Showing papers in "Japanese Journal of Crop Science in 1976"

Effect of Carbon Dioxide Concentration on Growth and Dry Matter Production of Crop Plants : 1. Effects on leaf area, dry matter, tillering, dry matter distribution ratio, and transpiration

Abstract: Crop plants at the 5 to 7-leaf stages possessing C3 (barley, rice, and soybean) and C4 (barnyard millet and maize) pathways of photosynthesis were cultured for 15 days in transparent growth chambers placed outdoors under 4 different carbon dioxide (CO2) concentrations from 1/2 to 10 times the normal atmosphere (ca. 350 ppm) to make clear the effects of various CO2 concentrations on growth and dry matter production. The following results were obtained: I. Increases in plant height and leaf area were promoted by high CO2 concentrations, but the degree of promotion was relatively small. At a low concentration (160 ppm), plants often elongated and had narrow drooping leaves as compared to control plants under normal CO3 concentration. 2. Increase in dry weight was promoted by high CO2 concentrations and suppressed by a low concentration. This increase proceeded up to about 3 times (sometimes 10 times) the normal concentration, and this was effected mainly through the increase in net assimilation rate. The C3- and C4-plants responded differently to CO2 concentrations, the latter giving less suppression at a low concentration and less promotion at high concentrations than the former. 3. Tillering in barley and rice was accelerated by high CO2 concentratoins and withheld by a low concentration. In rice plants, observed at the 7-leaf stage, the promotion of tillering took place at the 4th node, and the appearance of tillers was made steadier at the 2nd and 3rd nodes by high CO2 concentrations. 4. Distribution ratio of dry matter in rice and maize was in a marked contrast. In rice plant distribution to leaves was less and that to roots was increased at high CO2 concentrations, while in maize such a tendency was not observed at all. 5. Transpiration rates (dm-2 day-1) were smaller at higher CO2 concentrations. At a low concentration, the promotion of transpiration was enhanced day by day as the treatment proceeded. On fine days, the leaf temperature was about 1°C lower at a low CO2 concentration and about 1°C higher at higher concentrations as compared to control plot, but no difference was observed on cloudy days.

High Temperature Injury of Ripening in Rice Plant : V. On the barly decline of assimilate storing ability of grains at high temperature

Abstract: A jabonica rice (cv. Norin-17) was used to test the effects of high temperature treatment (day-night, 35-30°C) combined with the treatments which increase or decredse the available carbohydrate amount per grain, upon the ripening of rice grains. 1) Under high temperature, the rate of ripening was much higher at an early ripening period, but the inflow of assimilates into grain ended earlier (2 to 3 weeks after flowering), resulting in lower 1000-kernel weight than that of normal outdoor temperature. 2) At both high and normal temperatures, 1000-kernel weight was incredsed by thinning the panicle branches and was decreased by leaf-cutting or fertilizer dificiency. At high temperature, panicle thinning increasd 1000-kernel weight about 10%, while at normal temperature about 20%. 3) At both temperatures, the amount of TAC (total sugar plus crude starch) accumulated in each shoot was greatest at the no-treatment control, being fllowed in order by fertilizer deficiency, panicle-thinning and leaf-cutting. The total nitrogen accumulatlon was also greatest at the control, being followed by panicle-thinning, leaf-cutting and fertilizer deficiency. Panicl/Straw ratios in dry weight and in TAC amount at high temperature were lower than at normal temperature, indicating a relativelvy less TAC translocation into the panicle, leaving relatively more amount in the straw at high temperature. 4) An addition of CO2 to the ambient air combined with the above treatments did not increase the 1OOO-kernel weight at both temperatures indicating that CO2 amount was not limiting in this experiment. 5) The 1000-kernel weight did not increase at all after moving the plant from high to favorable temperatures if the plants had been treated at high temperature about 2 weeks after anthesis, whether the as-similate amount which should be stored in each grain was increased or decreased. (3) It was assumed that the main cause of early stoppage of maturation with a small 1OOO-kernel weight at hightemperature was an early decline of storing ability of assimilates in panicle rather than the decficiency of assimilate amount in the plant

Effect of Plant Water Deficits at Various Growth Stages on Growth, Grain Yield and Leaf Water Potential of Irrigated Grain Sorghum

Abstract: In pot trials at Bushland, Texas, USA, leaf water potential in grain sorghum subjected to water deficit decreased as severity of drought stress increased and fell to -22 to -30 bar compared with lowest values of -19 bar with adequate water supply. Water deficit decreased growth, and deficit during booting decreased grain yields to a greater extent than deficit during vegetative growth. Deficit treatments which decreased the number of grains/ear did not decrease 1000-grain weight. With adequate water evapotranspiration was highest during the boot stage. It was concluded that the critical period for drought stress in grain sorghum was from the boot stage until flowering

