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34.3:

ืฆืžื—ื™ื ื•ืกืงื•ืœืจื™ื ื—ืกืจื™ ื–ืจืขื™ื

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Seedless Vascular Plants

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ื™ืฉื ืŸ ืฉืœื•ืฉ ืงื‘ื•ืฆื•ืช ืขื™ืงืจื™ื•ืช ื”ืžื›ืกื•ืช ืืช ื—ื™ื™ ื”ืฆื•ืžื— ืขืœ ืคื ื™ ื›ื“ื•ืจ ื”ืืจืฅ ืฆืžื—ื™ื ืœื-ื•ืกืงื•ืœืจื™ื™ื. ืฆืžื—ื™ื ื•ืกืงื•ืœืจื™ื™ื ื ื˜ื•ืœื™ ื–ืจืขื™ื ื•ืฆืžื—ื™-ื–ืจืขื™ื. ืฆืžื—ื™ื ื•ืกืงื•ืœืจื™ื™ื ื ื˜ื•ืœื™ ื–ืจืขื™ื ื”ื™ื• ื”ืจืืฉื•ื ื™ื ืฉื”ืชืคืชื—ื• ืžืขืจื›ื•ืช ื•ืกืงื•ืœืจื™ื•ืช ื”ืžืชืžื—ื•ืช ื”ืชืืžื” ืฉืขื–ืจื” ืœื”ื ืœื”ืคื•ืš ืœืฆืžื—ื™ื ื”ื’ื‘ื•ื”ื™ื ื”ืจืืฉื•ื ื™ื ื‘ื›ื“ื•ืจ ื”ืืจืฅ.ื›ื™ื•ื, ืฆืžื—ื™ื ื•ืกืงื•ืœืจื™ื™ื ื ื˜ื•ืœื™ ื–ืจืขื™ื ืžื™ื•ืฆื’ื™ื ืขืœ ื™ื“ื™ ืœื™ืงื•ืคื™ื˜ื™ื ื•ืžื•ื ื™ืœื•ืคื™ื˜ื™ื. ืœื™ืงื•ืคื™ื˜ื™ื ื›ื•ืœืœื™ื ืงืœื‘ืžื•ืกืก ืกืคื™ื™ืงืžื•ืกืก ื•ืงื™ืœื•ื•ืจื˜ืก, ืจืื•ื™ ืœืฆื™ื™ืŸ, ืฉืืฃ ืื—ื“ืžื”ืœื™ืงื•ืคื™ื˜ื™ื ืื™ื ื ื˜ื—ื‘ื™ ืขืœื™ื ืืžื™ืชื™ื™ื, ืฉื”ื ืฆืžื—ื™ื ืœื-ื•ืกืงื•ืœืจื™ื™ื. ืฉืจื›ืื™ื ื›ื•ืœืœื™ื ืฉืœื•ืฉื”, ืกื•ื’ื™ ืฉืจื›ื™ื ื•ืงืจื•ื‘ื™ื”ื.ื›ืžื• ื›ืœ ื”ืฆืžื—ื™ื, ืฆืžื—ื™ื ื•ืกืงื•ืœืจื™ื™ื ืœื ื˜ื•ืœื™ ื–ืจืขื™ื ืžืฆื™ื’ื™ื ื—ื™ืœื•ืคื™ ื“ื•ืจื•ืช ื‘ืžื—ื–ื•ืจ ื—ื™ื™ื”ื, ื›ืคื™ ืฉืžื•ืฆื’ ื›ืืŸ ื‘ืืžืฆืขื•ืช ืฆืžื— ืฉืจืš ื›ื“ื•ื’ืžื. ื”ืžืฉืžืขื•ืช ื”ื™ื ืฉื”ื ืžื‘ืœื™ื ื—ืœืง