Plant Hormones Flashcards
Plant hormones are produced in?
very low concentration
Hormones control?
plant growth and development
-by affecting the division, elongation and differential of cells
What is auxin used for?
used for any chemical substance that promotes cell elongation in different target tissues
Major role in the growth response of cells to auxin?
proton pumps
-according to acid growth hypothesis
cell elongation in response to auxin?
- auxin increases the activity of proton pumps
- the cell wall becomes more acidic
3.Wedge-shaped expansions, activated by low pH, separate cellulose microfibrils from cross-linking polysaccharides. The exposed cross-linking polysaccharides are now more accessible to cell wall enzymes.
4.The enzymatic cleaving of the cross-linking polysaccharides allows
the microfibrils to slide. The extensibility of the cell wall is increased. Turgor causes the cell to expand. - with the cellulose loosened, the cell can elongate.
Role of auxin in lateral and adventitious root formation?
involved in the formation and branching of roots
auxin as?
- herbicides
- overdose of auxins can kill eudicots
auxin in secondary growth?
-by inducing cell division in the vascular cambium and influencing differentiation of secondary xylem
cytokinins?
- stimulate cell division
- produced in actively growing tissues
- roots, embryo, fruits
- work together with auxin
factor of control of apical dominance?
- cytokinins
- auxin
- ability of a terminal bud to suppress development of axillary buds
cytokinins: control of apical dominance
if the terminal bud is removed
plant become bushier
cytokinins: anti aging effect
retard the aging of some plant organs
cytokinins: anti aging effect how?
- by inhibiting protein breakdown
- stimulationg RNA and protein synthesis
- mobilizing nutrients from surrounding tissues
why do florist use cytokinins?
to keep cut flowers fresh
gibberellins can effect?
- stem elongation
- fruit growth
- seed germination
gibberellins: stem elongation
gibberellins stimulate growth of both leaves and stems
-in stems, gibberellins stimulate cell elongation and cell division
gibberellins: fruit growth
- auxin and gibberellins must be present for fruit to set
- gibberellins are used commercially (@spraying of Thompson seedless grapes)
effect of abscisic acid?
- seed dormancy
2. drought tolerance
abscisic acid: seed dormancy
- ensure the seed will germinate only when there are optimal condition
- high level of ABA in maturing seeds inhibit germination and induce production of certain proteins ( help to withstand extreme dehydration)
abscisic acid: drought tolerance
-ABA is the primary internal signal that enables plants to withstand drought
-when plant begin to wilt,
ABA accumulates in leaves and causes stomata to close rapidly (to reduce transpiration, prevent water loss)
why plants produces ethylene?
-response to stresses such as -drought -flooding -mechanical pressure -injury -infection
ethylene: apoptosis
burst of ethylene :
- cells
- organs
- whole plant
ethylene: leaf abscission
- change in the balance of auxin and ethylene controls leaf abscission
- process that occurs in autumn when a leaf falls
ethylene: fruit ripening
A burst of ethylene production in the fruit
•Triggers the ripening process
•Enzymatic breakdown of cell wall component
softens the fruit
•Conversion of starches and acids to sugar
makes the fruit sweet
where auxin is found in plant?
embryo of seed, meristems of apical buds, young leaves
where cytokinins is produced?
synthesized in roots and transported to other organs
where gibberellins is produced?
meristems of apical buds and roots, young leaves, embryo
where is abscisic acid is produced?
leaves, stems, roots, green fruit
where is ethylene is produced or found in a plant?
tissues of ripening fruit, nodes of stems, aging leaves and flowers