On the Direction of the Crown Root Growth of Rice Plants

Abstract: The direction of the crown root growth of rice plants cultured in a pot and in a paddy field was observed. In case of the culture in a 1/2, 000 a Wagner pot (diameter: 255 mm), the direction of the crown root growth was observed by a method of measuring a length of each crown root cut off vertically by a tin cylinder (diameter: 150 mm) (Fig. 1). In this case, it was found that each crown root grew in a linear pattern (Fig. 2), and it was certain that a length of the crown root having grown horizontally would be much shorter than that having grown vertically (Fig. 1). Meanwhile, in case of the culture in the paddy field with higher grain yield, the direction of the crown root was observed by means of an improved monolith method (Fig. 3). As a result of these observations, we could classify the crown roots of rice plants cultured both in the Wagner pot and in the paddy field into the following three types according to their growing directions. (1) The upper primary roots grew horizontally, regardless of the position on a stem of the "shoot unit" they emerged. (2) The lower primary roots grew in various directions, i.e. horizontally, oblique downwards and vertically. (3) Most of the primary roots emerging from the prophyll "shoot unit" of a tiller grew vertically, even when the tiller bud was dormant (Fig. 9). Here, a shoot of rice plants is designated as comprising the following two types of "shoot units" (Fig.4A). One is a "shoot unit" that consists of a leaf blade, a leaf sheath, a stem portion with upper and lower primary roots and a basal tiller bud (Fig. 4B, also refer to Kawata et al.3)). The other is a prophyll "shoot unit", located singly at the base of each tiller, that consists of a prophyll and an adjacent lower stem portion with primary roots and lacks a basal tiller bud (Fig. 4C). There was a remarkable difference in the growing direction of the lower primary roots depending on whether the plants were cultured in the pot or in the paddy field. Namely, the lower primary roots mostly grew horizontally in the pot, while they grew oblique downwards or vertically in the paddy field. There was generally no correlation between the diameter and the growing direction of the crown roots. Why did the direction of the crown root growth of rice plants vary in the above-mentioned three types? The results of our observation in this respect gave us many suggestions on the possible geotropic responses in the roots and further investigations are required to continue.

The Growth Responses of Soybean Plant to Photoperiod and Temperature : I. Responses in vegetative growth

Abstract: An early cultivar "Wase-Furisode" was used as a material plant. Characters of vegetative growth under the combinations of two photoperiods (LD: 14 hr, SD: 9 hr) and five temperature regimes (day-night, 35/30, 30/25, 25/20, 20/15, and 15/10°C) were compared both at the same chronicle date (the 16th day of treatments, A-plot) and at the same growth stage (6.5 trifoliate stage, B-plot). The results are summarized as follows: 1) Both shedding of cotyledons and flowering were hastened as the temperature increased, but the former occurred at the two trifoliate leaf stage and the latter at the stage of five trifoliate, in spite of the different earliness under different conditions. 2) At A-plot, stem height, leaf area, and total dry weight per plant increased with increasing temperatures and under LD condition. Nodule weight was greatest at 30/25° and decreased with decreasing temperatures. Leaf appearance rates increased with increasing temperatures and were greater under LD than under SD at lower temperatures. Water content (%) and SLW of lamina increased with decreased temperatures, the former being higher under SD and the latter under LD than under the respective opposed day-lengths. Lamina to stem ratio had a tendency to increase at lower temperatures and was greater under SD. Top to root ratio increased with increased temperature, being little affected by photoperiod. 3) At B-plot, the qualitative characters such as SLW, lamina to stem ratio, top to root ratio changed similarly as at A-plot, but water content of lamina decreased with decreasing temperatures. Stem height and mean internode length reached a maximum at 25/20° under LD, but increased with increasing temperatures under SD. Leaf area reached a maximum at 30/25°, while total dry weight, stem weight per 1 cm length tended to increase with decreasing temperatures, being very small at 35/30°. Nodule weight per plant and nodule size became greater as the temperature decreased. In general, branching occurred more abundantly and at lower nodes as the temperature decreased. 4) At A-plot, RGR had the keen correlations with both RLGR and NAR (r=0.978 and r=0.960, respectively), but at B-plot it correlated strongly only with RLGR (r=0.967). Correlations between total dry weight and nodule weight (r=0.920), roots weight and nodule weight (r=0.921) were also very strong at B-plot. 5) From the results obtained, it may be concluded that the optimum temperatures for vegetative growth of soybean plant are 30-35° day temperature or 32-33° mean daily temperature.

High Temperature Injury of Ripening in Rice Plant VI. Enzyme activities of kernel as influenced by high temperature

Abstract: To clarify the cause of early clecline of assimilate storing ability of grains by high temperature during ripening period, enzyme activities of kernels which may be concerned with the ability was compared at high and normal temperature with the progress of maturation. 1) Respiration rate of kernels declined with the prbgress of ripening, more rapidly at high temperature reachihg the lowest level at two weeks afrer anthesis. Oxygen uptake by kernel mitochondria followed a similar pattern as kernel respiration and ADP/O ratio at high temperature reached zero at thh 14th day, whereas that at normal temperature remained fairly high until maturity. When ADP/0 radio at high temperature rapidly declined, available starch still femained in the straw although of small amount. Water percentages of kernels rapidly and that of leaf-blade gradually decreased with the progress of ripening, being always lower at high temperature. 2) Carbohydrate and nitrogen contents of kernels paralleled with 1000-kernel weight during ripening at both temperatures, but protein-N at high temperature stopped to increase before the 14th day of treatment and non-protein-N gradually incrcased thereafter. 3) Phosphorylas activityj reached a maximum at the 1Oth day and theh gradually decreased at both temperatures, being lower at high temperature. 4) Yellowing of spikelet was first recognized At rachilla portion and occurred earlier at high temperature Succinic-dehydrogenase activity at rachilla disappeared at the 16th day and soon yellowing started. Kernel enzyme activities seemed to declin earlier than disappearance of succinic-dehydrogenase activity at rachilla. 5) It was suggested that the early decline of assimilate storing ability of grains at high temperature had a close relation to early decline of physiological activities of kernel cells

