In order to elucidate the process of the occurrence of delayed stem maturation (DSM) plant, a comparative study on the difference of ripening process between normal matured plant and DSM plant (defined previously by author) were performed by using three varieties of soybean plant, Nagahajiro from Hokkaido, Kari-kei 73 from Tohoku, and Orihime from Kyushu. There was a great difference between a normal matured soybean plant and a DSM plant. Leaves on the main stem of the DSM plant fell slowly in comparision with those in the normal matured plant. In DSM plants, the upper two or three leaves on their main stem remained stuck to the stem tightly, while all the leaves of the normal matured plant fell by harvest. After physiological maturity, the water content in the stem on normal matured plants rapidly decreased, whereas in DSM plants, it remained at a high level. In normal matured plants, the color of the pod-walls changed into brown within several days. In contrast the period for the color change in DSM plants, lasted for about 2 weeks. These facts indicate that there are harmonious maturation (normal matured) of top organs (leaf, petiole, stem, pod-wall, seed) and inharmonious maturation (DSM) in soybean plant. Therefor, we propose that the former be called conformable maturation (CM) and the latter unconformable maturation (UCM).

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The development of lateral roots on the primary roots of the main stem was studied. The lateral roots studied included all kinds of roots, i.e., secondary and tertiary, and the thin and the thick type of the secondary root. Comparisons were made among the different shoot units. The upper and the lower crown roots from the same shoot unit were also compared. Elongation of the secondary as well as of the tertiary roots stopped by the time when the primary root completed its elongation or slightly afterwards. Lateral roots of the seventh to ninth shoot units had the longest final length. Most secondary roots were located at around 6-30 cm from the base of the primary root. In this region of the lower crown roots, the number of the secondary roots was the largest at the seventh to ninth shoot unit. On the upper crown roots, there were more secondary roots at the higher-positioned shoot units. There were more secondary roots per primary root in the eighth or ninth shoot unit. The tertiary roots were more densely developed in the higher-positioned shoot units. The higher-positioned shoot units developed thinner lateral roots.

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Following the previous paper on the development of lateral roots of the main stem, similar investigations were conducted on tillers. As in the main stem, lateral roots emerged acropetally along the primary root of the tiller, and their elongation ceased at or slightly after the primary root stopped its elongation. In the tiller VII whose appearance is considered as an average, the final length and the diameter of the laterals, the total number of the secondary roots per primary root, and the maximum density of the secondary roots on the primary root axis, all decreased towards the higher-positioned shoot units. On the contrary, the density of the tertiary roots (i.e., number per cm of the secondary root) increased towards the higher-positioned shoot units. These features were, in general, similarly found in the main stem for shoot units higher than the ninth. Lateral roots development of later-appeared tillers was similar to those found in the higher-positioned shoot units of the tiller VII and the main stem.

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Quantitative studies on the root system formation were carried out on a rice cultivar which was intermediate in leaf number (16) on the main stem. The components of the root system studied included root number, root length, total volume and surface area, for all kinds of roots, i.e., primary, secondary and tertiary. The percentage of the root system formation was as high as 40% in the main stem and 20% in the tiller VII at about 30 days before heading. Within the next 20 days or so, active growth continued in the main stem. In the tiller VII, active growth continued slightly longer. In the main stem as well as the tiller VII, the root system formation completed just after heading. The ultimate size of the root system of the main stem was 120, 580 in number, 1, 085m in length, 24cm³ in volume 3, 622cm² in surface area. In the tiller VII, the root size was 50, 145 in number, 464m in length, 11cm³ in volume, 1, 532cm² in surface area. The total root size of a single hill estimated from these data was 1, 284, 640 in number, 11, 764m in length, 272cm³ in volume and 39, 000cm² in surface area.

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Differences in the root system formation among cultivars with different numbers of leaves on the main stem were compared. The roots studied were those from the second and the third highest shoot units with crown roots. The final lengths of the secondary and the tertiary roots of Ishikari [which had the least number of leaves on the main stem (11-12)] were longer than in Toyonishiki [with moderate number of leaves (15-16)] and Reiho [with most leaves (20-21)]. The number of the secondary roots per primary root was the largest in Ishikari, intermediate in Toyonishiki, and the smallest in Reiho. However, there was no clear difference in the density of the secondary roots along the primary roots. The density of the tertiary roots was higher in the upper primary roots of Toyonishiki and Reiho. The differences in the diameter of any kinds of lateral roots among the cultivars were unclear. The total number, total length, total volume and surface area of the lateral roots per primary root, all were the largest in Ishikari, the least in Reiho and intermediate in Toyonishiki. At specific time before heading, a high percentage of root system formation was attained in Reiho, whereas in Ishikari the percentage was low. Toyonishiki gave an intermediate value in this regard. The three cultivars completed their root system formation in the same order.

