The development of the dormancy breaking chemical substances that should be able to control weeds-simultaneously is significant to research reasonable weed control methods.
In this present paper, as a link of studies on the termination of dormancy in cleaver (Galium aparine L.) seeds and for the development of the dormancy breaking substances, the role of seed coats of dormancy seeds, and the histological and physiological changes during the process to termination of dormancy have been investigated.
1) According to the histological observation during dormancy, the cleaver seed coat is of thin and plane figure, and yet the endosperm cells are constituted with thick cell walls and arranged irregularly.
The embryo is embedded in the schizogenous intercellular space in the center of the endosperm. And then on germination, the embryo elongates throughout the new schizogenous intercellular space in the endosperm at the top of the embryo.
2) Some physical and chemically resolving treatments are not able to break the dormancy in cleaver seeds, and, in the dry seeds, the phenomenon of inhibition water absorption cannot be observed.
It is evident that the dormancy in cleaver seeds should not be originated in hard seed coat as well as Milk vetch (Astragalus sinicus L.) seeds.
3) The water absorption rate of cleaver seeds does not change in the process to the termination of dormancy (30°C incubation), but the respiration activity (O₂-uptake) is decreased remarkably.
Moreover, when the seeds are incubated in the optimum temperature for germination (10°C incubation) the histological aspects of the incubated seeds are much similar to those of dormancy seeds and the elongation of the embryo tissue can not be observed till the seeds germinate.
During the period, the respiration of seeds, however, is activated and the oxgen uptake rises gradually. On the contrary, the hardness of seeds are reduced in a high degree.
These results signify that the action of dormancy breaking in cleaver seeds should be promoted by two temperature steps, that is at first by 30°C and at fast by 10°C.

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In this present paper, the effects of some chemicals on the breaking of dormancy have been examined in cleaver seeds of which the ecological features, and the histological and physiological changes during dormancy were partially investigated.
These results may produce the useful data for the development of the dormancy breaking chemicals and the establishment of reasonable weed control methods.
1) The NIP emulsion does not take any effect on the breaking of dormancy, but, when the seeds are soaked in NIP emulsion with 30°C, the rate of dead seeds in the treated seeds increases in a high degree, with increase of soaking terms of seeds and the concentration of NIP emulsion.
Some diphenylether derivaties synthesized, however, have not much effect on the dormancy cleaver seeds.
2) Except gibberellic acid, the dormancy breaking chemicals that became generally known, for instance, kinetin and KNO₃ etc. can not have any effect on the breaking of dormancy and the death of seeds.
3) The gibberellic acid in a high concentration accelerates remarkably the breaking of dormancy in cleaver seeds in which the dormancy breaking by high temperature (30°C) have not been much promoted.
We can guess that the gibberellic acid should not accelerate the germination, but impel a certain point in the metabolism of the breaking of dormancy.

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The germination of Digitaria adscendens seeds which had been stored in dry storage after harvested. were examined. The results were as follows:
(1) Even under the favorable condition in light, temperature, and moisture, about 50 days were required to start the germination of the freshly harvested seeds; but after the ageing in dry condition, the speed of germination was accelerated.
(2) The effect of light on breaking of seed-dormancy was weaker in a lower intensity than in the higher.
(3) High temperature (40°C) was effective for breaking of dormancy and it was possible to make the dormant seeds germinated by furnishing with a temperature of 40°C for five days.
(4) The effect of light on the germination of partially awakened seed was found to be very clear, and the irradiation after soaking of the seeds for 24 hours was more effective.
(5) The length of irradiation which required for the germination was shorter at high intensities, but the irradiation time was longer than a definite time, the difference between the light intensities became to be obscure.
(6) When it became lower than the minimum temperature needed for germination, the effect of light even on the partially awakened seeds was diminished.

