Rapid and reversible nitrate inhibition of nodule growth and N2 fixation activity in soybean (Glycine max (L.) Merr.)

Nodulated soybean (Glycine max. (L) Merr. cv. Williams) plants were hydroponically cultured, and various combinations of 1-week culture with 5 or 0 mm nitrate were applied using 13-d-old soybean seedlings during three successive weeks. The treatments were designated as 0-0-0, 5-5-5, 5-5-0, 5-0-0, 5-0-5, 0-5-5, and 0-0-5, where the three sequential numbers denote the nitrate concentration (mm) applied in the first-second-third weeks. The size of the individual nodule was measured periodically using a slide caliper. All the plants were harvested after measurement of the acetylene reduction activity (ARA) at the end of the treatments. In the 0-0-0 treatment, the nodules grew continuously during the treatment period. Individual nodule growth was immediately suppressed after 5 mm nitrate supply. However, the nodule growth rapidly recovered by changing the 5 mm nitrate solution to a 0 mm nitrate solution in the 5-0-0 and 5-5-0 treatments. In the 5-0-5 treatment, nodule growth was completely inhibited in the first and the third weeks with 5 mm nitrate, but the nodule growth was enhanced in the second week with 0 mm nitrate. The nodule growth response to 5 mm nitrate was similar between small and large size nodules. After the 5-5-5, 5-0-5, 0-0-5, and 0-5-5 treatments, where the plants were cultured with 5 mm nitrate in the last third week, the ARA per plant was significantly lower compared with the 0-0-0 treatment. On the other hand, the ARA after the 5-0-0 and 5-5-0 treatments was relatively higher than that after the 0-0-0 treatment, possibly due to the higher photosynthate supply associated with the vigorous vegetative growth of the plants supplemented with nitrate nitrogen. It is concluded that both soybean nodule growth and N₂ fixation activity sensitively responded to the external nitrate level, and that these parameters were reversibly regulated by the current status of nitrate in the culture solution, possibly through sensing of the nitrate concentration in roots and / or nodules.     

Effect of exogenous salicylic acid supply on nodule formation of hypernodulating mutant and wild type of soybean

Soybean plant is characterized by a systemic autoregulatory control system of nodulation (autoregulation) by initial infection with rhizobia, and plants commonly display a systemic acquired resistance (SAR) to pathogenic microbe infection related to salicylic acid (SA) signal transmission. We investigated the effect of exogenous SA supply on soybean nodulation to determine whether SA affects the autoregulation of nodulation. Seedlings of the hypernodulating mutants NOD1-3, NOD2-4 and their parent cv. Williams were treated or not treated (control) with a 100 μmS-SA solution at 5 d before the inoculation of Bradyrhizobium japonicum strain USDA110. The nodule dry weight and the number of nodules of the wild type soybean Williams exhibiting autoregulation drastically decreased by the addition of 100 μm SA. The decrease in the nodule number was not caused by the reduction of the rhizobium number in the medium. Salicylic acid inhibited only early nodule formation and did not affect the growth of formed nodules. The inhibitory effect of SA on the nodulation of NOD1-3 and NOD2-4 was significantly less pronounced than that in Williams. These results indicate that SA is directly involved in signal transmission in the autoregulation, and that SA or the SAR induced by SA stimulates the autoregulation of nodulation in soybean.     

Amino acid metabolism in plant leaf

Recent studies have shown that the incorporation of ammonium nitrogen into amino acids in the leaves is strictly dependent on light (1-4). It is speculated that the effect of light on ammonium assimilation may be through the synthesis of the precursors of amino acids, or by the supply of the energy required for amination and amidation with organic acids. In the Vicia faba chloroplasts Givan et al. (1) exhibited that the synthesis of glutamic acid from a-ketoglutarate was linked with the generation of reduced pyridin nucleotide by photosynthetic electron transport. Mitchell and Stocking (2) suggested the direct coupling of glutamine formation with photophosphorylation in the pea chloroplasts. On the other hand. the processes of nitrate assimilation are more indebted to light than those of ammonium assimilation, because the former ones involve the reduction of nitrate to ammonium which is believed to be light-dependent (5). Canvin and Atkins (6). and Atkins and Canvin (7) reported that the incorporation of ¹⁵N-labeled ammonium and nitrate into amino acid fractiom was depressed by the dark treatment and by photosystem inhibitors; 3-(3′,4′-dichlrophenyl)-1-1-dimethylurea (DCMU) and carbonyl-cyanide-m-chlorophenyl-hydrazone(CCCP).     

