Motoki Ikeda

Distribution of K, Na and Cl in Root and Leaf Cells of Soybean and Cucumber Plants Grown under Salinity Conditions

The element contents in the compartments of root and leaf cells of soybean and cucumber plants grown for 8 d in a nutrient solution containing 50 mM NaCl, 25 mM CaCl2 or 50 mM NaCl+4.75 mM CaSO4 were examined by X-ray microanalysis of freeze-substituted dry sections. Sodium accumulated in the vacuoles rather than in the cytoplasm and apoplastic space in the root cells of the soybean plants, leading to the difficulty in the transport of Na to leaves in soybean. Salt injury of soybean is considered to be caused by the accumulation of Cl at high concentrations in all the compartments of root and leaf cells. In contrast, the accumulation of Na in the cytoplasm of the root and leaf cells might disturb the metabolism and lead to the occurrence of salt toxicity in cucumber plants, which are tolerant to Cl due to the stimulation of Cl accumulation in vacuoles when the Ca concentration was high in nutrient media.

Stimulation of dark carbon fixation in rice and tomato roots by application of ammonium nitrogen

Abstract Dark carbon fixation was investigated in roots of rice plants, an ammonium-tolerant species and tomato plants, an ammonium-sensitive one during periods of growth on nutrient media containing ammonium, ammonium nitrate, or nitrate as the nitrogen source. Application of ammonium nitrogen immediately stimulated the dark carbon fixation in the roots of both plants. The stimulation was greater in the plants grown on ammonium media than in those grown on ammonium nitrate media. The increase in the rates of dark carbon fixation continued in rice plants for 7 d whereas in tomato plants the rates reached the maximum value at day 1, and then gradually decreased. Most of the 14C fixed for 3 h remained in the roots: 75–90% in rice plants and 65–80% in tomato roots. Soluble fixation products were composed of amino acids and organic acids. Organic acids were more labelled than amino acids. Amino acids were more labelled in both plants grown on ammonium and ammonium nitrate media than in those grown on nitrate ...

Organic acid metabolism and root excretion of malate in wheat cultivars under aluminium stress.

The effects of aluminium (Al) on the metabolism of organic acids synthesised via nonphotosynthetic carbon fixation in the roots and on malate exudation were investigated in Al-tolerant Shirosanjyaku (SH) and Al-sensitive Chikushikomugi (CK) wheat cultivars labelled with bicarbonate-(14)C. Aluminum triggered the excretion of (14)C into the solution, especially in the SH that excreted 2.5 times more (14)C than the CK. The loss of radioactivity (about 10%) into the solution represented a small drain in the (14)C reserve found in the roots. In the organic acid fraction within the roots, malate contained the greatest amount of (14)C, and this amount decreased rapidly with time in both cultivars. The disappearance of radioactivity in the malate resulted from metabolism and translocation rather than to root efflux. Aluminium decreased the malate concentrations in roots of both cultivars. The Al-sensitive cultivar had higher concentrations of malate regardless of the presence of Al. It was therefore assumed that the decrease of malate concentration in roots under Al stress did not result from the decline in malate synthesis but due to an increase in malate decomposition. This response was interpreted as the result of the Al-induced stress and not as the cause of a differential Al-tolerance between the wheat cultivars. An important component of the differential Al tolerance between SH and CK is the greater ability of the Al-tolerant cultivar to excrete malate from the roots, which is independent of its internal concentration in the roots.

Effects of nitrate application on growth, modulation, and nitrogen fixation of nitrate-tolerant mutants of soybean

Abstract Nitrate-tolerant mutants of soybean (Glycine max L. Merr.) cv. Bragg, nts1116 and nts1007, were cultured hydroponically to study the effects of nitrate on plant growth, nodulation, and nitrogen fixation compared to the parent cultivar Bragg. The vegetative growth of nts1116 was the most active. Absorption rate of nitrate increased with the duration of the treatment. The absorption rate was slightly higher in nts1116 compared to ntsl007 and Bragg. Nitrogen accumulation of the nitrate-treated plants through biological nitrogen fixation was larger in the order of ntsl007, nts1116, and Bragg. However, N accumulation from nitrate did not differ among the 3 lines. Nitrate reductase activities in the nodules were the highest in Bragg followed by nts1116 and nts1007, regardless of the nitrate treatment and assay time, and were negatively correlated with the nodule masses. Ureide concentration was the highest in nts1007 followed by nts1116 and Bragg, and was positively correlated with the nodule masses an...

Nodulation of Rj-soybean varieties with Rhizobium fredii USDA 193 under limited supply of nutrients

Abstract The compatibility between rhizobia and host plants for nodulation was determined based on the genetic and physiological properties of both symbionts. It has been observed that soybean varieties carrying the Rj-gene were not nodulated effectively by certain strains or groups of rhizobia. Soybeans carrying the Rj 2-gene, Rj 2-varieties, were found to nodule ineffectively by the rhizobial strains belonging to the 3-24-44 and 122 serogroups (Caldwell 1966). In the same way, Rj 3- and Rj 4-varieties were found to nodule ineffectively by strains USDA 33 (Vest 1970) and USDA 61 (Vest and Caldwell 1972), respectively.

