Herbicidal compounds, N-(3, 4-dichlorophenylcarbamoyl)-N-methyl glycine·H₂O (CD) and N-(3, 4-dichlorophenylcarbamoyl)-N-methyl β-alanine methyl ester (MCMD) bear a marked structural resemblance to diuron, respectively. Consequently, influence of CD and MCMD on photochemical electron transport in chloroplasts isolated from leaves of wheat, large crabgrass, spinach and rough pigweed was examined, together with that of diuron, as a reference chemical. It is interesting to find out whether inhibitory activities of CD and MCMD against the Hill reaction and cyclic photophosphorylation are altered by the addition of the antidote OM.
(1) Herbicides CD and MCMD seemed to have almost no inhibitory activity on photochemical reaction system, showing an approximate median inhibition at 10^-4M. OM was completely inactive below 2×10^-3M.
(2) Inhibitory activity of MCMD was higher than that of CD. I₅₀ (half inhibition M) values of CD and MCMD on the Hill reaction by the above described broadleaf chloroplasts were higher than those by the above described monocotyledon chloroplasts. The results were not compatible with herbicidal activities tested by foliar application.
(3) Inhibitory activities of CD and MCMD against the above mentioned photochemical reactions were not reduced by the addition of OM. On the contrary, those inhibitory activities were strengthened by the addition of OM.

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Molecular size and hydrophobic property (log P) of α, ω-diaminoalkanes (DA) in connection with antidotal action of OM and chemical structure of cutin were considered in some detail. A speculative mechanism of antidotal action by OM for herbicides was postulated from the above described consideration.
(1) The reduction of CD injury to wheat was little under the condition of OM dissolved into Hogland nutrient solution. Similarly, diuron injury to cotton was not reduced by OM under the above mentioned treatment.
(2) It was presumed that a good relationship between the antidotal action to CD-injury to wheat and cold injury of radish by the foliar-applied DA and molecular size as well as log P of DA.
(3) From a consideration about chemical structure, component and biosynthetic pathway of cutin, it was thought that, probably, cutin bears a fair number of space apertures corresponding to the distance of octamethylene unit. Therefore, it seems likely that the OM wedges inserted into space openings result in antidotal effect.

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This experiment was conducted to clarify the effects of soil moisture on germination and emergence of seeds of upland weeds, grasses and common crops. The plants used in this experiment were large crab-grass (Digitaria adscendens Henr.), common lamb's quarters (Chenopodium album L.), Polygonum nodosum Pers., common purslane (Portulaca oleracea L.), Chufa (Cyperus microiria Steud.), livid amaranth (Amaranthus lividus L.), goose grass (Eleusine indica Gaertn.), Rhodes grass (Chloris gayana Kunth), green panic (Panicum maximum), upland rice (Oryza sativa L.), peanut (Arachis hypogaea L.), soybean (Glysine max (L.) Merill), corn (Zea mays L.), grain sorghum (Sorghum bicolor (L.) Moench) and African millet (Eleusine coracana (L.) Gaerth).
1) Seeds were setted in the soils having different soil moisture contents. Each plants showed the highest emergence percentage at the condition of 54.6% (pF 1.5) of soil moisture percentage on dried soil basis. Emergence percentage reduced and average length of time for emergence increased with decreased soil moisture percentage. The reduction of emergence percentage of weeds and grasses with decreased soil moisture percentage were more remarkable than that of common crops. The minimum soil moisture content allowing emergence of common crops was estimated about 20% of soil moisture percentage and that of weeds or grasses was estimated 25-30%. The difference of emergence with decreased soil moisture among weeds was not clear in this experiment.
2) The moisture absorbing power of seeds was related to the difference of emergence percentage with different soil moisture contents. Glucose was mixed with distilled water to obtain desired osmotic presseres, and seeds were germinated in water solutions having different osmotic presseres. From the results of this experiment, the moisture absorbing power of seeds was large in common crops and was small in weeds and grasses. The growth of plants was depressed at the condition of high osmotic presseres.
3) The soil moisture percentage of the surface of the ground (0-1cm) fell to 25-30% after several days of watering in the fields, and this was below the minimum soil moisture contents allowing emergence of weeds. But, soil moisture in lower layer (1-2cm) was relatively stable, so it was clear that a little difference in location of seeds was the important factor for emergence of seeds.

