Nine varieties of kidney bean were tested for their stem elongation responstes to CA-3 through application of leaf spray. Their sensitivity was variable, a variety Mantle was the most sensitive one, and Masterpiece was the least sensitive one. In leaves of GA-3 sensitive verieties, the applied GA-3 remained unchanged. But in leaves of other varieties, GA-3 seemed to be converted into an unknown type, of gibberellin, which was detected at Rf 0.3-0.4 on the paperchromatogram of iso-propanol/ammonia water/water (10 : 1 : 1) solvent.

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Applied GA-3 was not altered in leaves of rice plants and kidney bean var. Mantle, one of the most sensitive varieties to GA-3, when those were treated with GA-3. But, GA-3 was changed to an unknown gibberellin in leaves of kidney bean var. Masterpiece, one of the least sensitive varieties to GA-3. Experimental results indicate that GA-3 itself has growth promoting effect on both kidney beans and rice plants, while the unknown gibberellin has not the effect. The fact that this unknown gibberellin exerts growth promoting effect on rice plant and not on kidney bean varieties can be explained by the result that this unknown gibberellin is easi1y converted to GA-3 in rice leaves, but not so in leaves of kidney beans.

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In this experiment, effects of soil moisture content, cultural temperature and a seed size on the strength of plulnule-elongation in paddy rice plants were examined using unbonded gauge type transducer (UT 1kg) and balancing null recorder in darkness. This strength shows mechanical vigour of plumule to push a thing up with the tip of it. The plumules of rice plants were raised under the covering soil of l.6-6.5 cm.The following results were obtained. 1. Effect of soil moisture content on the strength of plumule-elongation in a paddy rice variety, Hoyoku, in japonica type was little under the conditions ranging from l0 to 15 percent of moisture content. The strength decreased with increasing of soil moisture content. It was more evident in short plumules than in long plumules (Table l, Fig. 2). 2. The strength of pltlmule-elongation in paddy rice plants which did not elongate mesocotyl (Hoyoku in japonica type) was maximum in the plumules of 1cm long, and it decreased with growing of plumules. In particular, the strength decreased strikingly in the plumules of about 4 cm long (Fig. 3. 4). On the other hand, the strength in rice plants which elongated mesocotyl (treated-Hoyoku, Hatishail in indica type) was almost the same strength in all stages of plumules (1∼6cm) (Fig. 4). 3. The strength of plumule-elongation in a paddy rice plant, Hoyoku, was more vigorus in the plumules which were cultured under warm conditions (20-30°C) than those under cool condition (17°C). At 17°C, the strength was about 1/4 as Compared with that of 30°C (Table 3). 4. In some paddy rice varieties in japonica type, possitive correlation was observed between the strength of plumule-elongation and a seed size (r=0.512) (Fig. 5).Also, in a paddy rice variety, Hoyoku, the more seed size was large, the more strength of plumule-elongation was vigorous (Table 4).

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Quantitative distribution of protein, lipid, phosphate and potassium in rice kernel was investigated by comparison of contents in l, OOO kernels which were milled in different rate. A friction type test mill for l0g sample was used for milling. Conclusion was shown in Fig.5. Changes with milling time of protein and kernel weight in milled rice were almost similar. Content of protein in highly-milled rice was about 90% as compared with the content in brown rice. From these facts it is considered that starch tissue of kernel is rich in protein. Lipid was one of the most rapidly decreased component by milling, and content of lipid in highly-milled rice was about 23% as compared with the content in brown rice. This fact may Show that lipid in rice kernel exists almost in bran especially in aleuron layer. Content of phosphate and potassium also shows considerable rapid decreases but more slowly than the decreases of lipid. Reducing curve of these component resembles together. Content of phosphate and potassium was respectively 43% and 39% as compared with the contents in brown rice. Perhaps phosphate and potassium may be components of phitin which is contained in aleuron grain and in protein body.