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The influences of root pruning intensities were investigated as to the root regeneration and the most efficient pruning intensity was discussed. The root pruning treatments were conducted in five degrees of intensities in late September 1982, using 4-year old plants (Camellia sinensis (L.) O. Kuntze cv. Yabukita). The amount of roots removed by pruning ranged from 20% (Treatment V) to 80% (Treatment I) of the total weight of roots per plant (Table 1). The weight of the lignified roots sampled in the treatment I and II were considerably below as compared with those in the treatment III-V and the weight of the white roots in the treatment III was greatest, inclusive the control. The prominent increase in white roots was recognized not only around the pruned part but in the basal part of decapitated lignified roots. To estimate the root regenerating potential after pruning, index (a), (b), (c) and (b×c) were invented. Although index (b) increased with thickness of decapitated lignified roots, index (a) and (b×c) were maximum in the treatment III and minimum in both treatments I and II. It is concluded that root pruning intensity is one of the factors controlling the effects of root pruning practiced for effecient rejuvenation of root systems.

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Grain yield, total dry weight and harvest index of twelve and twenty-three wheat varieties, including short-and long-culm types, were measured in 1985 and 1986. In 1986, the percentages of cell wall and cellular components in the culm were also measured by the detergent method. Long-culm varieties had higher total dry weight, but lower harvest index than short-culm varieties in both years. The grain yields of long-culm varieties were, however, higher in 1985 (dry conditions), but lower in 1986 (wet conditions) than those of short-culm varieties. Grain yield was correlated positively with total dry weight in 1985, but with harvest index in 1986. The weight of cell wall constituents in the culm attained a maximum-just after anthesis and maintained a near maximum value until maturity in almost all varieties. The culm dry weight and the weight and percentage of cell wall constituents measured at the milk-ripe stage were larger in long-culm varieties than in short-culm ones, and correlated positively with total dry weight at maturity. On the other hand, the weight of cellular contents increased until the milk ripe stage and then decreased, suggesting that reserve materials stored in the culm may be translocated to the grain after the milk ripe stage. The percentage of cellular contents was about 10% higher in short-culm varieties than in long-culm ones at the milk ripe stage.

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In the previous paper, the effective regrowth rice shoots were classified into two types, (1) SS (surviced shoots); their young panicles were not cut off and continued to grow after cutting and attained to heading, (2) NS (new shoots) ; they had reached the stage of axillary buds by the time of cutting, and newly developed until the heading. This paper gives detailed information regarding the characteristics of the NS. Each NS has one prophyll and two or three leaves (NS[2] and NS[3]). NS[3] were found mainly in the plot L (cut at a low level:7.5 cm over the ground). The ear length, the number of primary rachis-branches and the number of grains of NS[3] were similar to those of NS[2]. The order of the leaf blade lengths was bL1 (flag leaf)>bL2 in the NS[2] and bL2>bL1>bL3 in the NS[3]. Almost all the NS were produced from the third tillers (bT3, which were wrapped by the third leaf counted downward from the flag leaf) or from the fourth tillers (bT4). Most of NS emerged two leaves before heading. Therefore, the cutting practice at the proper time in the young panicle developing stage of the rice plant may be able to induce simultaneous heading in cultivars which have genetically different heading time.

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To examine the effect of contaminating soil on the measurement of root weight, roots of several cereals grown in pots were recovered from soil and determined their soil contents. Soil remained on the washed root samples at ripening stage (heading stage in 1977, full-ripe stage in 1981) varied from 27.0% to 63.8% on the average of 41.3% of 4 species examined in 1977, and from 13.7% to 36.6% on the average of 25.2% of 4 species and 2 varieties in 1981. Soil on the washed root samples at vegetative stage ranged from 5.6 to 14.3% on the average of 9.0% of 2 species and 2 varieties. When roots were washed after separated from their mother stems soil contamination was decreased to the extent within 10%. Further washing by cutting roots into segments decreased soil contamination significantly within 5%, although the loss of fine roots and tips by the impairment increased up to around 30%. Although an thorough washing efficiently reduces soil contamination within 5% in the present study, determination of the ash free organic matter of root samples is recommended to avoid errors caused by the differences in soil property as well as in plant conditions.

