We tested a grain production model experimentally under field conditions. The model is a simple, mathematical expression that describes the increase of grain weight (ΔG) as a function of the total dry-matter production (ΔW). It has two parameters: grain growth potential (ΔGp) and the maximum mobilizable reserves of the non-grain plant parts (Sp). Both of these parameters are to be determined experimentally. The model is originally developed for the relation between the increase of grain (i.e., yield) and the total dry-matter production of a single plant over a whole grain-filling period. Two rice cultivars, Nipponbare and Milyang 23, were grown in an irrigated field. Both cultivars were subjected to thinning and shading treatments after heading, so that they were under six radiation levels during the grain-filling period. Plants were harvested at 0 day, 15 days, 30 days and 45 days after heading to determine the responses for each 15 days in the early, the middle and the late grain-filling stage. The model predictions fit generally well the experimentally determined ΔG-ΔW relations, although the results for the late grain-filling stage were less satisfactory. We therefore conclude that our model is valid for a shorter term response of rice population. The model seems to be useful as a component of a mechanistic crop production model.

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Tillering of the 2nd to 11th main stem nodes in potted, direct-seeded rice plants was artificially controlled by the removal of tillers on specific nodes. Treatments consisted of limiting tillering on one main stem node only, on 2, 3, or 5 consecutive main stem nodes, or on 2 or 5 non-consecutive main stem nodes. Grain productivity of the tillers at different nodal positions and the influence of the number and position of other tillers on grain productivity of the specific nodal tiller or group of tillers were investigated. 1. Main stem flag leaf number and panicle weight increased as the number of tillering nodes decreased and tillers shifted higher on the main stem. 2. Tillering date and survival rate of primary tillers positioned from 2nd to 6th main stem nodes were not influenced by the other primary tillers. In contrast, the presence of lower nodal tillers delayed tillering and decreased survival rate of tillers above the 6th node. Panicle weight was not influenced by nodal position, but the number of days from tillering to heading or flag leaf number of primary tillers were higher at lower nodes. 3. Generally, lower node had higher panicle weight or grain productivity mainly due to higher panicle number. However, grain productivity of specific nodal tiller or group of tillers was greater when other tillers were fewer or positioned at more distant higher nodes. 4. As compared to the control, plants with only one or two tillering nodes at or above the middle of the main stem had lower panicle number and straw weight per plant, but panicle weight was more than 80% of the control due to the greater mean panicle weight in spite of the greater percentage of high order tillers. Consequently, panicle/straw weight ratio was also higher in these treated plants.

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To clarify high yielding factor of F₁ hybrid rice in China, characteristics of dry matter production was examined by means of growth analysis and canopy structural analysis with special reference to native varieties, old-improved (1960-1970) and new-improved (1970-) varieties, belonging to indica-type rice, in the Zhejiang State, China. The brown rice of the F₁ hybrid rice showed about two times of the yield of native varieties and 1.1-1.5 times of old-and new-improved varieties. The high yield of the F₁ hybrid rice was resulted from the increased biomass (total dry weight) than the harvest index. The remarkable biomass increase in the F₁ hybrid rice was mainly due to the high CGR rather than its longer growth period as compared with other common rice varieties. The mean value of CGR for 30 days before heading stage in the F₁ hybrid rice was 30 g/m²/day. This high CGR was supported by high LAI in the canopy than NAR. And the high LAI maintained during the whole growth period was due to favorable canopy structure having high plant height, and thick and heavy stems. The light extinction coefficient of the F₁ hybrid rice at the heading stage was smaller than those of native and old-improved varieties. Distribution profile of the leaf in the F₁ hybrid rice showed pylamidal type, namely, the distribution pattern of the leaf was equally large from the top to the under layer of the canopy. Leaf photosynthetic rates in the F₁ hybrid rice were not significantly different from the other common rice varieties at four growing stages. It can be concluded from these results that high yield of the F₁ hybrid rice was realized by the remarkable high biomass production based on high LAI and an ideal canopy structure favorable for intercepting light for the long growth period.

