9.3 Plant Growth Flashcards
What are the 2 types of meristems?
Apical: height growth, in shoot and roots
Lateral: width growth, in cambium
Where does stem growth, forming new branches, occur?
In nodes, which comprise of remaining meristematic tissue, forming an axillary bud.
What do auxins do?
Auxins are hormones that promote apical growth and inhibit lateral growth (apical dominance).
What is pruning?
Pruning is cutting of the shoot/terminal bud of the plant, which will allow lateral buds to develop and thus the plant becomes bushier and not higher.
What do auxin efflux pumps do in shoots?
They set up a concentration gradient of auxin within tissue. The cells with more auxin get longer, thus the whole branch bends to the side with less auxin.
What do auxin efflux pumps do in roots? Why is it different from shoots?
In roots, auxins inhibit cell growth, and thus the cells with more auxins get shorter. It is different because different genes are activated in roots and in shoots.
How do auxins promote cell growth in shoots?
Auxins activate H+ pumps in the cell membrane, so more H+ goes from cytoplasm into the cell wall, breaking some of the cellulose fibres, so more water comes into vakuole from outside, elongating the cell. Auxin also makes the cell wall more flexible.
What are the 2 main tropisms?
Phototropism: light receptors redistribute auxin to the darker side, so that plant grows towards light
Geotropism: auxin will accumulate on the lower side of the roots, because of gravity
What is micropropagation?
Only meristems of a plant are cut off and put in sterile agar to grow with growth hormones.
What are the advantages of micropropagation?
Virus-free as meristems do not contain vascular tissue, cloning/you know what you’ll get, cheap, easy (even for sexually reproducing plants/e.g. orchids)