Histogenesis of Lemma in Japonica Paddy Rice

Abstract: An anatomical study was carried out on the tissue differentiation and growth of lemma in Japonica paddy rice, cultivars Sachikaze and Reimei. Every kind of tissues composing lemma such as outer- and inner- epidermis, hypodermis, parenchyma and vascular bundles had initiated before the lemma's rapid growth. With the beginning of lemma's rapid growth, both sides epidermes undertook such cell differentiations as uneven mitosis of epidermal cells followed by initiation of macro- and micro-hairs, and formation of tubercles in outer epidermis, and as initiation of stomata and microhairs in inner epidermis. After the rapid growth remarkable schlerization was made especially in hypodermis and outer epidermis. First sign of the differentiation of tubercles was the accumulation of a kind of substance which was not so well stained by Delafield's haematoxylin as to nucleus at the contacts of four large epidermal cells, forming a dome-like protuberance in basal portion of which some "zig-zag shaped structures" were constructed. And later the protuberance was covered by translucent membrane. Multicellular macrohairs were newly observed in the outer epidermis besides needle like trichomes and microhairs. Although both macrohairs and microhairs initiated from small epidermal cells, they differed each other on their developmental processes. Those of macrohairs were that whole small cells expanded and elongated before the enlargement of tubercles, but those of microhairs were that a portion of the small cell's wallprojected at the point of which was extremely narrowed by tubercles situated at their both sides, followred by moving the small cell's nucleus into that protuberance. It was, therefore, clarified that developmental process of tubercles was differed from those of macro- and micro- hairs, and that histogenetical center of outer epidermal cell was on the macro- or micro- hairs which were situated at the concave of both sides tubercles. Judging from that multicellular macrohairs and microhairs initiated in the beginning of lemma's rapid growth and withered in almost the same time with the end of its growth, it was suggested on the physiological functions of those hairs that they might have some relations to the rapid growth of lemma. The fact that both stomata and microhairs initiated densely at the near of vascular bundles in inner epidermis was considered that there might be some physiological correlations among them.

The Effect of Farmcompost Application to the Paddy Field on the Formation of Superficial Roots of Rice

Abstract: The supericial roots of rice emerge after the spikelet differentiation stage and concentrate near the soil surface, forming a net with many branched roots. A long-time application of farmcompost to the paddy field in the Agricultural Experiment Stations of Aomori and Fukushima Prefectures for forty-five years and fifty-five years, respectively, was proved to accelerate the development of superficial roots of rice. The superficial roots of rice in these farmcompost-applied fields had the following characteristics over the control. (1) Most of the primary roots distributed near the soil surface (up to 3 cm depth). (2) The length of the thick secondary roots was longer than those of control. (3) The density of the formation of the secondary roots on the primary roots and that of the tertiary roots on the thick secondary roots were higher than those of the control. (4) Additional lateral root branches, for instance, the fifth lateral roots, were observed. (5) "Lion-tail-like roots" remarkably decreased in number. The data obtained through this investigation are not sufficient to clarify how the superficial roots with such characteristics were developed. Further studies are needed for this clarification

The Fate of Fertilizer Nitrogen Applied to the Paddy Field and its Absorption by Rice Plant : VII. Relationships between the absorption of nitrogen by the rice plants and the growth of the plants

Abstract: Field experiments were carried out in order to study the relationships between the nitrogen absorption by rice plants grown under various cultural conditions and the growth of the plants. The results obtained are as follows; 1) It was found that the rate of nitrogen absorption by the rice plants was the greatest just before the neck node differentiation stage throughout all the growth stages. The greatest rate of nitrogen absorption by the plants at this stage was positively correlated to the length of culms, the sum of lengths of lower three internodes, the sum of lengths of upper three leaf blades (excepting those of the plots of nitrogen top-dressing), and the number of spikelets per panicle (excepting those of the plots of no basal nitrogen, nitrogen top-dressing at the neck node differentiation stage and at the stage of reduction division), respectively. 2) The amount of plant nitrogen per unit area at the early stage of spikelet differentiation was positively correlated to the number of panicles per unit area. Furthermore, the amount of nitrogen in plant per unit area at the ear mergence was positively correlated to the number of spikelets per unit area. 3) It was previously shown by Matsushima et al (3, 4, 5, 6) that lodging resistance and light utilizing efficiency of rice plants were improved by the decrcase of the length of culms, the sum of the lengths of lower three internodes, the sum of the lengths of upper three leaf blades and the number of spikelets p6r panicle and by the increase of number of panicles and spikelets per unit area. In order to obtain the growth of rice plants mentioned above, the rate of nitrogen absorption by rice plants must be decreased just before neck node differentiation stage and be increased at the other growth stages. It was recognized that early transplanting and high plant density was effective means to permit the desirable rate of nitrogen absorption by rice plants and to increase the rice yield per unit area.

