These studies were carried out to obtain some informations on the mode of action of CMMP (solan).
CMMP was compared with the same anilides, DCMP (karsil), DCPA (propanil), and DCMA (dicryl) on the main site of herbicidal action, and the schema on the mode of action was proposed.
(1) The inhibiting action of CMMP on photosynthesis was compared with that of DCPA on intact plants. In consequence, both of CMMP and DCPA inhibited photosynthesis strongly after the treatment.
(2) It is assumed that the recovery of photosynthesis of a CMMP resistant plant, mitsuba (japanese honewort), is different from the antidote such as DCPA which is hydrolysised in rice plant.
(3) Hill reaction of spinach chloroplast was strongly inhibited by CMMP as same as DCMP, DCPA and DCMA. This is suggested that the main site of herbicidal action of their acid amides is an inhibition of photochemical action and the rate of inhibition of Hill reaction has no relation with their substituted radicals.
(4) The inhibition of CMMP to respiration was compared with those of DCMP, DCPA and DCMA by using roots of rice plants and water foxtails. In consequence, all of these compounds showed inhibition at the concentration of 2.5×10^-3M. The descending order is as follows: DCPA>DCMP>CMMP>DCMA. Therefore, it appears that the inhibition of anilide to respiration is related with their side chain.
(5) The combination of CMMP, DCMP, DCPA and DCMA with chlorophyll takes place apparently and this reaction is considered as one of the reactions of herbicidal action.
(6) The herbicidal effect of CMMP, DCMP and DCMA except for DCPA was particularly reduced by spraying chlorophyllin, although all of these acid amides are similarly included in anilides.
(7) From the results obtained, the following schema on the mode of action of CMMP is shown tentatively in Fig. 8.
The process of death of susceptible plants is as follows: the first step is inhibition of biosynthesis of chlorophyll, the second step is inhibition of photosynthesis and photophosphorylation, and the third step is destruction of chloroplast.
In tolerant plants photosynthesis and photophosphorylation are so inhibited as in susceptible plants, but tolerant plants are resistant for inhibition of chlorophyll biosynthesis and destruction of chloroplast. This resistance is considered to be a cause of the survival of tolerant plants.
It is also considered that the reduction of effect of CMMP by spraying of chlorophyllin is caused by relative increase of active chlorophyll in the second step mentioned above.