Effects of plant growth regulators and other compounds on flow of latex in Hevea brasiliensis

Eighty-nine compounds have been tested for their ability to promote the flow of latex from Hevea brasiliensis after tapping. The twenty-four substances which showed significant activity were: twelve chloro- and fluoro-phenoxy alkylcarboxylic acids substituted in the 4-, 2, 4- and 2, 4, 5- positions, two chlorinated benzoic acids, α- and β-naphthaleneacetic acid, 3-indolylacetic acid, 2-methoxy-4-diethylamino-6-isopropylamino-1, 3, 5- triazine (methoxy-ipazine), N,N-diallyl-α-chloroacetamide (CDAA), 1,1′-dimethyl-4,4′-bi-pyridilium-2A (paraquat), neomycin, dichloro-m-xyienol, and phenyl mercury acetate and chloride. Despite the many replications the high variability of the yield data does not allow of a precise classification of the relative activities. The most active compounds were 2, 4-dichloro-5-fluorophenoxyacetic acid and 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T), although 2, 4-dichlorophen-oxyacetic acid (2, 4-D) gave increases in yield comparable to those of 2, 4, 5-T in some of the trials.