Konjak plants were grown under different light intensities; full sunlight, 30, 50 and 70% shading. Leaf anatomy was studied with a light microscopy and the following results were obtained. 1. The corm dry weight increased by shading and statistically higher values were obtained from plants in shading as compared with those in full sunlight (Table 1). 2. The length of whole leaf and each leaflet increased with decreasing light intensity, but the width of leaflets was not affected by shading. Accordingly, the leaf area increased about 3-30% by shading (Table 2). 3. The thickness of upper and lower epidermis, palisade and spongy tissues in leaflets decreased with decreasing light intensity. The number of cell layers in palisade and spongy tissues also decreased by the shading treatment (Table 3, 4). 4. The total palisade cell surface area per unit leaf area was decreased with decreasing light intensity, because of decrease in number of cells and cell volume, but the intercellular space of palisade tissue was larger in leaves developed in shade than those in full sunlight (Table 5). 5. The above-mentioned anatomical changes of the leaflet were more remarkable at the base of the leaflets than those at the top portion. 6. The number of chloroplasts per unit leaf area in palisade tissue was greatest at 1-2 weeks after shading treatment and decreased thereafter with aging. The number of chloroplasts of leaves grown under 50% and 70% shading decreased more gradually than those under full sunlight (Fig. 4). Based on these observations, the relationship between photosynthetic rate and anatomy of the leaflet was discussed.

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Two lowland rice cultivars, Yamabiko and Tokai No. 31, were grown either in single or mixed cropping at three levels of planting density (40, 20 and 10 hill/m²) in three cropping seasons (early, normal and late planting) in 1969. Each plot was replicated two times. The community grown in mixed cropping was expected to have higher yield than single cropping due to its deeper canopy. Single plant per hill was grown in a square plantation. The leaf stratified structure of each plot was evaluated on the basis of F₁ and F₂ scores obtained by the method as described in the previous paper. The relationship between the leaf stratified structure and yield was analysed mainly for mixed cropping. The results are as follows: 1. The relationship between F₁ or F₂ score and the leaf stratified structure and the seasonal trend of leaf stratified structure were virtually the same as in the previous paper: F₁ score increased with the increase of the leaf weight percentage (see the previous paper for definition) in the upper stratum, followed by the simultaneous decrease of the percentage in the lower stratum, while F₂ score increased with the decrease of the percentage in the middle stratum. The leaf weight percentage in the upper stratum increased as the crop grew (Table 1 and 2; Fig. 1, 2 and 3). 2. The leaf stratified structure and top dry weight appeared to be independent of each other as was found in the previous paper. 3. High and positive correlation between yield (hulled rice) and top dry weight at each growth stage was found in many plots as was found in the previous paper. This trend was found more clearly in Tokai No.31 than in Yamabiko and at late cropping season than early cropping season (Table 4). 4. In the plots showing the higher correlation between yield and F₁ or F₂ score, the yield increased when the leaf weight percentage was larger in upper stratum at tillering stage, while the higher yield was resulted from the higher leaf weight percentage in lower stratum during panicle formation and heading stages (Table 5). These were in contrast with results of the previous experiment conducted in 1968, and this difference between yeas was thought to be due to the difference of weather. 5. The correlation between yield and F₁ or F₂ score was found to be relatively high when top dry weight and leaf dry weight were greater. On the other hand, the yield was more correlated to the top dry weight in a crop of smaller leaf canopy (Fig. 4, Table 6). 6. The relative yield difference (R_y) between single and mixed cropping was calculated as, R_y = (γ_m - γ_s) ÷ γ_s × 100(%), where γ_m is the total yield of Yamabiko and Tokai No.31 grown in mixed cropping and γ_s is the mean yield of two cultivars grown in single with same treatment. Then, the F₁ and F₂ scores of the average leaf stratified structure of the two cultivars grown singly in each plot at four growth stage were calculated in the order: (1) The leaf dry weights of two cultivars were summed up regardless of their height. (2) Furthermore, leaf dry weight was evenly divided into five vertical strata whose height was regarded as same as Yamabiko. (3) The percentages of leaf dry weights in five strata to the total leaf dry weight were calculated. (4) They were standardised to constitute the standardised vector of leaf weights of five strata. (5) The vector was multiplied by the eigenvector to calculate the average F₁ and F₂ scores of single cropping, which makes it possible to compare these scores with others found in mixed cropping. Then, each score of single cropping was subtracted from the score of the corresponding plot of mixed cropping. [the rest omitted]