The Fate of Fertilizer Nitrogen Applied to the Paddy Field and its Absorption by Rice Plant : VIII. Comparative studies of the fate of basal nitrogen and the absorption of nitrogen by rice plant in different paddy fields

Abstract: The behavior or basal nitrogen and absorption of nitrogen by the rice plants in two different paddy fields, Odawara and Takadate, were compared. The results obtained are as follows; 1) The soils of both fields belonging to Gray-Brown Soil were poor ill soil oraganic matter, and were poorly drained. However, the clay contents and CEC values of the plowed layers were much greater in Takadate than in Odawara. Furthermore, the clay fraction of Takadate soil was dominated by montmorillonites. On the other hand, the amounts of nitrogen mineralized by incubation at 30°C were treater in Odawara soil than in Takadate soil. 2) The amount of soil ammonium nitrogen in both fields decreased exponentially after transplanting, and almost all of it was disappeared at the accumulated effective thermal index (AETI) of about 400. The decrease of soil ammonium nitrogen in both fields was shown as an exponential equation of AETI. Soil ammonium nitrogen derived from basal nitrogen was disappeared about the same time. 3) The amounts of nitrogen per unit area absorbed by the rice plants (y) in both fields were indicated to be closely related to the AETI (x). An exponential equation (y=cdx) was obtained for the early growth stage, and linear one (y=ax+b), for the middle and late growth stages. The crossing point of these equations was the AETI of about 400. However, there were some differences in the parametcrs between Odawara and Takadate. It was assumed that the limiting factors were the ability of nitrogen absorption of the rice plants, for the exponential part, and the rate of mineralization of soil organic nitrogen, for the linear part. 4) The average recoveries of basal nitrogen (60-70 kg-N/ha applied) in the rice plants were 43% in Takada, and 27% in Odawara, reflecting the ammonium absorption of the plowed layers as mentioned in 1). On the other hand, the amounts of soil nitrogen absorbed by the rice plants at the ear mergence were 71 kg-N/ha in Odawara, and 44 kg-N/ha in Takadate, reflecting the amounts of nitroten mineralization by incubation. 5) The amounts of residual basal nitrogen in plowed layers were 16% in Takadate, and 19% in Odawara. Therefore, the total recoveries (the recovery of basal nitrogen in the rice plants and residual basal nitrogen in the plowed layers) were 68% in Takadate and 46% in Odawara. Since the water permeability of both fields was extremely small, it was assumed that almost all of unrecovered basal nitrogen was lost by denitrification.

Ecological Studies on the Photosynthesis of Winter Cereals : III. Changes of the photosynthetic ability of various organs with growth

Abstract: Changes with growth in photosynthetic ability of various organs, such as leaf blades, leaf sheaths, culms (parts without leaf sheaths) and ears of barley, wheat, oat and rye plants sown in autumn were measured during 1969-74 (table 1). Photosynthetic rates were measured under controlled conditions in assimilation chambers with artificial illumination of 0.6 ly·min-1. Respiration rates were measured in dark chambers. In both measurements, surface temperature of each organ was kept either at 14-18°C (Nov.-Mar.) or at 18-23°C (Apr.-Jun.). All samples were collected from the fields, cut off from adjacent organs, and measured. Field study of dry matter production of six-rowed barley, wheat and oat was conducted. Due to being various photosynthetic organs other than leaf blades, a new index LAI* was introduced, which was obtained from mutiplying LAI (leaf blade area index) by the ratio of total gross photosynthesis of a productive tiller to leaf blades. Net assimilation rate calculated by using LAI* was named NAR*. The main results obtained are summarized as follows; 1. Changes with growth in the ability of photosynthesis and dark respiration of leaf blade. The mean gross photosynthesis of whole leaves of a shoot was found to be high during winter in six-rowed barley, wheat and rye, but low in oat (fig. 3). After heading date, their values decreased gradually in all of the four crops. A detailed study of changes of photosynthetic rates of some leaves of wheat and rye sown in 1973, clearly showed that the life span of the leaves grown in winter was long, but the one grown in spring (at the stage of culm elongation) was half of the one in winter (fig. 4, 5). The third leaves on main stems of both crops, which developed before winter, decreased gradually their photosynthetic ability in winter. On the other hand, the fifth leaves which developed in winter showed high photosynthetic ability during long winter period. The dark respiration of leaf blades was clearly found to be of higher value during winter than spring in all four crops (fig. 3). 2. Photosynthetic ability of various organs in ripening stage (including two-rowed barley): In ripening stage, the gross photosynthesis of leaf blades per a productive tiller decreased more drastically than that of the other photosynthetic organs in all crops (fig. 7). The contribution of each organ to the total gross photosynthesis of a productive tiller was calculated on the assumption that every organ were equally illuminated. In the early ripening stage the contribution of leaf blades was high, but at the later stage decreased drastically in all crops (fig. 8). In the early ripening stage the contribution of leaf blades of two-rowed barley was low compared to the other crops, and those of ears were low in wheat and rye. In the later stage the contribution of culms of rye became higher. On the other hand, the contribution of leaf sheaths of two-rowed barley and rye were found to be higher than the other crops, through whole ripening stage (fig. 8). 3. Growth analysis of dry matter production: Both NAR and NAR* from middle to late April were more than 3.6 times of those in winter in six-rowed barley, wheat and oat. This fact did not agree with the results of the measurements of photosynthetic ability (table 3, fig. 3). It is presumably concluded that winter cereals cannot display enough their photosynthetic ability because of injurious environment of winter in field, especially low temperature. Growth pattern of dry matter of oat was characteristically different from those of six-rowed barley and wheat (table 3, fig. 12). Both six-rowed barley and wheat kept more than four of LAI* during the period from culm elongation stage to the early ripening stage (table 3). This clearly shows that the various organs other than leaf blades play in an important role for the production of photosynthates.