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Effect of temperature was investigated on structure of the wheat mesophyll consisting of the longitudinally elongated arm-pa1isade cells (TP-type cells) and the rice mesophyll consisting of the transversely elongated arm-palisade cel1s (TP-type ce11s). In the first experiment, anatomical observations were made of the third leaf blades of wheat grown at day/night temperatures of 9/9O°C, 17/12°C, 24/19°C and 32/27°C.the results obtained were as follows. 1) The longest leaf blades were formed at 24/19°C whereas the maximal values of leaf blade width, mesophyll thickness and interveinal distance were gained at 17/12°C. 2) Surface/volume ratio of the LP-type cells increased with increasing temperature, as a result of increase in number of protubctfances and decrease in diameter of protuberances 3) So far as the unit leaf area was concerned, the number of mesophyll cells and the total cell surface area increased with increasing temperature. In the second experiment, anatomical observations were made of the lOth leaf blades of rice grown at temperatures of 17/12°C, 24/19°C and 30/25°C. The results obtained were as follows :1) The shortest leaf blades and the thickest mesophyll were formed at 17/12°C. 2) The number of protuberances developed by TP-type cell decreased with increasing temperature. The longest protuberances were formed at 17/12°C. 3) When the unit leaf arca was taken into consideration, the number of mesophyll cells and the total cell surface area increased at 17/12°C. Changes in mesophyll structure with increasing temperature from 17/12°C to 24/19°C were larger than those with increasing temperature from 24/19°C to 30/25°C. From the results of these expeliments, it may be concluded that the wheat leaves grown at higher temperatures and the rice leaves grown at low tempelature (17/12°C) have a mesophyl1 structure like as sun leaves.

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Relative amounts of DNA per. nucleus in rice cells, which were produced by aseptic culture, were measured microspectrophotometrically and compared with that in cells of other species of plants. The nuclei were stained by Feulgen reaction using cold hydrolysis technique. The density was estimated by scanning method at 0.5 or l.0 πm line interval with the wave length of 560nm, employing UMSP-1. The rice nuclei had an average diameter of 4.7 pm. They were very small size compared with those of other crops, being about one half of those in oat and corn. The nuclear DNA in rice cells isolated in liquid medium was about 80 per cent of those in root tip cells. While, mung bean had 2.1 times and oat and corn had 12 times in the contents for the rice nuclei. In rice, relative proportions of 4C nuclei was very small in the free cells, but 5 and 13 per cent were observed in the root tip cells and the callus cells, respectively. However 17 per cent in mung bean and 39 per cent in corn were observed for the 4C nuclei.

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The properties of rice kernel starches of Norin-17 (Japonica type) and IR-8 (Indica type) ripened from fertilization to maturity under different air temperatures combined with photoperiod, light intensity and air-humidity were compared by testing their alkali decomposition value and X-ray diffraction pattern. The alkali decomposition values of Norin-17 were always lower than those of IR-8, indicating that the former is more resistant to alkali. In the regime of this experiment, higher air-temperatures especially during daytime decreased the value. At higher temperatures longday condition seemed to decrease it. Light intensity and air-humidity had little effect on the value. Under the differential conditions tested, X-ray diffraction patterns of Norin-17 varied from type II to type III, while those of IR-8 varied from type I to III with a wider range. Norin-17 starches ripened under the lowest or the highest temperature showed type II, in cotrast, IR-8, starches was type I when matured at lower temperatures or very cool night temperatures, but showed type III when ripened at the highest temperature. At such high temperatres as 35-25 or 30-20°C, type II and type I under shortday condition changed to type III and II, respectively, under longday condition. The patterns were little affected by air-humidity, but were influenced by light intensity; type I and type II under weak light condition changed to type II and III, respective1y, under strong light. In general, alkali decomposition value and X-ray diffraction patterns varied parallel, but sometimes with discrepancy, the cause of which is not clear.