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In order to make clear the high yielding capacity of the F₁ hybrid rice in China, the characteristics of grain production was examined by the yield components analysis and with reference to the source of contents accumulated to the grain during the ripening period with the same varieties used in the previous paper. It became obvious from the yield components analysis that there was a highly positive correlation between total number of spikelet per unit land area and brown rice yield (Fig. 1). High yield in the F₁ hybrid rice was largely depended on spikelet number (ca. 40, 000/m²) as compared with common rice varieties. The total number of spikelet in the F₁ hybrid rice was due to increased spikelet number per one panicle rather than panicle number per one hill. The F₁ hybrid rice showed comparatively high percentage of tilled-spikelet (ca. 80%) in spite of its huge number of spikelet. This was caused by higher ratio of LAI to total number of spikelet (Source-Sink ratio) during the ripening period. Generally, brown rice yield is decided by the total amount of photosynthetic products, a carbohydrate stored in culm and leaf sheath before flowering, and of assimilate accumulated during the ripening period. In this experiment, the ratio of the storage translocated from the culm and leaf sheath to the spikelet was larger in the F₁ hybrid than in common rice varieties. In addition, there was a highly positive correlation between translocated storage and brown rice yield (Fig.4). This fact suggests that a comparatively high percentage of ripened-grain in the F₁ hybrid rice was attributed to the amount of storage. It can be concluded from the results mentioned above that high yield of F₁ hybrid rice was realized by both factors: 1) remarkable large number of spikelet and 2) comparatively high percentage of ripened grain, which was attained by the high ratio of the storage translocated from the culm and leaf sheath and by high LAI during the ripening period.

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In order to clarify the effects of physical stress on the internode elongation of soybean (Glycine max Merr. cv. Fukuyutaka), mechanical stimulation was given to pot-grown plants by stroking upper part of shoot with a dusting brush continuously for 15 to 180 seconds per day during certain period of different growth stages. The mechanical stimulation inhibited the internode elongation on the main stem, but did not affect yield characters (Table 2). The inhibition was limited on the upper elongating internode subjected to stimulation and was more when treated during the period from floral differentiation to the beginning of flowering stage (Table 2 and Fig. 1-A). As the longer the stimulating time was, the more the internode elongation was depressed (Fig.2). When the mechanical stimulation was given to one of the two same-sized branches emerged from the cotyledonary nodes on the Y-shaped plant which was forced to form by removing apical shoot above the nodes, the inhibition of internode elongation occurred on the stroked branch but not on the other branch, suggesting that the stimulus was not transmitted from a treated to an untreated branch. From these results, the main stem elongation of soybean could be reduced by the mechanical stimulation without affecting reproductive characters including seed yield.

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This study was carried out to clarify the aspects of transplanting injury and recovery from it in rice plant by the comparison of top and root growth, water content or organic constituents etc., in transplanted seedlings with those of non- transplanted ones raised under the same conditions. Transplanted seedlings did not show any symptom of leaf wilting in appearance, in spite of pruning 18% of root in dry weight. Leaf water content of these seedlings, however, decreased as compared with those of the non transplanted ones and this resulted in the inhibition of top growth rate, viz. transplanting injury, during about three days after transplanting. In transplanted seedlings showing inhibited top growth rate, the amount of carbohydrate, especially of total sugar, markedly increased, but those of nitrogen decreased as compared with the non-transplanted ones. The increasing ratio of carbohydrate was greater in order of stem > leaf sheath > leaf blade in top. The accumulated carbohydrate, especially in the stem, was preferencially utilized to promote the rooting of transplanted seedlings. After rooting, growth rate and carbohydrate or nitrogen content in the transplanted seedlings was restored to the same level as in the non-transplanted ones. These results suggest that growth retarding just after transplanting played a very important role in promoting the rooting process, that is, seedling establishment.

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Dry matter yields of the leaf blade, the stem with leaf sheath and the dead parts of napiergrass, Pennisetum purpureum Schumach, cv. Merkeron in the first year of growth were compared among Tokyo, Nagoya, Fukuoka, Miyazaki, Naha and Iriomote Island. Yield of the leaf blade at the final harvest in the plants grown without cutting was lower at the southern sites. However, the regional differences in the yields of the stem and the dead parts of the above plants and yield of each part of the plants harvested at early- or middle-August, were not related with the regional differences in the length of productive period and the climatic conditions. In the aftermath by the cutting mentioned above, yields of the leaf blade and the stem were higher at the southern sites. The productive structure and the feeding value to ruminants of the uncut plants and the aftermath, in terms of dry matter yield of leaf blade and yield ratio of stem to leaf blade, were significantly correlated with cumulative temperature and were inferior at the southern sites.

