Flashcards in lecture 7 Control of plant development Deck (72)
What is the role of a plant growth regulator?
PGRs play an important role. The idea that their individual roles can be defined by the nature of the response to each of them (auxins -> cell expansion, cytokinin -> celldivision) doesn’t fit the facts and must be discarded. At different times they can function in either of 2 rather different types of interaction:
How are plant growth regulators developed?
PGRs may be generated by development in one part of theplant (xylem differentiation in lfs -> auxin, senescence orripening -> ethylene, plastid differentiation -> gibberellins,ripening fruit tissue ->abscisic acid, cell division in root tips ->cytokinin).
Phase 1 of leaf morphogenesis determines:
a) leaf position
A permanent change in position of a plant part in response to external stimuli is called ____.
a)a circadian movement
c)a sleep movement
d)a turgor movement
b) a tropism
a)cause cells to divide
c)inhibit cell elongation
d)cause buds and seeds to go dormant
e)none of the above
a)cause cells to divide
a) is a gas
b) interacts with auxin in leaf abscission
c)promotes seed germination
d)all of the above
e) b, c and d
d) all of the above
The leaf abscission zone is:
at the base of the petiole
at the base of the leaf blade
at the apical meristem
above the axillary bud
none of the above
a) at the base of the petiole
A number of angiosperm species grow in locations where they are periodically submerged in seawater, these plants
e)none of the above
Plants adapted to grow on acidic soils are termed:
Which of the following genera of angiosperms DOES NOT contain insectivorous species:
In relation to PGR other parts of the same plant may be programmed to produce an?
appropriate developmental response, WHATEVER IS APPROPRIATE FOR THAT TISSUE OF THATSPECIES AT THAT DEVELOPMENTAL STAGE. The constant feature is the link between the particular PGR and the particularDevt which produced it.
The same PGR is produced in response to?
certain stimulus. But, the plant response to the PGR is species, tissue and time specific!
How are PGRs synthesized in response to an environmental signal?
(drought -> abscisic acid, light -> gibberelins, mineral nutrients -> cytokinins, physical stress -> ethylene).
The most important co-ordinating influence on primaryvegetative growth, and differentiation, shoot branching and cambial activity is?
auxin synthesized in developing leaves.
This auxin is swept root tip wards by a process termed?
polar transport (at 1cm per hr) as the xylem differentiates and the contents of vessels lyse through the living parenchymacells of the stele.
Cell expansion determining internode length is auxin-dependent, so the?
developing leaf influences the size of internodes below it that will support and supply it.
Tropic curvature enables?
the expanding internodes to respond to light and gravity, but the mechanism remains obscure.
The environmental signals are picked up by ?
specialized plastids (chloroplasts, chromoplasts, amyloplasts & aleoplasts’).
Statoliths are large?
amyloplasts which do not disappearwhen the plant is starved and, unlike other starch grains, are ‘loose’ inside the cell, rolling down to the lowest point when the plant is tilted.
Phototropism, growth in response to?
the direction of light is mediated by a yellow flavoprotein photoreceptor maximally sensitive to blue light.
Sensitivity to phototropic stimuli in coleoptiles correlates with special bright yellow plastids unique to cells of the?
Leaves have statoliths in the?
Only stems have the bundle sheaths in the?
In roots the bundle sheaths are in the?
The most likely explanation behind the sensitivity is?
that the specialised plastids influence the transport of auxin fromthe polar transport stream in the stele tothe expanding tissues of thecortex, blocking the radial outwards movement of auxin on the illuminated or upper side.
Differentiating leaves export gibberellins which promotes?
cell expansion (& directly regulate the activity of the subapicalmeristem, promoting cell divisions that increase internode length).
Growing root tips export cytokinins, which promote?
ell expansion in leaves, but not in stems.
When more mineral nutrients are available in the soil more?
cytokinin is exported from roots, and leaves are larger in response.
Cell expansion is also sensitive to?
ethylene, part of a response to physical stress.