gravitropism in plants; • The model was independently proposed by Nikolai Cholodny (University of Kiev) in 1927 and by Frits Warmolt Went (California Institute of Technology) in 1928, both based on work they had done in 1926;
growth in gravitropism and phototropism; • Rate of growth depends on the concentration of auxin; • Both gravity and unidirectional light affect the movement of auxin;
for for development of plant organs; • Complex and well coordinated active transport of auxin molecules from cell to cell throughout the plant body; • Plant can react to external conditions and adjust to them, without requiring a nervous system.
responsive elements ! • Some impermeable auxins show their effects without entering the cell; • Sometimes auxin responses are too fast to be mediated by gene transcription; • Auxin regulates the abundance and activity of the plasma-membrane-located H+-ATPase; • Auxin regulates potassium and chloride channels and chloride-uptake transporters;