Plant Reproduction and Development Quiz

Plant Reproduction and Development

Gametophyte and Sporophyte

• Gametophyte: a stage in the life cycle of a plant that is haploid, producing gametes via mitosis, which fuse to form a zygote that develops into a sporophyte.
• Sporophyte: a stage in the life cycle of a plant that is diploid, producing haploid spores by meiosis in structures called sporangia.

Flower Parts and Functions

• Pistil or carpels: the innermost whorl of the flower, the female reproductive structure, bearing the female sporangia (megasporangia).
• Stigma: the part of the pistil where the pollen grain attaches during pollination.
• Ovule: contains the female sporangia or megasporangia, eventually becoming the seed.
• Style: the part of the pistil that serves as the stalk of the stigma, leading to the ovary.
• Ovary: found at the base of the pistil, containing one or more ovules, eventually becoming the fruit.

Plant Types based on Reproductive Structures

• Monoecious: a plant type having male and female reproductive structures in separate flowers on the same plant.
• Dioecious: a plant type having male and female reproductive structures in separate flowers on different plants.

Gametophyte Development through Gametogenesis

• Male gametophyte: microsporangium in the anther contains numerous microsporocytes, each undergoing meiosis to produce four haploid microspores, which develop into pollen grains (containing two sperm nuclei and one tube nucleus).
• Female gametophyte: megasporangium in the ovule contains megasporocytes, one of which undergoes meiosis to produce four haploid megaspores; three degenerate, and the remaining megaspore divides mitotically three times, forming an embryo sac with eight haploid nuclei.

Pollination

• Pollination is the transfer of pollen grain from the anther to the stigma.
• Wind pollination: found in conifers, pollen is transferred through chance events.

Life Cycles of Non-Flowering Plants

Moss Life Cycle

• No external fertilization occurs, as sperm need water to swim to the egg.
• Limitations: need for water, limited dispersal, and slow reproduction.

Fern Life Cycle

• Conifers have reduced gametophytes.
• Male gametophyte is contained in a dry pollen grain.
• Female gametophyte is a few cells inside the structures that become the seed.

Conifer Life Cycle

• Conifers are wind-pollinated plants.
• Pollination occurs when pollen lands on the scales of female cones.

Flowers and Pollination

The Four Major Whorls

• Sepals
• Petals
• Stamens with anther and filament
• Carpels with stigma, style, ovary, and ovule

Types of Flowers

• Complete: having all four whorls
• Haplontic life cycle: the haploid stage is multicellular, and the diploid stage is the fertilized egg cell
• Haplodiplontic life cycle: includes multicellular diploid (sporophyte) and haploid (gametophyte) generations
• Diplontic life cycle: the diploid stage is multicellular, and the haploid stage is represented by single-celled gametes

Angiosperms (Flowering Plants)

• Produce reproductive structures called flowers in their sporophyte stages
• Have a characteristic life cycle that includes alternation of generations

Asexual and Sexual Reproduction

• Asexual reproduction: natural “cloning,” where parts of the plant produce roots and become an independent plant
• Sexual reproduction: requires fusion of male cells in the pollen grain with female cells in the ovule

Alternation of Generations

• Plants alternate between haploid and diploid generations
• Allows for both asexual and sexual reproduction
• May be animal-aided or wind-aided

Self-Pollination and Cross-Pollination

• Self-pollination: occurs when pollen from the anther is deposited on the stigma of the same flower or another flower on the same plant
• Cross-pollination: transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species