9.3 Growth in Plants

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First found May 22, 2018

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Respond to changes in the environment
Regulate growth
Regulate reproduction and flowering
Regulate water loss
Regulate growth by controlling mitosis and
cell division
Undifferentiated tissues that become many
different types of tissues
Located where plants exhibit major growth
Apical Meristems
◦ Located at the top and the root
of plants
◦ Allows for growth of new leaves
and flowers
◦ Allows roots to grow down into
the soil
◦ Elongation of plant
Lateral Meristems
◦ Responsible for secondary
growth in woody plants
◦ Allows them to increase stem
and root thickness
Animal embryos have a fixed number of parts
that will develop and are considered
determinate growth
◦ 2 legs, 2 arms, 10 fingers/toes etc.
The growth in plants is much different and is
considered to be INDETERMINATE.
◦ Meaning apical meristems can continue to increase
the lengths of stem and root throughout the life of
a plant and can produce any number of extra
branches of the stem or root. They can also
produce any number of extra leaves or flowers.
Occur in the shoot apex
Provide cells needed for extension of the
stem at that location
Also important for development of leaves.
A directional movement in plants in response
to a stimulus
Type of Tropism
Response to light
Response to gravity
Response to touch
Response to temperature
Response to substance
Response to water
Responsible for phototropism
Affects cells on the dark side of the plant
◦ causes the cells away from light to elongate
When light shines directly down on a plant
shoot auxin is equally distributed this causes
the plant to grow straight
This hormone is released in abundance of
blue light in the shoot tip.
Auxin efflux pumps can set up concentration
gradients of auxin in plant tissue.
◦ Moves Auxin from cytoplasm to cell wall
◦ Lower concentration on light side and higher
concentration on dark side.
Auxin influences cell growth by changing the
pattern of gene expression.
◦ These genes cause secretion of H+ ions into cell
walls that loosen connections in the cellulose fibers
that allow cells to expand.
The practice of rapidly multiplying stock plant
material to produce a large number of plants,
using modern plant tissue culture methods.
◦ Can create virus-free strains of existing plants
◦ Can propagate rare species - Orchids
Uses tissue from shoot apex, nutrient agar
gels and growth hormones
Used in plants to increase population faster
than seeding time would allow

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