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The present study examined the influence of humidity on the photosynthesis in rice plants grown at a high or low humidity. 1) Plants were grown for 2-3 weeks at a high-intensity light with high or low humidity. Photosynthetic rate measured under high-intensity light was higher for plants grown in low humidity than those grown in high humidity. However, when it was determined under low-intensity light, the rate of the latter was higher than that of the former (Fig. 2). 2) The specific leaf weight was greater in the plant grown in low humidity than in that grown in high humidity. It had possitive correlation with photosynthetic rate under high-intensity light, but negative correlation, though it is not significant, under low-intensity light (Fig. 3, 4). 3) The photosynthetic rate was measured under high- or low-intensity light at various air humidities. Irrespective of light intensity, the more humid the atmosphere during photosynthesis measurement, the higher the photosynthetic rate of leaves of the plants grown under both low and high humidity (Fig. 5). Furthermore, the photosynthetic rate decreased, when the air humidity was lowered during measurement of photosynthesis, while it increased when the humidity was increased during measurement (Fig. 6). 4) Stomatal resistance decreased with the increase in humidity, suggesting that stomatal aperture increased with the rise of humidity (Table 1). These results suggested that air humidity which influences stomatal openining is a direct factor affecting photosynthesis and air humidity under which plants were grown for 2-3 weeks before photosynthesis measurement also has some effect on leaf morphology, which results in dfferences in photosynthetic rate.

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Protein-N in rice grains is known to be derived mainly from the leaf among the vegetative plant parts during grain development. However, in the previous report, we revealed that top-dressed N during grain filling increased the protein content of grains. The tracer experiment using ¹⁵N labelled ammonium nitrogen in the rice plant also made clear that top-dressed ¹⁵N was more effectively translocated into grain protein as compared with basal-dressed N. The present study was conducted with an attempt to investigate the translocation of ¹⁴N derived from basal-dressing or ¹⁵N from top-dressing into developing grains. For this purpose, the individual leaf blades as a nitrogen-source organ or ears as a sink were removed at the flowering stage, respectively. The results obtained are as follows: 1. As for ¹⁴N- or ¹⁵N-distribution of various plant parts, there were significant differences in the contents of ¹⁴N and ¹⁵N between the leaf positions on the culms. Particularly, ¹⁵N content in the upper leaf blades was much higher than the lower ones, and the reverse was true in the lower leaf blades. Therefore, ¹⁵N/¹⁴N ratio in the upper leaf blades was higher than the lower ones. 2. Experiments in which individual leaf blades were removed at the flowering stage showed that a decreased level of source-N in the remained leaf blades and leaf sheath + culms corresponded well to a decrease in the level of sink-N, indicating that source-N in the leaf sheath + culms was mobilized by the leaf removal treatments. Furthermore, it was found that from changes in ¹⁵N/¹⁴N ratio of the various plant parts ¹⁵N in the upper leaf blades was more rapidly transported into sink than ¹⁴N, while ¹⁴N-transport in the lower leaf blades occurred in advance of ¹⁵N-transport during the early ripening period. 3. These results suggested that ¹⁵N-compounds in the leaf blades derived from top-dressed ¹⁵N were more mobile than ¹⁴N-compounds from basal-dressed ¹⁴N, probably the former contributing to soluble protein such as Fraction-1 protein, and the latter to insoluble protein such as cell membrane protein. 4. During the ripening period, there were rapid decreases in the free amino acids as well as total nitrogen contents in the leaf blades. Among the free amino acids, decreases in methionine level well correlated with decreases in total nitrogen level of the leaf blades. Furthermore, it was suggested from the removal experiment of ears as sink that glutamine and γ-aminobutyric acid were the main compounds for transport of nitrogen from source to sink during the grain filling period.