Effect of Auxin Concentration on the Callus Induction from Various Organs of Rice Seedlings

Abstract: 1. Callus tissues were induced by various concentrations of 2, 4-dichlorophenoxyacetic acid (2, 4-D) from different organs, roots, mesocotyls, internodes, nodes, coleoptiles, leaf sheaths, and epidermal cells of scutellum of Oryza sativa and roots, leaves and stems of Echinochloa crus-galli, Nicotiana tabacum, and Vicia faba. 2. Callus induction is more remarkable in some organs of young rice seedlings than old ones with lower level of 2, 4-D. 3. Different concentrations of 2, 4-D are necessary for callus induction from different organs and diverse species. Tissues and organs in rice seeds, from which callus is able to be induced, are strikingly varied by different concentrations of auxin. 4. The concentration of auxin for callus induction is dependent on a sort of auxins used; IAA, NAA, or 2, 4-D. The difference of auxin concentration for the callus induction corresponds with the difference of auxin activity of the substances used. 5. Effect of kinetin on callus induction in rice seeds is not only undistinct but also repressive. 6. Thiamine is required for growth of rice cultures but it is not essential for callus induction in rice seeds. 7. It is discussed on the effects of the cutting of seedlings on callus induction in rice. 8. The tissues from which the callus is originated in various concentrations of 2, 4-D is histologically investigated on rice seeds and segments excised from the seedlings. Anatomical studies indicated that the initiation of callus in various organs resembled to the initiation of the adventitious root, except for epidermal cells of scutellum. 9. The organ differentiation in rice callus tissues is controled with various concentrations of 2, 4-D. Namely, callus tissues without root-like structures, callus tissues with root-like structures, abnormal roots and normal roots are formed as the concentration decreases.

The Interrelationship between Source and Sink of the Grafts of Wild Type and Improved Variety of Ipomoea

Abstract: This investigation was conducted to make clear the interrelationship between thc source (photosynthate donor, top part of sweet potato plant) and the sink (main photosynthate acceptor, tuberous root) from the side of tuberous root growth. The plants used for grafting were the cultivar (Okinawa No.100) (Ipomoea batatas Poiret), the wild type (IB63005) [1.trifida (H.B.K.)Don.], and the interspecific hybrid between wild type and cultivar (IB66403, IB66502). The wild type plants and interspecific hybrid plants were inferior in thickening growth of tuberous roots to the cultivar. For the purpose of study of interrelationship between source and sink of photosynthates, twelve kinds of sample grafts were cultured. The study results are as follows: (1) The dry weights of whole plants and tuberous roots of the plants grafted on 0kinawa No.1OO stock were far superior to those grafted on the wild type and interspecific hybrid stocks. In general, the dry matter production ranked higher in order of quantities: The grafts of Okinawa No.10O stock>the grafts of IB66502 stock>the grafts of IB66403 stock>the grafts of IB63005 stock. (2) The growth of tuberous roots was promoted in case of grafts of Okinawa No.100 stock. The growth of tuberous roots was small in case of grafts of wild type and interspecific hybrid stocks. In addition, the starch content in the tuberous roots was high in case of grafts of Okinawa No.100 stock notwithstanding their large tuberous roots. (3) In case of grafts of wild type and interspecific hybrid stocks, it was observed that the dry weights of tuberous roots were Small. The growth of pencile type roots and the fibrous roots was promoted. In case of top part of grafts, a decided increas was found in the dry weight of the stems. The starch contents in their leaf blades, leaf petioles, stems, and fibrous roots were higher than those the grafts of cultivar stock. (4) Total 14C-radioactivities of the plants ranked higher in order: the grafts of Okinawa No.100 stock > the grafts of IB66502 stock. In case of grafts of Okinawa No.100 stock, high 14C translocation rates to tuberous roots were found after twenty-four hours and seven days after the exposure to 14CO2gas, and high 14C translocation rates to stems were found on the seventh day after the exposure to 14CO2gas. (5) From the above-mentioned facts, it may be considered that the interrelationship between source and sink is close in case of grafts of Ipomoea, and that the sink function is active. It can also be considered that the sink action has effects on the parts of the source

High Temperature Injury of Ripening in Rice Plant : IV. Effect of high temperature on 14C-assimilation and translocation at an early ripening period

