Water Use Efficiency (WUE) is a very important concept to indicate the relationships between crop production and water use. However there are few reports of WUE of rice in humid regions. Our objectives were to compare the WUE among three different locations and cultivars of paddy rice (Oryza sativa L.). Field experiments were conducted at three locations, Matsue (in 1991, '92), Izumo ('91) each less than 20m above sea level, and Akana ('91) at 444m in eastern region of Shimane Prefecture using the two rice cultivars, Nipponbare and Koshihikari. WUE was calculated from estimated canopy transpiration (T) and crop top dry matter. The relationship between the top dry matter and accumulated T was well fitted by a linear regression for each location and cultivar. The WUE at Akana was slightly higher than those at the other locations. It was considered that the lower saturation deficit in the mountainous location caused the high WUE, because the differences among the WUE decreased by correction of the saturation deficit. The WUE values of two cultivars were 4.0g kg^-1 (cv. Nipponbare) and 4.6g kg^-1 (cv. Koshihikari), respectively. There were no between-year differences in WUE at Matsue. We concluded that WUE of rice is almost constant for a given cultivar under humid conditions with similar meteorological profiles, although correction for the saturation deficit is required when there is a large difference in humidity between cultivated regions and years.

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The effects of salty wind on the brown rice weight and quality of rice were investigated using a wind tunnel. Two varieties, cv. Hinohikari, cv. Yumehikari, were grown in 1/2000a Wagner's pots containing paddy field soil. The brown rice weight of a plot (non-salty water and non-water sprinkling) was 36.2 g/plant, D and H plots (weak wing treatment; 7.1±1.6 m/s, strong wind treatment; 14.4±4.3 m/s) with salty water treatment were 11.0 g/plant, 15.0 g/plant, respectively and under the condition of 60l/40 min water sprinkling treatment after salty water treatment were 21.7∼22.1 g/plant. The effects of salty water, water sprinkling, wind speed and treatment time on brown rice weight and 1000 grain weight were analyzed by the type I quantification method. According to the result of analysis of salty water treatment of brown rice weight, category scores were 6.47 and -9.71, and the partial correlation was 0.949. On the other hand, with water sprinkling treatment on brown rice weight, category scores were -1.87 and 2.81, and the partial correlation was 0.655. However, the partial correlation of wind speed or treatment time with brown rice weight was low.

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Cultivar difference on dry matter production and grain production in two-rowed barley (Hordeum distichum L. emend, LAMARK) of warm regions in Japan were investigated from 1987 to 1989. Fifteen Japanese cultivars and nineteen foreign cultivars in 1987/1988, and four Japanese cultivars and eleven foreign cultivars in 1988/1989 were grown under field conditions. The full heading stage of Japanese cultivars except New Golden and Kanto Nijyo 19 in 1987/1988 was in the early of April, but the foreign cultivars except WI-2727 was in the late of April. The top dry weight of Japanese cultivars was 615-1001 g m^-2, and that of the foreign cultivars was 744∼1088 g m^-2. The top dry weight of late maturing cultivars in the full heading stage was higher than that of early and middle maturing cultivars. The LAI of Japanese cultivars was 3∼4, and Nishinochikara was 4.97, higher than the early maturing cultivars. The maturing stage of Japanese cultivars except New Golden, Daisen Gold and Kanto Nijyo 19 was in the middle of May. The grain weight were 408∼544 g m^-2. The harvest index (HI) of breeding cultivars in Japan in recent years was 41∼42 and that of Hakei 86-107 was 46.1.

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Cultivar differences of effeciency of solar energy utilization (Eu) and efficiency of solar energy utilization in grain (Eu grain) in two-rowed barley (34 cultivars) were investigated from 1987 to 1988. The relationship between accumulated solar radiation and top dry weight at the vegetative stage from the sowing date to full heading stage was proportional (r=0.875^***). Eu in Japanese cultivars was less than 1.0%, but Eu of Koru, Bomi, Kym and Menuet in foreign cultivars was higher than 1.0%. Eu of Kawa Saigoku, Kanto Nijo 19 and WI-2585 at the ripening stage were 1.303%, 1.328% and 1.340%, respectively, but other Japanese cultivars were 0.8∼1.2%. Eu of Keg, Koru, Bomiand Kanto Nijo 19 at maturity was higher than 1.1%. Eu grain in Miho Golden, Kawamizuki, Ishukushirazu, Nishinochikara, Saikai Kawa 43, Hakei 86-107, Hakei 87-39, WI-2727, Bomi, Kym, Ida and Flare was higher than 0.40%.