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In the previous paper, it was revealed in rice plant that ¹⁵N-labelled ammonium nitrogen top-dressed at the flowering stage was more effectively absorbed and translocated into grain proteins as compared with ¹⁴N supplied as basal-dressing. On the basis of these data, it was estimated that the relative distribution of N to sink was 40∼50% for basal-dressing and ca. 70% for top-dressing. This report presents the results of two experiments which were conducted to examine the translocation rate of three sources of nitrogen supplied as basal-dressing, top-dressing I (at the spikelet initiation stage) and II (at the flowering stage) in combination with the treatments on removal of the upper or lower leaf blades at the flowering stage. The results obtained are as follows. 1. Most of the ¹⁵N from top-dressing I was distributed in the upper leaf blades and ears as sink, whereas the distribution of ¹⁵N from basal-dressing was found in the lower leaf blades and leaf sheath + culms. However, ¹⁵N top-dressed at the flowering stage was continuously translocated into sink during the ripening period and incorporated rapidly into reserve protein such as glutelin. 2. The transport into sink of ¹⁵N-labelled ammonium top-dressed at the flowering stage was more rapid than basal-dressed ¹⁵N, and even in the rice plant from which all leaf blades were removed at the flowering stage, the rate of ¹⁵N transported into sink increased up to 63% of the untreated plant. These results indicate that most of the ¹⁵N derived from top-dressing at the flowering stage was directly translocated into sink via culms from the roots.

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[in Japanese]

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The pressure chamber technique is now widely adopted for the measurement of leaf water potential. The technique is simple and rapid, but several precautions are necessary to ensure reliable results. It is especially important to prevent rapid water loss after leaf excision, as demonsterated by TURNER and LONG. This study was undertaken to examine the effects of the rate of pressure increase and of transpirational water loss on the estimate of the leaf water potential in rice by the pressure chamber technique. A lowland rice cultivar, Nipponbare, was used throughout the study. Gauge reading of a pressure chamber was affected by the rate of pressure increase under both high and low irradiances (Fig. 2). The reading first increased with pressurization rate up to 0.1 to 0.2 bar/s and thereafter declined slightly or remained almost constant. No difference was found in water loss from a leaf during measurement between rapid and slow rates of pressure increase (Table 1). The leaf to be sampled was covered with a vinyl-bag just before severing. The leaves from well watered plants in the naturally-lit glasshouse in which temperature, humidity and windspeed were controlled were used. From these results, together with the fact that acceptable agreement was obtained between the water potentials measured by the pressure chamber techique with pressurization rate of 0.3 bar/s and thermocouple psychrometry for rice leaves with stomata closed, we have decided that the rate of 0.2 bar/s is appropriate for rice and used in the following measurements. Similar rate, 0.36 bar/s, is used by O'TOOLE and MOYA although TURNER suggests the rate of 0.05 bar/s. We found large differences between fresh weights of a leaf covered with a vinyl-bag and a leaf left uncovered after excision (Fig. 3). Rapid water loss after excision was also evident in terms of RWC (relative water content) as well as water content per unit leaf area in leaves without a vinyl cover (Table 2). According to the moisture retention characteristics for the rice leaves we used (Fig. 4), decrease in RWC of the uncovered leaf in the first 30 seconds was equivalent to the lowering of the water potential by approximately 5 bar. On the other hand, corresponding decrease in the water potential of the covered leaves was only 1 bar. Recovery of the leaf water potential after rewatering was distinct when the leaf was covered with a vinyl-bag just before sampling (Fig. 5). Change in the leaf water potential in response to irrigation was vague and values were significantly lower when the measurements were taken in the leaf without a cover. These results suggest that the water potential in adequately sampled leaves only reflects dynamic response of plant water status to environment properly. Relation between the leaf water potential and RWC appeared to be relatively stable during the grain-filling period (Fig. 6). From above results we conclude that a large discrepancy between the leaf water potentials measured with a pressure chamber and a thermocouple psychrometer, as found in traspiring rice leaves, is primarily due to rapid water loss after excision as a result of an inadequate sampling techique. The thermocouple psychrometry, too, may be questioned for the following reasons. Since a small piece of leaf tissue is used in this technique, number of samples should be carefully determined so as to represent the leaf as a whole. Significant gradients in water potential may exist in transpiring leaves, as suggested by the large differences in RWC along leaf blade (Fig. 7). Small size of the sample creates another problem. Since the psychrometry measures the relative humidity in the chamber generated by the chemical potential of all water in the leaf sample, dilution effect by apoplastic water may lead to the overestimate of the leaf water petential. BARR and KRAMER found that the smaller the sample size was, the higher the leaf water potential as measured with a thermocouple psychrometer was. Thus, p