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The present authors investigated the adequate spray time of paraquat for the control of crabgrass, and as the result they made clear that paraquat sprayed in the twilight at sunset damaged crabgrass most remarkably. The result suggested that because the paraquat sprayed at sunset penetrated into the foliage of crabgrass without decomposition by ultraviolet rays and the herbicidal activity appeared slowly accompanied with gradual increase of light intensity in the next morning, paraquat could easily move within the plant and therefore the herbicidal action spread in all over foliage. While, in the high intensity of sunlight, because paraquat was not only decomposed by ultraviolet rays but the phytotoxicity was also extremely acute, and therefore the tissue of foliage of crabgrass was rapidly damaged and paraquat moved scarcely within the plant, the herbicidal effect of the paraquat sprayed at daytime was less effective than at sunset.

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The effect of some external factors such as temperature and herbicide concentration of culture solution containing prometon (2-methoxy-4, 6-bis (isopropylamino)-s-triazine), light- and solution-exposure time on the phytotoxicity of the herbicide to seedling of cucumber (Cucumis sativus L.) was studied in a controlled environment growth chamber. Uptake of root-fed prometon was quantitatively assayed by counting.
The phytotoxicity was increased as increased with all factors studied, being due to preceding prometon uptake by root. It was likely that, among these factors, the greatly affected was temperature, so that the remarkably great variation in plant injury at 26.7°C and 16.7°C, as compared with the variation with 8×10^-6M and 4×10^-6M of prometon concentration, was found. Regardless of environmental conditions studied, 50 percent growth reduction in cucumber was caused by absorption of 3.36×10^-3mg of prometon per plant, reaching within 36 hours of solution exposure at high temperature. It was observed that a little loss of once absorbed compound from the plant back into solution occurred during dark period at low temperature.
In a study of comparative phytotoxicity of six related s-triazine herbicides, it was shown that the phytotoxicity to cucumber was dependent on kind of substituted function group on the triazine ring; phytotoxicity was greater in the order of methylmercapto>chloro>methoxy in the 4 position and ethyl>isopropyl in the 2 position.

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Simazine, simetryne, atrazine, atratone and ametryne were applied directly to crabgrass (Digitaria adscendens Henrald) in foliar spray with a surfactant (NK 6601, Nippon Kayaku Co.). The surfactant increased markedly the leaf injury of simazine, atrazine and atratone, while it did not do so much in the case of simetryne and ametryne.
In order to obtain the preliminary evaluation of surfactant, its effect on photosynthesis was surveyed. Rice plant, barnyardgrass, crabgrass and soy-bean plant were treated with directed simazine sprays, and the photosynthesis in a chamber was measured. Results showed that the surfactant would enhance the penetration of herbicides.

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(1) In the case of pre-emergence application, the effect of HE-314 (3-methylphenyl-4′-nitrophenylether) EC was slightly inferior to NIP EC (TOK EC). The herbicidal effect of HE-314 EC applied on flooded condition was greater than on dry land condition.
(2) HE-314 has a contact herbicidal effect.
(3) Being different from the other diphenylether type herbicides, HE-314 has a selective herbicidal effect between rice plant and barnyard grass in the case of post-emergence application. This selective herbicidal effect is not lost under flooded condition and even greater than under dry condition, while Propanil has no selectivity under flooded condition.
(4) The selectivity between rice and barnyard grass under flooded condition is highest at 2 to 4 leaf stages of rice plant and barnyard grass, respectively.
(5) HE-314 acts on both plumules and roots, while NIP (TOK) acts on only plumule. Only in the case of plumules, the selective herbicidal action of HE-314 among Gramineae was observed, while not in the case of the action on roots.
(6) HE-314 has a very strong action on the retardation of root emergence and of its elongation, while other diphenylether herbicides have no effect on roots. But the damage caused by absorption through roots is so little as NIP (TOK).
(7) Although HE-314 has a very strong action on roots under solution culture, the action was reduced when mixed with soil.
It is considered that the soil itself must be related to the action in some way, but light seems not to give any influence to the action.
(8) No selective action was recognized between rice and barnyard grass on the retardation of root emergence and elongation and on the absorption action from root.
Therefore, it is obvious that the selective herbicidal effect of HE-314 is due to the action on leaf and stem.
(9) HE-314 seems to be a contact type herbicide, although there is a little tendency of translocation in the body of barnyard grass.
(10) The herbicidal selectivity of HE-314 among species of weeds, at pre-emergence in flooded condition and post-emergence treatment in dry land condition was in the following order.
Ordinary broad leaf weeds≥Gramineae>Spike rush
While, at the treatment on flooded condition there was a tendency as follows.
Gramineae≥Ordinary broad leaf weeds>Spike rush