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Efficiency of solar energy utilizatiion (Eu, %), efficiency of solar energy conversion (Ec, %) and conversion efficiency were determined for two-rowed barley (cv. Nishinochikara) plant grown in warm regions in Japan. Absorbed solar radiation during the stage from internode elongation to heading was about 56% of the total supplied solar radiation, and that in the ripening stage was about 70%. Absorbed solar radiation (SR_α) in the growing period was 865.02 MJ m^-2, equivalent to about 40% of the total solar radiation. Ec at the internode elongation to heading stage was 3.94%. Eu and Ec were 1.47% and 2.13% in the ripening period, both of which accounted for 1.09% and 2.71% in the whole growing period, respectively. These values were equal to those of rice grown in the same regions in Japan. Top dry weight was variable in proportion to SR_α, and Cs (Conversion efficiency) was 2.32g MJ^-1, The value of Cs determined in the early and middle ripening stages were 1.79g MJ^-1 and 1.17g MJ^-1, respectively.

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The large variations of sink capacity of spikelets (S_W), the assimilate reserved in the culm/leaf sheath of rice plant until the heading stage (C) and the assimilate produced during the ripening period (ΔW) were promoted by using several varieties from panicle number to panicle weight types, and by combining top dressing, cutting leaf and thinning treatments. From the above experiments, the influencing forms of ΔW/S_W, and C/S_W upon the ratio of ear weight increase (ΔE) to S_W (ΔE/S_W) were discussed. The percentage of fertile grains (1-p; p, the percentage of sterile grains) was connected more closely with C/S_W than with ΔW/S_W. C seemed to function as buffer stock to maintain the sink activity of spikelets, when ΔW is not equal to the demand of spikelets for assimilation products (sink potential). ΔW/S_W contributed chiefly to the increase in ΔE/S_W through ΔE per fertile S_W (ΔE/[(1-p)·S_W]). From the above results, it was estimated that not only ΔW but also C is very important to improve ΔE/S_W.

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Effects of combined treatments of CO₂ (400, 660, 1200 ppm) and air temperature (outdoor tracking, outdoor +2°C) on growth and yield of rice (Oryza sativa L. cv. Nipponbare) grown in growth chambers under natural sunlight were investigated. The effects of container size (tank, 3.5 l pot) on growth and yield were also examined. Plants were grown under simulated paddyfield conditions. Growth parameters under the elevated CO₂ and temperature conditions were promoted at the maximum tiller number stage but not at the heading stage, without appreciable difference in such parameters. In the 660HT plot, dry weight increased about 30% at both stages compared with the 400NT plot. In the 1200HT plot, it increased more than that of the 660HT plot at the maximum tiller number stage but at the heading stage, the degree of promotion was decreased substantially. Dry matter distribution to leaf blades was reduced, and the nitrogen ratio in leaf blades were low in plants grown in both 660HT and 1200HT plants. In the 1200HT plot, the yield was remarkably reduced probably due to the high temperature sterility. Potted, limited-root-space plants grew smaller above-ground parts than did tank plants (less limited), without any difference in root production. From these results, the production processes of rice crop are discussed in terms of climate conditions predicted for the future.

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We have reported in a previous paper that the outside half-leaf had a smaller volume and deeper leaf color than the inside half-leaf. The half-leaf color was not dependent only on the difference in leaf volume but also on the ability of nitrogen absorption. The difference in nitrogen absorption was considered as another factor involved. We, therefore, measured the volumes of nodal roots on both sides of a half-leaf and found that the nodal roots of an outside half-leaf had a larger volume and higher ability of absorption. Considering that the difference in translocation and retranslocation of absorbed nitrogen might be involved as a third factor, we investigated the difference in the distribution of ¹⁵N fed to the roots on fixed tillers. It was found that absorbed ¹⁵N was translocated only to the side of ¹⁵N feeding tillers, and that each nodal root, being related to specific parts of tillers only, played an extremely limited role in distributing nitrogen. We further investigated the translocation of ¹⁵N applied to the surface of an outside or inside half-leaf to find how ¹⁵N was translocated through the midrib to an opposite half-leaf. It was found that ¹⁵N transferred to the top and base of a half-leaf and did not transfer across the midrib. Consequently, it was assumed that an outside half-leaf maintains its deeper leaf color.