Salt tolerance of Casuarina equisetifolia and Frankia Ceq1 strain isolated from the root nodules of C. equisetifolia

Effects of NaCl on the seed germination and growth of Casuarina equisetifolia seedlings and multiplication of the Frankia Ceq1 strain isolated from the root nodules of C. equisetifolia were examined. The germination rate of the seeds markedly decreased as the NaCl concentration increased and germination did not occur at 300 mM NaCl. The fresh weight of both shoots and roots of the seedlings treated with NaCl for 6 weeks apparently decreased as the NaCl concentration increased. However, root nodules were formed by inoculation with the Frankia Ceq1 strain in some seedlings treated with 300 mM NaCl and the viability of the seedlings at 500 mM NaCl was almost the same as that of the seedlings not subjected to the NaCl treatment. The Na⁺ concentration in the shoots sharply increased with the elevation of the NaCl concentration in the ambient solution, but the level was approximately 300 mM even in the seedlings treated with 500 mM NaCl for 6 weeks. On the other hand, the increase of the Na⁺ concentration in the roots by the NaCl treatment was much smaller than that in the shoots and the level was less than 150 mM. The growth of the free-living Frankia Ceq1 strain was approximately linearly suppressed as the NaCl concentration in the medium increased and the hyphae became somewhat thicker and shorter or disintegrated in the medium containing NaCl at a concentration above 150 mM. The Na⁺ concentration in the cells increased as the NaCl concentration in the medium increased, but the level was maintained at less than 30 mM even in the medium containing 500 mM NaCl. The cells whose growth was suppressed by the NaCI treatment grew actively again at almost the same rate as the control cells (not subjected to the NaCl treatment) when they were transferred to NaCl-free medium. These results strongly suggested that both C. equisetifolia seedlings and Frankia Ceq1 strain are highly tolerant to salt and this symbiotic system is useful for the recovery of the vegetation in areas with severe salt accumulation.     

Evaluation of readily available nonexchangeable potassium in soil by sequential extractions with 0.01 molar hydrochloric acid

Nonexchangeable potassium (K-ne), i.e. 1 M NH₄OAc-nonexchangeable K, often contributes significantly to plant nutrition. However conventional extraction methods often extract much more K-ne than plants even after intensive cropping, suggesting the difficulty in evaluating the amount of readily available soil K-ne. In this study, we used a milder extraction method (0.01 M HCl method) to examine its applicability to evaluate the amount of readily available K-ne in soil. In the first experiment, the concentration of K-ne in twenty surface soils sampled from agricultural fields in Japan and K-bearing minerals was determined by the 0.01 M HCl method, i.e. sequential extraction with 0.01 M HCl over a period of 10 d after removal of exchangeable K, and by conventional methods. The average percentage of the soil K-ne extracted by the 0.01 M HCl method amounted to 0.66% of the total K amount, and was much lower than that by a single extraction with 1 M HNO₃ (2.0%) or with 0.2 M sodium tetraphenylboron for 2 d (22%). In the second experiment, the amount of K-ne removed by chemical extractions was compared with that of K-ne removed by maize plants grown for 29 d in five of the above soils. The amount of the K-ne evaluated by the 0.01 M HCl method gave the highest correlation (p < 0.05) with that of the K-ne utilized by plants among the extraction methods applied. The amount of soil K-ne extracted by the 0.01 M Hel method could therefore become a suitable index of the amount of readily available K-ne in soil. Extraction of K-ne in soils after maize planting further indicated that plants had removed K-ne more intensively than the 0.01 < HCl method probably only from the rhizosphere, although a high correlation was observed between the amount of K-ne removed by the 0.01 M Hel method and that by plants. This implies that the estimation of the amount of K-ne utilized by plants requires not only soil chemical analysis but also the evaluation of the percentage of the soil volume where the plant-induced release of K-ne actually occurs.     

