Growth Stages Of Rice Plants Research Articles

The Fate of Fertilizer Nitrogen Applied to the Paddy Field and Its Absorption by Rice Plant : III. Fate of top-dressed nitrogen in the soil and its absorption by rice plant

The fate of top-dressed nitrogen (ammonium sulphate) enriched with 15N was investigated in the paddy field. The amounts of nitrogen applied were 30 kg per hectare in 1969 and 25 kg per hectare in 1970, respectively. The earlier was the top-dressing at the growth stage of rice plant applied, the longer stayed the ammonia derived from the top-dressed fertilizer in the plowed layer. This fact is approximately consistent with the duration of absorption of top-dressed nitrogen by rice plant. After harvest only 3 to 10 per cent of top-dressed nitrogen was found in the plowed layer. Since the drainage of the paddy soil was very poor, it was assumed that almost all of the unrecovered top-dressed nitrogen was lost by denitrification. The recoveries of top-dressed nitrogen were higher for the plots applied at the young panicle formation stage than for other ones. The earlier was the top-dressing applied, the longer the duration of top-dressed nitrogen uptake by the plant. And the later was the top-dressing applied, the higher the absorption rate of nitrogen by the plant. The amounts of soil nitrogen abosrbed by the plant were greater in all the plots with top-dressing nitrogen than in those without top-dressing. Therefore, the gross recovery of nitrogen in the plant was greater than the recovery calculated from the tracer.

Periodicity in the air-borne spores of the rice false smut fungus, Ustilaginoidea virens

The diurnal and seasonal periodicities in the air-borne spores of Ustilaginoidea virens , the rice false smut fungus, were studied by sampling air at 1 m. above ground level continuously with a Hirst trap located in a rice plot transplanted with Co. 13 seedlings surrounded by plots with Mtu. 19 . The seasonal changes observed in the daily mean concentrations were given, along with information on the growth stages of rice plants in the plot. It was found that the maximum incidence of spores in the air occurs over a period of about 4 weeks which coincides with the ‘heading’ phase of the rice plants, indicating that both early and late infections are possible. On normal dry days the air-borne spores of the fungus exhibited a regular and sharply defined diurnal periodicity with the daily maximum recurring at 22.00 hr. From the 2-hourly changes in the catches during two selected periods it was shown how rainfall affects this diurnal rhythm by reducing the incidence of spores. The highest hourly estimate recorded was c . 328,200/m. 3 of air.

Effects of Some Cultural Conditions on the Development in Later Growth Stage of Rice Plant in the Ill-drained Paddy Field

Effects of Some Cultural Conditions on the Development in Later Growth Stage of Rice Plant in the Ill-drained Paddy Field

A Method for Estimating Damage by Cool Weather in Rice Production

Until the recent time in the northern part of Japan, there used to be many disastrous years for rice production, whenever unseasonably cool weather occurred in the summer. Lately, however, especially since 1955, the rice production in that part has rapidly increased, and even in years of the cool summer it has become not so much decreased as in the past years. This is due to the recent advance in the technique of rice cultivation in cold districts. But, it can not be considered yet that the danger of cool domage has been completely swept away in cold districts. If the extremely low temperature would happen there, it is not difficult to suppose the occurrence of reduced rice production.It is very important therefore, for the improvement of research on prevention methods against cool damage more efficiently, as well as for the deciding of the food policy, to estimate beforehand where the damage will occur or how much it will be, under the level of advanced technique and similar bad weather conditions as in former years. The author has designed a new method of estimating damage by cool weather and danger grade for cool damage of rice plants, and requested the technicians of all prefectures in cold districts to try to get the estimation by using his method. As his method of estimation, however, only indicates the basic ways and means, the technicians in each prefecture must decide by themselves the most suitable values for the conditions tentatively given in this method. The results obtained in every prefecture will be published elsewhere.The most important parts of the method reported in this paper are as follows1. There are three types occurring in cool damage, i. e., delay, injury, and mixed types.When the growth of rice is considerably delayed mainly due to unseasonably cool weather during its vegetative growth period, the ripening period comes during the low temperature of autumn and results in a reduced crop. This is called the delay type of cool damage. The preiods in which rice is most sensitive to low temperature during its growth are those at the reduction division stage of reproductive cells and at the flowering stage respectively. The rice plants suffer from non-ripened grains due to a temporary low temperature during such reproductive growth periods. This is called the injury type. If the above-mentioned two types of cool damage occur simultaneously, it is called the mixed type.Therefore, the next three relations may be important indexes for estimating damage, i. e., relations between (1) the decrease rate in the production and the air temperature during the ripening period, (2) the decrease rate and the air temperature at the reduction division stage, and (3) the decrease rate and the air temperature at the flowering stage.2. The respective values of these three relations can be prepared from many past results of investigations and experimental reasearch in each prefecture.The decrease rate may be easily got by both these relations and the course of air temperature given in one of the years in which cool damage occurred in the past.3. First of all, however, it is necessary for this estimation to decide the growth stage of rice plants. The flowering stage is almost the same as the heading stage. The reduction division stage is during a period from 10 to 15 days before the heading stage, and the ripening period is the period of 40 days after heading. Then, if the heading stage can be fixed, these three growth stages may be easily decided. Since the accumulated air temperature from sowing to heading is said to be constant for each variety of rice plant, the heading day of the rice plant concerned can be fixed by summing up the daily air temperatures from sowing day till the day on which the accumulated value reaches the constant.4. The result of the estimation in a prefecture, in practice, is obtainable by summing up the results in many small areas such as towns and villages. And the