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(1) When HE-314 EC was applied on flooded pots under non-seepage condition, almost all of the active ingredient remained in water layer until two to five days after the application and there was little active ingredient on the soil surface during these periods. HE-314 content in the soil surface increased gradually and reached the maximum about 8 days after application. HE-314 seems to remain in the soil surface over 40 days after application.
(2) In the application of HE-314 EC on flooded condition, the active ingredient dispersed into water layer at early period showed contact herbicidal effect against leaves and stems of weeds, while that settled down gradually on the soil showed an activity as a pre-emergence herbicide. Therefore, it seems to be very important to control the water level in flooded condition for 7 days after application.
(3) In the comparison of the methods of post-emergence application, the order of herbicidal activity was as follows:
dropping on flood water>spraying on leaves after drainage>dropping on the soil after drainage.
When HE-314 EC is sprayed on leaves and stems of weeds or applied on soil surface after drainage respectively, we can restore the herbicidal activity by flooding at an early period after the application.
(4) By drainage within 3 days after application on flooded condition, the active ingredient in water might be carried away, consequently the activity, especially, the contact herbicidal one in water would be lost. While, drainage 4 or 5 days after application showed almost the same results as nondrainage check.
(5) The deeper the depth of flood water was, the more active HE-314 EC was to be against such a taller grass as barnyardgrass. On the other hand, the herbicidal activity of HE-314 increased against such short weeds as broad leaf weeds under a shallow water condition. It seems to be very important to flood to cover weeds enough with water, and to make higher the concentration of the active ingredient in water as much as possible.
(6) Regardless of the seepage rate, contact herbicidal effect of HE-314 in flooded condition remained constant, as far as water level was maintained at the same extent as that of application. However, after the flood water was drained off, the herbicidal activity of HE-314 decreased very much.
(7) Areas of leaves and stems of weeds submerged in water, contacting period with herbicide-containing water, concentration of the active ingredient in water and the maintenace of flooded condition would be very important for the herbicidal activity of HE-314.
(8) HE-314 did not cause any phytotoxicity to transplanted rice plants regardless of the depth of flood water.

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Studies on the rice injury and weed control by methyl-N-(3, 4-dichlorophenyl) carbamate (swep; MCC in Japan) were made in field and pot experiment to decide the optimum application time in dry period in direct-seeded rice culture.
Rice plants were not injured at rates of 30 to 50g/a of swep when applied at pre-emergence and before developing of the 1st leaf. However, young rice plants having 2 or 3 true leaves were injured heavily.
Swep was very effective at the rate of 50g/a for barnyard grasses when applied before emergence or before having about 4 leaves of the grasses. Other common annual weeds were controlled satisfactorily.
Then, although swep was applicable at the period between sowing and shooting stage of rice, the spraying at shooting stage was most effective.
The results are discussed with respect to the combination of weeding methods in dry-seeded rice culture.

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Studies on the injurious effect of methyl-N-(3, 4-dichlorophenyl) carbamate (swep; MCC in Japan) on rice plants were made in pot experiments under various spraying conditions.
Rice plants before or soon after emergence were tolerant to swep, but the susceptibility became greater as the growth stage advanced. By the spraying of swep at the 2.5 to 3 leaf stage rice plants were injured mostly and some were killed, while the rice seedlings having one true leaf were resulted a slight injury.
These injurious effects were greater in the manufactured formulations of 1966 than of 1965. Seedlings grown feebly under partially shaded sun-light were more susceptible.