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Experiments were undertaken to clarify the relation between the development of above-ground parts and shoot roots of growing young cane. Five varieties of cane cuttings were planted under various conditions (soil, vermiculite, age of cuttings, date of planting and fertitiy of soil). After germination, the emergence of leaves and shoot roots were observed. The results obtained were summarized as follows: 1. The first shoot roots did not emerge until the 13th leaf (8 leaf scales plus 5 complete leaves) emerged, and the first shoot roots originated from the 6th basal node of young shoot. This relation was recognized at all the conditions examined. Basing on the above finding, the rooting of the shoot roots may be predicted by counting the leaves of above-ground parts. 2. The shoot roots of a given node emerged and elongated simultaneously with the leaf of a node which is higher than the former by seven. In other words, when a leaf was emerging, the 7th node counted downward from the one to which the leaf was attaching, posessd the ability of rooting, and this relation was maintained throughout the whole growing stages of cane. This fact may give a scientific foundation to the usual practices for preparing cuttings from a sugar cane shoot.

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In some cases of direct sowing culture in the Kanto district, there is observed a year by year decrease in yield. The purpose of this experiment is to clarify the reasons for this decrease. The experiment wes carried out on wel1-drained paddy fields from 1968 to 1970. Experimental plots were divided by the number of years of direct sowing culture-first year plot, second year plot, third year plot and long term plot, and the combination of the amount of nitrogen application-0, 12 and 18g per square meter. Results obtained are as follows : 1. Growth and yield. Both the plant growth in the early stage and the yield were greater in the first year plot than in the long term plots. However there were found of apparent differennces in these properties among the second year plot, third year plot and long term plot. 2. Inorganic nitrogen in the soil. The movement of inorganic nitrogen in the soil in the first year plot apparently differed from that in the long term plot. In the first year plot, the amount of ammoniacal nitrogen was higher and the amount of nitrate nitrogen was lower than in the long term plot, in the early stage of upland condition. Accordingly, the ratio of nitrate nitrogen to total inorganic nitrogen in the soil was lower in the first year plot. However there were no significant differences among the second year plot, third year plot and the long term plot, in relation to the amount of inorganic nitrogen and its composition. 3. These results were observed for all nitrogen applicaltion levels in this experment. 4. It may be concluded from the abovefacts, that the better growth and yield of rice in the first year of direct sowing culture are attributed to the retardation of nitrification of inorganic nitrogen inthe soi1 in the early stage of upland conditions.

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Basing on the facts that the decrease of photosynthetic rate and the increase of respiratory rate of the crop p1ants as exposed to sulfur dioxide, the experiment was undertaken to prove the decrease of dry matter production in rice plants by sulfur dioxide treatment for long Period. The results obtained were as follows ; 1. The number of tillers in rice plants was decreased with an increase in the concentration of sulfur dioxide, but the results of the investigation on the effect of sulfur dioxide on the plant height and leaf age in rice plants by sulfur dioxide did not show any significant differences. 2. Total dry weight (leaves+stems+roots) of rice plants was gradually decreased with an increase in the concentration of sulfur dioxide and an extention of treatment hours for which the plants were exposed to the gas. A typical injury by sulfur dioxide was hot discovered on the leaf-blade and-sheath both during and after treatment. 3. Net assimilation rate and increase rate of dry mattr(ΔW)in the rice plants were markedly decrcased by sulfur dioxide treatment for long period.

