The Effects ofN-1-Naphthylphthalamic Acid and (2-Chloroethyl)-phosphonic Acid on the Gravity-induced Lateral Transport of 2, 4-Dichlorophenoxyacetic Acid

Abstract

N-1-Naphthylphthalamic acid markedly reduced the polar lateral movement of 2, 4-D-[1-¹⁴C] induced by gravity in horizontal segments of Helianthus hypocotyl. The pattern of this inhibition resembled the inhibition of basipetal polar transport, suggesting that both polar movements are operated by essentially the same physiological mechanisms though there are indications of sensitivity differences between the two systems. Ethrel pretreatment of segments, though inhibiting the basipetal transport of 2, 4-D by 33 per cent over the concentration range 0.2 to 2.0 per cent, has little significant effect on gravity-induced lateral polarity of movement, suggesting that ethylene does not act directly on the auxin transport system.