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The chromosome numbers in the pollen mother cells of Scirpus juncoides Roxb. var. hotarui Ohwi, S. juncoides Roxb. var. ohwianus T. Koyama and S. wallichii Nees were investigated, and recognized as follows:
1. The numbers of chromosomes in the PMC of S. juncoides var. hotarui, S. juncoides var. ohwianus and S. wallichii were 22, 37 and 36 respectively.
2. The chromatin bridges were not observed in the I- and II-anaphase in these three species.

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Since the year 1973, each of several herbicides commonly used in rice have been applied annually on paddy field in order to find out the effect on weed succession in early-season rice culture. The results of successive application for five years are reported here.
Weed population became specific to the applied herbicides depending upon their selectivities. In some plots where herbicides effective only for annual weeds were applied successively, some tolerant weed species were increased. In other plots where herbicides, effective for both annual and perennial weeds, were applied successively, little change in the weed population was observed.
These results suggest that the herbicides which are less effective for some weed species should be restricted in successive application for two or three years. In the case of further successive application, we should pay attention to give other weeding methods for remaining weeeds.

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The dwarfish symptoms in growing rice plants which had occurred at Chiba prefecture in 1978 were investigated. The results obtained were as follows.
1. The rice plants in question had following typical symptoms, that is, the half or 2/3 plant height compared with normal, dark green color of the leaves, irregular occurence of the tillers, small amount of the root-development, and brown color of the roots.
2. The occurence places shown such dwarf rice plants in paddy fields were classified as follows, that is, corner part appearance in a field, parallel appearance to levee, ridge-line appearance, spotty appearance, and whole hill appearance in a field.
3. In the fields shown such plants mentioned above, the herbicides contained benthiocarb were applied without fail, and their fields had had chiefly an application of fresh rice straw before the cultivation at last autumn or that spring.
4. The oxidation-reduction conditions in the soil in question showed a positive reduction condition, that is, it was about -60mV for pH 6.0 compared with about +10mV in the normal growth condition.
5. The discrimination in the soil texture shown the dwarfish symptoms was difficult owing to these plants being occurred in various soils, such as loam, coarse loam, sand, and others.

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There are three kinds of so-called “hotarui”, Scirpus juncoides Roxb. var. hotarui Ohwi, S. juncoides Roxb. var. ohwianus T. Koyama and S. wallichii Nees in Japanese paddy rice fields of which seedlings are so like one another that they are hardly distinguishable. The present authors studied the effects of granular formulations of CG102 (4.4% (w/w) piperophos+1.1% (w/w) dimethametryn), TH63 (4.4% (w/w) piperophos+1.1% (w/w) dimethametryn+10.0% (w/w) bentazon), piperophos [4.4% (w/w)], dimethametryn [1.1% (w/w)] and bentazon [10.0% (w/w)] on these three kinds of Scirpus to establish a control method which gave the desirable effect.
1. CG102 and TH63 showed excellent effects on S. juncoides var. hotarui even under heavy water leakage condition. The herbicides also showed high effects on S. juncoides var. ohwianus and S. wallichii, but these effects were reduced under water leakage condition. The reduction of the effects of TH63 on S. juncoides var. ohwianus and S. wallichii under remarkable water leakage condition was prevented by keeping the water depth shallow, 1cm at the treatment of TH63.
2. S. juncoides var. hotarui was susceptible to all the three active ingredients, especially dimethametryn, but the other species were susbeptible to only piperophos. The effects of simultaneous applications of piperophos and dimethametryn or piperophos, dimethametryn and bentazon were higher than those of single application of eacsh active ingredient.

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Removal of lead, cadmium and copper using water hyacinth (Eichhorina crassipes Solms) from the solution polluted by the metals were studied. The plant was floated for one day on 2l of the solution containing the metal at various concentrations, and amount of the metal taken up by root of the plant was determined. Lead was taken up at the highest amount, followed by cadmium and copper. The maximum amount of lead taken up by the root in the experimental conditions was estimated at about 70mg per g dry root. Lead taken up from the solution containing sodium phosphate was determined in small quantities. The decrease of lead content of the root was caused by decrease of avilable lead in the solution. Sorption of the metal by water hyacinth was activated by stirring of the metal solution using magnetic stirrer or air pump.