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We carried out this experiment to clarify the growth of culms of Japonica type rice cultivars under deep water conditions with special reference to lodging resistance of culms. We used four Japonica type paddy rice cultivars which are different in plant type. Plant types of Nipponbare and Sasanishiki are high tillering type, and Koganenishiki and Tsukinohikari are ear weight type. Deep water treatment was started from the time of the 8th leaf emergence in main stem and was kept to the ripening stage. The water depth (about 25cm) was deep enough to submerge the sheath of the 7th leaf of the main stem. In the deep water plot at the ripening stage, the diameter of all the cultivars was remarkable large and the breaking strength of the basal elongated internodes tended to increase. However, the breaking strength of the deep water plot was interior to that of the control plot when the internode was the same diameter as the control plot. In the deep water plot, remarkable development of lysigenous aerenchyma, with a diameter as much as 3.5 times that of the control plot, was observed and the occupation ratio of lysigenous aerenchymas in the cross section of elongated internodes was about 13.7% while in the control it was about 1.5%. The remarkable development of lysigenous aerenchyma may be one of the structural adaptations to aquatic conditions and may play an important role as a passage of air. However, this structural adaptation caused the elongated internode tissue to become insufficient by remarkable development of lysigenous aerenchyma, and this led to a decline in the contribution of the thickening of the basal elongated internode to the breaking strength.

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The palatability and physiochemical properties of milled rice produced on different types of soils and latitudes were studied in order to improve the culture technique to produce good eating quality rice. There was locational difference, we found that the differences in soil types had a great influence on palatability. No clear relationship between the altitude and palatability was found. The palatability of rice produced on Light-colored Andosols (LAN) was inferior to that of rice produced on other soil types: Fine-textured Yellow soils, Fine-textured Brown Lowland soils, Gravelly Gray Lowland soils. The protein content of rice produced on LAN was significantly higher than that of rice produced on other soil types. Protein content was significantly correlated with the palatability using rice grown in various locations. On the other hand, amylose content and amylographic characteristics were not related to palatability. The results lead to the conclusion that the main cause of the deterioration of palatability of rice grown in LAN was increases in protein content due to increases in nitrogen released from LAN during the late stage growth period of rice plant. Therefore, it is important to restrict the amount of nitrogen absorbed by rice plant i.e., improvement of the method of fertilizer application and soil improvement, in order to improve the eating quality of rice grown in LAN.

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Edible canna was grown from late April to November at either 0.5m×1m or 3m×3m spacing in the experimental field of the University of Tsukuba to clarify leaf area development and changes in leaf photosynthesis with leaf age and growth as a basis of high productivity. The leaves unrolled during a 6-9 day interval. In the middle growth stage, individual leaf area in the upper layers was larger than in the lower layers. On July 23 and August 16 when LAI attained 7 and 9, respectively, about 70% of the leaf area was occupied by the upper 4 leaves. The maximum net photosynthetic rate was 19.1μmol m^-2 s^-1 (June 9) and the photosynthesis of the upper leaves did not become saturated at 1, 000μmol m^-2 s^-1 PPFD. The maximum rate, however, tended to decrease gradually with growth. After July, when plants began rapid growth, net photosynthetic rates of leaves in the canopy decreased rapidly with a decrease in light by mutual shading. Judging from the leaf area and net photosynthesis at each leaf position, the upper 4 leaves in the canopy substantially contributed to the dry matter production of this crop after the middle growth stage.