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Effects of excessive soil moisture on dry matter production and seed yield of soybeans (c.v. Tamahomare) were studied in an upland field which was converted from paddy field. Flooding treatments were made in the furrows to the depth of 5 to 8 centimeters for 8 to 10 days at three different stages : flower-bud differentiation, the flowering and the middle of ripening. The earlier the growth period was, the greater were the effects of excessive soil moisture on dry matter production and seed yield. The elongation of main stems, the extension of leaf area and the increase of dry weight were markedly suppressed by the treatment at the flower-bud differentiation stage, but such suppression was reduced at the flowering stage. Decrease in seed yield by the flooding treatment at the flower-bud differentiation stage was attributed to decrease in the number of pods and the percentage of fertile pods. At the flowering stage, decrease in seed yield was due to decrease in the number of pods. At the middle of ripening stage, dry matter production was decreased due to the acceleration of leaf yellowing and defoliation. The resultant decrese in seed weight brought about decrease in seed yield.

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Using the same materials as reported in the previous paper, effects of excessive soil moisture on bleeding, stomatal aperture and mineral absorption of soybeans (c.v. Tamahomare) were studied. The earlier the growth stage was, the greater were the effects of excessive soil moisture on bleeding, stomatal aperture and mineral absorption. Soybeans were damaged not only by excess moisture but also by drought when they were grown under excessive soil condition followed by insufficient precipitation at the early growth stage when the plant community was not well developed such as at the early stage of flower-bud differentiation. This was because new roots which emerged during the treatment were damaged. Therefore, sufficient precautions must be taken against excess moisture injury at the early growth period, and in case drought damage is predicted, irrigation seems to be an effective practice.

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Effects of holding of cut-sprouts in sweet potato on the field establishment of cut-sprouts, the formation and the yield of tubers were investigated in the field condition with polyethylene film mulching using cv. Koganesengan and Kokei 14 in 1985 and 1986. The holdings were carried out under the condition with 13.5±1°C, 80±3%RH and weak light. Most leaf blades in the non-holding cut-sprouts wilted down to the soil surface after planting, whereas few leaves wilted down to the soil surface in the 5-10 day holding cut-sprouts. Although the survival ratio of cut sprouts was nearly 100% in every treatment, the number of leaves and transpiration rate of the 2nd or 3rd leaves from the terminal one at 1 or 2 weeks after planting were higher in the 5-10 day holding than in the non-holding. At 5 weeks after planting the number and the dry weight of tubers in the holding were higher than in the non -holding. The total dry weight and leaf area tended to increase with the holding practice. Although there was no significant difference in the tuber yield among the holding periods in 1985, higher yields at 1% significant level were obtained in 1986, and the number of tubers and average weight of a tuber tended to increase in the holding. The increases of total dry matter and harvest index were found in the holding. These seemed to bring about the yield increase in the holding.

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Dry matter productivities and growth parameters of napiergrass (Pennisetum purpureum Schumach, cv. Merkeron) were compared between the plants grown from seedlings with high fertilizer inputs at Tokyo and at Miyazaki. The dry matter yields of whole plants at the end of growing season were 39.3t/ha at Tokyo and 51.8t/ha in 1984 and 40.1t/ha in 1986 at Miyazaki. In comparison with Miyazaki, Tokyo had disadvantages for production such as shorter duration of productive period and lower levels of temperature as well as solar radiation, except for temperature level in summer, which was similar at the two sites. In summer, however, the rate of increase in leaf area index (LAI) at Tokyo was higher with a lower extinction coefficient and a higher net assimilation rate. This resulted in a steeper increase in crop growth rate (CGR) owing to the increase in LAI and a higher maximum CGR at Tokyo than at Miyazaki, and diminished the aforementioned disadvantages involved in the production at Tokyo.