Alleviation of manganese toxicity and manganese-induced iron deficiency in barley by additional potassium supply in nutrient solution

Barley plants were grown hydroponically at two levels of K (3.0 and 30 mm) and Fe (1.0 and 10 μm) in the presence of excess Mn (25 μm) for 14 d in a phytotron. Plants grown under adequate K level (3.0 mm) were characterized by brown spots on old leaves, desiccation of old leaves, interveinal chlorosis on young leaves, browning of roots, and release of phytosiderophores (PS) from roots. These symptoms were more pronounced in the plants grown under suboptimal Fe level (1.0 p,M) than in the plants grown under adequate Fe level (10 μm). Plants grown in 10 μm Fe with additional K (30 mm) produced a larger amount of dry matter and released less PS than the plants grown under adequate K level (3.0 mm), and did not show leaf injury symptoms and root browning. On the other hand, the additional K supply in the presence of 1.0 μM Fe decreased the severity of brown spots, prevented leaf desiccation, and increased the leaf chlorophyll content, which was not sufficient for the regreening of chlorotic leaves. These results suggested that the additional K alleviated the symptoms of Mn toxicity depending on the Fe concentration in the nutrient solution. The concentration (per g dry matter) and accumulation (per plant) of Mn in shoots and roots of plants grown in 10 μm Fe and 30 mm K were much lower than those of the plants grown in 10 μm Fe and 3.0 mm K, indicating that additional K repressed the absorption of Mn. The concentration and accumulation of Fe in the shoots and roots of the plants grown in 10 μm Fe and 30 mm K were higher than those of the plants grown in 10 μm Fe and 3.0 mm K, indicating that the additional K increased the absorption of Fe under excess Mn level in the nutrient solution. The release of PS, chlorophyll content, and shoot Fe concentration were closely correlated.     

H2 15O translocation in rice was enhanced by 10 μm 5-aminolevulinic acid as monitored by positron emitting tracer imaging system (PETIS)

5-Aminolevulinic acid (ALA) acts to increase chlorophyll biosynthesis, photosynthesis, cold stress tolerance, and salt tolerance at low concentrations. We studied the effects of ALA on H₂ ¹⁵O translocation from the roots to the shoots of rice plants (Oryza sativa L. cv. Nipponbare) in real time by a positron-emitting tracer imaging system (PETIS). When the plant was treated with 10 μm ALA, the velocity of the H₂ ¹⁵O translocation from 2 to 12 min after absorption increased to 126, 137, 140% that of the control at 1.5, 2.5, and 3.5 h after ALA treatment, respectively. However, ALA did not affect the H₂ ¹⁵O translocation within 0.5 h of treatment. When the plant was treated with 0.1 mM ABA at 4 h after 10 μm ALA treatment, the velocity of the H₂ ¹⁵O translocation decreased at 0.5 h after ABA treatment. Those observations suggested ALA might be absorbed and transported to the guard cells within 1.5 h and functioned to expand the stomatal aperture.     

Occurrence of laminar opaline silica in some Oregon Andosols

Laminar opaline silica was first found in the 0.2 to 5 μ fraction and most abundant in the 0.4 to 2 μ fractions of young Japanese Andosols by Shoji and Masui (1969a, b). It was noted that the A horizon of a profile tends to be relatively rich in opaline silica whereas the B or C horizon, in allophane (Shoji and Masui, 1972a, b). They (I972a) distinguished four types of opaline silica particles such as circular, elliptical, rectangular, and rhombic, of which the circular and elliptical types predominate. It has been suggested that the formation of opaline silica is favored by a plentiful supply of soluble silica in the early weathering stage of Andosols, the supersaturation of silica by surface evaporation of soil solution, and the suppression of aluminum activity in the soil solution by the accumulation of soil organic matter (Shoji and Masui, 1972b; Wada and Harward, 1974). The purpose of the present short communication is to describe the occurrence of laminar opaline silica particles in some Oregon Andosols, U.S.A.     