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The leaf area index at silking time with relation to grain and dry matter production was examined on 2 corn varieties, Tomorokoshi Ko No.7 (varietal hybrid) and Yellow. Dent corn (open-pollinated variety), planted at 4 plant populations on the soils of 3 different fertility levels in 1967. The results are as follows. 1. Grain weight per LAI decreased as LAI increased and there was apparently a linear relationship between LAI and the logarithm of grain weight per LAI at each soil fertility level. The similar relationship was found between LAI and the logarithm of total dry matter weight per LAI in Tomorokoshi Ko No.7. From the relationships a method of estimating. optimum LAI at silkingtime to maximize grain and total dry matter yield was developed. 2. The optimum LAIs for grain production estimated by the method were 2.32, 3.76 and 4.91 for Tomorokoshi Ko No.7, and 2.51, 4.63 and 5.10 for Yellow Dent corn, at low, medium and high soi1 fertility levels, respectively. The optimum LAIs for the total dry matter production of Tomorokoshi Ko No.7 were 4.88, 5.34 and 6.85 at low, medium and high fertility levels, respectively. These results showed that the optimum LAIs for grain and total dry matter production increased as the soil fertility increased. 3. The flat LAI-grain yield curve near the optimum LAI suggested that near-maximum grain yields would be obtained in a wide range of LAI near the optimum LAI. 4. Tomorokoshi Ko No.7 possess an inherent capacity to produce grain weight per leaf area much more than Yellow Dent corn. 5. The optimum LAIs were larger in total dry matter production than in grain production. Therefore, it was suggested that larger LAIs with higher plant populations have an advantage in total dry matter production for silage.

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In order to clarify the ability of assimilation and translocation at different developmental stages of leaf, the following experiments were conducted. Experiments : By exposing the leaves at different stages of developnlent, from emergence to full expansion, in the ¹⁴CO₂, the stagle when the developing leaves start to translocate their assimilates was examined. Classification of development stages after leaf emergence.to full expansion was followed by Carlson's 10 morphologic development stages.All the test plants, except a particular leaf at different development stages, were covered with aluminium foil, and ¹⁴CO₂, was fed for 1 hour. Immediately after feeding of ¹⁴CO2, aluminium foil was removed and the plants were kept in outdoor conditions. Twenty four hors after feeding of ¹⁴CO₂, the plants were harvested and radioautoglaphs were taken. Experiment 2: The ability of assinlilation, and the rates of respiration, translocation and retaining of assimilates at different ages of leaves after the full expansion stages were compared using radioisotopic techniques. Plants were fed ¹⁴CO₂ for lO min. and immediately after treatment, selected plants-one third of the total plants-were harvested and radioactivity of ¹⁴C in the leaves was counted. Half of the remaining plants was kept in the growth chamber of 20°C afer ¹⁴C assimilation. To avoid the translocation of assimlates, leaves of another half of the plants were cut at the petioles 2 cm below leaflet, and put into the glassflask, fi1led with distilled water. They were kept in the same growth chamber. Forty eight hrs. after ¹⁴CO₂ treatment, the plants were harvested and radioactivity of ¹⁴C in the leaves was counted.It is considered that : 1) radio-activityof ¹⁴CO in the leaves inlmediately after ¹⁴CO₂ feeding shows ability of assimilation, 2) ¹⁴C remaining in the leaves 48 hrs. after ¹⁴C assimilation shows the assimilates retained by the assimilating leaves themselves. 3) decrease of ¹⁴C in the detached leaves shows the amount of consumption in respiration, and 4) the amount of ¹⁴C translocated was calculated from these figures. Results of these two experiments are as follows : 1. The leaves of ladino clover are one of the strongest sinks at the early development atage. With the growth of leaves, a change occurs in the function of leaves from sink to source. When developing leaves reached about 65-70% of their maximum leaf area, they started to translocate assimilates. 2. In the case of matured leaves in general, the younger the leaves, the higher the ability of assimilation except leaf Number 1. As for the release rate in respiration, younger leaves utilize a large portion of assinmilates in respiration, and they also retain a large portion of assimilates in their leaves. Therefore, the amount of translocation of younger leaves is not so much. Consumption in respiration and retaining amount decrease in the leaves at middle age. Total amount and rate of translocation of the assimilates are the grleatest in the case of leaves at middle atage (leaves of Number 3 to 6 from growing points), followed by older leaves. 3. Middle and older leaves retain a fairly large porion (15 to 20%) of assimilates in their assimilating leaves themselves.