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The differences in growth and grain yield of seven wheat varieties cultivated in soils belonging to four different groups were examined under the same fertilizer conditions during two growing seasons, 1982-84. Plant growth was most vigorous in the Gray Lowland Soils (GLS). In the Red Soils (RS) tillering stopped and the leaf color became pale in late January. In the Thick High-humic Andosols (THA) and the Light-colored Andosols (LCA), tillering and leaf emergence rates were lower than in the other soils from the start of the tillering stage. The young spike and culm elongation occurred earlier in RS and later in THA and LCA. Grain yield was 649 g/m² in GLS and 440-500 g/m² in the other soils. Lower yield in RS was due to the decline in the spike number and grain weight per spike, whereas in THA and LCA it was due to the decrease in the spike number. These differences in the growth and grain yield of wheat in each soil were mainly associated with the soil fertility and soil temperature patterns. The varieties with the greatest yield was differed with each soil. In the most fertile soil, GLS, the yield of Asakazekomugi was the highest, because of the higher percentage of productive tillers (ca. 50%), large spike number, and less lodging which reduced the loss of grain weight per spike. In THA and LCA, the yield of Norin 64 was the highest, because of the vigorous tillering activity and the larger spike number. In RS the yield difference among varieties was not significant.

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The objective of the present study was to obtain basic knowledge necessary for monitoring the physiological and ecological status of crops in fields by remote methods. The texture of reflectance within corn and soybean canopies was estimated from drum scanner analysis of color photographs, and compared with the actual distribution of leaf chlorophyll concentration (Chl) in the canopy. A model that estimated leaf Chl using multispectral remote sensing techniques was also examined. Actual Chl within the canopy had a near normal distribution (Fig. 2). However, the distribution of optical density in canopy photographs usually had a bimodal distribution pattern, which did not correspond with the actual distribution of Chl of leaves (Fig. 3A∼B, Fig. 4A∼B). The mean value of optical density was strongly affected not only by the color of each plant element but also by the degree of shading and angle of each leaf (Fig. 3C, Fig. 4C). The difference between the distribution mode and mean was reduced by avoiding the shaded parts (Fig. 4D). The spectral reflectance data from both crops revealed that wavelengths centered at 550 nm (Red) were most sensitive to the canopy Chl, while those in a near infrared region 750∼1, 050nm (NIR) were least sensitive. Statistically significant correlations were found between the ratio of NIR to Red reflectances (850nm/550nm) and leaf Chl for corn (0.68) and soybean (0.83). Differences between the regression lines for the two crops were attributed to leaf thickness (SLA)(Table 1, Fig. 5).

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The effect of leaf water potential on the photosynthetic rate and diffusive conductance in the leaf of rice plants was studied at different levels of leaf-air vapor pressure difference. The photosynthetic rate and diffusive conductance decreased rapidly to 50-60% and 25-40% of its maximum with decreasing leaf water potential from -1.5 to -5 bar, respectively. However, they slowly declined when leaf water potential decreased to lower than -5 bar (Fig. 1). Furthermore, the photosynthetic rate and diffusive conductance in leaves with high leaf water potential decreased with increasing leaf-air vapor pressure difference (Fig. 3) ; air humidity had a direct effect on the photosynthetic rate and diffusive conductance, independent of leaf water potential when leaf water potential was high (Figs. 3 and 4, Table 1). When leaf water potential decreased to lower than -5 bar, the photosynthetic rate and diffusive conductance were not significantly affected by the increase in leaf-air vapor pressure difference (Fig. 3). These results and the relation of diffusive conductance to photosynthetic rate at different leaf water potentials and leaf-air vapor pressure difference (Figs. 2 and 5) suggested that the cause for the decrease in photosynthetic rate differed in leaves with high and low leaf water potentials. In leaves with high leaf water potential where air humidity had a direct effect on the photosynthetic rate and diffusive conductance, the photosynthetic rate decreased due to the decrease of CO₂ supply through stomata to mesophyll. On the other hand, in leaves with low leaf water potential where the diffusive conductance was considerably low, the photosynthetic rate decreased due to the decrease of photosynthetic activity in mesophyll in addition to the decrease in the CO₂ supply (Fig.6).

