Lecture Notes5

Induces stomatal closure mutant plants wilt unless

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Unformatted text preview: re: • Mutant plants wilt unless grown in constantly humid conditions. Gibberellins (p. 650; 613). Kurosawa (1926) “Foolish seedling disease” caused by a parasitic fungus: Gibberella fujikuroi. Gibberella Other Japanese scientists isolated the factor: Other gibberellin. Synthesized in young shoot tissues & developing Synthesized seeds seeds Transported via xylem & phloem. Action of Gibberellins Action Stimulates cell division & Stimulates elongation. elongation. Induces seed germination. Stimulates bolting & flowering in Stimulates bolting biennials. biennials. Brassinosteroides: (P. 652). Brassinosteroides Brassinosteroides: Growth promoting steroid hormones. Growth Produced in all parts of plant: Produced Usually act locally near site of synthesis. At least 70 related compounds known. At Brassinolide most widespread. Required for normal growth: Wide range of developmental roles. Cell division & elongation, differentiation of vascular Cell tissue, photomorphogenesis, flower & fruit development, etc. development, External Factors & Plant Growth (Ch 28) (Ch The Tropisms: The Tropisms Plant growth responses: (bending curving) because of Plant external stimulus (p. 660). external Phototropism: Growth in response to directional light Elongation on shaded side of growing shoot tip: Went’s Experiment: Auxin-permeated agar blocks Went’s cause seedling tips to bend. cause • Auxin migrates to shaded side, stimulating elongation. Gravitropism (p. 662; 623) 623 Growth in response to gravity. Calcium involved: Ca++ moves to upper side of shoots, lower side of roots. lower Auxin & cytokinin also involved. Percep...
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