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Plant growth is influenced by transport of water, ions and hormones under various environmental stresses. If acetylcholine (ACh) mediates the opening and/or closing of ion channels in plants just as in animal systems, it is important to detect such evidence. The effect of heat stress on the acetylcholinesterase (AChE) activity and Ca²⁺ as a trigger of ACh release can be determined in selected organs of dark grown Zea mays seedlings. The enzyme activity in the coleoptile node was 3-7 fold higher than that of other organs. By heat stress, the AChE activity increased about 20% in the node. Cytochemical evidence for AChE activity was found only in the node. This reaction appeared in the cortical cells around the vascular system. After heat stress, the localization of AChE was radicaly changed in the node. AChE activity was detected in all endodermal cells surrounding the vascular system. Further, fluorescent labeled Ca²⁺ in the node was identified in cortex cells around the vascular system, epidermis and adhering peripheral cortical cells with a laser scanning confocal microscope. Following heat stress, Ca²⁺ was found more in the cortical cells and whole endodermal cells between the cortex and stele. The appearance of AChE and Ca²⁺ in endodermal cells after heat stress seems to be correlated with ACh function controlling ion channels.

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Response of potato genotypes (Solanum tuberosum L.) to increase in planting density was examined. Three potato cultivars (Irish Cobbler, May Queen and Dejima) and two planting densities (5 and 10 plants per m²) were employed. Increase in planting density caused the main stem length to increase and the number of branches and the leaf area per plant to decrease irrespective of the cultivar. Stolon growth and number of stolons per plant was not affected by increase in planting density, but the percentage of productive stolons was decreased by increase in planting density. During the experimental period, all cultivars showed upward trends in crop growth rate (CGR), net assimilation rate (NAR), tuber growth rate (TGR) and economic assimilation rate (EAR) under both densities. Plants under high density had higher TGR and EAR values and achieved them at an earlier stage than those under low planting densities. Increase in planting density decreased the dry weights per plant of leaves, stems and tubers but it increased dry weights per unit area. Percentage of dry matter partitioned to the tubers was high under high planting density. High density increased total and marketable tuber yield per unit area but decreased per plant yield of all three cultivars. High density markedly reduced both average tuber weight and average marketable tuber weight. Dejima outyielded the other cultivars. Range of optimum planting densities for marketable tubers will be higher for Dejima than Irish Cobbler and May Queen.

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Changes in the number and size of spikes, grains, endosperm cells and starch granules was examined in relation to the limited assimilates caused by shading treatments. Spring wheat canopy (Triticum aestivum L. cv. Haruyutaka) was covered with a 95% shading cloth so as to cause failure in the assimilation at the initial, early and late grain filling phases; initial shading, from two days before anthesis until seven days after anthesis; early shading, from seven days until 14 days after anthesis; and late shading, from 14 days until 21 days after anthesis. The grain yield decreased (11% as compared to no shading) due to a decrease in the number of grains (17%), especially decreasing (62%) at the third floret position in the initial shading, while a decrease of one grain weight at all floret positions resulted in 20% and 16% decreases in the grain yield in early and late shadings, respectively. The reduction of grain weight was not due to a decrease in the number of endosperm cells, but to a decrease in the size of large starch granules. Differences in the effects of shading on changes in sink characters could be explained in terms of the physiological process of grain formation.

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A regression analysis was conducted on four grain filling phases to evaluate differences in plant growth and assimilate accumulation in spring wheat varieties. Three varieties, early semi-dwarf Haruyutaka bred in Hokkaido Japan, early semi-dwarf Norin 61 bred in Kyushu Japan and late tall Selpek bred in Germany were selected in the present experiments. Plants were sampled everyday throughout the grain filling period to measure total dry weight, ear dry weight, water soluble carbohydrate (WSC) in culm and the weight of the culm structure. According to the growth and accumulation pattern, four grain filling phases were determined and a regression equation was fitted to each phase. The characteristics of these varieties are described. Haruyutaka had an intensive growth of culm structure during the initial phase. WSC was kept high until cessation of photosynthesis, then translocated into grain rapidly during the long final phase. Norin 61 had a long early phase with a moderate rate of WSC accumulation in culm. The grain growth rate was kept high even during the final phase. Selpek had the longest duration of the initial phase but the lowest rate of culm structure growth during this phase. The rates of grain growth and WSC accumulation in culm were higher during the early phase. This analysis seemded to be helpful to assess the regional grain yield with physiological characteristics of genotype.