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In order to make clear the factors affecting the ripening, four cultivars (Nanching 11, Suweon 258, Akenohoshi and Yamabiko) were examined on ordinary paddy field. The former three cultivars produced about 40, 000 grains/m² and cv. Yamabiko did 27, 000/m² at 3.5-5 of maximum leaf area index each. Yields of brown rice were ranging 5-6 tons/ha on all cultivars. The percentage of fully ripened grains in each cultivar, which expressed by the ratio of weight of 1, 000-whole-grains to weight of 1, 000-winnowed grains, was obtained as follows, 93% in cv. Yamabiko, 80% in cv. Nanching 11, 77% in cv. Suweon 258 and 73% in cv. Akenohoshi. The weight of 1, 000-raw-grains at 15 days after heading showed a high positive correlation to 1, 000-whole-grains of harvest time in all cultivars (r=0.978). It seemed that the final weight of 1, 000-whole-grains was strongly affected by a volume of young kernel at the milk-ripe stage. The weight of raw-grain, showing kernel's volume, highly correlated to the sucrose content per grain at 5 days after heading in each cultivars (r=0.981). As a result of multiple regression analysis, both factors the leaf area per grain and the rachis-weight per grain, could be expronated the sucrose content per grain at 5 days after heading, i.e., standard partial regression coefficients were shown 0.786 in the former and 0.431 in the latter (R=0.936), respectively. It is concluded that the highest value of ripening of cv. Yamabiko owed to its highest amount of the leaf area per grain among the four cultivars.

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To clarity the physiological and ecological characteristics of high yielding varieties in rice plants, the yield, its components and the process of dry matter production were compared between the cultivar Akenohoshi, a new high yielding variety, and the cultivar Nipponbare, a Japanese standard variety. The yield was 170kg/10a higher in Akenohoshi than that in Nipponbare due to higher dry matter production and larger spikelet number per unit area in Akenohoshi with larger panicles compared with those in Nipponbare. The process of dry matter production was examined by growth analysis method. The crop growth rates were higher at all stages and especially much higher at the ripening stage in Akenohoshi owing to higher net assimilation rates as compared with those in Nipponbare. Leaf area indices at the panicle formation and ripening stages were not different significantly between the two varieties. Net assimilation rates were affected by the canopy structure related to leaf arrangement and photosynthetic rates of leaves in the canopy. As the light extinction coefficient at the panicle formation and ripening stages was not significantly different between the two varieties it was assumed that the difference in the net assimilation rates between the two could be due to the difference in the photosynthetic rates of leaves in the canopy. Furthermore, the process of dry matter accumulation in the panicle was compared and was discussed from the point of the senescence of the panicle.

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This study was conducted to examine the hypothesis suggested in the previous paper that the difference in the net assimilation rate between the rice cultivars Nipponbare and Akenohoshi was probably caused by the difference in the photosynthetic rates of leaves in the canopy. The difference of the maximum photosynthetic rate of the uppermost expanded leaf in a day was very small between Nipponbare and Akenohoshi. However, the extent of the decrease in the photosynthetic rate during leaf senescence and in the afternoon with sufficient light intensity during diurnal course of the photosynthesis was smaller in Akenohoshi than that in Nipponbare. Thus the photosynthetic rates were maintained at higher level near the photosynthetic capacity in Akenohoshi compared with those in Nipponbare. Furthermore the cause why these differences existed in the photosynthesis between the two varieties was examined by measuring water absorption ability through roots. The resistance to water flow through plants was smaller and the exudation rate was larger in Akenohoshi than those in Nipponbare, which was probably related to smaller top-root and leaf area-root weight ratios in Akenohoshi. It can be concluded from these results that the higher photosynthetic rate in Akenohoshi was owing to its higher water absorption ability and physiological activity in roots.

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Pot-cultured cv. Nipponbare was used as the material. "Shoot vigor" was ranked based on the number of surviving flowers on the panicle at heading. The numbers of primordia of flowers and rachis-branches formed were estimated as the sum of the number of surviving ones at heading and that of vestiges of aborted ones. The results were as follows. (i) The lower the rank of shoot vigor, the fewer was the flower primordia formed on a panicle mainly due to the smaller numbers of the primary rachis-branches bearing secondary ones and of the secondary rachis-branches formed on a primary one as well. (ii) The lower the rank, the larger was the proportion of degenerated flower primordia to the total flower primordia formed. The major type of degeneration of flower primordia differed in accordance with shoot vigor. In vigorous shoots, it was degeneration together with degenerating secondary rachis-branches while in weak ones that with the primary rachis-branches. (iii) The lower the rank, the smaller was the proportion of surviving flowers on the secondary rachis-branches to the total at heading. (iv) The lower the rank, the larger was (number of flower primordia formed) / (leaf area at heading). However, (number of surviving flowers at heading) / (leaf area at heading) was almost constant among shoots irrespective of vigor due to the larger percentage degeneration of flower primordia on the weaker shoots.