ืžืžื—ื–ื•ืจ ื—ื™ื™ื”ื ื›ื’ืžื˜ื•ืคื™ื˜ ื”ืคืœื•ืื™ื“ ื•ื”ื—ืœืง ื”ืฉื ื™ ื›ืกืคื•ืจื•ืคื™ื˜ ื“ื™ืคืœื•ืื™ื“ื™. ื‘ื“ื•ืžื” ืœืฆืžื—ื™ื ืฉืื™ื ื ื•ืกืงื•ืœืจื™ื™ื ื’ื ืฆืžื—ื™ ื•ืกืงื•ืœืจื™ื™ื ืžืชืจื‘ื™ื ื‘ืืžืฆืขื•ืช ื ื‘ื’ื™ื, ื•ืœื ื‘ืืžืฆืขื•ืช ื–ืจืขื™ื.ื”ื ื‘ื’ื™ ื”ื ื”ืคืœื•ืื™ื“ื™ื ื•ืžืคื•ื–ืจื™ื ืขืœ ื™ื“ื™ ืžื‘ื ื™ื ื‘ื”ื ืงืจืื™ื ืกื•ืจื™, ืžืงื•ื‘ืฆื™ื ืขืœ ื”ื—ืœืง ื”ืชื—ืชื•ืŸ ืฉืœ ื”ืขืœื™ื. ื”ืกื•ืจื™ ืขืฆืžื ืžื›ื™ืœื™ื ืกืคื•ืจื ื’ื™ื” ืจื‘ื•ืช. ืขื ื”ื’ื™ืขื ืœื‘ืฉืœื•ืช, ื”ืกืคื•ืจื ื’ื™ื•ืช ื”ืœืœื• ื ืคืชื—ื•ืช ื•ืžืคื–ืจื•ืช ืืช ื”ื ื‘ื’ื™ื ื”ืคืœื•ืื™ื“ื™ื.ื”ื ื‘ื’ื™ื ื’ื“ืœื™ื ืœืื—ืจ ืžื›ืŸ ื‘ืืžืฆืขื•ืช ืžื™ื˜ื•ื–ื” ื•ื™ื•ืฆืจื™ื ืืช ื”ื’ืžื˜ื•ืคื™ื˜ ื”ื”ืคืœื•ืื™ื“. ื‘ืฉืœื‘ ื”ื’ืžื˜ื•ืคื™ื˜ ืฉื”ื•ื ื‘ื“ืจืš ื›ืœืœ ืงื˜ืŸ ืžืื•ื“ ื•ื ืžืฆื ืขืœ ืคื ื™ ื”ืงืจืงืข ืื• ืžืžืฉ ืžืชื—ืช ืœืคื ื™ ื”ืฉื˜ื— ื ื•ืฆืจื™ื ื’ืžื˜ื™ื ื”ื”ืคืœื•ืื™ื“ื™ื ืขืœ ื™ื“ื™ ืžื™ื˜ื•ื–ื”. ื’ืžื˜ื•ืคื™ื˜ ื™ื—ื™ื“ ื”ื•ื ื“ื• ืžื™ื ื™ ื•ืžืคืชื— ืฉื ื™ ืžื‘ื ื™ื ืฉื•ื ื™ื ื”ืื ืชืจื™ื“ื™ื” ื•ื”ืืจื›ื’ื•ื ื™ื” ื”ืžื™ื™ืฆืจื™ื ื’ืžื˜ื•ืช ื‘ืฆื•ืจืช ื–ื›ืจ ื•ื ืงื‘ื” ื‘ื”ืชืืžื”.ื›ืžื• ื”ืฆืžื—ื™ื ื”ืœื-ื•ืกืงื•ืœืจื™ื™ื, ื’ืžื˜ ื”ื–ืจืข ื”ื–ื›ืจื™ ืžื ื•ืคื” ื•ื“ื•ืจืฉ ืžื™ื ื›ื“ื™ ืœื ืกื•ืข ืœื’ืžื˜ ื”ื ืงื‘ื” ื‘ืขืงื‘ื•ืช ืžื•ืฉืš ื›ื™ืžื™ ืœืžืฆื™ืืช ื”ื‘ื™ืฆื”. ืžื›ื™ื•ื•ืŸ ืฉื”ื’ืžื˜ื™ื ื‘ื’ืžื˜ื•ืคื™ื˜ ื‘ื•ื“ื“ ื™ื”ื™ื• ื–ื”ื™ื