Asexual Reproduction in Plants

•Produces offspring genetically identical to parent

•Also known as vegetative reproduction

Methods

A. Runners: horizontal, above-ground stems

example: Bermuda grass

B. Bulbs: short, underground stem

examples: onion, daffodil, tulip

C. Rhizomes: horizontal, underground stems

examples: ferns

D. Tubers: swollen, fleshy underground stems

example: potato

Germination

• Water and oxygen are needed for a seed to sprout.

• Germination: process in which a plant embryo resumes its growth.

• The first sign of germination is the emergence of the root, also known as radicle.

Plant Life Spans

1. Perennials: live for several years

• May reproduce often during their life

• May be deciduous or evergreen

• Stems woody or herbaceous

• Examples: trees, shrubs, daffodils, vines

2. Annuals: complete their life cycle in one growing season.

• Almost all are herbaceous.

• Examples include sunflowers, beans, corn, many weeds.

3. Biennials: take two growing seasons to complete their life cycle.

• Produce flowers during the 2nd season

• Examples include carrots and onions

Plant Growth and DevelopmentPlant 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,

II. HormonesII. Hormones

AuxinAuxin is a growth-promoting chemical that is a growth-promoting chemical that causes causes stems to bendstems to bend..

Experiment on page 598Experiment on page 598 Auxin accumulates on the dark side of a plant Auxin accumulates on the dark side of a plant

and causes the cells to and causes the cells to elongateelongate.. Another hormone is Another hormone is ethyleneethylene, which is a , which is a gas.gas. Ethylene stimulates fruit Ethylene stimulates fruit ripeningripening..

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