Learning Goal 4 Analyze Plant Reproduction and Development

Plant Reproduction  Reproduction in Plant Cells – Chromosome Number - Reproductive Cycle in Plants Alternation of Generations - Mosses and Ferns – Gymnosperms – Angiosperms – Sexual VS Asexual Reproduction - Plant Growth and Development Hormones – Tropisms – Photoperiodicity –

Reproduction in Plant Cells Mitosis Cell division resulting in identical daughter cells. Chromosome number and genetic composition remains constant.

Meiosis Cell division resulting in daughter cells that are not identical. Chromosome number is cut in half and genetic composition is different.

Diploid Cells have their full compliment of chromosomes (2n). Haploid Cells have half their full compliment of chromosomes (n).

Alternation of Generations Alternation of haploid (n) and diploid (2n) phases The diploid generation is known as the sporophyte. The haploid generation is known as the gametophyte.

Male gametophytes produce sperm (male gametes). Female gametophytes produce eggs (female gametes). When a sperm cell fertilizes an egg cell they produce a zygote.

Mosses and ferns alternate haploid and diploid phases. There are two distinct generations of the plant. One generation is haploid and the other diploid. The haploid or gametophyte generation is prominent in mosses. The diploid or sporophyte generation is prominent in ferns.

MOSS LIFE CYCLEFERN LIFE CYCLE

Conifers The sporophyte (diploid) is the familiar adult of the species. Meiosis produces the haploid gametophytes (male and female) from the male and female cone scales.

The male gametophyte forms the male pollen grain and its attached air bladders. This allows for wind pollination. The pollen contains sperm cells and tube cells, which fertilize an egg cell of the female scale when they are brought into contact. The zygote than develops into an embryo inside a seed.

Dominant adult generation is the sporophyte also. In angiosperms, flowers contain the organs for sexual reproduction Pollen grains arise from microspores in anthers Eggs and other cells of female gametophytes arise from megaspores

Alternation of generation life cycles are examples of sexual reproduction because it involves male and female gametes uniting to form zygotes. Plants can also reproduce asexually through a process called vegetative propagation. Many plants reproduce using a combination.

Hormones Chemicals that regulate the growth, development, and function of an organism. Plant cells produce hormones that bring about physiological changes within plant tissues. Each type of hormone affects changes in particular cells known as target cells. HormoneProcess Regulated or Influenced giberillinsCell division and cell elongation cytokininsCell division and fruit development absicisic acidOpening and closing of stomata (controlling water lost through transpiration and formation of winter buds that put plant in dormant state) ethyleneRipening of fruit (spoiling releases ethylene which stimulates ripening of surrounding fruit);metabolic activity (i.e., producing female flowers to increase fertilization). auxins Growth factors (tropisms ) Mostly cell elongation

A tropism is an involuntary response of an organism to an external stimulus such as light, water, gravity, or nutrients. Phototropism A plant’s response to light. Stems move toward light, roots move away.

Gravitropism (Geotropism) A plant’s response to gravity. Shoots grow up and roots grow down.

Thigmotropism A plant’s response to touch. Causes some plants to wind around objects or for leaves to close up upon being touched.

Plants respond to relative periods of light and darkness. Light-sensitive chemicals in the leaves trigger a response in the plant, which encourages growth, flowering, or other reactions.

1. Sporophyte - 2. Gametophyte – 3. Pollen – 4. Anthers – 5. Megaspores – 6. Vegetative propagation – 7. Plant Hormones – 8. Tropisms – 9. Phototropism – 10. Photoperiodicity –