ื’ื ื˜ื™ืช ื‘ื’ืœืœ ืžื•ืฆืื ื”ื”ืคืœื•ืื™ื“, ื‘ื“ืจืš ื›ืœืœ ืžืชืจื—ืฉื™ื ื”ืฆืœื‘ื•ืช ื‘ื™ืŸ ื’ืžื˜ื•ืคื™ื˜ื™ื ืฉื•ื ื™ื. ืฉืจื›ื™ื ื™ื›ื•ืœื™ื ืœืžื ื•ืข ื›ืœ ื”ืคืจื™ื” ืขืฆืžื™ืช ืขืœ ื™ื“ื™ ื”ื‘ืืช ื‘ื’ืจื•ืช ื”ืื ืชืจื™ื“ื™ื•ืช ื•ื”ืืจื›ื’ื•ื ื™ื” ืฉืœื”ื ื‘ื–ืžื ื™ื ืฉื•ื ื™ื.ืœื‘ืกื•ืฃ, ื”ื‘ื™ืฆื” ื”ืžื•ืคืจื™ืช ืชื’ื“ืœ ืœืกืคื•ืจื•ืคื™ื˜ ื“ื™ืคืœื•ืื™ื“ื™ ื—ื“ืฉ ืžื”ื–ื™ื’ื•ื˜ื” ื”ื“ื™ืคืœื•ืื™ื“ื™ืช ืฉืœ ื”ื’ืžื˜ื•ืคื™ื˜ ื•ืชืฉืœื™ื ืืช ืžื—ื–ื•ืจ ื”ื—ื™ื™ื ืช ื›ืžื• ืฆืžื—ื™ ื–ืจืขื™ื ืฆืžื—ื™ื ืœื-ื•ืกืงื•ืœืจื™ื™ื ืœื ื˜ื•ืœื™ ื–ืจืขื™ื ื™ืฉ ืžื—ื–ื•ืจื™ ื—ื™ื™ื ืฉื ืฉืœื˜ื™ื ืขืœ ื™ื“ื™ ืกืคื•ืจื•ืคื™ื˜ื™ื. ืขื ื–ืืช, ื‘ืฉื•ื ื” ืžืืฃ ืžืฉื•ืฉืœื•ืช ื”ืฆืžื—ื™ื ื”ื’ื“ื•ืœื•ืช ื”ืื—ืจื•ืช, ื”ื’ืžื˜ื•ืคื™ื˜ื™ื ื”ืงื˜ื ื™ื ืฉืœื”ื ื™ื›ื•ืœื™ื ืœื—ื™ื•ืช ื‘ืื•ืคืŸ ืขืฆืžืื™ ื›ืœื•ืžืจ ื”ื ืื™ื ื ืžืกืคืงื™ื ื”ื–ื ื” ืœืกืคื•ืจื•ืคื™ื˜, ืื• ื“ื•ืจืฉื™ื ื–ืืช ืžื”ืกืคื•ืจื•ืคื™ื˜. ื ื™ืชืŸ ืœื˜ืขื•ืŸ ื›ื™ ื”ืžืืคื™ื™ืŸ ื”ืขื™ืงืจื™ ืฆืžื—ื™ื ื•ืกืงื•ืœืจื™ื™ื ื ื˜ื•ืœื™ ื–ืจืขื™ื ื”ื•ื ื”ืจืฉืช ื”ืžื™ื•ื—ื“ืช ืฉืœ ืจืงืžืช ื•ืกืงื•ืœืจื™ืช, ื”ื“ื•ืžื” ืœื–ื• ืฉืœ ืฆืžื—ื™ ื”ื–ืจืขื™ื.ื”ืชืืžื” ื–ื• ืืคืฉืจื” ืœื”ื ืœื”ืขื‘ื™ืจ ืžื™ื, ื—ื•ืžืจื™ื ืžื–ื™ื ื™ื ื•ื—ื•ืžืจื™ื ืื•ืจื’ื ื™ื™ื ืื—ืจื™ื ื•ืœื”ืฉื™ื’ ื’ื“ืœื™ื ื’ื“ื•ืœื™ื ื™ื•ืชืจ ืžื” ืฉื”ื‘ื“ื™ืœ ืื•ืชื ืžืงืจื•ื‘ื™ื”ื ื”ืœื-ื•ืกืงื•ืœืจื™ื™ื.

