Rice Culm Research Articles

Variation in the incidence of H2-oxidizing chemolithotrophic bacteria in rice grown under different cultivation conditions

The incidence of H2-oxidizing chemolithotrophic bacteria associated with rice grown under continuous wetland, upland, and rainfed wetland conditions was studied by14C-autoradiographic technique in a neutral soil at IRRI (Maahas) and an acid rainfed wetland soil (Luisiana). In Maahas soil, H2-oxidizing chemolithotrophic bacteria were not detected in the endorhizosphere, rhizosphere, and nonrhizosphere soil of rice grown under dryland conditions. Under continuously flooded conditions a very large population of these bacteria were found in the endorhizosphere but not in the oxidized and reduced soil. A very low population of these bacteria were found in the endorhizosphere and basal culm of rice grown under rainfed wetland conditions at Luisiana. Bacteria isolated from Maahas wetland rice and inoculated to rice seedling planted in Luisiana soil failed to establish. Both Maahas and Luisiana soils consumed externally supplied H2 and produced H2 and CH4 almost at the same rate when they were amended with rice straw or sucrose. This paper discusses possible causes of variation in the number of these bacteria and their distribution in rice grown under different cultural and soil conditions.

Ultrastructure of elliptical and diffuse bundles in the vegetative nodes of rice.

The second and fourth nodes from the top of rice culm were harvested at the times of flag leaf emergence and heading respectively. Ultrastructural observation has been made on the elliptical and diffuse bundles in particular reference to solute movement in the node. 1. In the phloem of elliptical bundles, which are continuous with the large bundles of leaf, both the sieve elements and phloem parenchyma cells increased in number and showed a ratio of about one to two. A sieve element was connected by plasmodesmata with the plural number of phloem parenchyma cells (Fig. 1). In the border region between phloem and xylem, the parenchyma cells with dense cytoplasm were interconnected by plasmodesmata (Fig. 2). It is assumed that the solutes actively move in the symplast between phloem and xylem. 2. The elliptical bundles contain numerous xylem transfer cells, in which the wall ingrowths were formed on the walls contacting with tracheary elements. The mitochondria with developed cristae and the plastids with peripheral reticulums were contained in the xylem transfer cells (Figs. 3 and 4). A large amount of plasmodesmata was found in the walls between xylem transfer cells and bundle sheath cells, between bundle sheath cells and fundamental parenchyma cells and also between fundamental parenchyma cells (Figs. 4, 5, 6 and 7). It can be (considered that the solutes absorbed from transpiration stream by xylem transfer cells are transferred actively to fundamental parenchyma via bundle sheath cells. 3. In the phloem of diffuse bundles which are surrounding the elliptical bundles and are continuous with the large bundles of internode, the number of sieve elements was about 3.5 times as many as phloem parenchyma cells and the sieve elements were partitioned by numerous sieve plates (Fig. 8). The phloem parenchyma cells of diffuse bundle contained abundant mitochondria, plastids, rough endoplasmic reticulum and ribosomes (Figs. 9 and 10). It is suggested that the phloem parenchyma cells play an important role in climbing of photosynthate in the phloem of diffuse bundle through energy supply.

Histological Studies on Breaking Resistance of Lower Internodes in Rice Culm : VI. Structure and breaking resistance of lower internodes grown in different environments

Histological Studies on Breaking Resistance of Lower Internodes in Rice Culm : VI. Structure and breaking resistance of lower internodes grown in different environments

Histological Studies on Breaking Resistance of Lower Internodes in Rice Culm : III. Morphology of the breaking parts and a dynamic consideration of the breaking

The external breaking forms of elongated internodes in rice culms were observed, and were classified into three patterns basically, namely, the broken type (Fig. 1), the split type (Fig. 2) and the separated type (Fig. 3). The broken type was the most frequent in the lower internodes both in the breaking test by hands and in the lodged culms by natural force like as wind and rain (Table 1). Histological observations on the breaking parts by free hand sections indicate that the breakings seem to begin from the epidermis and cortical fibers and extend to parenchyma. In fold parts of the broken type failure, the cortical fiber cells are bent remarkably and divided longitudinally in each other, but are not cut off transversely (Figs. 4-7). In split parts of the broken and the split type failure, most of the epidermal and cortical fiber cells are divided in middle lamella. The parenchymatous cells in breaking parts are broken irregularly (Figs. 8-10). A dynamic consideration is attempted to clarify the mechanism which causes the three patterns of the breaking forms in the lower internodes. In a bent internode, bending stress and shearing stress seem to cause as illustrated in Figs. 11 and 12. Therefore, the compressive stress acting on the concave and the tensile stress acting on the convex seem to cause the failure of the broken type and the separated type, respectively. The shearing stress, on the other hand, acting on the transverse plane seem to cause the failure of the split type (Figs. 11 and 12).

