The effect of some substituted phenoxyacetic acids on the respiration of three species of fern : a thesis presented at Massey Agricultural College in partial fulfilment of the requirements for the degree of Master of Agricultural Science in the University of New Zealand

Abstract

The problem of control ot weeds in agricultural land has long confronted man, and toxic chemicals have been employed for half a century in eradication or suppression of weeds. The last two decades have seen a tremendous expansion in the use and variety of applications, principally because of the development ot translocated organic compounds of a growth regulatory type which very often are highly selective. Some indication of the interest in chemical weed control, for example with the substituted phenoxyacetic acids, can be seen in the fact that in the U.S.A. alone over twenty million pounds of 2.4-D is manufactured annually. The volume of research has likewise been tremendous. Norman et al. (1), reviewing the field in 1950 covered some three hundred and fifty new papers for the previous year on phytotoxicity. The mechanism of action of growth regulatory type herbicides is an important problem, particularly in so far as it may throw light on the physiology of plant growth and development, and their control by plant hormones. The general approach is still largely empirical, involving a high degree of speculation in the selection and synthesis of new compounds followed by trial and error tests in the laboratory, glasshouse and fields. Detailed physiological studies have been limited and it is only by such study that the principles of toxic action can be laid down. This study is an attempt to examine one small facet, the effect of plant regulators on respiration of a complex and rapidly expanding field of endeavour.