Topic 9.3: Growth in Plants Flashcards
(26 cards)
What kind of growth do most plants have?
indeterminate growth
What is indeterminate growth?
The ability to continuously grow (under the right conditions)
Growth in plants is concentrated in …
the meristem at the tip of the roots and shoots.
What is the meristem made up of?
undifferentiated cells (unspecialized cells)
What is the apical meristem?
areas for growth on the roots and shoots of the plant.
What does the apical meristem do in the roots?
elongates it and makes the roots grow deeper into the ground
What protects the meristem in the roots?
the root cap
What does the apical meristem do in the shoots?
increases the length of the stem to develop leaves and other above ground structures. (done through mitosis)
In the axillary buds, apical meristems create…
dormant meristems (where the leaf joins the stem, that have the potential to grow into new shoots or branches)
How do plants respond to changes in the external environment?
by changing the number of cells that the meristem produces
Plant hormones are usually…
small organic molecules (simpler than animal hormones)
What is auxin?
a plant hormone than is synthesized at the apical meristem and is transported down the stem.
What do auxins do?
cell elongation and inhibits the growth of the axillary (side) buds, causing the plant to grow vertically (upwards)
The further auxin travel from apical meristem, …
the lower it’s concentration becomes
Auxin inhibits the growth of…
the axillary buds
Define Apical dominance
when the shoot of the of the plant grows while also preventing the growth of the axillary buds.
Define tropism
when the plant grows in a particular direction because of the external stimulus (ex: light, gravity, ect.) (plant shoots respond to their environment through tropisms.)
Define phototropism
the response of the plant to light
Define geotropism
the response of the plant to gravity
Shoots usually show —– phototropism and —— gravitropism.
positive , negative
Roots generally show ——phototropism and ——- gravitropism
negative, positive
Why do roots and stems grow unevenly?
because of the uneven distribution of auxin along the growing roots and stems, which makes cells grow unevenly, also causing them to bend in a particular direction.
The concentration of auxin that elongates shoot cells by accumulating the the side of the stem, inhibiting the growth of the cells in the…
root
How does auxin move from one cell to another?
1) Apical meristem has phtotoropins (detect light intensity)
2)If light is equally bright on all side of the shoot tip, auxin will move symmetrically down (via specialized protein pumps)
-Auxin influx carriers carriers in their apical (top) cell)
-Auxin efflux carriers in their bottom (basal) cell membranes.
3) There will be even cell growth and vertical extension of the stem.
——————————————-
if there is a difference in light intensity on different sides of the shoot…
-Phototropism will make some kinds of auxin efflux carriers to increase on the internal lateral (side) membrane.
-so auxin will be transported to the shaded side of the plant
-the shaded side will experience greater cell elongation
- stem will bend towards light