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We previously found that in direct sowing of paddy rice into flooded soil, soil in the vicinity of the seed coated with oxygen generator (calcium peroxide) was oxidized at first, and then, reduced locally and rapidly from about the time of germination. We supposed that this had much to do with unstableness of emergence in DIPPS, and investigated the effect of the local soil reduction on germination and emergence. (1) The reduction occurred even in inviable seeds, but it was rapid in viable ones especially in germinated seeds. The reduction began in the peripheral area of embryo concurrent with or a little before germination. Thus, germination was supposed to be one of the causes for the local and rapid reduction in the vicinity of the coated seed. (2) The possibility of the reduction inhibiting germination was supposed to be small. However, the percentage of germinated seeds which failed to emerge increased when the degree of reduction on the day and on the next day of germination exceeded a certain limit. Thus, the local reduction in the vicinity of the coated seed was supposed to be one of the major causes for the decline of emergence in DIPPS. (3) A few more days prolongation of the soil oxidizing effect of calcium peroxide would most probably result not only in an improvement but also in a stabilization of emergence.

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Relation between the strength of shedding resistance and morphology of separation zone (SZ) were investigated. Varietal differences in the morphological features of separation surface were observed with a scanning electron microscope. Separation in the abscission layer (AL) formed a "separation pit" at the base of rachilla and a "separation pileus" at the terminal of pedicel. Although diameters of separation pileus, vascular bundle and pedicel did not always relate with the strength of resistance, the height of pileus showed a highly negative correlation with the strength; whereas separation angle showed a very high positive correlation. In easy shedding varieties, separation started at the marginal portion of AL and proceeded inward with the progress of maturation and dehydration. The separation was rather noticeable on the abaxial side of AL. The cell walls of AL were thinner and melted more severely at the merginal portion. In shedding resistant varieties, however, formation of AL was obscure and separation usually occurred at a curved portion of pedicel by its breaking. Inferior spikelets as compared with superior ones had a poorly developed morphorogical structure of SZ and showed better separation of AL and weaker shedding resistance. A sclerenchymatous fiber tissue developed around the vascular bundle sheath. The development of the fibrous cell wall was remarkable in shedding resistant varieties. Pits were seen in the walls between abscission cells and adjacent cells. Density of the pits was lower in lesser shedding resistant varieties. In the wild species, the formation of AL extended far into the bundle sheath region and the development of fibrous tissue was very poor. Shedding, in general, may be regulated by a relative extent of the AL formation and the development of sclerenchymatous fiber tissue, though it depends upon the mechanical strength of fibrous tissue in the case of resistant varieties.

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The leaf photosynthetic rate of pot-cultivated rice plants was measured under the condition of artificial lighting and, at the same time, its relations to their some relevant characters were examined with five different varieties of rice plants, Musashikogane, Akenohoshi, Sweon 262, Nanking 11, and RP 9-3. In the case of low light intensity (10 klx), no striking difference in the photosynthetic rate among the varieties was found in the period from the maximum tiller number stage till the heading stage, whereas in the ripening stage the rate of all the varieties dropped remarkably. In the case of high light intensity (60 klx), the photosynthetic rate decreased as the growing stages proceeded.The japonica type varieties had a high photosynthetic rate at the maximum tiller number stage, while the indica-japonica hybrid variety had high rate in the booting stage. Nanking 11, an indica type variety, showed a photosynthetic rate similar to that of the japonica type varieties. Sweon 262, an indica-japonica hybrid variety, seems to have a high photosynthetic ability compared with the japonica type varieties. In the change of respiration rate according to the number of days after transplanting, it was observed that the respiration rate of the japonica type and the indica-japonica hybrid type varieties decreased more than that of the indica type varietics. The respiration rate of all the varieties tested decreased according to the number of days after transplanting. A close correlation was observed between chlorophyll contents and the photosynthetic rate at 60 klx.

