The redistribution of auxin during gravitropism in maize roots.
The redistribution of auxin during gravitropism in maize roots
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Transcript of The redistribution of auxin during gravitropism in maize roots
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The redistribution of auxin during gravitropism in maize roots
![Page 2: The redistribution of auxin during gravitropism in maize roots](https://reader036.fdocuments.in/reader036/viewer/2022062719/56813194550346895d9804a8/html5/thumbnails/2.jpg)
Developmental effects of auxin
¤ Regulate apical dominance
¤ Promote lateral and adventitious root formation
– even though auxin inhibit the primary root elongation
¤ Delay the onset of leaf abscission
¤ Regulate the floral bud development
¤ Promote fruit development
¤ Induce vascular differentiation
![Page 3: The redistribution of auxin during gravitropism in maize roots](https://reader036.fdocuments.in/reader036/viewer/2022062719/56813194550346895d9804a8/html5/thumbnails/3.jpg)
Developmental effects of auxin
¤ Regulate apical dominance
¤ Promote lateral and adventitious root formation
– even though auxin inhibit the primary root elongation
¤ Delay the onset of leaf abscission
¤ Regulate the floral bud development
¤ Promote fruit development
¤ Induce vascular differentiation
![Page 4: The redistribution of auxin during gravitropism in maize roots](https://reader036.fdocuments.in/reader036/viewer/2022062719/56813194550346895d9804a8/html5/thumbnails/4.jpg)
Regulate apical dominance– apical bud inhibits the growth lateral buds
+ TIBA (efflux inhibitor) in
lanolin placed below the shoot
apex Axillary bud formation
Direct-inhibition model
Auxin is synthesized in the shoot apex and is transported basipetally to the axillary buds
( [auxin] gradient)
axillary buds are more sensitive to auxin than other shoot tissues
+ IAA inhibits the growth
of lateral buds
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However¤ After decapitation 4 h, the level of IAA is 5-fold increase
¤ Applied auxin directly to terminal bud, [auxin]shoot, axillary bud outgrowt
h
¤ radiolabeled auxin does not enter basipetal the bud
¤ axr1 mutant (unable to respond to auxin), much branching phenotype
¤ Transgenic plant (02):
auxin-responsive promoter + luciferase (LUX) gene
decapitated the expression of LUX increase in and around the axillary buds
¤ After decapitation, an increase in cytokinin imported from root via xylem,
Add cytokinin in axillary buds bud growth
(but bud growth prior to the increase of cytokinin)
¤ After decapitation, ABA level decrease, in some species.
¤ Carotenoid cleavage product
¤ Grafting studies
Root signals interact with auxin in the xylem ongoing research
Web Essay 19.4
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Auxin induce vascular differentiation– is polar and occurs from leaves to roots
Auxin
Cytokinin
Xylem and phloem differentiation: high auxin conc.
Only phloem differentiation: low auxin conc.
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Auxin promote fruit development
produce auxin
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The commercial uses of synthetic auxins
¤ prevention of fruit and leaf drop
¤ promotion of flowering
¤ induction of parthenocarpic fruits – seedless fruits
¤ thinning of fruit
¤ rooting of cutting
¤ herbicide for dicot weeds