This experiment was conducted to investigate the effect of phthalimido-methyl-0, 0-dimethyl-phosphorodithioate (Imidan) known as an acaricide and its possible metabolic products on the growth of plant, when sprayed on the leaves of rice plant. The results are summarized as follows.
1) Possible metabolic products of Imidan, the following compounds were synthesized or recrystallized for the present experiment.
a) N-Hydroxymethyl phthalimide
b) Phthalimide
c) Phthalamidic acid
d) Phthalic acid
e) Anthranilic acid
f) p-Amino benzoic acid
g) p-Hydroxy benzoic acid
h) Benzoic acid
2) Among the above materials, a), c), d). e). and Imidan were dissolved in a buffer solution respectively to be 10 and 20 p.p.m and tested with the wheat coleoptile straight growth method.
According to the results, Imidan inhibited the growth of coleoptile in both 10 and 20 p.p.m., whereas the others showed much better growth than the control, especially phthalamidic acid in 10 p.p.m.
It appears that Imidan itself inhibits the coleoptile growth, whereas the metabolites derived from Imidan through various metabolisms, including hydrolysis in plant tissues show growth-regulating activity. (refer: Table 1, Fig. 1)
3) 20, 100 and 200 p.p.m. solutions of Imidan emulsion in xylene were prepared. The lengths of shoot ant root of rice seeds germinated on the re-respective media were measured after 12 days. The data shoved that root was much more elongated in Imidan 20 p.p.m., whereas shoot in Imidan 100 p.p.m., respectively, than in the xylene control.
An interesting finding was that xylene used as solvent had a tendency to inhibit seriously the root growth of rice seed. (refer: Table 2.5).
4) The emulsions of concentrations in 10, 25, 50 and 100 p.p.m´s of control, Imidan, N-hydroxy methyl phthalimide, anthranilic acid, and phthalmide, respectively, were sprayed twice on the rice plant on pot. After a certain period of time lengths of rice culms were measured, showing that plots treated with Imidan and N-hydroxy methyl phthalimide exhibited much more growth than those of control and the others.
5) Leaven and stems of rice plant were sampled and extracted with dried acetone at the intervals of 3-, 5-, 7-, and 14 days after treated with Imidan 250 p.p.m. emulsion. This sample extracted with acetone was purified by means of prechromatographic purification method with acetonitrile and paperchromatographed to detect the following metabolic products.
Imidan (Rf: 0.97-0.98), N-hydroxy-methyl phthalimide (Rf: 0.87) phthalimide (Rf: 0.86-0.87), phthalamidic acid (Rf: 0.13-0.14), phthalic acid (Rf: 0.02-0.03), benzoic acid (Rf: 0.42-0.43), p-amino benzoic acid or p-hydroxy benzoic acid (Rf: 0.08-0.09), and unidentified compounds (Rf: 0.73, 0.59, 0.33, 0.23, 0.07).
In addition, in the early stages. such ass 3- and 5 days nonhydrolyzed Imidan and its first hydrolytic product, N-hydroxymethyl phthalimide were detected in relatively large amounts, whereas in the last stages of 7- and 14 days due to further decomposition, the afore-mentioned two materials were reduced in the amount and p-hthalic, phthalamidic. benzoic, and p-Hydroxy benzoic, or p-Amino benzoic acids were detected in a considerably large amount. It is, therefore, believed that most of Imidan applied to the leaves of rice plant may be decomposed within almost 14 days. In the light of above observations it is considered that Imidan itself is not involved in plant growth regulating activity, whereas various phthaloyl derivatives produced in the course of metabolism (namely, enzymic action) in plant tissues may have such effect.
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