Adsorption strength of zinc for soil humus

Soil humus plays a significant role in the cation exchange of a soil. YOSHIDA (1) showed that, as a general rule, divalent ions such as calcium and magnesium were adsorbed more strongly onto humus than monovalent ions such as ammonium and potassium in an ion-exchange reaction. He did not, however, describe the behavior of heavy metal ions. BREMNER et al. (2) first suggested that soil organic matter forms complexes with polyvalent cations. HIMES and BARBER (3) found that soil organic matter reacts with divalent metal ions in a manner similar to the chelation reaction. Reviews of the soil organic matter-metal complex have been written by BREMNER et al. (2) and KAWAGUCHI, MATSUO and KYUMA (4).     

Arsenic extractability with phosphate and citrate from peat collected in Bangladesh

Abstract

Arsenic extractability with various solutions from peat samples collected in Deuli Village, Bangladesh, was investigated to reveal the leaching mechanisms of arsenic in sediments to groundwater. Peat layer was distributed at the depth of 7–8 m in the sediments, and the peat samples collected and used in this experiment contained 137 mg kg^?1 arsenic. A wide range of pH values and concentrations of phosphoric acid and trisodium citrate was used for the extracting solutions. Arsenic extractability with Hel (25–1,000 mM) or NaOH (20–500 mM) at different pH values ranged for 30 to 60% in strong acid or alkali, while was less than 0.1% in the neutral pH range against the total content. Extraction of arsenic with 100 mM phosphoric acid and 100 mM trisodium citrate was about 20% even at a neutral pH, while the extractability with these solutions at concentrations below 1 mM was similar to that with distilled water. These results suggest that competitive exchange and / or chelating action are / is the prior possible mechanism for arsenic leaching from peat. However, the experimental conditions such as pH value or phosphate anion concentration differed from those in the study area where the pH of groundwater was almost neutral and the phosphate anion concentration was only 0.01 mM. Moreover, since the experiment was conducted using a batch system under oxidative conditions and not using a continuous flow system, the importance of the oxidation-reduction potential in the sediments and organic matter content in the groundwater should be investigated.     

Cadmium concentrations in the phloem sap of rice plants (Oryza sativa L.) treated with a nutrient solution containing cadmium

To obtain direct evidence for the translocation of cadmium (Cd) via the phloem, we measured the Cd concentrations in the phloem sap of 5-week-old rice plants (Oryza sativa L. cv. Kantou) treated with a nutrient solution containing Cd. The phloem sap was collected from the leaf sheaths through the cut ends of stylets of the brown planthopper (Nilaparvata lugens Stål.). Cd concentrations in the phloem sap from the plants treated with 10 and 100 µM Cd for 3 d were 4.6 ± 3.4 and 17.7 ± 9.8 µM, respectively. Detection of Cd in the phloem sap indicated that Cd was translocated via sieve tubes in rice plants. Cd concentrations in the xylem exudate collected from the cut basis of the leaf sheaths of the plants treated with 10 and 100 µM Cd for 3 d were 18.9 ± 6.4 and 64.2 ± 14.6 µM, respectively. Cd concentrations in the phloem sap were significantly lower than those in the xylem exudate, indicating that Cd is not concentrated during the transfer from xylem to phloem. To our knowledge, this is the first determination of Cd concentrations in the phloem sap of plants, and the first direct proof that Cd is translocated via sieve tubes in rice plants.     

Amino acid composition of rice callus tissue grown with different kinds of nitrogen sources

There have been several papers dealing with the difference in chemical composition between callus tissue and normal parent tissue. WEINSTEIN, TULECKE, NICKELL, and LAURENCOT (1–3) revealed, in a series of papers, that the contents of amino acids, sugars, and nucleic acids often differed strikingly between callus and normal tissue of Agave toumeyana Trel. (1), Ginkgo biloba, L. (2), and PAUL's scarlet rose (3). STEWARD, THOMPSON, and POLLARD (4) also reported that the content of some amino acids of rapidly growing and randomly proliferating tissue is outstandingly different from that of normal tissue.     

