plant growth and development Flashcards
what is plant growth and development?
understand the diversity of plant structures and life histories, need to understand role that signal response pathways play in their growth and development
what are signal response pathways?
hormones and environmental stimuli alter behaviour of target cells
plants are very plastic to their environment
different responses in different tissues
what can signals do?
induce changes in cell’s shape or internal structure
influence cell’s metabolism
alter gene activation and rate of protein synthesis
set in motion events that modify existing cell proteins
where do the receptors bind to?
target cell’s plasma membrane on ER or cytoplasm
what does the binding of the receptors do?
triggers release of internal second messenger that diffuse through cytoplasm
provides chemical signal that alters cell functioning
what is auxins?
mainly indoleacetic acid (IAA)
where is auxin synthesized?
apical meristem
developing leaves and embryos
what tissues does auxin affect?
growing tissues
buds
roots
leaves
fruits
vascular tissue
what are the effects of auxin?
governs growth responses to light and gravity
growth and elongation of stems
promote lateral roots and dormancy in lateral buds
inhibits lead abscissions
inhibits growth of lateral meristem
what is tropism?
plants respond to environmental stimuli (light) and grows towards the light
how does auxin move?
through polar transport from the tips of developing leaves towards the stem
what type of plants have a high sensitivity to auxin?
monocots
what is the most common type of gibberellins?
GA1 is most common
where is gibberellin synthesized?
root and shoot tips
young leaves
developing embryos
what effects does gibberellins have of plant tissues?
stems
developing seeds
what are the effects of gibberellins?
promote cell divisions and growth and elongation of stems
promote seed germination
increase internodal distance
where is abscisic acid synthesized?
in the leaves
what tissues are effected by abscisic acid?
buds
seeds
stomata
what are the effects of abscisic acid?
promotes responses to environmental stress
inhibiting growth/ promoting dormancy
stimulates stomata to close in water stressed plants
where is ethylene synthesized?
shoot tips
roots
leaf nodes
flowers
fruits
what tissues are affected by ethylene?
seeds
buds
seedlings
mature leaves
flowers
fruit
what are the effects of ethylene?
regulates elongation and division of cells in seedling stems and roots
regulates senescence and abscission of leaves, flowers and fruits
what is senescence?
again of living organisms
removal of seed pods in soybean delays senescence since ethylene is not produced
what is dehiscence?
shed ripened grains
what is indehiscence?
hold on to ripened grains
what does ethylene promote?
horizontal growth
what is the most abundant cytokinin?
zeatin
where is cytokinin synthesized?
mainly root tips
what tissues are effected by cytokinin?
shoot apical meristem
leaves
buds
what are the effects of cytokinin?
promote cell divisions and growth and elongation of stems
promote seed germination
inhibits leaf aging
what are brassinosteroids?
group of steroid hormones
where are brassinosteroids synthesized?
young seeds, shoots and leaves
what tissues are mainly effected by brassinosteroids?
mainly shoot tips
developing embryos
what are the effects pf brassinosteroids?
stimulate cell division and elongation
differentiation of vascular tissue
what are jasmonates?
JA derived from fatty acids
where are jasmonates synthesized?
roots
seeds
probably other tissues
what tissues are effected by jamonates?
various tissues including damaged ones
what are the effects of jamonates?
in defense response
promote transcription of genes encoding protease inhibitors
possible role in plant responses to nutrient deficiencies
what are plants chemical defense system?
prevent or mediate damage to plant tissues from infectious bacteria, fungi, worms or plant eating insects
what is a hypersensitive response?
isolates infection site by surrounding with dead cells
salicylic acid induces synthesis of pathogenesis related proteins
what is secondary metabolites?
commonly mediate a plant’s antagonistic interactions
not essential for growth and life but help with a plant’s defense against with pathogens and herbivores
what is gene for gene recognition?
enables plants to recognize pathogen chemically an mount defenses against it
what is systemic acquired resistance?
provides long term protection against some pathogens
what is phototropism?
growth response to directional light source
blue light receptors trigger auxin transport
auxin triggers differential cell elongation
what is gravitropism?
growth response to earth’s gravitational pull
- statoliths move in response to gravity
what it thigmotropism?
growth in response to contact with a solid object
what is thigmomorphogenesis?
mechanical stress causes the stem to add girth
- caused by frequent strong winds, rainstorms, grazing animals and even farm machinery
what is nastic movement?
reversible response to nondirectional stimuli
- movement in leaves, leadlets and flowers
what are circadian rhythms in plants?
24 hours cycles even when environmental conditions remains consistent
- regulated by a biological clock and helps ensures that of
single species do the same
what is a biological clock?
internal time-measuring mechanisms with a biological basis
- adapt organisms to recurring environmental changes
what are environmental cues can reset clocks?
enables seasonal adjustments in growth
development and reproduction
what is photoperiodism?
responses to change in relative length of daylight and darkness
allows biological clock to be reset for seasonal adjustments to day length
controlled by phytochrome
what is phytochrome?
blue green pigment
converts to active form during daylight when red wavelengths dominate
reverts to inactive form a sunset at night or in shade when far red wavelengths predominate
what does phytochrome control?
types of enzymes produced in particular cell
used to sense long nights of autumn in preparation for dormancy
what is a flowering response?
long day plants
short day plants
intermediate day plants
day neural plants
what is a long day plant?
flowers in spring or summer when day length is long relative to night
what is a short day plant?
flower in late summer or autumn when day length is relatively short
what is an intermediate day plant?
in between long and short day plants
what is a day neutral plant?
flowering not affected by photoperiod