Histological Studies on Breaking Resistance of Lower Internodes in Rice Culm : IV. The roles of each tissue of internode and leaf sheath in breaking resistance

In order to clarify the roles of EF (epidermis-cortical fiber compound) and P (fundamental parenchyma) in breaking resistance, several dynamic characteristics of the fourth internode from the top of rice culm, var. Koshihikari, were studied at the time of harvesting. Breaking strength and deflection of PEF (whole internode tissues) and P, obtained by shaving off the EF from PEF, were measured with aid of the stalk bending hardness tester (type EO-III). Tensile strength, compressive strength and shearing strength were measured by traditional methods used in the material testing. These data are shown in Table 1. Some calculations with these data verify that EF/P ratio in YOUNG's modulus, tensile strength and compressive strength are 113, 63 and 19, respectively. Besides, the tensile strength of EF in rice internode was ascertained to be almost the same to that of the xylem tissue of boxwood (Buxes microphylla var. suffruticosa Makino). Moreover, about 89% of bending stress (tensile and compressive stress) is supported with EF, and about 78% of shearing stress is supported with P in the bended internode. Therefore, with regard of bending stress, the internode of rice culm can be considered dynamically to be a pipe composed of thin EF as illustrated in Fig. 1. The value of maximum stress M can be obtained by the formula (6), and d2t [(diameter of internode)2×(thickness of EF)] can be considered to be a very important factor in breaking resistance. On the other hand, the main role of P in breaking resistance is to prevent sectional deformation and to maintain cylindrical form in the bended internode. Breaking strength of the fourth internodes with or without leaf sheath was investigated in the ripening period as shown in Fig. 2. The breaking strength had a peak soon after heading and a minimum at 25-30 days after heading. It may be thought that the slight increase in breaking strength at the time of harvesting was caused by reaccumulation of starch in the internode.

Histological Studies on breaking Resistance of Lower Internodes in Rice Culm : II. Ultrastructural and histochemical observations on the secondary wall formation.

In this paper, we report an observation with light and electron microscope on the process of the secondary wall thickening and lignin accumulation in the cells of the 4th internode from the top of rice culm, var. Koshihikari. Materials for ultra thin sections were fixed in 2-4% glutaraldehyde, postfixed with 1-2% osmium tetroxide, and embedded in Spurr's resin. Meshes were stained with uranium and lead. For histochemical detections of lignin, free hand sections, 60-80 μm in thickness, were treated with Maule's reagents (M-reaction) and phloroglucinol-HCl (P-reaction). The secondary wall of the cortical fibers makes a start of thickening just after the cell has completed its elongation. It usually consists of three layers; S1, S2 and S3. In crease in secondary wall thickness is associated with increase in number of Golgi apparatus, Golgi vesicles, exocytosis and invagination. The ribosomes are often present as polysomes on the rough endoplasmic reticulum, some of which connect with the plasmalemma (Figs. 1-4). The fiber cells have smaller diameter and thicker walls in the outer rows near the epidermis than those in the inner rows which sometimes lack S3 layer. The secondary walls of the tips of fiber cells thicken more slowly and are thinner than those of the central part (Fig. 5). The epidermal long cells have a large number of small papillae, and a number of large ones on both sides of the short cells, but a fewer papillae on the small vascular bundle (Fig. 6). The aspects of cell organelles at their wall thickening stage are similar to those in the cortical fibers (Figs. 8-10). At this stage, silica deposition cetripetally progresses from the inside of cuticular layer in all the outer walls of the long cells, especially in those of the silica cells (Figs. 9-12). As for the parenchyma cells, a large vacuole is formed from an early stage of cell development, and conspicuous invaginations are often seen accompanying with ribosomes (Fig. 13). No lignin is detected in elongating cell walls except those of the protoxylem vesseles. On and after beginning of the secondary wall thickening, M-reaction begins by appearing (Fig. 14A). On and after beginning of the S2 layer thickening, P-reaction follows up the traces of M-reaction. M-reaction decreases in the part where P-reaction is positive (Fig. 14B). In the 4th mature internode, P-reaction is generally intensive in thc epidermis, cortical fibers and small vascular bundle. M-reaction is thc most intensive in the large vascular bundle sheath (Fig. 14C). In a fiber cell, P-reaction is the most intensive in the middle lamella-primary wall complex and decreases centripetally. On the contrary, M-reaction is intensive on the faint parts of P-reaction, but both reactions are not obvious in the parenchyma. In briefly saying, P- and M-reactions relate complementally each other. The secondary wall thickening and the lignin accumulation in the 4th internode of the cultivar terminate about 5 days after heading and entirely complete after next 10 days.

