THE METABOLISM AND RADIAL MOVEMENT OF GROWTH REGULATORS AND HERBICIDES IN WILLOW STEMS

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Summary

The metabolism of IAA, NAA, MCPA, 2.4-D, 2.4.5-T, MH, TCA and paraquat was investigated in bark strips and stem segments. Both IAA and NAA were extensively metabolized (up to 80% and 40% respectively of the applied compound was converted into other compounds in 24 hours). The principal metabolite of IAA appears to be IAA asp. 2.4-D, paraquat, TCA and MH were metabolized to a small extent (maximum of 2% in 24 hours), whilst no metabolites were detected from MCPA-i-14C and 2.4.5-T-I-14C. The decarboxylation rate of I-14C-labelled IAA, NAA and the phenoxyacetic acids was low, IAA having the greatest rate (maximum of 4% of the total activity applied given off as 14CO2 during 48 hours).

Investigation of the relative mobilities of the non-metabolized compounds from xylem to phloem, and from phloem to the xylem stream, revealed that MH, MCPA and 2.4-D were the most mobile in both directions, TCA and paraquat the least mobile. A comparison of the mobilities of IAA and its metabolites, and NAA and its metabolites, centrifugally and centripetally across the wood was also made. NAA appears more mobile than its metabolites in both directions. In contrast, IAA seems to be more mobile than its metabolites only in a centripetal direction, the converse being found in centrifugal movement.

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