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The experiment was conducted, in Nagara-cho, Chiba Prefecture in 1979, to confirm the occurrence of dwarfing symptom of rice plant in paddy field sprayed with benthiocarb herbicide.
1. Benthiocarb was first applied on May 4th, immediately after the transplanting, and the second application of benthiocarb was made 25 days after the transplantation. The dwarfing symptom appeared in 30 to 35 days after the first treatment, and the symptom developed remarkably in 45 to 56 days after the treatment. Thereafter, the growth of rice was fairly recovered. Leaf dying due to simetryne application was also observed at the early stage of dwarfing symptom.
2. The dwarfing symptom was not observed both in control plots and in the plots where benthiocarb herbicide was applied, for the first time, 25 days after the transplanting. In all the plots where benthiocarb was applied immediately after the transplantation, the dwarfing symptom of rice was observed with difference in degree of state among the plots. The dwarfing symptom occurred notably in the plots of vast volume application, and in case the same amount of benthiocarb was applied, the dwarfing symptom occurred notably in the plots where fresh rice straw was incorporated in autumn of previous year.
3. The plant height of rice with dwarfing symptom was below the normal height. Rice plants developed two types of abnormal symptoms: (a) dwarf plant with increased number of tillerings, (b) dwarf plant with retarded number of tillerings. In the former case, the number of ears on the main stem was decreased and the tillering from 4 to 7th nodal position in the primary tiller was retarded. However, the primary tiller from above the 8th nodal position and also, the secondary tiller increased.
4. Yield of rice was decreased remarkably when the dwarfing symptom occurred severely. The decrease of yield was caused by the decrease of number of spikelets per ear and lowering of percentage of ripened grains. In case of remarkable leaf dying, decrease of number of ears caused the decrease of yield.
5. The oxidation-reduction potential in the soil was reduced remarkably 25 days after the transplanting. The degree of reduction was lowest in the incorporation plot of fresh rice straw in autumn, followed by spring incorporation plot, then non-incorporation plot. The difference among the three plots was small.

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A herbicide benthiocarb [Saturn^®, S-(4-chlorobenzyl) N, N-diethylthiocarbamate] and a metabolite dechlorinated benthiocarb (S-benzyl N, N-diethylthiocarbamate) were determined in soil and water samples from many plots of a paddy field tested on the dwarfing of rice plant caused by benthiocarb application.
Contents of the metabolite in soils varied with wide range according to dates and sites sampled. In soils sampled to a depth of 10cm, only trace amounts of the metabolite were at first detected, but the contents started to increase on 25 days after the herbicide application and reached to maximum between 35 to 45 days after the application, and then, decreased rapidly. High levels of the metabolite were detected in soils from plots damaged severely with dwarfing, furthermore, in soils near to plants damaged severely with dwarfing. The contents of the metabolite were higher at the upper layer (0 to 5cm), and were very low at the lower layers in soil. The metabolite was also detected in water samples in the same way as the soils.
The metabolite is known as a highly phytotoxic substance to rice plant, so the contents of the metabolite in soil and water could almost perfectly account for the dwarfing of rice plant. Residue of benthiocab itself in soil and water does not affect so fatally to rice plant. Therefore, we conclude that the occurrence of dechlorinated benthiocarb from the herbicide in soils caused the dwarfing of rice plant.

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1. In order to investigate the emergence depth of main weed seeds, seeds of 10 species were sown in Wagner pots (1/2, 000 are) at 1, 5 and 10cm depth on May 1974, and in the field at 0, 1, 3, 5 and 10cm depth on November 1978. These studies were carried out at Kitamoto, Saitama.
2. The maximum emergence depth of each species were as follows:
Echinochloa crus-galli var. praticola, Commelina communis: 10cm
Digitaria adscendens, Polygonum lapathifolium, Acalypha australis, Chenopodium album: 5cm
Fatoua villosa: 3cm
Portulaca oleracea: 2cm
Cyperus microiria: 1cm
The maximum emergence depth of Amaranthus lividus varied from 1cm to 5cm.
3. Emergence percentage of Digitaria adscendens and Cyperus microiria varied with days after harvest. Namely, emergence percentage of these species passed over one year after harvest were higher than that of these species within one year after harvest. This fact correlated with light requirement for germination. Especially, Cyperus microiria seeds maintained high light requirement even at one year after harvest.
4. Emergence percentage at soil surface of Polygonum lapathifolium and Commelina communis were very low as compared with that at 1 or 3cm depth.

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