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Generally, the sample size in a sample survey can be calculated according to the coefficient of variation among the characters to be studied and also the desired precision of the survey. In the case of rice plants, however, sufficient information is not available regarding coefficient of variation in their quantitative characters. In order to obtain sample size of a sample survey in a field experiment, the coefficients of variations of characters were investigated under various conditions for a period of three years. This study was made using hand-transplanted rice of the fixed number of seedlings per hill as generally practiced in cultivation experiments. The difference of the variation coefficients due to the year, field, cropping season, variety of the crop, and the direction of planting rows was small unless cultivation management was exceptionally loose, and it was judged that differences in these cultivation conditions hardly affect the sample size for a crop survey. The difference of the variation coefficients due to differring planting densities was too large to ignore. In this study, using rice plants grown in a standard density, statistical estimation was made on the coefficients of variation in quantitative characters at each growth period of the max tiller number stage, full heading stage and maturing stage. Then, the sample sizes in six cases of differing desired precision were computed, using the estimated coefficient of variation.

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Rice plants, cv. Koshihikari were grown on a fine-textured gley paddy soil at Fukui Pref. Agric. Exp. Stn.. Plants were grown under full (control plot) and 78% of full solar radiation (shaded plot) with shade cloth from panicle formation stage till heading. Effects of shading on root length density (RLD), root length, root distribution and grain yield of rice plants were determined. Samples taken both in and between hills, at the 0-20 cm soil depth, showed that RLD was lower in shaded plot than in control plot. There was no significant difference in RLD between shaded and control plots at the 20-30 cm soil depth. The total root length per 10 a (30 cm depth) was estimated with RLD. The total root length of shaded plot (38, 100 km/10 a) was 20% less than the control (49, 200 km/10a). The grain yield in shaded plot was approximately 10% lower than the control. The main effect seemed to be a decrease in the number of grains per head, however, there was also a decrease in percentage of ripened grains and grain weight. These results indicate that solar radiation during panicle formation to heading affects root system morphology and grain yield of rice plants. Also there are strong relationships between both mass and distribution of roots and grain yield of rice plants.

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Using the same materials reported in the previous paper, the effect of shading (78% of full solar radiation) from panicle formation stage to heading, on the number, form, type and growth direction of primary roots of rice plants were investigated. Shading decreased the number of 'elongated roots' and 'stunted roots' per hill and per culm respectively, but it had no effects on the composition and the number of productive culms. The total number of primary roots of shaded plot was about 90% of that of control plof A remarkable decrease in primary root number by shading was observed in the 11th and 12th shoot units where emergence and elongation of primary roots took place just during the shading treatment. The number of 'stunted roots' in the 11th shoot unit, and further the number of 'elongated roots' as well in the 12th shoot unit were decreased. Shading affected the type of 'elongated roots' in the 11th and 12th shoot units, the type A (less tapering) roots tended to decrease, on the other hand, the type C (highly tapering) roots tended to increase. Shading had no effect on the growth direction of primary roots, however, their number at each direction tended to decrease proportionately. From the above investigations, it was assumed that both the mass and the morphology of primary roots developed during panicle formation till heading have close relationships with grain yield of rice plants.

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In field experiment conducted using dormancy released unshelled-seeds of cv. Chico peanut, ssp. fastigiata, the single stand emergence by apical seed occurred in high percentage. When unshelled-seeds were sown horizontally and dosal suture down and 2 cm in depth without compaction of covered soil, the pods, which contain apical seed cotyledons and rooted basal seed, penetrated above ground. Consequently, apical seed's epicotyl grew alone while basal seed died due to drying. Unshelled-seeds sown 5 cm in depth and covered with packed soil induced similar apical seed emergence, but the pods were at the position initially sown in the soil. The same single stand emergence also occurred by naturally dormancy-broken fruits of large-seeded cultivars in the field, but the pods had moved to the below of crusted soil surface. These results suggest the existence of a mechanism which induces a priority of apical seed in emergence over basal seed by the time lag in natural dormancy breaking within a fruit. Thinner pericarp of the beak of pod will serve it by an easiness to dehisce. This may be a mechanism to control the competition among the individual plants emerged from geocarpic fruits developed closely together around a mother plant under natural growing conditions. Shallow sowing of unshelled-seeds with less soil resistance for emergence seemed to enhance the occurrence of single stand emergence.