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In order to establish the direct sowing in flooded paddy field in such cool region as in Hokkaido, it is very important to stabilize the growth during the early stage of the plants, In view of this, and to clarify the relation between the varietal differences of rice seeds to germinate at low temperature and the degree of establishment of seedlings under the conditions of direct sowing in flooded Paddy field, the authors made some experiments in 1968 and 1969, by using 36 varieties as the experiment materials. The yielded results are summarized as follows ; 1. Regarding the relation between the germinability of paddy rice seeds at low temperature and the percentage establishment of seedlings, in 1968, in which water temperature after seedings was relatively low, significant positive correlation was observed. And in 1969, in which water temperature after seeding was relatively high, correlation was not so high, but if four varieties which widely slipped out of the whole tendencies were excluded, very significant positive correlation was also obtained. 2. In 1968, the decrease of percentage establishment of seedlings was mainly resulted from the increase of premature decay of seedlings, while in 1969, it was resulted from the increase of the floating and turned down seedlings. 3. With respect to the relation between the percentage establishment and the dry matter weights of seedlings and of roots, significant positive correlations were observed in both years. 4. The authors reported previously that there were positive signiftcant correlations between germinability at low temperature and the degree of elongation of seedlings and of root at early stage of growth. Thus, to sum up these results, it becomes clear that the germinability of paddy rice seeds at low temperature was a useful characteristic to ensure the stability of establishment seedlings nuder the condition of direct sowing in flooded paddy field in such cool regions as in Hokkaido. 5. As to the relationship between the percentage establishment of seedlings and T/R ratio in dry weights of seedlings, a significant positive correlation was observed in 1969, even though only one variety "wasebozu" which differed widely from the whole tendencies was in existance.

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The experiment was carried out under the condition combining the shading periods (20days, 40 days, 60 days after emergence) and the shading grades (shade 1; 60% of the solar radiation, shade 2; 40% of that, shade 3; 25% of that). The results obtained were as follows. 1. As the shading period became longer and the shading grade higher, not only the early growth during the shading treatment but also the late growth after that was inhibited more remarkably. 2. The first and the last day of flowering, especialy the latter, were delayed with the prolongation of the shading period and with the increase in the shading grade, resulting in the prolongation of the flowering period. The development and growth of the vegetative and the reproductive branches were suppressed by the shading, and consequently, the total number of flowers decreased. 3. The shading at the early growth stage inhibited the fructification of the early flowers, and reduced the number of the mature pods per plant and the shelling percentage, resulting in the decrease in the yield. 4. It was considered that the critical light condition at the early growth stage of peanut plants to recover the subsequent growth and to gain the yield apporoximately similar to that of the plants grown under the natural light condition was 60% of the solar radiation during 60 days after emergence, 40% during 40 days, or 25% during 20 days.

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It is necessary for the fructification of peanut that after flowering the peg elongations and penetrates into the soil. The authers examined the peg elongation and the relation of that to the fructification of peanut, and obtained the following results. 1. Above the ground, the peg elogated at the remarkable rate from a week after. flowering, reached ultimately a length of 15 to 16cm. It was observed that the peg length was reduced with the delay in the flowering date. 2. The peg length of the pods was varied with varieties, namely, was shorter in the order of Chiba No.43 (runner type), Chiba-handachi (intermediate type), and Java No.13 (erect type). The peg length of the pods was shortened with the delay in the sowing time, and that of themat ure pods was shorter than that of the immature pods. 3. The pegs borne on the high position branch of the main stem, on the high order branch and on the node near the apex of the branch required the long terrestrial elongation to penetrate into the soil and to fruit. 4. It was recognized that there were the high negative correlations between the peg length and the weight of one mature pod and of one seed. The similar correlation between the peg length and the weight of one seed (r =-0.824**) was obtained, when the terrestrial peg elongation was varied by changing artificially the distance of the branch from the ground.

