Plant Developmental Responses Phototropism positive Gravitropism negative positive

Plant Developmental Responses

Phototropism positive

Gravitropism negative positive

Thigmotropism

Heliotropism Sun rising over horizon Morning Noon Afternoon Old Fig. 36. 11

Nastic movements Open Leaflet Pulvinus Vascular tissue Closed Decrease of turgor in parenchyma cells Parenchyma cells retaining turgor (c) Mimosa Cross-sectional views Old Fig. 36. 08 c

Venus fly trap (vulnerable)

Fig 6 -2 Cell communication eg: hormones Signal transduction pathway (induction)

Auxin structure

The Darwins’ work on phototropism + coleoptile of grass seedling - - +

Frits Went’s experiment

What’s happening?

effects a. promotes cell growth b. shoot phototropism c. root gravitropism d. apical dominance e. differentiation of vascular tissue f. prevents leaf abscision

effects a. promotes cell growth b. shoot phototropism c. root gravitropism d. apical dominance e. differentiation of vascular tissue f. prevents leaf abscision

Apical dominance (released)

effects a. promotes cell growth b. shoot phototropism c. root gravitropism d. apical dominance e. differentiation of vascular tissue f. prevents leaf abscision

used in agriculture/horticulture to: 1) promote (adventitious) rooting of cuttings 2) cause uniform flowering & fruit set 3) 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 set 3) to give seedless fruit 4) synthetic auxins used as herbicides 5) promote growth & differentiation in tissue culture

Plant tissue culture

Gibberellin structure Eiichi Kurosawa Margaret Radley Bernard Phinney

effects a. promotes stem growth b. induce flowering c. break dormancy in buds & seeds d. lower temperature threshold of growth e. increase yields f. increase size of fruit & distance between g. enhance starch digestion

Phinney’s dwarf corn

effects a. promotes stem growth b. induce flowering c. break dormancy in buds & seeds d. lower temperature threshold of growth e. increase yields f. increase size of fruit & distance between g. enhance starch digestion

(b) Do not post photos on Internet

effects a. promotes stem growth b. induce flowering c. break dormancy in buds & seeds d. lower temperature threshold of growth e. increase yields f. increase size of fruit & distance between g. enhance starch digestion

Fruit set (without seeds), size and spacing

effects a. promotes stem growth b. induce flowering c. break dormancy in buds & seeds d. lower temperature threshold of growth e. increase yields f. increase size of fruit & distance between g. enhance starch digestion

Seed germination (part of “malting” for making beer)

Cytokinin structure Carlos Miller Related to adenine Folke Skoog

effects a. promotes cell division b. cell enlargement c. tissue differentiation d. works with auxin in apical dominance e. chloroplast development f. stimulation of cotyledon growth g. delay of senescence h. used in plant tissue culture

Delay senescence

effects a. promotes cell division b. cell enlargement c. tissue differentiation d. works with auxin in apical dominance e. chloroplast development f. stimulation of cotyledon growth g. delay of senescence h. used in plant tissue culture

Plant tissue culture

effects a. promotes cell growth b. ripening in some fruit c. leaves to abscise d. chlorophyll to bleach e. flower pigments to fade structure

Abscisic acid structure Frederick Addicott effects a. inhibits cell growth b. make buds & seeds dormant c. stomates to close

Brassinosteroids discovered in 1970 (J Mitchell & others) involved in: cell division, cell elongation, vascular development, seed germination, light responses

“Florigen” Graft Day-neutral plant grafted to long-day plant Long-day induction (short night) Both plants flower

Photoperiodism (long-night) Also: intermediateday plants day-neutral plants (short-night)

Phytochrome Proteins that change shape

Order of red & far-red illumination affects lettuce seed germination

Etiolation

Cryptochrome: a blue light sensor Blue light (protein structure)

Circadian rhythms eg: sleep movements

Necrotic lesions

Jasmonic acid

salicylic acid methyl-salicylate