Histological Studies on Breaking Resistance of Lower Internodes in Rice Culm : V. Histological observations of breaking process and slip planes formation with polished thin sections

Histological Studies on Breaking Resistance of Lower Internodes in Rice Culm : V. Histological observations of breaking process and slip planes formation with polished thin sections

Ascocarp production of Magnaporthe salvinii in culture

Nutritional and physical factors affecting ascocarp production of the causal agent of rice stem rot, Magnaporthe salvinii , were studied in a cross between Japanese isolates. Mature ascocarps were produced on several agar media with rice culms. The optimum temperatures for mature ascocarp production were from 22 to 26 °C. Light and dark greatly influenced ascocarp production, since no mature ascocarps were produced in continuous darkness.

Histological Studies on Breaking Resistance of Lower Internodes in Rice Culm : I. Observation on histogenesis of elongating internodes with light and electron microscope

Histogenesis of the 4th internode from the top of rice culm, var. Koshihikari, was observed in the rapidly elongating stage with light and electron microscope. The materials, for preparation to electron microscope, were fixed with 2-4% glutaraldehyde, postfixed with 1-2% osmium tetroxide, and embedded in Spurr's resin. Meshes were stained with uranium and lead. Proliferation and enlargement of the tissues at the base of internode bring approximately 30% increase in diameter, reduction by half in thickness of the fundamental parenchyma and duplication in total thickness of the epidermis and cortical fibers (Fig. 1). Epidermal cells, just above the intercalary meristem, differentiate to long and short cells (Fig. 3). The short cells again differentiate to silica cells, cork cells and trichomes (Figs. 4 and 5). The long cells elongate in the range of 35 mm above the intercalary meristem and attain a length of about 200μm. Cortical fiber cells divide anticlinally, periclinally and radially in the zone of intercalary meristem, and in the range of 35 mm above it, they elongate rapidly to a length of average 1.2 mm (Figs. 6-9). Meanwhile, the number of periclinal rows in cortical fibers increases from 3 to 5-7, and the cell arrangement falls into disorder by intrusive growth. The intercalary meristematic cells have dense cytoplasm, and contain a number of starch grain and osmiophilic globules, which decrease during cell elongation. Dense cytoplasm, a large number of mitochondria and ribosomes are represented by the tips of the cortical fiber cells growing intrusively (Figs. 10-13). We think, therefore, that the developmental activities of the cortical fibers are reflected in the tissue thickness, the number of periclinal rows, the degree of rows irregularity and the cell length.

Starch Metabolism in the Leaf Sheaths and Culm of Rice

The levels of starch and dextrin, free sugars, soluble protein, and enzymes involved in starch metabolism-alpha-amylase, beta-amylase, phosphorylase, Q-enzyme, R-enzyme, and ADP-glucose starch synthetases-were assayed in the leaf sheaths and culm of the rice plant (Oryza sativa L., variety IR8) during growth.Starch accumulation in the leaf sheaths reached a maximum 10 to 11 weeks after transplanting, the time of development of the rice panicle. Maximal concentration of free sugars occurred earlier. Starch and sugars in the leaf sheaths and culm decreased rapidly during grain development.During starch accumulation, the starch granules of the leaf sheaths increased slightly in size and its gelatinization temperature decreased. The molecular size of amylose and amylopectin and amylose content of the starch were similar in both culm and leaf sheaths.Changes in the level of soluble protein paralleled changes in starch level in the leaf sheaths. Among the enzymes, only synthetase bound to the starch granule paralleled the level of starch in the leaf sheaths and in the culm. ADP-glucose, but not UDP-glucose, was utilized as a glucosyl donor by these starch synthetases. Zymograms of these extracts showed only one alpha-amylase band, one beta-amylase band, two phosphorylase bands, and one Q-enzyme band.

