Plant Biology: Key Definitions

Definitions

• Pollination is the transfer of pollen from the anther to the stigma.
• The cuticle is a waxy layer that prevents water loss.
• Rhizoids are root-like structures found in non-vascular plants.
• Thallus is an undifferentiated plant body seen in algae and liverworts.
• Oogamous reproduction involves a large immotile egg and small motile sperm.
• Gemma is an asexual reproductive structure.
• Protonema is the filamentous juvenile stage of moss gametophytes.
• Xylem is vascular tissue that transports water.
• Phloem is vascular tissue that transports nutrients.
• Fronds are the leaves of ferns.
• The carpel is the female part of a flower, containing the stigma, style, and ovary.
• Vascular tissues consist of xylem and phloem.
• Alternation of generations is a life cycle that alternates between haploid (gametophyte) and diploid (sporophyte) stages.
• Anther is the pollen-producing part of the stamen.
• Gametophyte is the haploid generation that produces gametes.
• Sporophyte is the diploid generation that produces spores.

Double Fertilization

• During double fertilization, the pollen tube grows into the ovary, releasing two sperm; one fertilizes the egg to form a zygote, while the other fuses with two polar nuclei to form triploid endosperm.
• Endosperm's importance is that it nourishes the embryo.
• Angiosperm seeds are enclosed in ovaries, which develop into fruits.
• The fusion of gametes results in a diploid zygote, which develops into a sporophyte.
• The haploid generation is the gametophyte, and the diploid generation is the sporophyte.
• Spores are formed via meiosis, while gametes are formed via mitosis.

Dominant Generations

• In mosses, the gametophyte generation is dominant.
• In ferns, gymnosperms, and angiosperms, the sporophyte generation is dominant.

Monocots vs. Dicots

• Monocots have one cotyledon, while dicots have two.
• Leaf veins are parallel in monocots and net-like in dicots.
• Vascular bundles are scattered in monocots and ringed in dicots.
• Flower parts are in multiples of 3 in monocots and in multiples of 4 or 5 in dicots.
• Roots are fibrous in monocots and taproot in dicots.

Flower Reproductive Parts

• The male part of a flower is the stamen, which includes the anther and filament.
• The female part of a flower is the carpel, which includes the stigma, style, and ovary.

Bryophytes and Gymnosperms

• Bryophytes lack vascular tissue and rely on diffusion and moisture for reproduction, limiting their size.
• Gymnosperms reproduce via cones (male pollen cones and female seed cones).

Plant Phyla Identification

• Ferns belong to the phylum Pteridophyta.
• Whisk ferns belong to the phylum Psilotophyta.
• Club mosses belong to the phylum Lycopodiophyta.
• Pines belong to the phylum Coniferophyta.
• Liverworts belong to the phylum Marchantiophyta.
• Horsetails belong to the phylum Equisetophyta.
• Roses belong to the phylum Anthophyta.
• Hornworts belong to the phylum Anthocerotophyta.
• Mosses belong to the phylum Bryophyta.
• Mormon Tea belongs to the phylum Gnetophyta.

Moss Characteristics

• Moss spores are found in a capsule (sporangium) on the sporophyte.
• Mosses are non-vascular plants, with a dominant gametophyte generation; they have rhizoids and spores, and require water for reproduction.
• Moss eggs are produced in archegonia.
• The moss life cycle includes a dominant gametophyte, with a sporophyte dependent on the gametophyte, spores, protonema, and a new gametophyte.

Fern Traits

• Ferns are vascular plants with fronds, rhizomes, and spores on the undersides (sori) of their leaves, and exhibit alternation of generations.
• A fiddlehead is a young, coiled fern frond.

Fern vs. Moss

• Fern sporophytes have fronds, rhizomes, and roots.
• Moss gametophytes have a leafy structure.

Reproduction

• Mature microspores become pollen grains.
• Bright flowers indicate animal (insect/bird) pollination.
• Gametes are transferred by animals, wind, and water.
• Flower parts include sepals, petals, stamens, and carpels.
• After pollination, the pollen tube grows, and sperm travel to the ovule.
• Fruit develops from the ovary and serves seed dispersal purposes.
• The seed structure contains an embryo.

Plant Evolution and Adaptations

• The ancestors of plants are green algae (Charophytes).
• Early plant challenges included desiccation, structural support, UV radiation, and reproduction on land.

Plant Groups

• Bryophytes include mosses, liverworts, and hornworts.
• Vascular plants have xylem and phloem, roots, lignin, and a dominant sporophyte generation.
• Non-seed plants include ferns, horsetails, and club mosses.
• Gymnosperms include pines, spruces, and ginkgos.

Plant Characteristics

• Plant cells have cellulose cell walls and chloroplasts, undergo alternation of generations, are multicellular, and are autotrophic.

Double Fertilization Steps

• Pollen lands on the stigma.
• A pollen tube grows into the style.
• Two sperm enter the ovule.
• One sperm fertilizes the egg, forming a zygote.
• The second sperm fuses with polar nuclei, forming the endosperm.