Formulation of humic substances coated fertilizer and its use to enhance K fertilizer use efficiency for tomato under greenhouse conditions

A greenhouse experiment was conducted at Land Resources Research Institute, NARC, Islamabad to examine the impact of humic substances (HSs) coating on potassium fertilizers use efficiency. Tomato variety “Rio Grande” was used. The treatments applied were T1= Control (N, P at 250 and100?mg kg^?1 respectively), T2?=?N, P?+?K at 200?mg kg^?1 as SOP, T3?=?N, P?+?K at 200?mg kg^?1 as NPK blend, T4?=?N, P?+?K at 200?mg kg^?1 HSs coated SOP) and T5?=?N, P?+?K at 200?mg kg^?1 HSs coated NPK blend. Results indicated a positive impact of sole and HSs coated products on agronomic traits, nutrient concentration, fruit quality traits, flower number, fruit umber, fruit weight, chlorophyll contents, fresh and dry biomass, tissue water contents, diameter and fruit mineral composition. The response of afore said traits to applied treatment varied.     

Mineralogy of gel-like substance in the pumice bed in Kanuma and Kitakami Districts

A characteristic gel-like substance has been noticed around weathered pumice grains in the pumice beds of Kanuma near Utsunomiya and of Kitakami, Iwate prefecture. This substance was first studied by SHIOIRI (6) in 1934, and reported as allophane according to its chemical composition, refractive index, and dye-adsorbing nature similar to the colloid of volcanic ash soils of the Onji-type. Recently, KUWANO and MATSUI (5) remarked that the colloidal film in the Kanuma and Imaichi pumice beds diffracted x-rays at about 8 and 33 Å, and they presumed that this substance might be an early transitional material from allophane to some crystalline clay minerals. KANNO (2) and KANNO et al. (3) examined this gel-like substance from Imaichi and Kitakami districts precisely by the x-ray diffraction, differential thermal, infrared spectroscopical, electron microscopical, and chemical methods, and they concluded that the substance was a mixture of poorly crystallized montmorillonite, allophane in various weathering stages, and free sesquioxide, although there was no positive evidence of montmorillonite. YOSHINAGA and AOMINE (7) noticed that the properties of imogolite designated by themselves bore a striking likeness to those of the gel-like substance reported by KANNO et al. (3), and they considered that both substances were essentially of the same kind irrespective of occurrence.     

Effect Of Mineral Nutrition on Metabolic Change Induced in Crop Plant Roots (I)

Attempts have long been made to study the effect of mineral nutrition on the metabolic substances in excised roots from a numcer of plant species, but very little attention has teen given to an approach to the problem by using the bleeding sap from crop plants. Recently, however, an increasing number of reports about the occurrence of organic substances in bleeding sap from crop plants has completely revised an old view that xylem sap was essentially a rather dilute aqueous solution of inorganic salts. Evidence has already been obtained which suggests a significant role for the root system as a centre of metabolism and an upward transport of metabolites from the root via the xylem to the leaf. Although analyses of the nitrogenous compounds present in bleeding sap from herbaceous plants have shown glutamine and asparagine to be the most important constituents, in some species of plants nitrate nitrogen may be a predominant nitrogenous compound. Besides ami des and nitrate, the presence of amino acids in bleeding sap has ceen shown by Kulayeva, Silina, and Kursanov ¹⁾ for pumpkins, Wieringa and Bakhuis ²¹ for Lupins, and DIE³⁾ for cucumbers and tomatoes.     

Occurrence of 4-methyleneglutamine and 2-oxo-4-methyl-3-pentene-1,5-dioic acid in leaves and stem of tulip plants

Abstract

The presence of 4-MeGln in the tulip plant was discovered by ZACHARIUS et al. (1954), and it was found that this amide generally occurred in the leaves of almost all the species of genus Tulipa (FOWDEN and STEWARD 1957a). The 4-MeGln compound has been detected in every part of the tulip plant, i.e., bulb scales, roots, basal plate, young shoots, leaves, stern, and flower (FOWDEN and STEWARD 1957a, b; OHYAMA 1986; OHYAMA et al. 1985, 1988a, b; ZACHARIUS et al. 1954, 1957). Especially 4-MeGln was found to be a major soluble N constituent in the leaves and stem of tulip of the flowering stage (OHYAMA et al. 1985; OHYAMA 1986).     