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Using shoots having shoot vigor rank (SVR) 1, 5 and 9 in part I, the aspects of development of rachis-branches and flower primordia (FP) were examined at the level of individual primary rachis-branches (PRB)in relation to their positions on the rachis. (i) The lower the SVR, the fewer the FP of the panicle because of the fewer PRB on a panicle and the fewer FP on a PRB. (ii) In all the shoots, percentage degeneration (PD) for PRB, secondary rachis-branch (SRB) on surviving PRB, FP on surviving SRB, FP situated directly on surviving PRB and whole FP on a PRB was all largest at the basal PRB and decreased with rising PRB position on the rachis. (iii) Comparing the PRB situated at the equivalent position, the lower the SVR, the higher was PD for PRB and FP on surviving SRB, while that for SRB on surviving PRB, FP situated directly on surviving PRB and whole FP on the PRB was nearly constant among shoots. However, PD based on the numbers for the whole panicle was larger also in the latter three in the weaker stems because they have less upper PRB in which degeneration scarcely occurs. (iv) The lower the SVR, the smaller was the proportion of surviving flowers on SRB to the total surviving ones almost evenly at each PRB on a panicle.

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Winter cereals (hulled barley, naked barley, wheat, rye and oat) were grown under waterlogged (W) and drought (D) conditions from seven weeks after sowing up to maturity. Their growth, dry matter production and transpiration coefficients were compared with those grown under moderate soil moisture (M) conditions in order to quantitatively evaluate their waterlogging and drought tolerances. Plant growth was relatively depressed under both W- and D-conditions as compared with that under M-conditions. Naked barley, wheat, rye and oat produced more dry matter of a whole plant under D-conditions than W-conditions, while hulled barley produced more dry matter under W-conditions than D-conditions. We evaluated that the former crops had relatively large drought tolerance capacities (RLDTC) and the latter crops had relatively large waterlogging tolerance capacities (RLWTC). We considered that a crop is stable to W- or D-conditions when the ratio of its transpiration coefficient under W- and D-conditions to that under M-conditions is close to or below 1.0, and is susceptible when the ratio is above 1.0. Among the crops with RLDTC, rye and oat were very susceptible, and naked barley and wheat were relatively susceptible, while hulled barley, which had RLWTC, were stable to W-conditions. All of the crops were stable to D-conditions. The waterlogging and drought tolerances of these cereals were discussed in relation to the growth and function of their root systems under W- and D-conditions.

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The growth of upland rice, a species with a relatively large waterlogging tolerance capacity, and maize, a species with a relatively large drought tolerance capacity, under waterlogged, moderate soil moisture and drought conditions were investigated from seeding to heading stage by means of growth analysis. Upland rice showed more vigorous growth in terms of dry matter production and RGR under waterlogged conditions than drought conditions, and a reverse trend was evident in maize. Analyzing RGR into its components, NAR with an additive effect of LAR principally determined RGR in upland rice, while NAR showed a clear correspondence with RGR in maize. Nitrogen (N) concentration in leaf blades of both species showed considerably close relationship with NAR and thus RGR. The difference of the ratios of N content in leaf blades of a plant to the number of roots, which were considered to express the root activity, also well corresponded with those in NAR and RGR for both species. Furthermore, intimate relationships between RGR of roots and NAR were also found. These facts indicate that the distinct growth responses which upland rice and maize showed under waterlogged and drought conditions well reflected the capacity of waterlogging and drought tolerances of each species ; and the responses largely depended on the activity and the growth of roots exhibited under those different soil moisture conditions.