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In the first place of this work the present study was conducted to settle a measurement method of the stomatal aperture in the leaves of the rice plant under the paddy field. The measurement methods used here were the infiltration and the micro-relief impression methods. The aperture of the stomata in the infiltration method was expressed in terms of the numbers of solutions penetrating the leaf and this was referred to as the infiltration score. A score of 1 represented injection by l0 per cent iso-butanol+90 per cent ethylene glycol solution (No.1 solution) only which penetrated the stomata with small aperture. A score of 5 represented injection by all solutions containing less than 50 per cent ethylene glycol which penetrated the stomata with wide aperture. In the micro-relief impression method the transparent negative celluloid micro-relief impressions of epidermis were prepared and the pore width of the stomata were measured microscopically. The aperture of the stomata, distributed even in the small portion of the epidermis in the leaf, showed much variation from each other; for example, the range of the pore width was from 0.5μ to 1.2μ, but these variations did not depend on the position where the stomata were situated along the large or small veins, and near the edge or the midrib of the leaf. A linear relationship was obtained between the infiltration score and average pore width of a large number of the stomata in the leaves of the various developmental stages of the rice plant under various weather condition. Almost same score was obtained for the stomatal perture in the upper and lower epidermis of the leaf. The aperture of the stomata in the middle part of the leaf were a little larger than those in the base or top part, but sometimes these differences could not be found. From these results it is concluded that the infiltration method using iso-butanol ethylene glycol mixture solution is suitable for measuring the aperture of the stomata of the leaf in the rice plant under the paddy field.

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The diurnal movements of the stomata in the leaves of various developmental stages of the rice plant under various weather conditions in submerged paddy field were studied by using the infiltration method for measuring the aperture of the stomata. The course of the diurnal movement of the stomata in the leaves of the rice plant grown under submerged paddy field was much affected by weather conditions from day to day. In a sunshiny day the aperture reached the maximum at about 8.30-9.00 a.m. and then decreased very quickly to only 1/2 or less of the maximum in the afternoon. On the contrary, in a cloudy day or not so fine day the aperture increased slowly in the morning to reach the maximum at about noon and in the afternoon the aperture was still kept wide for sometime. From the tillering stage to the heading stage the maximum of the aperture per day was practically the same irrespective of the weather condition except under very low light intensity. However after the heading stage the maximum per day became less. Furthermore, after reaching the maximum per day the aperture decreased more quickly compared with those before the heading. When the aperture became small in the afternoon of a sunshiny day the stomata of the leaves in the rice plant which were covered with polyethylene bag for 20-30 minutes opened again up to near the maximum in the day. From these facts it is assumed that the cause why the aperture of the stomata decreases in the afternoon of asunshiny day or after the heading stage may be due to the water unbalance in the leaves of the rice plant grown under submerged paddy condition.

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The present study was conducted to clarify the differences of the aperture of the stomata and their diurnal movement of a leaf due to its position on the stem. In the fully-expanded leaves, the higher the position of a leaf on the stem, the wider was its stomatal aperture. The stomatal aperture of an expanding leaf was smaller compared with those of the adjacent lower fully-expanded leaf. During elongation stage of the internode the aperture of the most upper fully-expanded leaf was not so wide as in the adjacent lower one. The diurnal movements of the stomata of the leaves on a stem were different from each other depending on their position on the stem. Especially in the sunshiny day the stomatal aperture of the upper ful1y-expanded leaf did not decrease so quickly as those of the lower one in the afternoon, after reaching the maximurn per day, and this phenomenon could be more distinctly recognized after the heading stage. The results that the aperture of the stomata and their diurnal movement in the leaves were different from each other owing to their position on the stem were discussed in connection with the vascular, especially xylem, in the leaf sheath or the internode, the leaf age and the root age.

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?? ?? ?? ?? ?? ?? ?? ?? - ?? - ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? Hicks ?? Burley 21 ?? ?? ?? ?? ?? ?? ?? ?? ¹⁴CO₂ ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ¹⁴C ?? ?? ?? ?? 々 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? .50, 000 Lux ?? ??, Burley 21 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ¹⁴C ??, Hicks ?? ?? ?? ?? ?? ??, ?? ?? ?? ??, ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? stage ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ¹⁴C ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ?? ?? ?? ?? ?? ??, HC ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? . ?? ?? ?? ??, ?? ??, Hicks ?? ?? ?? ??, Burley ?? ?? ?? ?? ¹⁴C ?? ?? ?? ?? ?? ??, ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? .