Fractionation of foliar absorbed phosphorus by paper electro-phoresis

Fractional analysis of phosphorus compounds in plant tissue has been carried out by many workers, and reported on tobacco plant by Holden (1) and Komatsu (2). The fractional distribution of foliar absorbed phosphorus was investigated by Yatazawa (3) who indicated that the phosphorus was first converted into the phosphate-ester as an intermediate substance on the phosphorus metabolism. The methods of fractional analysis used by these authors were based on the method proposed by Page and Umbereit (4) in which they used trichloroacetic acid as the first extracting reagent. Recently, in order to separate the protein bound phosphorus, Wildmann, Campell and Bonner (5) adopted the salting-out method without using trichloroacetic acid. They reported that the protein-bound phosphorus plays an important role and is in the dynamic state. Fujiwara and Kadowaki (6) paid attention to the phosphorus bound to cytoplasmic protein as energy-rich phosphate compounds, and adopted the method so as to separate such compounds. In order to reveal the utilization of foliar absorbed phosphorus by the tobacco plant, the fractional distribution of phosphorus was examined. In this paper, the degree of change to organic phosphorus was taken as an index of phosphorus utilization. Paper electrophoresis was used for this purpose because the inorganic and the protein-bound phosphorus could be separated easily.     

Method of extracting organic acid from flooded soil

Investigations on the extraction and determination of organic acids in flooded soil have been reported by TAKAI (1) and TAKIJIMA (2). TAKAI applied water to extract acids from soil and determined them by BULLEN's method (3). However, TAKIJIMA reported that organic acid could not be completely extracted by TAKAI's procedure, especially in soil with a high organic matter content such as muck and peaty soils, and proposed an extraction procedure with 0.5 N sulfuric acid. He also discussed the absorption of acids by soil.     

Effect of phosphorus deficiency and seasonal variations on growth and essential oil content of Japanese mint(M. Arvensis L. Var. Piperascens)

In a previous communication from this laboratory it has been indicated that mint plants respond typically to different environmental conditions (day length and temperature) by marked alterations in growth, and synthesis of essential oil (SINGH and SINGH, 1968a (1)). Similar work on M. piperita L. carried out by several workers clearly shows that the mineral nutrition and metabolism of this plant are equally affected by environmental changes (CRANE and STEWARD, 1962 (2) ; RABSON, 1965 (3) ; STEWARD et al. 1959 (4)), and the metabolic consequences which flow from deficiencies of nutrient elements are greatly influenced by these factors, e. g., lack of phosphorus under short days is accompanied by greater accumulation of amides than under long days and, therefore, causes decrease in other soluble constituents, viz. amino acids (CRANE and STEWARD, 1962).     

Dispersion of humic allophane soils with supersonic vibration

The difficulties in dispersing volcanic ash soils of Japan and New Zealand have been considered to be due to the association or aggregation of allophane (3, 5, 7–10). In particular, MIYAZAWA (9) has obtained evidence that stable microaggregates of Humic Allophane soils derived from volcanic ash have been formed by dehydration of allophane. Recently, several investigators (2, 4, 6, 8, 9, 12) have pointed out that ultrasonic vibration is effective in dispersing the fine particles of soils. With respect to the applicability of supersonic vibration to the particle-size distribution analysis of Humic Allophane soils, MIYAZAWA (9) stated that the maximum dispersion, as measured by the clay content, was obtained only with supersonic vibration using an acidic medium. KOBO and OBA (8) reported that calgon (sodium hexametaphosphate) as a dispersing agent was successfully applicable to most Humic Allophane soils, but the use of HCI was necessary for some highly allophanic subsoils, and that the effect of supersonic vibration on dispersion of the soils is attributed to the breakdown of aggregates larger than 20 microns in diameter. They also recommended a mixture of 10g of soil and 50 ml of water and 20 min. exposure for a supersonic vibrator (10 Kc, 300 W). With respect to the applicability of vibration treatment in the particle-size distribution analysis of Humic Allophane soils containing volcanic glasses in abundance, some apprehension may be entertained about the breakdown of primary minerals, especially of volcanic glasses (9, 10).