Plant Developmental Responses
Phototropism
positive
Gravitropism
positive
negative
Thigmotropism
Old Fig. 36.11
Sun risingover horizon
Morning Noon Afternoon
Heliotropism
Old Fig. 36.08c
(c) Cross-sectional views
Parenchymacells retainingturgor
Decrease ofturgor inparenchymacells
Vasculartissue
Pulvinus
LeafletOpen
Closed
Nastic movements
Mimosa
Venus fly trap
(vulnerable)
(induction)
Fig 6-2
Cell communication
Signal transduction pathway
eg: hormones
Auxin
structure
The Darwins’ work on phototropism
coleoptile of grass seedling
+ +- -
Frits Went’s experiment
What’s happening?
effectsa. promotes cell growthb. shoot phototropismc. root gravitropismd. apical dominancee. differentiation of vascular tissuef. prevents leaf abscision
effectsa. promotes cell growthb. shoot phototropismc. root gravitropismd. apical dominancee. differentiation of vascular tissuef. prevents leaf abscision
Apical dominance(released)
effectsa. promotes cell growthb. shoot phototropismc. root gravitropismd. apical dominancee. differentiation of vascular tissuef. prevents leaf abscision
used in agriculture/horticulture to:1) promote (adventitious) rooting of cuttings 2) cause uniform flowering & fruit set3) to give seedless fruit 4) synthetic auxins used as herbicides 5) promote growth & differentiation in tissue culture
Rooting cuttings
used in agriculture/horticulture to:1) promote (adventitious) rooting of cuttings 2) cause uniform flowering & fruit set3) to give seedless fruit 4) synthetic auxins used as herbicides 5) promote growth & differentiation in tissue culture
Plant tissue culture
Gibberellin structure
Margaret Radley
Bernard Phinney
Eiichi Kurosawa
effectsa. promotes stem growthb. induce floweringc. break dormancy in buds & seedsd. lower temperature threshold of growthe. increase yieldsf. increase size of fruit & distance between g. enhance starch digestion
Phinney’s dwarf corn
effectsa. promotes stem growthb. induce floweringc. break dormancy in buds & seedsd. lower temperature threshold of growthe. increase yieldsf. increase size of fruit & distance between g. enhance starch digestion
(b) Do not post photos on Internet
effectsa. promotes stem growthb. induce floweringc. break dormancy in buds & seedsd. lower temperature threshold of growthe. increase yieldsf. increase size of fruit & distance between g. enhance starch digestion
Fruit set (without seeds), size and spacing
effectsa. promotes stem growthb. induce floweringc. break dormancy in buds & seedsd. lower temperature threshold of growthe. increase yieldsf. increase size of fruit & distance between g. enhance starch digestion
Seed germination (part of “malting” for making beer)
Cytokinin structure
Carlos Miller Folke Skoog
Related to adenine
effectsa. promotes cell divisionb. cell enlargementc. tissue differentiationd. works with auxin in apical
dominancee. chloroplast developmentf. stimulation of cotyledon
growthg. delay of senescenceh. used in plant tissue culture
Delay senescence
effectsa. promotes cell divisionb. cell enlargementc. tissue differentiationd. works with auxin in apical
dominancee. chloroplast developmentf. stimulation of cotyledon
growthg. delay of senescenceh. used in plant tissue culture
Plant tissue culture
structure
effectsa. promotes cell growthb. ripening in some fruitc. leaves to abscised. chlorophyll to bleache. flower pigments to fade
Abscisic acid structure
effectsa. inhibits cell growthb. make buds & seeds
dormantc. stomates to close
Frederick Addicott
Brassinosteroids
discovered in 1970 (J Mitchell & others)
involved in:
cell division,
cell elongation,
vascular development,
seed germination,
light responses
Day-neutral plant graftedto long-day plant
Both plants flower
Long-dayinduction(shortnight)Graft
“Florigen”
Photoperiodism
(long-night)
(short-night)
Also: intermediate-day plants
day-neutral plants
Phytochrome
Proteins that change shape
Order of red & far-red illumination affects lettuce seed germination
Etiolation
Cryptochrome: a blue light sensor
(protein structure)
Blue light
Circadian rhythms eg: sleep movements
Necrotic lesions
Jasmonic acid
salicylic acidmethyl-salicylate