Transcript Asexual Reproduction in Plants

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
Methods
A. 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. 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.

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
SPOROPHYTE
PHASE
fertilization
meiosis
GAMETOPHYTE
PHASE
– moss gametophytes look like green
carpet
– moss sporophytes shoot up as
stalklike structures
sporophyte (2n)
capsule
spores (1n)
gametophyte (1n)