Abstract: The effects of high temperature (day-night, 35-30°C) upon photosynthesis and assimilate translocation to panicle were investigated by application of 14C02 to the whole plant at several ripening stages. 1) Translocation rate of 14C-assimilates into panicle was very low at 25-2O°C, leaving much 14C in the straw. Rising night temperature to 25°(25-25°C) increased the rate equivalent to those at 35-35°C and 35-30°C. Therefore, a great difference was found in the translocation rate between daily mean temperature of 25°(25-25°C and 2325-20°C). 2) At high temperature, 14C assimilated at an early ripening stage was found one week later in grains as mueh as 80% of total shoot 14C, but that assimilated two weeks after flowering remained much in the straw with a decreased amount in the grains. At outdoor natural temperature, one the contrary, the percentage of 14C found in the grains progressively increased as the ripening stage at which 14C was assimilated advanced until two weeks after flowering. 3) At high temperature, 14C assimilated at an early ripening stage translocated uniformly to all grains, but that assimilated two weeks after flowering moved little or much in the grains of upper or lower part of a panicle, respectively. Under outdoor condition, 14C assimilated at an early ripening stage moved much to the upper grains with a little accumulation in the lower grains. Thereafter it moved equally to all grains and still accumulated in upper or early flowered grains even at two weeks after flowering. 4) Just after 14C2 application for half an hour, 90% or 80% of total 14C assimilated were contained in ethanol-soluble fraction in leaf-blade or leaf-sheath plus stem, respectively. 0ne week after 14C2 application, however, much of 14C was found in ethanol-insoluble fraction in straw, especially so in leaf-blade. This tendency was little changed by temperature or ripening stage. In the grains, less 14C was found in ethanol-insoluble fraction at high temperature than at normal temperature. When 14C was applied at a middle ripening stage, the less 14C accumulation was found in starch and protein fraction at high temperature as compared with that at normal temperature, especially so in the lower grains of a panicle. 5) There was little difference in apparent photosynthesis between the plants ripened at high and normal temperatures as long as being deduced from 14C assimilation

The Fate of Fertilizer Nitrogen Applied to the Paddy Field and its Absorption by Rice Plant : VI. Influence of a thermal factor on the soil ammonium nitrogen and the absorption of nitrogen by rice plant

Abstract: The influence of a thermal factor on the soil ammonium nitrogen and its absorption by rice plants grown under the field and controlled conditions were studied. It was shown that the absorption of nitrogen by the rice plants was closely related to the accumulated effective thermal index (AETI) given by T. Hanyu and T. Uchijima (1962). The amount of nitrogen per unit area absorbed by the plants (y) grown in the field was closely related to the AETI consisting of an exponential equation (y=cdx) for the early growth stage and linear one (y=ax+b) for the middle and late growth stages. The crossing point of these equations was the AETI of about 400. The similar equations excepting the b parameter were obtained for both low and high dosages of basal nitrogen. But the crossing point of these equation was varied by the cultural conditions, especially plant density and placement of fertilizer. Soil ammonium nitrogen decreased exponentially after transplanting. Almost all of the nitrogen disappeared at the AETI of about 400, or at the commencement of ear-primodia formation. Therefore, it was assumed that the rate of nitrogen absorption of the rice plants was the limiting factor in the exponential part. On the other hand, the rate of supply of soil ammonium nitrogen, or the rate of mineralization of soil organic nitrogen was assumed to be the limiting in the linear part.

Effects of Temperature and Soil Water Content during Grain Filling Period on the Yields of Grain Sorghum

Abstract: This experiment was conducted to determine the effects of tempcrature and soil water content during grain filling stage on grain yields in terms of dry matter production, sink capacity of grains and distribution of materials produced of grain sorghum (Sorghum bicolor (L.) Moench). Early hybrid variety, NK129, was seeded in pots in June 3, 1974 and was grown outdoors until the end of flowering. Then the plants were subjected to 35°C/25°C, 30°C/20°C and 25°C/15°C of day/night temperature in the phytotron under natural light conditions during the ripening period. Soil water contents were maintained in moderate water and drought conditions in each temperature. The plants were harvested when seed coat hardened. Results obtained are as follows. 1. Grain yields in the moderate soil water conditions were little affected by temperatures. However, grain yields in drought conditions were reduced at high temperature and the highest yield in drought conditions was obtained at 25°C/15°C. 2. Crop growth rates in moderate water conditions were higher at 35°C/25°C and 30°C/20°C than at 25°C/15°C, but total dry matter accumulation during grain filling pericd did not differ among temperatures because maturing times were prolonged at lower temperature. On the other hand, crop growth rates at 25°C/15°C and 30°C/20°C in drought conditions were higher than at 35°C/25°C, and total dry matter accumulations at harvesting time were the highest at 25°C/15°C and the lowest at 35°C/25°C. 3. Net assimilation rates in moderate water conditions showed the trend of higher values at higher temperatures, but net assimilation rates under drought conditions were higher at 25°C/15°C than at 35°C/25°C. Crop growth rate was positively correlated with net assimilation rate. 4. Sink capacity of grains estimated from weight per 1000-grain at harvesting time was limited by the interaction of high temperature and drought conditions, and it was not affected by low temperature of 25°C/15°C. Early hardening of seed coat is possibly one of the cause of limitation. The greater part of grain yields at 35°C/25°C and 30°C/20°C under drought conditions resulted from materials translocated from vegetative organs to grains. 5. Grain yields were mainly affected by dry matter accumulation during grain filling period, but the contribution of materials translocated from vegetative organs could not be neglected for grain yield under drought conditions. Favorable temperature for grain production will be different with soil water contents. Favorable temperature in this experiment was over a range of 35°C/25°C to 25°C/15°C under moderate soil water conditions, but it was in a little lower range of near 25°C/15°C under drought conditions

Studies on Large Vascular Bundles in Paddy Rice Plant and Panicle Formation : I. Relationships between the number of lage vascular bundles in the culm and the plant types