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Regarding the phytotoxicity over rice plant, some experiments were carried out to investigate propanil detoxication in various conditions of cultivation and in the growth stages of rice plant and barnyardgrass by these tissue homogenates.
1. In rice plant cultivated with each excessive quantity and deficiency of nitrogenous, phosphoric and potassium fertilizers, propanil decomposing activity of the excessive quantity plot was almostt equal with the standard plot, while in the deficiency decreased very much.
2. Much different was not recognized in propanil decomposing activity among the flooded, the dried and the shaded plots.
3. Propanil decomposing activity of blade and sheath of rice plant and barnyardgrass from 1.5th leaf stage to 8th leaf stage was examined using these tissue homogenates. The homogenate of rice plant in early stages had high propanil decomposing activity and lowest during 4th-5th leaf stage, the weaning stage. After 5th leaf stage the activity was as high as in early stages.
4. In the homogenates of barnyardgrass, propanil decomposing activity was epual at each stages from 1.5th to 8th leaf stage and very lower than rice plant.

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(1) Cyclohexenylcyclohexanone (CHCH) showed a synergistic action on the herbicidal activity of propanil, especially in a mixture, propanil: CHCH=2:1, which was named STI-100. In this combination, the selectivity between rice plant and barnyardgrass was still maintained.
(2) The effects of various properties of surfactants on the herbicidal activity of STI-100 were surveyed.
(3) Decreased extent in herbicidal activity by a rainfall was smaller in STI-100 than in propanil itself.
(4) In the case of propanil, the evening spray was the lowest in the herbicidal activity; while in STI-100 the effect was very small.
(5) The effect of growth stages on the damage of rice plants by both propanil and STI-100 was also surveyed.

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Joint inhibiting effect of a mixture of DBN (dichlobenil, 2, 6-dichlorobenzonitrile) and TPN (Daconil, tetrachloro-isophthalonitrile) on the growth of young buds of rice seeds was tested under a lighted laboratory condition at 25°C. The experimental data obtained as the relations of concentrations of each chemical and their 1 to 1 combination to the average length of young buds were analysed statistically at a time by FINNEY's method regarding quantitative observation, then the parallelism of these three regressions was tested. The relations between concentrations of chemicals and the average length of young buds could be fitted satisfactorily by the three parallel regression lines shown as equations: Y₁=3.4499-2.5407x, Y₂=5.3108-2.5407x, and Y₃=4.5141-2.5407x. Subscript numbers 1, 2, 3 denote for DBN, TPN and their 1 to 1 combination respectively. For this reason, the result was tested for similar joint action according to FINNEY's method which is specific for testing for similar joint action when the probit regression lines of the mixture and its constituents are parallel. From the First two of these equations, the potency of TPN relative to that of DBN was given by ρ=0.1852. If the DBN and TPN act similarly, the regression equation of the mixture in a proportion of π₁:π₂=1:1 could be predicted theoretically as Y₃′=a₁+blog(π₁+ρπ₂)+bx=4.0271-2.5407x. The measure of synergism calculated from these empirical and theoretically predicted equations was Δs=0.4870, and it showed antagonism. The variance of Δs was calculated by the following equation which was slightly modified the equation (8.11) in FINNEY's Probit Analysis:
V(Δ_s)=s²/(π₁+ρπ₂)²H²[π₁₂/₁Snw+ρ²π₂²/₂Snw+(π₁+ρπ₂)²/₃Snw+{π₁y₁+ρπ₂y₂-(π₁+ρπ₂)(y₃-Δ_s)}²v₁₁/b²].
The test of significance of antagonism obtained may be carried out as a Χ² test taking, Χ²_[1]=Δ²_s/V(Δ_s). The calculated result 17.33 showed the indication of antagonism was significant at Pr=0.05, so that DBN and TPN jointly acted in antagonistic way in inhibiting the growth of young buds of rice seeds.