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Photosynthetic activities of four rice cultivars of India was investigated by employing a new method deviced by Tsuno. The improved cultivars Vijayamahsuri, Sonamahsuri, HR 35 and HR 59 and the local scented cultivar Basmati were used. The temperature optimum for photosynthesis was found to be 38°C in all cultivars in the experiment done by the new method. Cultivars Vijayamahsuri and Sonamahsuri had a relatively high ability to photosynthesize under low light intensities. The chlorophyll content of the leaves affected significantly the rate of CO₂ uptake. Photosynthetic activity of the leaf differed not only with the cultivar but also with its position on the culm. At the ripening stage the flag leaf in cvs. Vijayamahsuri and HR 35 showed the highest photosynthetic capacity, whereas in cv. Sonamahsuri the second and third leaf assimilated greater amounts of CO₂ than the flag leaf did. A close correlation was found between the chlorophyll content and the photosynthetic ability of the leaf, when pooled for all the upper three leaves of four cultivars, except for the case of leaves in cv. HR 59 with only a slight difference in chlorophyll content. We considered that the method deviced by Tsuno and newly introduced here will be available for the test of photosynthetic activity of crop plant, especially for the researches dealing with a great number of materials.

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The excised rice root was cultured by using two separate media. The root base was supplied with 12.5% of sucrose via scutellum, while the root tip was immersed in the inorganic nutrients of MS medium diluted 4 times. Different concentrations of brassinolide were supplied via either root tip (root medium) or root base via scutellum (scutellum medium). Brassinolide supplied to the scutellum medium stimulated the excised root growth at a concentration of 10^-8 M, while application of the same concentration to the root medium was found to be drastically inhibitory. Although the single application of either brassinolide (10^-8 M) or figaron (10^-8 M) to the scutellum medium detectably stimulated root growth, a mixture of them applied to the scutellum medium was shown to be inhibitory for root growth, especially for primary root length while the lateral root length was stimulated. On the other hand when GA₃ was supplied to the scutellum medium the primary root length showed a recovery from the slight inhibition observed when brassinolide was applied alone. Results revealed that dispite the observed superiority of the mixture of brassinolide and GA₃ in stimulating root growth and the antagonistic effect in the case of brassinolide and figaron, their regulatory effects seemed to be through a different mode of actions.

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Using absorption change at 703 nm induced by an actinic light, non-destructive estimation of P700 content, the amount of photosynthetic unit, was attempted by a flash spectrophotometer designed for the measurements of living leaf segments. The estimated P700 contents by this method agreed well with those determined by the conventional chemical method with remarkable reduction of times required for measurements. The crop leaves with higher chlorophyll a/b ratios were found to show smaller sizes of photosynthetic unit (chlorophyll/P700).

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Two rice cultivars of the high yielding semi-dwarf type, Vijayamahsuri and Sonamahsuri, and two cultivars of the tall scented type, HR 59 and Basmati, were investigated on their plant growth. Cultivar Vijayamahsuri showed the greatest productivity in dry matter of every plant organs, e.g., leaves, stems and roots. LAI of cv. Vijayamahsuri was also greatest. In cv. Basmati, a shallow planting of 2.3 cm in depth was apparently effective in increasing the number of tillers, dry matter production, root length and LAI. High yielding cultivars Vijayamahsuri and Sonamahsuri showed a similar tendency of the light distribution in the plant canopy, indicating the same value of the light extinction coefficient (0.29). In contrast, plant populations of cvs. HR 59 and Basmati showed rather lower values of extinction coefficient, that is, the lower parts of the populations could receive a relatively high intennsity of the light. Chlorophyll contents of the upper four leaves varied with cultivars as well as with the leaf position on the culm. It is of interest that in chlorophyll contents of the leaves, cvs. Vijayamahsuri and Sonamahsuri exceeded cvs. HR 59 and Basmati and either the second or the third leaf from the top is highest in most cases. We consider that a high efficiency in dry matter production in cvs. Vijayamahsuri and Sonamahsuri are mainly due to higher content of chlorophyll of the leaves.