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Improvement of wheat flour quality, an increase in grain nitrogen content accompanied by an increase in grain yield, is required through cultivation techniques and breeding program. Changes in nitrogen content in grains and vegetative organs were investigated to clarify nitrogen metabolism in four grain filling phases in spring wheat. Three cultivars including semi-dwarf Haruyutaka with early maturity bred in Hokkaido in Japan, semi-dwarf Norin 61 with early maturity bred in Kyushu in Japan, and tall Selpek with late maturity bred in Germany were selected for the present experiments. Plants from each cultivar were sampled at intervals of a few days throughout the grain filling period in 1993. In 1992, Haruyutaka canopy was covered with 95% shading cloths for three grain filling phases; the initial phase from two days before anthesis to seven days after anthesis, the early phase from seven to 14 days after anthesis, and the late phase from 14 to 21 days after anthesis. Haruyutaka required more nitrogen for grain filling during its earlier phases than Norin 61 and Selpek. This fact resulted in a higher remobilization of nitrogen from vegetative organs into grains in Haruyutaka (73%) than in Norin 61 (49%) and Selpek (47%). Shading treatments did not affect the nitrogen content in grains until a week before maturity. However, the nitrogen in vegetative organs for each shading was translocated into grains rapidly during the last week of the final phase, with the result that the nitrogen content in each shading grain was higher than no shading. As strategies to achieve both high yield and high nitrogen percentage in grain, it appeared that much nitrogen must be accumulated in vegetative organs and allocated to more active photosynthetic organs until anthesis, and that more nitrogen must be absorbed from soil during earlier grain filling phases, then completely translocated into grains during the final grain filling phase.

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Photosynthetic activity determined as O₂ evolution (OER) and the amounts of Rubisco activase, Rubisco, total soluble protein and chlorophyll were investigated in the 10th leaf of rice, Oryza sativa L. cv. Nipponbare, in relation to its aging. The Rubisco activase content increased until the 17th day after leaf emergence, at which time it attained its maximum and accounted for 1.43% of total soluble protein; thereafter, it decreased rapidly. This change was most remarkable compared to the other leaf constituents examined. The Rubisco content had already reached its maximum 3 days after leaf emergence and had begun to decrease earliest among the leaf constituents. The OER depended linearly on the leaf Rubisco content below the value of 3 g m^-2, but tended to saturate above this value. On the contrary, the amount of Rubisco activase and OER were linearly correlated during the life span of the leaf. The in vivo Rubisco activity, as the OER per unit Rubisco content, increased exponentially with the increased Rubisco activase/Rubisco ratio. These results show that the amount of Rubisco activase is closely related to the photosynthetic rates in rice leaf from its emergence through senescence, and suggest that in vivo Rubisco activity can be restricted by Rubisco activase content, particularly when the leaf is young and accumulates excess Rubisco.

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For the topological analysis of plant root systems, two sets of topological indices have been proposed; the ratios of measured altitude (a) and total external pathlength (Pe) to the expected value of the respective parameter when lateral root branching is assumed to occur randomly {a/E(a), Pe/E(Pe)} and to the maximum value of the respective parameter when all lateral roots emerge from the main root axis (herringbone type) {a/Max (a), Pe/Max (Pe)}. We traced the timecourse changes in these indices with root system development of two rice cultivars grown with the excised root tip culture method, and evaluated their adaptability for the actual complexity of the branching pattern. The a/E (a) and Pe/E (Pe) did not adequately express the progress of complication with root growth and the difference between cultivars in branching pattern because root system size substantially affected the values. On the other hand, changes in a/Max (a) and Pe/Max (Pe) showed close correlation with those in several root developmental characters such as the number and mean branching order of lateral roots (MBO). Thus, we conclude that a/Max(a) and Pe/Max(Pe) are better indices than a/E(a) and Pe/E (Pe) for the topological characterization of morphology in the developmental study of rice root systems.

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Aging pattern of rice seminal root system grown under submerged soil conditions was evaluated by the measurement of succinic dehydrogenase (SDH) and peroxidase (POD) activities with special reference to the difference between the basal 11 cm-portion of the seminal root axis (SRA) and the lateral roots (LR) initiated from this portion. SDH activity in both SRA and LR showed high levels just after their initiation, and subsequently these activities decreased sharply with aging. The activity in LR always exceeded that in SRA. The percentage of the LR that positively reacted to the reduction assay of triphenyltetrazolium chloride was 100% in the first 4 days after initiation, followed by a drastic decrease ranging from 14 to 24%. Even at heading stage, however, about 8% of the LR still showed a positive reaction. In contrast, POD activity in both SRA and LR increased with aging. The activity in LR, again, always exceeded that in SRA, and attained the highest level which was 3.6 times higher than that in SRA at heading. This elevation of POD activity with aging was discussed in terms of induced protective reaction which may delay senescence. These results indicated that the senescence of SRA precedes that of LR, and LR plays a major role in the physiological activity of the seminal root system. In addition, the rice seminal root system was found to be alive up to the heading.