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In the previous papers^5'6'7) the authors reported that under laxuriant growth conditions the restriction of nitrogen supply during the period from 70 to 90 in the leaf-number index brings about not only improvement of plant types but also favourable chemical compositions of the plant, and, as a result of it, the percentage of ripened grains as well as the yield of rice is much increased. (This rice-cultivation method has come to be widely known as the V-shaped rice-cultivation.) On the other hand, if the rice plant is subjected to the low temperature (lower than 17°C) at the reduction division stage, the number of non-fertillized grains is tremendously increased. The authors therefore, considered that in this case the favourable chemical compositions (such as a high C/N ratio) of the rice plant grown under the V-shaped rice cultivation would serve to decrease the number of non-fertilized grains. Following up this argument, the authors grew rice plants with restricted nitrogen supply during the period from 70 to 90 in the leaf number index, and further subjected the rice plants to a low temperature (16-17°C) at the reduction division stage f or 3 days or 7 days, and finally examined the percentage of non-fertilized grains of the plants thus treated, comparing with that of non-treated plants for three seasons. The results obtained may be summarized as follows. 1. The number of non-fertilized grains due to the low temperature is much larger in the 7-day-treatment than in the 3-day-treatment, and the percentage of non-fertilized grains (the ratio of the number of non-fertilized grains to the total number of grains) is always smaller on the nitrogen-restricted plants than on the non-treated plants regardless of the number of grains per panicle. 2. The sum of the number of non-fertilized grains and that of degenerated grains is also larger in the 7-day-treatment than in the 3-day-treatment, and its ratio to the total number of differentiated grains (spikelets) (the number of survived spikelets plus the number of degenerated spikelets) is always smaller on the nitrogen-restricted plants than on non-treated plants. 3. From the result mentioned above it has likely been proved that the restriction of nitrogen supply during the period from 70 to 90 in the leaf-number index serve to increase the low temperature resistance of the rice plant at the reduction division stage. Moreover, one reason of it has been ascribed to the favourable chemical compositions such as a high C/N ratio in the plant. (See table 3.) 4. The heading date is delayed by 1.5 days in the 3-day-treatment and by 3 days in the 7-day-treatment, while it is promoted by 4 days in the nitrogen-restriction treatment.

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In order to investigate the effect of ratio of non-photsynthetic organ to photosynthetic organs (C/F ratio) on the photosynthesis in mulberry tree, photosynthetic rates were compared in the following three plots at the same leaf order. Treatments were conducted early in July. A; Shoots were pruned to remain half number of leaves. B; Shoots were pruned in the same way as in A plot and all of the lateral buds were removed. C; untreated. The results obtained are as followrs; (1) Photosynthetic rate of the remained leaves was higher in A and B plot than C plot unti1 35 days after treatment. Photosynthetic rate of A plot exceeded B plot during the first 2 weeks after treatment, but thereafter, B plot was higher than A plot. (2) C/F ratio increased suddenly in A and B plots immediately after treatment, but ratio in A plot fell down gradually and reached the level of untreated one 35 days after treatment on the contrary, ratio in B plot rose after a little decrease. High correlation was recognized between photosynthetic rates and C/F ratios. (3) Content of 80% hot ethanol-soluble reducing sugar was highest in C plot except 35days after treatment. Ethanol-soluble reducing sugar content in B plot was higher than A plot in the first two weeks after treatment, but thereafter, A plot exceeded B plot. (4) The increased photosynthetic rate in the pruned trees was associated with the decreased sugar concentration in the remained leaves which was caused by the enbancement of assimilate translocation from the remained leaves to 1ateral buds or other organs.

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