Abstract: 1. In case of early-maturing rice variety Honen-wase, the correlation coefficients between the number of large vascular bundles in the first (highest) internode and the number of the primary branches of the panicle, the number of paddies per panicle, the weight of a panicle were γ=0.903, γ=0.877 and γ=0.850, respectively. And a fairly intimate interrelationship (γ=0.948) was noticed between the number of the primary branches and the number of paddies per panicle. 2. As the difference between the number of large vascular bundles in the first elongated internode and that in the second elongated internode showed the same tendency with the difference in the number of panicles per hill, it was regarded that the ratios of the number of large vascular bundles in the first elongated internodes to that in the second elongated intermode displayed the plant types' own characteristics; that is, the ratios of panicle-number type varieties, biased panicle-number type varieties, medium panicle-number type varieties, biased panicle-weight type varieties, and panicle-weight type varieties, stood at 1:3, 1:2.75, 1:2.5, 1:2.25, and 1:2, respectively.

Studies on White-Belly Rice Kernel : V. On the occurrence of white belly during the development of rice kernel, with special reference to the moisture content of kernel

Abstract: These studies in series were devoted to clarify the characterstics of white belly rice kernel which had an opaque part at the ventral portion of its endosperm. In this experiment, the stage of initiation of white belly in the developing kernel and the relationship between occurrence of white belly and dehydration of kernel were investigated. The varieties used were Nihonkai, Kinmaze, Norin no. 8, Gohyakumangoku (Sakamai) and Sekaiichi (upland rice) of Japonica and Keikyakusen of Indica type of rice. The following results were obtained. I. Stage of initiation of white belly in fresh kernel differed with variety. In case of varieties which characterized by high occurrence and large size of white belly (external-internal white belly type), the initiation began 15-18 days after flowering when the kernel gained 89-95% of dry weight and 28-29% of moisture. The varieties featured by small white belly (external white belly type), on the other hand, initiated white belly 24-32 days after flowering when the kernel nearly attained its maximum dry weight and the moisture content of kernel decreased to 23-25%. Percentage of white belly increased with the progress of maturation and dehydration. The highest value of white belly was indicated with the attainment of maximum dry weight in case of external-internal white belly type and that of full ripe stage in case of external white belly type. 2. Initiation of white belly in dry kernel occurred earlier than that of fresh kernel. In case of external-internal white belly type, the stage of initiation was 12-15 days after flowering when the kernel had 33-34% of moisture and dry weight index value of 79-83. Whereas, in case of external white belly type, the initiation occurred 19-23 days after flowering when the kernel had 26-29% of moisture and dry weight index value of 88-92. The percentage of white belly increased with the development of kernel and reached at its highest value when the kernel just before attained maximum dry weight in case of external-internal white belly type and when the kernel attained maximum dry weight in case of external white belly type. 3. When the premature fresh kernel were dried artificially, the white belly appeared as the moisture content decreased and the moisture content at which the white belly initiated differed with the kernel age. 4. In fresh kernel, the moisture content of ventral portion was higher than that of dorsal portion, but this moisture state was reversed after the kernel was dried. This phenomenon seemed to indicate that the ventral portion of kernel had less deposition of storage matter and stronger dehydration capacity than the dorsal portion. It was also thought that this phenomenon might be related to the formation of porous tissue of white belly on the ventral portion of kernel. 5. In the premature fresh kernel of Gohyakumangoku a white core variety, the white core occurred with the progress of artificially dehydration in the same way as that of white belly, but the occurrence of white core was associated with slightly lower moisture range than that of white belly. 6. The occurrence of white belly was influenced by the condition of drying. And the dryings which resulted to the rapid dehydration of premature kernel increased the occurrence of white belly.

Chamber Method for Estimating the Primary Productivity : of Rice Plant Population

Abstract: When the dry matter productivity estimated by the chamber method (ΔW") was compared with that observed by the biomass method (ΔW), it was experienced that the former sometimes gave lower estimation than the latter. To clarify the reason of their disagreement in terms of the ventilation rate to the chamber, the continuous measurements of photosynthesis and respiration from 6 to 10 days by using big chambers (1.3 m in width, 10 m in length and 1.5 m in height) were conducted. The amount of air supply to the chambers were 19.1 m3/min, 75.6 m3/min, and 122 m3/min, respectively. Results are summarized as follows. 1. By comparing the environmental factors inside the chamber with those under natural conditions, it was found that the difference increased with solar radiation. The difference decreased as air supply increased and when the ventilation rate exceeded 156 times/hr, environmental factors inside the chamber almost coincided with the outside one. 2. When the air volume supplied to the chamber was small, the light-photosynthesis curve showed a light saturation form, but the photosynthetic rate under strong light intensity increased with air volume supplied, and shape of the light curve became more linear. 3. CGR obtained by the biomass method (ΔW) and CGR estimated by the chamber method (ΔW") agreed well at a certain amount of air supply to the chamber, and it was 75.6 m3/min (156 times/hr) in this experiment. But, when the amount of air supply to the chamber was too small or too large, ΔW" was often under estimated. 4. Using the mathematical model, we tried to find the causes to decrease the photosynthesis in the chamber under the small amount of air supply. The experiment shows that main cause was high temperature inside the chamber and thc decrease of CO2 concentration also affectcd it a little. The effect of wind speed, which changes the boundary layer resistance to CO2 transfer of a leaf, on photosynthesis was found not so much. 5. The photosynthetic rate observed in the afternoon was somewhat smaller than that in the morning. As the daliy total radiation became higher, not only photosynthesis during the daytime (Pnet), but also the respiratory loss during the succeeding night (RN) increased. 6. RN/P ratios were 16.7 and 14.4% in botting and heading stages. These values were obtained when ΔW" was almost coincided with ΔW, and they were considerably smaller than the Values ever estimated