34.3:

ืฆืžื—ื™ื ื•ืกืงื•ืœืจื™ื ื—ืกืจื™ ื–ืจืขื™ื

Seedless Vascular Plants Were the First Tall Plants on Earth

Today, seedless vascular plants are represented by monilophytes and lycophytes. Ferns—the most common seedless vascular plants—are monilophytes. Whisk ferns (and their relatives) and horsetails are also monilophytes. Lycophytes include club mosses, spikemosses, and quillworts—none of which are true mosses.

Unlike nonvascular plants, vascular plants—including seedless vascular plants—have an extensive network of vascular tissue comprised of xylem and phloem. Most seedless vascular plants also have true roots and leaves. Furthermore, the life cycles of seedless vascular plants are dominated by diploid spore-producing sporophytes, rather than gametophytes.

However, like nonvascular plants, seedless vascular plants reproduce with spores rather than seeds. Seedless vascular plants are also typically more reproductively successful in moist environments because their sperm require a film of water to reach the eggs.

The Life Cycle of Seedless Vascular Plants

Like animals, seedless vascular plants (and other plants) alternate between meiosis and fertilization during reproduction. Meiosis is a cell division process that produces haploid cells—which contain one complete set of chromosomes—from a diploid cell—which contains two complete sets of chromosomes. Fertilization, by contrast, produces a diploid cell called a zygote through the fusion of haploid cells called gametes—sperm and eggs.

In most animals, only the diploid stage is multicellular, and gametes are the only haploid cells. Plants, however, alternate between haploid and diploid stages that are both multicellular; this is called alternation of generations. Alternation of generations is a feature of all sexually reproducing plants, but the relative size and prominence of the haploid and diploid stages differ among plants.

In seedless vascular plants (as well as seed plants), the diploid stage of the life cycle—the sporophyte—is dominant. For example, what most people recognize as a fern is the large, independent fern sporophyte. Sporophytes produce haploid cells called spores through meiosis.

A spore can germinate and develop into a gametophyte—the haploid stage of the life cycle—through mitosis. Gametophytes produce egg and sperm cells through mitosis (unlike animals, which produce gametes through meiosis). Most seedless vascular plants produce one type of spore that gives rise to a bisexual gametophyte. The gametophytes are smaller and less structurally complex than the sporophytes, but they can photosynthesize and do not depend on the sporophyte for nourishment or protection.

Egg and sperm cells fuse through fertilization, forming a diploid zygote. The zygote divides through mitosis to generate the familiar, fronded fern sporophyte—continuing the cycle.

Suggested Reading

Jones, Victor A.s., and Liam Dolan. 2012. "The Evolution of Root Hairs and Rhizoids." Annals of Botany 110 (2): 205–12. [Source]

Pittermann, Jarmila, Craig Brodersen, and James E. Watkins. 2013. "The Physiological Resilience of Fern Sporophytes and Gametophytes: Advances in Water Relations Offer New Insights into an Old Lineage." Frontiers in Plant Science 4. [Source]

Sigel, Erin M., Eric Schuettpelz, Kathleen M. Pryer, and Joshua P. Der. 2018. "Overlapping Patterns of Gene Expression Between Gametophyte and Sporophyte Phases in the Fern Polypodium Amorphum (Polypodiales)." Frontiers in Plant Science 9 (September). [Source]