Photodynamic Herbicides - Chlorophyll Biosynthesis and Technological Applications - page 381

Table 17.3 (continued)

DTH DTH DTH
ALA Mod A + M Template Mod ID Modulator Plant

Imidazole P00887P 1-(2,4,6-Triisopropylbenzene-

sulfonyl)imidazole

Pigweed 30 15 100

Imidazole P00887P 1-(2,4,6-Triisopropylbenzene-

sulfonyl)imidazole

Johnsongrass 30 0 20

Imidazole P00887P 1-(2,4,6-Triisopropylbenzene-

sulfonyl)imidazole

Corn 0 0 0

Furfural P00712P Nitrofurantoin Pigweed 50 0 90
Furfural P00712P Nitrofurantoin Cucumber 50 0 50
Furfural P00712P Nitrofurantoin Corn 0 0 0
Furfural P00552P Kinetin Pigweed 50 80 90
Furfural P00552P Kinetin Cucumber 50 0 50
Furfural P00552P Kinetin Corn 0 0 0
Only modulators that exhibited a negligible effect on corn or a rate of kill of 88 % or better on the
other test plants are reported, except for Thiaflavin T. Percent death was monitored 10 days after
spraying. Mod ID modulator identification number in the database, DTH ALA death due to 5 m M
ALA treatment, DTH Mod death due to 20 m M modulator treatment, DTH A + M death due
to 5 m M modulator treatment. Modulators that are effective by themselves without ALA are
probable inducers

ALA and TDPH modulators accumulated massive amounts of tetrapyrroles in
darkness (Rebeiz et al. 1991 ). Although Proto was the main tetrapyrrole that
accumulated, significant amounts of MPE and Pchlide were also formed. In the
light, the excised roots that accumulated tetrapyrroles, exhibited significant
phytotoxicity (Rebeiz et al. 1991 ).

17.7.2 Effects of TDPH on Attached Cucumber Roots

To determine the effects of TDPH treatments on attached roots, cucumber seedlings
were watered once with a solution consisting of 4 mM ALA and 3 mM modulator
(Chung and Rebeiz, unpublished). The treated seedlings were kept in darkness for
various periods of time prior to tetrapyrrole analysis and exposure to light. As was
observed with excised roots, the roots of intact seedlings watered with a solution of
ALA + 10-phenanthroline accumulated massive amounts of tetrapyrroles (Rebeiz
et al. 1991 ). In this case too the major tetrapyrrole pool that accumulated in
darkness consisted of Proto. However, this tetrapyrrole accumulation was not
toxic to the root cells in darkness. Even after 2 days in darkness no apparent
damage to the root system was observed. These results indicated that although
plant roots do react to treatment with ALA and TDPH modulators by accumulating
tetrapyrroles, they do not exhibit the phenomenon of dark tetrapyrrole-dependent
death which was observed in some insects (Rebeiz et al. 1991 ).