Studies on the Effects of Soil Temperatures on Rice Plant Growth : I. Effects of soil temperatures upon growth regulating substances and the metabolisms of carbohydrates and nitrogen (1)

Growth regulating substances, carbohydrates (sugars and starch), and nitrogenous compounds (proteid nitrogen and soluble nitrogen) were chemically analysed at various growth stages of rice plants, in order to show the relationship between soil temperature and those substances. Plants of different growth stages were subjected to various soil temperatures such as 30°C, 25°C, 15°C, 30°·20°C, and 30°·15°C (the last two in the series of temperature means changes from high to low) for 10 days. The results were as follows: 1) The contents of the growth-promoting-substances in roots at 15°C or 20°C were much more than those at 30°C. Their largest amounts were, however, found in the plots of alternating temperature. 2) The amount of growth promoting substances in root decreased as the plant grew. They were almost hardly detectable at the highest tillering stage, but they appeared again when the ear primordia began to differentiate. 3) Growth promoting substances were able to be extracted from leaf sheaths including young panicles in 30°C plot, but in 20°C plot they were scarcely recognizable. 4) Larger amount of proteid nitrogen seemed to be accumulated in 25°C and 20°C plots at each stage of growth than in 30°C and 15°C plots; especially in 30°·20°C plot its accumulation was most vigorous. 5) The metabolism and translocation of carbohydrates such as starch and sugars seemed to be most active at 25°C. Low temperatures such as 20°C and 30°·20°C, on the contrary, disturbed the migration of those substances to ear from culm.

Studies on the Evapo-transpiration from the Paddy Field in the Cooler Regions (1)

This paper deals with the results of measurement of evapotranspiration from the paddy fieild at Kuroishi City situated in the cooler region of Japan, from 1953 to 1956.The amounts of transpiration were below 1mm/day in the early growth stage of rice plants and increased gradually with their growth (Fig. 1). But, the amount of evaporation decreased with their growth (Fig. 6).The evapo-transpiration rates to the evaporation E obtained from the meteorological observation field lay within about 1.0-1.3 in the early growth stage and increased after the young ear formation stage. But the rates decreased again from about the tenth day after heading (Fig. 7).Two peaks of the transpiration rates to E were found after the young ear formation stage and the heading stage. From the index of growth amount ln (l and n mean respectively the plant length and the number of stems per unit area), the transpiration rate t/E (t means the amounts of transpiration) and the seasonal changes of τ(τ means t/E/ln×104), it was presumed that two peaks for t/E during irrigation period would probably be found for the case of ln.Total evapo-transpiration amounts throughout the irrigation period varied annualy from 440mm to 553mm and were 493mm on the average, showing 1.22 times as much as E. The average transpiration amount was found to be 0.45 times as much as the evapo-transpiration. The annual changes for the average transpiration amount were larger than the cases of the evaporation amounts obtained from the paddy field.