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This study was conducted to obtain some informations on the properties of a selective herbicide, solan (CMMP) for tomatoes. That is, selective action of solan for some crops and influence of spraying with other chemicals before and after spraying with solan were investigated.
(1) The following crops showed a highly tolerance to postemergence application of solan: tomatoes, carrots, parsley, Japanese honewort, strawberries, and peanuts. But eggplant, sugar beets, petunia, green pepper, onions, and cucumbers were highly susceptible to this herbicide.
(2) Action for carrots of solan decreased as growth of carrots advanced as same as in tomatoes. But carrots increased their tolerance much more rapidly than tomatoes, and carrots of three to four leaves stage got to maximum tolerance to solan, to which tomatoes reached after six to seven leaves stage.
(3) Some injuries were observed when Phenitrothion, carbaryl, or Dimethoate are sprayed before or after spraying solan. Therefore, a week is necessary for spraying, Phenitrothion, carbaryl and Dimethoate before or after spraying solan and three days for spraying EPN, Zineb, Maneb, and Triazine (Dyrene). Such chemicals as Bordeaux mixture, methiram, Captan, DDT, and DDT-DDVP mixture had no influence on the action of solan.

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(1) Three cases were found by increasing of the nitrogen fertilization on forage grasses as follows:
(a) Orchardgrass seeded in autumn predominated over the weeds, (b) both spring seeded orchardgrass and weeds increased, and (c) in the case of radino-clover seeded in autumn or spring weeds increased more than the forage crop, by the increase of nitrogen fertilizer.
(2) The effects of preceding crops on weed population were also surveyed.

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Auto-ecology of field horsetail was surveyed from the standpoints of emergence from spore, elongation of subterranean stem, emergence of root from vegetative stem, depth of emergence, effect of soil pH, effect of fertilization and so on.
For the purpose of the control of this weed in barley or wheat fields, the application of linuron and 2, 4-D (100g+200g in a. i, per 10 are) at the times between vigorous emegence stage of this weed and 15 days before the harvest would bring a good result. When next crop cultivation will be expected, the former application time should be selected.

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1) In southern part of Japan, the time of flowering of Artemisia princeps Pamp. is late september to early october. As the results of experiments the flowering was observed under short day (8 hours light), and did not under long day condition (continuous light).
2) Number of head per plant was 2, 000-14, 000, and a head consisted of about 15-17 florets. On the other hand, the rate of fructification of the florets was about 2-40 per cent, averaged about 20 per cent. From the results, number of seeds per plant was about 5, 000-40, 000.
3) About 20 days after flowering, the seeds had an ability of germination, and it reached maximum after about 50 days. This result showed that the seeds had no dormancy. From our observations, it seemed that the seeds germinate from late autumn to early winter and pass through winter season with cotyledonary plants.
4) Effect of temperature on germination of the seeds was as follows: minimum temperature; 0-5°C, optimum temperature; 20-30°C, maximum temperature; 35-40°C
5) The rate of emergence of cotyledonary plants war good under the soil of 10-20 per cent soil moisture content, and it decreased with the increase of soil moisture content. However, the seeds were able to germinate in boiled water, and it grown up to 6 leaf stage under the water.
6) The rate of emergence was also affected by the depth of seeding, and it decreased with the increase of the depth of seeding. As the effect of soil compaction of cover soil after seeding, in the plot of 0.1kg/cm³-compaction 30 per cent of seeds emerged at 0.5cm-seeding depth and did not emerge at 1.0cm-seeding depth. In the plot of 0.2kg/cm³-compaction no emergence occured even at the plot of 0.5cm-seeding depth.

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For the control of Cyperus serotinus Rottb. and Eleocharis tuberosa Shult. var Kuroguwai Makino, MCPA, amitrole, mixture of MCPA and amitrole, paraquat and dalapon were applied to foliage at four stages of the plants.
Applications of MCPA, mixture of MCPA and amitrole, paraquat before appearance of new tubers killed foliage almost completly and re-sprouting was prevented.
At the early stage of new tuber formation, the applications of amitrole, mixture of MCPA and amitrole, paraquat were effective. Abnormal shoots sprouted from tubers owing to these treatments.

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