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High yielding factors of F₁ hybrid rice was extensively examined from the time changes in the percent of non-structural carbohydrate (NSC%) and total nitrogen (N%) in the leaf blade, culm and leaf sheath. There was no large difference in NSC% of leaf blade (LB) between the F₁ hybrid rice and common rice varieties. However, NSC% of the culm and leaf sheath (LS) in the F₁ hybrid rice showed a higher value than common rice varieties. NSC% of LS in all common rice varieties decreased rapidly after the heading stage, and then increased again at the middle stage of ripening. On the other hand, that of the F₁ hybrid rice continuously decreased up to the harvesting stage. There was a highly positive correlation between the decreasing rate of NSC% and translocated products from the LS during ripening period. There was also a highly positive correlation between the decreasing rate of NSC% and grain yield. These results show that NSC in the LS moves to grain and contributes greately to the production of brown grain rice. The N% of the LB is higher than that of the LS in all varieties. N% of the F₁ hybrid rice was lower than that of common rice varieties in both plant parts. There was significant positive correlation between N% in the LB and grain yield when excluded the F₁ hybrid rice. These results show that a high yield of the F₁ hybrid rice depends more on the reserved carbohydrate accumulated in the LS before the heading stage as compared with common rice varieties.

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The patterns of variation with time on single-leaf photosynthesis (CER) varied among leaves according to the positions on the stem. In the second and the third leaves, CER under saturation light intensity was at the maximum at the full expansion, decreasing with time thereafter. CER of the flag leaf was rather low at the full expansion but increased rapidly attaining the double of the initial value after two weeks. After that, it decreased as in leaves at other positions. The CER increase in the flag leaf at the early stage was brought about by an increase primarily in stomatal conductance (g_s) and secondarily in mesophyll photosynthetic activity. The CER decrease observed in all leaves at later stages was resulted from a decrease primarily in mesophyll photosynthetic activity and secondarily in g_s. In the second and the third leaves, the initial slope of light-CER curve was at the maximum at the full expansion decreasing with time thereafter. In the case of the flag leaf, the slope was small at the full expansion, increasing considerably at first, but decreased later. The degrees of both increase and decrease were much larger than that of the slope variation in the second and the third leaves.

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Single leaf photosynthesis (CER) always rose by the treatment in which the ambient air around single leaves was temporarily humidified. This fact suggested CER was habitually depressed by water shortage even under the flooded conditions. Based on the extent of CER increase by the treatment, the degree of depression in CER by water shortage was estimated at various times of a day and at various growth stages after anthesis. The extent of increase by the treatment in flag leaves increased with time after anthesis ranging from ca. 5% (in the morning at anthesis) to ca. 40% (in the afternoon at full maturity). From the above mentioned results, it was concluded that the degree of depression in CER by water shortage increased with time after anthesis.

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It was previously, shown that the individual variation and the depression with time of day in single leaf photosynthesis (CER) were closely correlated with those in stomatal conductance (g_s). However, when g_s varies in parallel with photosynthetic activity of mesophyll, a close positive correlation can exist between g_s and CER even if mesophyll activity is the major factor in those kinds of CER variations. In such a case, it looks as if g_s were the only one or major factor bringing the CER variations. The objectives of this study was to estimate the degree of real contribution of g_s to the CER variations on the assumption that an ambient air humidifying treatment increases only g_s without affecting mesophyll photosynthetic activity. The conclusions are as follows : 1) One half of the individual variation in CER among flag leaves was caused really by the variation in g_s, and the other half, by that in mesophyll photosynthetic activity varying in parallel with g_s. 2) The depression in CER with time of day was caused mainly by a depression in g_s and to a small extent, by that in mesophyll photosynthetic activity.

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In order to clarify the eco-physiological characteristics of high yielding rice vaieties, yields, their components and the process of dry matter production were compared between the cultivar Milyang 23, Japonica × Indica hybrid high yielding variety, and the cultivar Nipponbare, a japanese standard variety, for five years from 1983 to 1987. The maximum yield of Milyang 23 in 1984 was 754 g/m², 32% higher than that of Nipponbare owing to higher dry matter production and more spikelets number per unit area. The process of dry matter production was examined by growth analysis method. Crop growth rates of Milyang 23 were higher after heading stage, especially at the early ripening stage, as compared with those of Nipponbare. It was not owing to larger mean leaf area index, but owing to higher net assimilation rate. Light extinction coefficient was lower in Milyang 23 at the early ripening stage owing to more erect foliage and smaller mutual shading effect of ears on the leaf canopy as compared with that of Nipponbare. To verify a role of smaller light extinction coefficient for increase in dry matter production in Milyang 23, thinning treatment (the planting density was reduced to half of the control) was done at three growth stages. Net assimilation rates increased by thinning treatment. The degree of increase in net assimilation rates by thinning treatment differed in the two varieties; that is, larger in Nipponbare with larger light extinction coefficient than that of Milyang 23 with smaller coefficient, especially at early ripening stage. These results indicate that the difference in net assimilation rates between the two varieties was mainly due to the difference in light intercepting characteristics. In order to clarify the difference of net assimilation rate between both varieties, further studies must be made on the characteristics relating to leaf photosynthesis which is thought to be one of the factors to maintain higher net assimilation rate in rice canopy.

