hormones Flashcards
what do hormones do in a plant ?
Control plant growth and development, coordinate metabolic activities, coordinate environmental responses.
are plant hormones produced in glands
no!!!
Hormone reception
Specific receptor for each type of hormone, located in the cell membrane. present in very low concentration
secondary messengers
connect receptor with response system. they transduce and amplify hormone signals.
what is the cell response to hormones
altered transcription of specific genes, transcriptional regulation.
altered activity enzymes, post-translational regulation.
What can environmental factors alter ?
Hormone biosynthesis, hormone transport, hormone conjugation to sugars, hormone perception, hormone degradation
Give examples of growth promoters
Auxin and gibberellin stimulate cell expansion.
Cytokinin stimulates cell division.
give examples of growth inhibitors?
Abscisic acid slow growth (dormancy)
Ethylene controls ripening and cell death
how does auxin play a role in apical dominance ?
Auxin is produced in apex and young leaves. Blocks growth axillary buds on lower stem. Responsible for apical dominance.
Give examples of Auxin
Indole acetic acid (IAA)- main natural auxin
2,4D - auxin like weed killer
Component agent orange- defoliant
What roots does auxin promote to form?
Lateral roots
What is auxin commercially used as?
rooting powder
Where is cytokinin produced?
in the root tip as well as the embryos
What is the most common type of cytokinin?
Zeatin
In what direction does cytokinin travel
roots to shoots
What does cytokinin do ?
promotes cell division
enhances sprouting axillary buds
anti-ageing
How do auxin and cytokinin work together?
A shoot will produce lots of auxin encouraging root growth.
A root will produce lots of cytokinin encouraging shoot growth.
Together auxin and cytokinin control the balance between root and shoot.
What hormones stimulates the growth of fruit ?
Auxin and or gibberellin
High levels of what hormone facilitate embryo dormancy?
abscisic acid
cotyledon
embryonic leaf
plumule
first true leaves
hypocotyl
stem below attachment point cotyledons
Radicle
embryonic root
What does dormancy facilitate ?
dispersal and survival
what hormone controls ripening?
ethylene
apoptosis
Programmed cell death