Studies on the Visible Injury to Rice Plants caused by Photochemical Oxidants : I. Identification of the leaf injury caused by photochemical oxidants

Abstract: At the beginning of July in 1970, reddish brown flecks appeared on the leaves of rice plants which were planted in the paddy fields in Kisarazu City and its environs, Chiba Prefecture. Since then, the outbreak of singular disease, resembling "Akagare" disease, has been observed in extensive paddy fields in Chiba Prefecture in every early summer (fig.1 and 2). The following results were obtained from the field surveys which were carried out to make clear the cause of the disease. The most severe injury appeared always on the second fully-expanded leaf from the top. As to the extent of injury, there were differences among varieties, but was no obvious difference according to cultivating or edaphic factors. Although the disease occurred simultaneously in extensive areas, any pathogenic mold fungi or bacteria could not be detected in the injured leaves. Immediately before the outbreak of the disease, in those areas air pollution chiefly photochemical oxidants occurred. At the same time with the outbreak of the disease, the leaves of several kinds of crop plants such as spinach, radish and corn suffered from the photochemical oxidants. An inference that the outbreak of this singular disease was caused by air pollution due to the photochemical oxidants was drawn from the results of field survey. Basing on this inference, rice plant were exposed artificially to ozone which is known as the principal element of photochemical oxidants. The results are as follows. Rice plant was so sensitive to ozone that reddish brown flecks appeared on their matured leaves when exposed to ozone of 0.15 ppm for a few hours. Injury by ozone (fig.4) was identical in symptoms and histological changes with the reddish brown flecks which occurred in the field (fig.3). When rice plant was grown in the filtered air chamber which is able to remove photochemical oxidants, the injury was coinpletely suppressed throughout the summer. From these results, it was concluded that the reddish brown flecks had been caused by photochemical oxidants

Photochemical Oxidants Injury in Rice Plants : 2. The effect of filtered ambient air on the growth and yield of rice plants

Abstract: The experiment was made to determine the invisible injury to rice plants by photochemical oxidants. Rice plants were grown in two filon chambers, the one with filtered ambient air and the other with unfiltered a ambient air, for the experimental period from transplanting to harvesting at the Central Agricultural Experiment Station, Konosu, Saitama. The rice plants in the filtered ambient air chamber were compared with those in the unfiltered ambient air chaember on growth, yield and visible injury of photochemical oxidants. Both the visible injuries on leaf blade and invisible injuries such as the reduction of the growth and rate of photosynthesis were observed in the unfiltered ambient air chamber. On the otherhand, no injuries were detected in the filtered air chamber. The rice plants in the filtered ambient air chamber were more numerous in number of panicles and spikelets per hill and in percentage of ripened grains, and higher in yield than those in the unfiltered one. It may be suggested that the reduction in growth and yield of rice plants in the unfiltered chamber could be mainly due to photochemical oxidants, because of high concentration of photochemical oxidants, averaged 3.74 pphm hourly monitored in Konosu, during the experimental period from 6th of June to 15th of October.

Studies on the Developmental Physiology in Rice Pollen : II. Relation between the amino acid metabolism and the structural changes in pollens

Abstract: The relation between the changes of amino acid metabolism and the structural alteration with special reference to the behavior of the vegetative and generative nucleus during pollen development were studied. At the one nuclear period no distinct difference was found in amino acid composition between anthers and other plant tissues and organs. In binuclear period in which a microspore nucleus divided into two nuclei, a vegetative nucleus and a generative one, the proline content comes to higher than that of other amino acids in anthers. At the middle of binuclear period proline was found to occupy about 20% of all amino acid content, indicating that the special feature of amino acid metabolism in pollen begins under the occurrence of a vegetative and a generative nucleus. At the beginning of trinuclear period having one vegetative nucleus and two sperm nuclei, proline was found to reach an amazing high content as like 50% of total amino acids in anthers. Thus accumulated synthesis of proline, known as the characteristic of amino acid metabolism in pollen, appears established at the trinuclear period. Activity of nuclei in pollen was examined by the size of nucleolus after acetocarmine staining since it has been considered as an indicator of the physiological activity of nucleus. At the one nuclear period, a large nucleolus just like as that of meristematic cells was found in a microspore nucleus. In the time when a microspore nucleus divided into a vegetative and generative nucleus, a nucleolus of the former was larger than that of the latter. With the occurrence of two sperm nuclei, the size of a nucleolus in vegetative nucleus began to decrease and the configuration of nucleus was obscure and its nucleolus disappeared in the day before flowering. On the contrary, nucleoli of two sperm nuclei derived from a generative one, were large and clear since then. On the basis of these results, it was assumed that the establishment of the special feature of amino acid metabolism in pollens and the occurrence of generative or sperm nucleus are correlated each other in time, and the accumulated production of proline may be regulated by the sperm nuclei, judging from the behavior of nucleolus