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Nutrient uptake and morphological features in 12 rice hybrids were compared with the corresponding parental values. The uptakes of ammonium-N, nitrate-N, phosphorus and potassium (in nutrient mg·plant wt g^-1·h^-1) were determined by using 25-day-old seedlings. The results revealed that: (l) Nutrient uptake showed desirable heterosis, unlike morphological features. (2) Nutrient uptake was larger in the order of potassium, ammonium-N, nitrate-N and phosphorus. Potassium was five times as uptake as phosphorus. These facts also were observed in the F₁ hyrbrids and their parents. (3) The degree of heterosis for nutrient uptake was higher in the order of nitrate-N, phosphorus, ammonium-N and potassium. The degrees for nitrate-N and potassium were 80% and 30%, respectively. (4) Plant weight and its heterosis did not show significant correlations to heterosis for nutrient uptake. (5) Correlations between nitrate-N and potassium uptake, and between the heterosis for their uptakes were highly positive significant. (6) It can be concluded that heterosis for physiological characters such as nutrient uptake appears before that for mophological characters, and that the higher nutrient uptake of the F₁ rice hybrid was presumably not dependent on their larger weight, but on the higher rate of physiological ability.

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To clarify the reason of lower yield in true seed planting (TSP) culture than that of ordinary transplanting culture of stem cuttings, the top and storage root growrth were investigated among six populations in TSP culture and two cultivars in ordinary culture. There was a large variance in the yield among the TSP populations which differed in parental clones. Especially, one of the TSP populations showed a high yield similar to the high yielding cultivar. The difference in the dry matter production among the materials during the period from late August to middle October, which was major cause of the yield difference, was mainly affected from the difference in the leaf efficiency (total dry weight increase/mean leaf dry weight). Since its leaf efficiency tended to be higher in the materials with the higher storage root weight ratio (storage root dry weight/total dry weight) in the late August, a close correlation was observed between the storage root weight ratio in the late August and the yield among the materials. The present results indicated that, with the aid of some cultural practices used to improve early top growth in the TSP culture, we could expect as high a yield in the TSP culture as in the ordinary culture, by using an excellent TSP population. It was also suggested that there was a large difference in storage root sink potential among the TSP populations, and it mainly governed the leaf efficiency and dry matter production during later storage root bulking period and thus the yield.

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In order to explore the physiological basis of the difference in photosynthetic depression by soil water deficit, the non-stomatal mediated photosynthesis (NSP) and ribulose-1, 5-bisphosphate carboxylase (RuBPCase) content were compared among different parts of a wheat plant grown under soil water deficit condition. The depression of NSP due to water stress was larger in the lower leaf blades than in the upper ones, and in leaf blades than in ear, sheath and stem. The content of RuBPCase was decreased by soil water deficit to a larger extent in the lower leaf blades than in the upper ones, and in leaf blades than in stem and leaf sheath. But, in the ear, the extent of RuBPCase decrease was relatively large, compared with that of photosynthetic depression. The results here suggest a possibility that the difference among plant parts in photosynthetic depression by soil water deficit is partly attributed to the different sensitivity of photosynthetic apparatus to water stress.

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As a physiological basis for the difference among parts of a wheat plant in photosynthetic depression by soil water deficit, the stomatal response to abscisic acid (ABA) was examined in an ABA-sprayed plant. An additional experiment was also conducted in order to confirm whether there is a direct inhibitory effect of ABA on non-stomatal mediated photosynthesis. About 1 hour after ABA was sprayed, photosynthesis (PS) and transpiration (Tr) in the leaf blades, the stem and the flag leaf sheath decreased to as low level as less than 10% of the initial rates. But, in the ear, the decreases of PS and Tr were not as much as in such parts as above-mentioned. This means that the stomata in the ear are less sensitive to ABA, which accumulates in water stress condition, than those in other plant parts. Non-stomatal photosynthesis was not inhibited by ABA addition to the reaction mixture in any part of a plant. It was suggested that photosynthetic depression by soil water deficit was not caused by the direct inhibition of photosynthetic mechanism by ABA, but by stomatal sensitivity to accumulated ABA.