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[in Japanese]

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The relationship between the number of primary roots and yield components was investigated by using 16 hills of rice plants grown on 4 different farmers' paddy fields. The data obtained were analyzed statistically on per-hill or per-plant basis. Throughout the analyses on both per-hill and per-plant basis, a high correlation was observed between the number of spikelets and the weight of ripend kernels, both of which were closely related to the number of primary roots. However, no notable variation was found either in the percentage of ripened kernel or in the thousand-kernel-weight. In the case of analyses per hill, the number of elongated primary roots showed a close correlation with the number of spikelets and the weight of ripened kernels. In contrast, the total number of primary roots as well as the number of 'stunted' primary roots did not show any relation with either of the yield components mentioned above. In the case of analyses per plant, close correlations were noted among most characters examined. These phenomena within a plant were attributed to the change in the number of culms, which were highly correlated with most of the other characters. When the partial correlations were examined by fixing the number of culms, the total number of primary roots and the number of elongated primary roots were the characters that exclusivery showed significant correlations with the number of spikelets or with the weight of ripened kernels. From the above investigations, it was assumed that among the primary roots, the elongated roots may have the utmost intimate relationship with the yield of rice plants.

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The relationship between the number of primary roots and yield components was investigated by using the same materials as in the preceding study. The primary roots were distinguished as elongated and 'stunted' roots. Elongated roots were further classified into three types, A, B and C, according to their morphological traits. The data thus obtained were analyzed statistically on per-culm or per-'shoot unit' basis in the case of primary roots, and on per-culm basis in the case of yield components. In the case of analyses per culm, the total number of primary roots and the the number of elongated primary roots showed significantly high correlations with the number of spikelets and with the weight of ripened kernels. The result was similar to that obtained in the preceding study. Among the three types of elongated primary roots, the number of type A roots, which are thick and long-elongated type, were most correlative to the yield components. The relationship between the yield components per culm and the number of primary roots of each 'shoot unit' were examined on main culms and on tillers, respectively. In this case, the 7th 'shoot unit' of main culms or the corresponding 'shoot unit' of tillers was the most remarkable 'shoot unit'. The number of elongated primary roots, particularly the type A roots, of this 'shoot unit', was found to be most correlative to the number of spikelets or the weight of ripened kernels.

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The relationship between the number of primary roots and yield components of rice plants was investigated, regarding variations among 4 different farmers' paddy fields. Many characters of panicles and of primary roots showed variations among the paddy fields, whether they were examined on per-hill or on per-unit-area basis. These variations were mostly associated with the number of fertile culms. Increase in the number of elongated primary roots during shoot growth also showed a similar trend to that in the number of fertile culms. However, when the average values of the characters of panicle and the number of primary roots were compared on per-culm basis, another kind of variations was noticed among the paddy fields. It was presumed, therefore, that the amount of various characters per unit area were not only affected by the number of fertile culms. A relatively constant ratio was obtained between the number of elongated primary roots and the characters of panicles; i. e, one elongated primary root corresponds to about two spikelets or 40 mg of ripened rice kernels. Throughout the paddy fields examined, the average value of 15, 000 elongated primary roots corresponded to about 600 g of brown rice yield per square meter.

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