Annuals: complete their life cycle in one growing season. Almost all are herbaceous. Examples include sunflowers, beans, corn, many weeds.
Biennials: take two growing seasons to complete their life cycle. Produce flowers during the 2 nd season Examples include carrots and onions
Plant Growth and Development I. Nutrients 1.Carbon dioxide and water for photosynthesis 2.Oxygen for cellular respiration 3.Minerals needed for growth Nitrogen, phosphorus, potassium Magnesium for photosynthesis
II. Hormones 1. Auxin is a growth-promoting chemical that causes stems to bend. Auxin accumulates on the dark side of a plant and causes the cells to elongate.
2. Another hormone is ethylene, which is a gas. Ethylene stimulates fruit ripening. 3. Cytokinins – stimulate cytokinesis, or cell division. 4. Gibberellins – produce dramatic increases in size
Environmental Influences I.Tropisms: responses in which plants grow either toward or away from a stimulus A. The bending of a plant toward the light is a positive phototropism. B. The downward growth of roots is a positive gravitropism. C. The upward growth of shoots is a negative gravitropism.
D.Thigmotropism is a response to touch. Coiling of a vine around a trellis is a positive thigmotropism.
II.Nastic movements are rapid, reversible responses to non-directional stimuli. Examples include opening and closing of flowers and closing of a Venus fly trap
III. Photoperiodism The response of a plant to the length of days and nights. Long-day plants produce flowers when days are longer than a certain number of hours. Examples: Irises
Short-day plants produce flowers when days are shorter than a certain number of hours. Examples: Poinsettias
Day-neutral plants do not require specific day lengths to flower. Examples include roses, potatoes
Plant life cycles alternate between producing spores and gametes. A two-phase life cycle is called alternation of generations. –haploid phase –diploid phase –alternates between the two fertilization meiosis SPOROPHYTE PHASE GAMETOPHYTE PHASE
–moss gametophytes look like green carpet –moss sporophytes shoot up as stalklike structures sporophyte (2n) gametophyte (1n) capsule spores (1n)