Interactive Effect of Salinity and Supplemental Calcium Application on Growth and Ionic Concentration of Soybean and Cucumber Plants

Effects of the application of supplemental Ca on the growth and mineral content and on the ion concentration of the sap of individual plant parts were investigated in soybean and cucumber plants that were treated with 50 mM NaCl. Treatment with NaCl reduced the growth of both kinds of plants and also the photosynthetic rate of the first cucumber leaf and the first soybean trifoliolate leaf at 7 d after the treatment. Increase of the Ca concentration in the medium alleviated the reduction of growth and photosynthetic rate, and its effect was more conspicuous in cucumber than in soybean. In the plant parts that contained high amounts of Na and Cl but a low amount of K with the NaCl treatment, the application of supplemental Ca decreased the Na content, increased the K content but did not affect appreciably the uptake and translocation of Cl. Because increasing Ca concentrations in the medium affected the contents of cations such as Na and K, the ameliorative effect of Ca was considered to be remarkable in cucumber plants where a high Na content resulted in growth inhibition due to salinity. On the contrary, the effect of supplemental Ca application appeared to be weak in soybean plants because in these plants, Cl might induce growth inhibition due to salinity and the application of supplemental Ca did not affect substantially the Cl status. In the NaCl treatment, the decrease in the concentrations of anions other than Cl− was more conspicuous in soybean plants than in cucumber plants. Hence anion imbalance due to excess Cl− might induce growth inhibition in soybean. In cucumber plants, the total cation concentration was slightly changed whereas the Na+ concentration increased with the decrease in the K+ concentration by the NaCl treatment. Cation imbalance that was caused by increased Na+ concentration and decreased K+ and Mg2+ concentrations might be responsible for the growth inhibition in cucumber plants. Increase of the Ca concentration in the medium affected only slightly the occurrence of such imbalance of cations or anions in both kinds of plants.

Responses to nitrogen sources and regulatory properties of root phosphoenolpyruvate carboxylase

Abstract Time course of changes in extractable root phosphoenolpyruvate carboxylase (PEP C) activity was investigated in wheat, barley, and tomato plants fed with different nitrogen sources. Ammonium-fed plants exhibited a 2–2.5-fold higher PEPC activity than nitrate-fed plants at 7 d after the onset of nitrogen supply. Western blot analysis revealed that the amounts of PEPC subunit proteins increased gradually as reflected in the extractable PEPC activity. These results suggest that the increase in PEPC activity may be due to de novo protein synthesis. PEPC was SO-fold purified from tomato roots after several chromatographic steps. Metabolite effects on the partially purified enzyme were also investigated under optimal or suboptimal conditions in terms of pH and concentrations of phosphoenolpyruvate. Organic acids and acidic amino acids inhibited the enzyme activity, while hexose phosphates stimulated it. Glutamine and asparagine produced in the course of ammonium assimilation hardly affected the activity.

Occurrence of glucosamine in higher plants

Abstract Occurrence of the unknown basic ninhydrin positive substance in young plant tissue supplied with a high level of ammonium nitrogen has been reported in the previous paper (1). This substance disappeared when the supply of ammonium nitrogen was stopped or the source of nitrogen was changed from ammonium nitrogen to nitrace nitrogen, and this substance was verg scarcely detected when the level of ammonium nitrogen in culture solution was as low as 3 ppm or the foren of nitrogen source was nitrace nitrogen. It is very interesting to identify this substance, as the occurrence of this substance is a distinctive character of the plant which han been supplied with a higher level of ammonium nitrogen and has developed the symptoms of ammonia toxicity.

Glucose metabolism in detached leaves of tomato plants grown with ammonium and nitrate as nitrogen sources

Abstract The metabolism of exogenous glucose-14C in the light and the dark was studied in the detached leaves of tomato plants grown with ammonium nitrogen and nitrate nitrogen. In the light, 14CO2, release and incorporation of glucose into insoluble materials were hardly affected at all by the nitrogen sources. Among the soluble labelled amino acids, serine had the greatest amount of label in the ammonium-plants while aspartate had the greatest amount in the nitrate-plants. This aspartate was synthesized from C3-compounds by carboxylation. During dark-light transition, the change in the composition of soluble amino acids was more rapid in the ammonium-plants than in the nitrate-plants. In the dark, 14CO2-release, which was ten times as much as in the light, was larger in the ammonium-plants than in the nitrate-plants; but the synthesis of high molecular compounds from glucose in the ammonium-plants was about half that in the nitrate-plants. So, it is considered that respiration operates sufficiently in t...

Effects of the Supply of K, Ca, and Mg on the Absorption and Assimilation of Ammonium- and Nitrate-Nitrogen in Tomato Plants

Abstract Forty-two-day-old tomato (Lycopersicon esculentum Mill. cv. Fukuju Nigo) plants were treated with complete, K-free, Ca-limited, and Mg-free nutrient solutions for 10 days using 2 mM NH4NO3 as the N source, which was replaced with 4 niM 15NH4Cl or Na15NO3 for the following 2 days to examine the absorption, translocation, and assimilation of inorganic N in relation to the supply of K, Ca, and Mg. The changes in the leaf nitrate reductase activity (NRA) were examined in tomato plants grown in nutrient solutions in which the form of N source and the supply of K and Ca were varied. Leaf contents of K, Ca, and Mg decreased to 38, 45, and 67% of those of the control plants in the low-K plants, the low-Ca plants and the low-Mg plants, respectively. Tomato plants absorbed NO3-N more efficiently than NH4-N. A larger amount of labelled N from NO3-N than from NH4-N was translocated to shoot. Removal of K from the nutrient solution slightly enhanced the absorption of NH4-N, but suppressed the absorption, tran...