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The temperature adaptation of five wild Glycine species of diverse geographic origin was compared with that of the cultivated species (G. max) under controlled conditions. The optimum temperature for germination was about 30°C for G. max and G. tomentella, 22°C for G. argyrea and 20°C for G. clandestina, respectively. In all the species examined, net CO₂ exchange rate per unit leaf area (NCE) appeared to be maximal at growth temperatures in the range from 18/13 to 30/25°C (8 h / 16 h, 16 h daylength) with little variation over this range. Four of six species exhibited no net CO₂ uptake in the light at 9/4°C after being exposed to successively lowered temperature, but G. clandestina retained a considerable net gain at this temperature. Across the species, NCE was correlated negatively with leaf size, but positively with specific leaf weight (SLW) or chlorophyll content. Most of the species revealed optimal temperatures for relative growth rate (RGR) in the range from 30/25 to 33/28°C. Across the species and growth temperatures, RGR was correlated more closely with relative leaf area growth rate (RLAGR) than with net assimilation rate (NAR). G. clandestina and G. latrobeana of cooler habitats adapted to low, temperature more strongly than other species, by increasing root/top ratio, SLW and chlorophyll content while maintaining a stable NCE. In contrast G. max tended, over a wide range of temperature, to express the greatest potential for leaf growth, leading to greater dry matter production at the expense of NCE.

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Excised-leaf water retention capability of spring wheat and winter wheat were tested. Cultivar differences were well differentiated when the decrease in leaf water content % was between 11 and 30. An increase in excised-leaf water retention capability and a decrease in leaf water content were seen during winter compared to summer. Drought hardened plants showed higher water retention capability. Excised-leaf water retention capability of the progenies from three crosses of winter wheat were evaluated. Frequency distribution patterns of the progenies showed the characteristic pattern of quantitative inheritance. Excised-leaf water retention capability of wheat seems to be a quantitative character governed by polygene action.

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Studies on the photooxidation of chloroplasts have been performed using carotenoid-deficient seedlings induced by the treatment with herbicides. The present study was made in association with the changes caused in the photosynthetic pigment content and ultrastructure when the chloroplasts in normal rice seedlings were subjected to photooxidation. When the seedlings grown under 16.2W/m² at 23°C were continuously exposed to the light intensity of 162 W/m² at 23°C, the chlorophyll content went on decreasing. The carotenoid content, however, did not show a significant change. Under the cycle of light and dark, the photooxidative destruction of chlorophyll went on decreasing with passage of the cycle, but no photooxidation was observed during the third cycle. On the other hand, the photooxidative damages of chloroplast structure were observed by electron microscopy. The appearance of RuBP Case crystal, the swelling of thylakoid membranes and the formation of plastoglobules were characteristic alterations. Especially, the electron density of grana thylakoids increased abnormally according to the lysis and release of membrane components. It appeared that the released materials transferred among the thylakoid interspaces to form the plastoglobules. When the seedlings were exposed to the sun light in the field, grana thylakoids were injured and plastoglobules become temporally prominent. However, the chloroplasts seemed to be recovered from the injury in the night.

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Potted rice plants were grown in the phytotron with different water temperature and water depth during the period from the spikelet differentiation stage to just before the young microspore stage, and then cooled at 12°C for 3 days at the young microspore stage to test their cool tolerance. The degree of cool tolerance at the young microspore stage was greatly varied with the temperature and depth of water before the critical stage. It was enhanced with raising the water temperature up to 25°C and with increased water depth up to 10 cm. Effect of the deep water irrigation as countermeasures against cool injury were experimented under the severe cool-temperature conditions in the phytotron. Yield-decrease due to cool air temperature during the critical stage was remarkably reduced by keeping the water depth at 10 cm before the critical stage, and it's effect was larger than that of the former deep water irrigation of 20 cm during the critical stage. Preventive effect of cool injury by combining the deep water irrigation before and during the critical stage was not additive but synergistic. Based on these results, we proposed the water management with a depth of 10 cm during the period from the spikelet differentiation stage to the young microspore stage as a newly devised countermeasure against cool injury.

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Solution of guazatine triacetate (1, 1'-iminodi [octamethylene] diguanidium triacetate, an agricultural fungicide ; BEFRAN^(R)) was sprayed onto wheat plants at a rate of 0.025 or 0.25% at seedling, pre- and post -anthesis stages. Guazatine promoted seedling growth without root fraction. When guazatine was sprayed at pre anthesis, the weight of a head was elevated by 25-27% mainly by increased number of grains and when sprayed at post-anthesis. it was elevated by 20% only by increased weight of a grain. At seedling and anthesis stages, the apparent photosynthetic rate increased by 8-16% but the transpiration rate was practically unchanged. Consequently water use efficiency increased up to 15% by guazatine.

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