lecture 7 Flashcards
(32 cards)
what is etiolation?
morphological adaptations for growing in darkness, such as a potato growing in darkness will produce unhealthy looking shoots and lacks elongated roots
what happens when a plant experiences de-etiolation?
stem elongation slows, leaves expand, roots elongate, and the shoot produces chlorophyll
what are the stages of cellular signaling
reception, transduction, response
what is reception?
a hormone or environmental stimulus interacts with a receptor protein in the plasma membrane
what is transduction?
relay proteins are activated as well as second messengers that pass the signal
what is response?
the passed signal ultimately activates cellular responses
what is the receptor in de-etiolation?
phytochrome, which is capable of detecting light. it is located in the cytoplasm
what are the 2 types of second messengers in de-etiolation
- Ca2+ ions
- cyclic G MP (cGMP)
the phytochrome receptor responds to light by: (2)
opening Ca2+ channels, which increases Ca2+ levels in cytosol
and activating an enzyme that produces cGMP
what is post translational modification?
involves modification of existing proteins in the signal response
what are the 5 major types of plant hormones
Auxin, Cytokinins, Gibberellins, Abscisic acid, Ethylene.
( the others are brassinosteroids, jasmonates, and strigolactones)
what is a tropism?
any growth response resulting in turning of all or part of an organs toward or away from a stimulus is a tropism. in short, its a growth response
what is auxin?
refers to any chemical that promotes elongation of coleoptiles
what is the major auxin in plants?
indoleacetic acid (IAA)
where is auxin produced?
produced in the shoot tips and is transported down the stem. it only moves from tip to base. this is called polar transport
what do auxin transporters do?
move the auxin out of the cell. so that the auxin can then enter the apical end of the next cell.
what is the acid growth hypothesis?
auxin stimulates/increases proton pumps in the plasma membrane, which lower the pH of the cell wall, activating expansins and enzymes that loosen the cellulose, with cellulose loosened the cell can elongate. auxin alto alters gene expression to stimulate a sustained growth response.
what are the major functions of auxin?
increases plasticity of cell wall
promotes elongation of shoots and formation of lateral and adventitious roots.
regulates development of fruits.
enhances apical dominance.
affects secondary growth by inducing cell division in the vascular cambium & influencing differentiation of secondary xylem
what are the practical uses for auxins?
the auxin IBA stimulates adventitious roots and is used in propagation of plant cuttings.
also, an overdose of auxin can kill plants, for EX, 2,4-D is used as a herbicide on eudicots
what are cytokinins?
they stimulate cytokinesis
where are cytokinins produced ?
in actively growing tissues such as roots, embryos and fruits
how do cytokinins slow the aging of some plant organs how?
they inhibit protein breakdown, they stimulate RNA and protein synthesis. mobilize nutrients from surrounding tissues, and slow progress of apoptosis, which is programmed cell death
if a terminal bud on a plant is removed, what would happen?
the plant would become bushier. allows the other buds to recieve more sugars for growth rather than it all going to the terminal bud
what are gibberellins?
are hormones with a variety of effects, such as stem elongation, fruit growth, and seed germination