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The distribution of arbuscular mycorrhizal colonies was assessed in a peanut (Arachis hypogaea L.) root system at early growth stage. Arbuscular mycorrhizal fungus (Gigaspora margarita Becker & Hall) was uniformly inoculated into non-sterilized soil. Peanut plants were grown in root boxes filled with the soil for 16 days inside a growth chamber. Approximately 66% of the total length of the mycorrhizal colonies was found on the 1st order latelral roots, while the rest was observed on the 2nd ones. In contrast, the tap root was scarcely colonized. On the 1st order lateral roots, regardless of the root length, it was evident that the frequency of the mycorrhizal colonies increased acropetally toward the root apex especially in the relatively aged roots that initiated on the proximal portion of tap root axis. In those lateral roots, the highest frequency of the mycorrhizal colony occurrence was recognized in the most apical part of the root, while many of relatively long colonies were found a little behind the root apex. However, the trend became unclear gradually in the relatively younger lateral roots initiated on the more distal potion of tap root axis. These facts clearly showed that in the 1st order lateral roots, the distribution and growth of mycorrhizal colonies are closely related with their initiating positions along tap root axis.

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Based on the plant age (AL) indicated by leaf number, we analyzed the elongation patterns of basal internodes from the third internode (IN3) through IN10. Using two cultivars, Syrup sorgo 2 (S2, late-maturing) and High-sugar sorgo (HI, early-maturing) grown under field conditions in 1993, 20 plants were sampled when the leaf blade of the 4th through the 14th just fully expanded, and every internode length in the main stem was recorded. All internodes in IN9 and IN10 were classified as 'elongated internodes' (EIN: defined as that with final length more than 1.0cm), while those from IN3 through IN6 were classified as non 'elongated internodes'(non-EIN: defined as that with final length less than 1.0cm). In IN7 and IN8, both EIN and non-EIN existed. The EIN rapidly elongated from AL (n+1) when the (n+1) th leaf had just fully expanded to AL (n+3) and reached its maximum length by AL (n+4). This elongation pattern was similar to that of IN10 through IN19 as was reported previously. The non-EIN elongated from AL (n+1) to AL (n+2) and reached its maximum length by AL (n+3). At log phase of internode growth, the elongation rate of non-EIN was remarkably lower than that of EIN. It was suggested that the formation of intercalary meristem did not occur in the non-EIN. It is not likely that the elongation pattern of EIN and that of non-EIN were influenced by the cultivars.

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Mesophyll protoplasts of mung bean (Vigna radiata L. Wilczek) were electrofused with cell suspension-derived protoplasts of adzuki bean (V. angularis Ohwi & Ohashi) and subsequently cultured for several days. The structural characteristics of fusion products and unfused protoplasts of parental species were examined using light and transmission electron microscopes. Fusion product was distinguishable from the parental species due to the concurrent existence of chloroplasts originated from mung bean and proplastids from adzuki bean. Heterokaryon performed a mixture of cytoplasms between fused parentals. However, chloroplasts from mung bean and proplastids and ER fragments derived from adzuki bean were still encountered on their initial sides. Chloroplasts became a little round in shape due to application of electric field. Electric stimulation also caused the fusion between organelles. The fusion product started to divide after 5 days in culture. Some of the dividing cells demonstrated unequal segregation of chloroplasts in the daughter cells.

