Chlorophyll synthesis modulators

Park H and Hoober JK (1997) Chlorophyll synthesis modulates retention of apoproteins oflight-harvesting complex II by the chloroplast in Chlamydomonas reinhardtii. Physiol Plant 101 135-142... 

In plants treated with these herbicides, damage is light dependent and closely correlated with the level of PPIX that accumulates. PPIX accumulation is apparently largely extraplastidic. Treatment with the porphyrin precursor 5-aminolevulinic acid (ALA), in combination with the heme and chlorophyll pathway inhibitor 2,2 -dypyridyl (DP), results in the accumulation of toxic levels of primarily Mg-PPIX monomethyl ester. DP deregulates porphyrin synthesis and ALA provides additional substrate. DP and other chlorophyll synthesis modulators in combination with ALA can increase the selectivity as well as enhance the efficacy of ALA as a herbicide. Exogenously applied porphyrins are far less effective as herbicides than treatment with compounds that cause plants to accumulate their own porphyrins. 

They hypothesized that the sensitivity of a species to ALA plus chlorophyll modulators is due to both extent of porphyrin synthesis and the chemical nature of the accumulated porphyrins. Thus, the greening group to which a species belongs could strongly influence... 

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