Selection of Index Leaf for Studying the Critical Concentration of Nitrogen in Rice Plants1

AbstractChanges in nitrogen (N) concentration in the last four leaves formed on rice (Oryza sativa L.) culms of three varieties growing in paddy in the Philippines during the rainy season were studied during the period from formation of flower primordia until after flower emergence. On the basis of stability of N concentration and sensitivity to N supply, the blade of the next‐to‐last leaf (second leaf below the panicle), excised at the time of flower emergence, was chosen as the index leaf.

Physiological and Ecological Studies of Rice Plant in Well-drained and Ill-drained Field. : (8) Distribution of silicified tissues of rice culm and silicate content in each internode as affected by diffierent cultural conditions.

Silicified tissues of rice culm were ascertained by following technique; the spodgrammes of internode, culm-node and leaf sheath-node were made, and then they were dissolved by heated dilute hydrogen chloride. As silicified tissue is insoluble, the silicified tissue in epidermis of internode, epidermis at the bottom of internode, inner parts of culm-node, node-plate and node-plate abutting on the culm could be observed under microscope as shown in Fig. 1-8. The culm differs from leaf blade in that the culm contains silicate in various tissues, while leaf blade contains was found silicate only in epidermis. Silicate content in internode was found closely related with growth stages and cultural conditions as summarized below: 1) Seasonal changes of silicate content in each internode indicate that percentages of silicate content at harvesting time are in higher level than that at heading time. 2) Relation with cultural conditions; a) As compared with ill-drained field, rice culm in well-drained field contained more silicate, especially in upper internodes (N1∼N3). b) In plot with heavy application of nitrogen, amount of silicate content in upper internodes was less. c) Silicate content in lower internode was high in plot with silicate calcium application.

Ecological Study on the Rice Varieties : V. Effects of the sowing time to the agronomical characters, or yielding capacity, time of young-ear differentiation, and elongation of internodes, in rice.

1). It carried out the ecological study on the main agronomical characters; e. g., yielding capacity, time of young ear differentiation, and elongation of upper stem internode, in rice plants taken by the movement of sowing time, for a research material to the planning of rice culture. 2). The numbers of elongated internodes in rice culm increase by the late croping, but in case of over-late croping these numbers decrease because of temperature in early fall. 3). The critical air-temperature of young ear differentiation in rice plant was 18°C., such as usual mentioned. However, in case of very short time exposure, the differentiation are not occurence even under this temperature. On the other hand, the elongation of internodes in a culm were possible in spite of very short time exposure, under available lowest temperature. 4). The elongation of terminal internode was clearly affected by low temperature, but the effect of low temperature to the internodes of stem lower part which being started elongation seems to be a little. 5). In the choice of rice variety forhigh yield, it should be thought the sum-temperature of them from seeding to heading; e. g., 2, 300°C in early croping, 2, 100°C in standard croping, and 1, 800°C in late croping. This problem, varietal responces to temperature, is very importance to the planning culture of rice, and to increase of effective yielding capacity in each varieties.

Studies on the Lysigenous Intercellular Space as the Ventilating System in the Culm of Rice and Some Other Graminaceous Plants.

This paper deals with the intercellular space in the culm, its distribution and process of development and its ecological and specific variations in rice and other graminaceous plants. As one of the ventilating systems in the internode of the rice plant, we can recognize aerenchyma in the lower unelongated internodes and Lysigenous Intercellular Space in the elongated ones. The lysigenons intercellular spaces in the culm and sheath are connected anatomically through the aerenchyma of the node with each other and also with the cortex of the root tissues. The development of the lysigenous intercellular spaces in the rice culm are affected by the environmental conditions. They develope rather better under excessively moist or akiochi -O2 lacking- conditions. It was found that, of gramineae, the lysigenous intercellular spaces in the culm of the speces particularly adapted to moist or excessively moist conditions were generally larger than those in the species adapted to dry or semi-dry conditions and that they develop more extensively according to the moistness of growing environments.