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In a rice embryo sac, there is an antipodal mass located at the opposite side of the micropyle, directly adjoining nucellar cells. Immediately after anthesis, the antipodal cells are characterized by the presence of numerous rough endoplasmic reticula and the prominent ingrowths of the wall parietal to nucellar cells. Additionally, they contain large-sized and irregularly lobed nuclei. The lobed parts of the nucleus are connected by narrow and short bridges composed of nucleoplasm and surround part of the cytoplasm, in which many plastids, mitochondria and rough endoplasmic reticula are evident. Most cell organelles are evenly distributed in cytoplasm around the nucleus and the terminal ends of endoplasmic reticula occasionally join the wall ingrowths protruding from the nucellus side. Some round-shaped structures with attached ribosomes are present in antipodal cytoplasm near the wall bordering a central cell. The nucellar cells in the neighborhood of the antipodal mass are already beginning to degenerate. It is proposed that this behaviour of antipodal cells and cell organelles is implicated in the possible role of the antipodals in apoplastic movement of nutrients from nucellar cells into a central cell in the embryo sac. Furthermore, we briefly describe the various routes of nutrient transfer in rice embryo sac.

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Drought tolerance is an important crop characteristic for maintenance of productivity under water deficit conditions. Interspecific differences among four gramineous crops (barnyard millet, maize, pearl millet and sorghum) in growth response to soil drying were studied. Seeds were sown in a sandy soil. Irrigation was stopped in some plots 16 days after sowing and was continued in others. Stopping irrigation increased resistance to water flow to between 2- and 21-fold. However, it decreased the soil water potential by -0.004 to -12.7 MPa, the relative growth rate (RGR) by 15 to 27%, the net assimilation rate (NAR) by 17 to 34% and the photosynthetic rate by 16 to 45%, respectively. Pearl millet and sorghum, which were identified as drought tolerant, displayed the lowest reductions in RGR. RGR was predominantly limited by NAR in all crops. The photosynthetic rate was preponderantly limited by stomatal conductance. Stomatal conductance correlated with leaf xylem water potential significantly. Pearl millet and sourghum showed the highest leaf water status. Root systems of all crops reached 140 cm soil depth. Under water stress, total root length was significantly reduced in maize, was not affected in barnyard millet, and was significantly increased in sorghum and pearl millet. Drought toleranace in sorghum and pearl millet was assoicated with sustained water uptake ability by increasing total root length and maintenance of high leaf water status under soil drying conditions at the vegetative growth stage.

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Modification of root system morphology caused by the inoculation of arbuscular mycorrhizal fungus (Gigaspora margarita Becker & Hall) was evaluated in peanut (Arachis hypogaea L.). Peanut plants were grown for 16 days in root boxes placed in a growth chamber with natural light. Inoculum of the fungus was uniformly mixed with the soil in root boxes, whereas in others, the soil was uninoculated to serve as a control. In each root system, the tap root axis was divided into 10-mm sections, where lateral roots remained intact, to evaluate the difference in lateral root development along the tap root. Two-way ANOVA in which the variation sources were divided into the inoculation treatment and section of tap root axis, showed significant effects of the inoculation on lateral root development. As for the root number, the effect was promotive for the 1st order lateral roots but inhibitive for the 2nd order ones, and as for the individual root length, inhibitive for the former but was not detected for the latter. Our conclusion is that the inoculation caused changes in root system morphology of peanut through lateral root development on the tap root, where the responses were different between 1st and 2nd order lateral roots.

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Taproot elongation rates (TRERs) of seedlings were investigated with the slant tube method for 27 genotypes of six food legume species in spring, and six selected genotypes of three species in autumn under irrigated and non-irrigated conditions. Shoot growth was also evaluated for comparison. In these experiments, we aimed to evaluate the plasticity in TRER of the species and their genotypes. In spring, most of the species and their genotypes were significantly different in TRERs. Combined ANOVA across the environments revealed that TRERs significantly responded to the environments, especially growing seasons between which root-zone temperatures were markedly different. Under irrigated conditions, TRERs were generally slower in autumn- than spring-grown plants. However, the significant species (genotypes)×environment interactions indicated that the plasticity in TRER differed among species. Comparison between two seasons showed that TRERs of cowpea were more plastic than those of chickpea and lentil, while an opposite trend was evident for shoot growth. TRERs of cowpea, mung bean and black gram (warm-season species) were strongly root-zone temperature dependent, while those of chickpea, grasspea and lentil (cool-season species) were less dependent or independent. Non-irrigated conditions tended to promote shoot growth, but did not affect TRERs of the genotypes of three species. However, the significant genotype×environment interaction due to different soil moisture regimes for lentil genotypes showed that genotypic difference also existed in plasticity triggered by soil moisture regimes.

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