Sexual Reproduction in Plants

• Involves production of haploid gametes

What is the function of this fruit?

Asexual Reproduction in Plants

•Produces offspring genetically identical to parent

•Also known as vegetative reproduction

MethodsA. Stolons, or runners: horizontal, above-ground stems example: Bermuda grass, strawberries

B. Bulbs: underground stems with modified leaves examples: onion, daffodil, tulip

C. Rhizomes: horizontal, underground stems examples: ferns, irises

D. Tubers: 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, or radicle

Plant Growth and Development

I. Nutrients1. Carbon dioxide and water for

photosynthesis2. Oxygen for cellular respiration3. Minerals needed for growthNitrogen, phosphorus, potassiumMagnesium 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.

http://www.kscience.co.uk/animations/auxin.htm

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 fertilizationfertilization

meiosismeiosis

SPOROPHYTE PHASE

GAMETOPHYTE PHASE

–moss gametophytes look like green carpet

–moss sporophytes shoot up as stalklike structures

sporophyte (2n)sporophyte (2n)

gametophyte (1n)gametophyte (1n)

capsule

spores (1n)