Plant Developmental Responses. Phototropism positive

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


Apical dominance(released)


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


(b) Do not post photos on Internet


Fruit set (without seeds), size and spacing


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

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Plant Developmental Responses. Phototropism positive