช ืคื™ืจื•ืช ืงื•ืœืงื˜ื™ื‘ื™ื™ื. ืœื‘ืกื•ืฃ, ื–ืจืข ืฉื ื‘ื˜ ืžืชืคืชื— ืœืกืคื•ืจื•ืคื™ื˜ ื‘ื•ื’ืจ, ืฉื™ื›ื•ืœ ืœื™ื™ืฆืจ ืคืจื—ื™ื ื•ืœื”ืชื—ื™ืœ ืžื—ื–ื•ืจ ื—ื™ื™ื ื ื•ืกืฃ.

35.2:

ืžื—ื–ื•ืจ ื”ื—ื™ื™ื ืฉืœ ืžื›ื•ืกื™ ื–ืจืข

Plants have a life cycle split between two multicellular stages: a haploid stage—with cells containing one set of chromosomes—and a diploid stage—with cells containing two sets of chromosomes. The haploid stage is the gamete-producing gametophyte, and the diploid stage is the spore-producing sporophyte.

Today, most plants grow from seeds and produce flowers and fruit; such plants are called angiosperms. Angiosperms begin as seeds—structures consisting of a protective seed coat, a nutrient supply, and an embryo. The seed develops into a sporophyte—the familiar, flower-producing plant form.

The reproductive life cycle of angiosperms begins with flowering. Stamens and carpels contain sporangia, structures with spore-producing cells called sporocytes. Sporophytes produce spores as either eggs or sperm, depending on their origin.

For example, male spores—called microspores—are produced within anthers at the tips of stamens. A microspore develops into a pollen grain—the male gametophyte. A pollen grain contains a tube cell and a generative cell, which develops into sperm.

A carpel consists of an ovary and its ovules. Female spores, called megaspores, are produced within ovules. A megaspore develops into an embryo sac—the female gametophyte—which contains the egg.

Pollination allows the sperm-producing pollen grain to reach the egg-containing embryo sac. While the embryo sac is stationary, pollen grains can be carried by wind, water, or animals.

For sperm to fertilize an egg, pollen released from the anthers must reach the sticky stigma at the tip of a carpel. Then, the tube cell of the pollen grain becomes a pollen tube, extending down the carpel to the ovule.

Angiosperms undergo a type of double fertilization that produces an embryo and an endosperm, a nutrient store. The embryo and endosperm are packed into a seed coat, forming a seed. As the ovules become seeds, the ovary typically develops into fruit that helps protect and distribute the seeds.

Suggested Reading

Bleckmann, Andrea, Svenja Alter, and Thomas Dresselhaus. 2014. “The Beginning of a Seed: Regulatory Mechanisms of Double Fertilization.” Frontiers in Plant Science 5 (November). [Source]

Endress, P. K. 2011. “Angiosperm Ovules: Diversity, Development, Evolution.” Annals of Botany 107 (9): 1465–89. [Source]