HORT301 Phytohormones

Phytohormones are Naturally produced in plants Chemicals regulating plant growth, development and differentiation Active at low levels Present in several major classes: a.Auxins b.Gibberellins c.Ethylene d.Cytokinins e.Abcisic acid f.Brassinosteroids

Gibberellic acid (GA) Seed germination Stem growth Fruit set GA Floral initiation

Gibberellic acid (GA) About 136 GAs with structural similarity Only a few are “active”: e.g. GA 1, GA 3, GA 4, GA 5 and GA 7

GA biosynthesis pathway Sumagic (Uniconazole-P ) Mutation in dwarf pea Ultradwarf: No GAs Dwarf: Contains : GA 20 Traces of GA 1 Tall: Contains: GA 1

Effects of GA on growth

Experiment A+B: Effect of GA/GA inhibitor on pea growth GA or Control solution GA inhibitor or Control solution Label pots (group and lab number, treatment) Measure internode length of 2x 5 dwarf and 2x 5 tall pea plants Measure internode length of 2x 5 dwarf and 2x 5 tall pea plants again after 2 weeks in class (MONDAY Oct. 5 th ) Treat dwarf plants with GA or Control solution Treat tall plants with GA inhibitor or Control solution

Auxins Phototropism Cell elongation Gravitropism Auxin Apical dominance Phyllotaxis Floral initiation Senescence in roots in stems

Auxin

Effects of IAA on segment elongation

Acid growth hypothesis

Experiment C: Effect of auxin/pH on segment growth Cut maize seedlings in exactly 1 cm long segments using a razor blade (15x) NOTE: Do not let the cut segments dry out! Label each dish Place five sections in a Petri dish containing either A) IAA (Auxin) solutions of M B) low pH water, pH 4.5 C) neutral pH water, pH 7.0 (control) Incubate overnight in the dark. The next day (Sept. 22nd) measure the total length of all segments after incubation Calculate mean value and standard deviation. Compare the segment length of each treatment

Ethylene Fruit ripening Cell expansion Seed germination Ethylene Apical hook Senescence

Experiment D: Effects of ethylene on soybean seedlings “Banana” Measure the height of the plants Place one pot each in a bag a) With a banana b) With a banana in a GreenBag c) Without a fruit Wait four days and come back to measure plant height again (FRIDAY Sept. 25 th )

Todays experimental plan GA treatment of dwarf mutant in pea Measure length of 2x 5 pea plants Apply GA or Control solution Measure length of plants again after 2 weeks (MONDAY 5 th ) GA inhibitor treatment of pea plants Measure length of 2x 5 pea plants Apply GA biosynthesis inhibitor or Control solution Measure length of plants again after 2 weeks (MONDAY 5 th ) Auxin treatment of maize seedling segments Cut maize seedlings in 1cm segments (15x) Place segments in IAA, low pH or Control solution Measure length of segments the next day (TUESDAY 22 nd ) Ethylene treatment of soybean seedlings Measure length of 3x 5 soybean plants Place pot with 5 plants in bag with banana, wrapped banana or no banana Measure length of plants again after 4 days (FRIDAY 25 th )

Pipettes P1000 P200 P uL = 1ml Use for: uL 200uL = 0.2ml Use for: uL 20uL = 0.02ml Use for: 2-20uL

Map of HLA greenhouse Tissue culture lab Zone 21

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