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In the analysis of dynamics of organic matter in the root-rhizoplane-soil system, it is essential to estimate various kinds of carbon flows in the system separately. Since a simple and rapid method for measuring root respiration was needed for this purpose, the authors developed the following method. A plastic syringe is used as the chamber. Sample roots are put into a syringe, in which the air is replaced with air of known CO₂ concentration and the syringe is kept at a constant temperature for a certain time. A volume of the air in the syringe is injected into the flow of N₂ gas in the tube which is connected to an infrared gas analyzer. The CO₂ concentration in the syringe is directly related to the reading of the analyzer. From the difference of the CO₂ concentration in the syringe before and after the incubation, the respiration rate of the roots is calculated. The details of the procedure were determined by the results of experiments regarding the effects of factors concerned.

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The time-courses of respiratory CO₂ evolution of fourteen plant species were examined to elucidate interspecific difference in respiration under the same environmental conditions. The effects of water deficiency and water logging on respiration were also examined in several plant species. The change in respiration rate with time were almost the same in all plant sepecies examined, though the levels of respiration rate were relatively higher in five C₄ plants than in three C₄ plants and six C₃ plants. They decreased after the onset of dark period followed by the temporary increase at midnight and declining again from 8 to 12 hours after the onset of dark period. Both water deficiency and water logging conditions strongly and immediately affected the time course of respiration rate. The temporary rise of the rate at midnight disappeared within one day in both cases. In plants sensitive to flooded conditions the second decrease of respiration rate around 8 to 12 hours after the onset of dark period also disappeared by water logging for 7 days. From these results, it was concluded that the internal processes relating to the change in respiratory CO₂ evolution with time were similar among fourteen plant species, and that respiration rate sensitively and quickly reflected the plant growth response to water conditions, which differed among species.

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In agricultural farming at Bukit Peninsula, Bali, Indonesia, cattle production has an important position as well as food crop production. However, the farmers very often experience shortage of forage for feeding Bali cattle because of seasonal drought. In order to solve this problem, Three Strata Forage System (TSFS) had been developed through the improvement of the traditional farming system (non-Three strata Forage System: NTFS) from the viewpoint of field system and selection of plant materials. In a TSFS-field, trees, shrubs, grasses and legumes were grown in the peripheral part and food crops were mixed-cropped in the inner part of the field while trees were grown only as a fence to protect food crops from animals in a NTFS-field. In this paper, the availability of TSFS for forage and food crop production was studied. Though food-crop yield of a TSFS-field was 35% lower than that of a NTFS-field, forage yield was 96% higher, so that forage was available all the year round in a TSFS-field. Furthermore, the weight of a cattle on TSFS-field increased at almost the same rate as a cattle on NTFS-field even with about 10% less forages. Consequently, the net income from the TSFS-field was 24% more than that from the NTFS field. These results indicate that TSFS is more useful and profitable as a field system in seasonal drought-prone area of Indonesia.

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A light and transmission electron microscope study was made on the disposition of an egg cell and two synergids in Oryza sativa ovules. After anthesis, one of the synergids is rather persistent while the other is degenerating with collapse of the plasma membrane and penetration of ground plasma into the space between the plasma membranes of the egg cell and the central cell. Spherical vesicles in degenerating synergids closely resemble polysaccharide particles in intact pollen grains. Singular cisternae in the central cells tightly associate with the plasma membrane which borders on the degenerating synergids. There are osmiophilic deposits in the narrow interspace between the plasma membranes of the egg cell and the persistent synergid or the central cell. The egg cell has a nucleus with two nucleoli. The persistent synergid has a malformed nucleus forced on a pocket portion of central cell. The portion is occupied by a large number of cell wall ingrowths. It is postulated from the cyto-histological features of ovaries that nutrition into the egg cells is supplied through transmembranal, symplastic and apoplastic routes.

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