Tōru Matoh

Two Chains of Rhamnogalacturonan II Are Cross-Linked by Borate-Diol Ester Bonds in Higher Plant Cell Walls

Polysaccharide moiety of the boron-polysaccharide complex (T. Matoh, K. Ishigaki, K. Ohno, J. Azuma [1993] Plant Cell Physiol 34: 639–642) isolated from radish (Raphanus sativus) roots has been shown to be rhamnogalacturonan II by glycosyl-linkage analysis and the presence of diagnostic monosaccharides, including apiose, aceric acid, 2-O-methylfucose, and 3-deoxy-D-manno-2-octulosonic acid. Removal of boron from the complex reduced the molecular weight by one-half without causing a significant increase in the number of reducing end groups, indicating that boron, as boric acid, links two rhamnogalacturonan II chains together to form the boron-polysaccharide complex.

Salt-induced damage to rice plants and alleviation effect of silicate

Rice plants were grown hydroponicaIly in the presence of either NaCI, sea water, or polyethylene glycol (PEG: average molecular weights of 7,800–9,000) at an osmotic potential of up to 186 mOsmol/kg, equivalent to 100 mM NaCI or 20% sea water, and the growth and mineral composition of the plants were compared. NaCI was the most detrimental agent, followed by sea water and PEG. Mineral contents, including nitrogen, phosphorus, potassium, and calcium were not significantly affected by the treatments. Removal of silicate from the culture solution brought about a more severe growth reduction in rice plants subjected to 100 mM NaCI stress. In the plants which received silicate, the contents of sodium in the shoots were nearly half of those in the shoots of plants which did not receive silicate.

Changes in the activities of ferredoxin- and NADH-glutamate synthase during seedling development of peas

Ferredoxin-glutamate synthase (EC 1.4.7.1) and NADH-glutamate synthase (EC 1.4.1.14) activities in pea seedlings (Pisum sativum L., cv. Alaska) were measured during germination and the early stages of growth. Both enzymes were detected at all stages in the developing roots and shoots, but their relative activities varied according to the growth stages. In shoots of 5-d-old seedlings, the ratio of the NADH-enzyme to the ferredoxin-enzyme was 72:28. However, the ferredoxin-activity increased rapidly and in shoots of 17-d-old seedlings, the activities were in the ratio of 3:97. Similar trends in these ratio changes were observed in the roots. In both tissues, the NADH-enzyme was shown to be predominant in the immature parts. When chloroplasts prepared from mature pea leaves were incubated with [14C]glutamine and 2-oxoglutarate, the production of [14C]glutamate was found to be light dependent and was inhibited by azaserine (3 mM) and 3-(3,4-dichlorophenyl)-1-1-dimethylurea (20 μM). In contrast, considerable amounts of [14C]glutamate were formed by chloroplasts from young leaves even in the dark. Addition of malate or dihydroxyacetone phosphate to the reaction mixture resulted in a twofold increase of this dark- and azaserine-sensitive [14C]glutamate formation.

EFFECTS OF SODIUM AND POTASSIUM SALTS ON THE GROWTH OF A HALOPHYTE

Seedlings of a coastal halophyte, Alriplex gmelini C.A.Mey were grown in water culture with varying concentrations and species of salts. Plants receiving nutrients supplemented with 50 mM NaCl gave the maximum dry weight yield compared with those receiving the higher or the lower concentrations of NaCl. Addition of 50mM KCl, 25 mM Na2SO4 or 25 mM K2SO4 to the basal culture solution also stimulated the growth to the same extent. However, higher concentrations of potassium salts, such as 250 mM KCl or 125mM K2SO4, exerted a more deleterious effect on the plant growth than sodium salts did. At a concentration of 250 mM NaCl or KCl addition, the KCl-treated plants showed a higher sodium plus potassium concentration than the NaCl-treated plants. Time course analysis revealed that the plants exposed to a concentration of 250 mM NaCl were able to maintain their internal sodium plus potassium concentrations around certain values, while the internal sodium plus potassium concentration in the 250 mM KCI-treated pla...

Function of the shoot base of salt-tolerant reed (Phragmites communis Trinius) plants for Na+ exclusion from the shoots

Abstract The function of the basal part of the shoot for salt tolerance of reed (Phragmites communis Trinius) was studied by 22Na+ uptake and histochemical experiments. Shoot-base girdling (3 s with hot air) increased the Na+ transport to shoot to 284% in 60 min and decreased the retranslocation of shoot Na+ to root to 24% in 30 min. These results suggest that Na+ exclusion from the shoot depends on the biological activity of the shoot base. Histochemical examination revealed that a high activity of vanadate-sensitive ATPase could be detected in the phloem region of the shoot base. This activity was completely inhibited by the hot girdling, suggesting that the phloem ATPase may be involved in the downward Na+ transport occurring in the shoot base of reed plants.

Nitrogen fixation of Sesbania rostrata: Contribution of stem nodules to nitrogen acquisition

Abstract Nitrogen contents, nodule numbers, and nodule dry weights of 6-week-oId Sesbania rostrata plants grown in sand culture with only root nodules, only stem nodules or with both were compared and the root nodules were found to contribute to nitrogen acquisition more significantly than the stem nodules. Similar findings were obtained in 15N2-fixing experiments. An 8-week-old plant with both stem and root nodules fixed 1.50 mg nitrogen in a 12 h light period, while the fixation decreased to 1.15 mg nitrogen after the removal of the stem nodules, suggesting that root nodules played major role in nitrogen fixation. However, acetylene-reducing activities per nodule dry weight were higher in the stem nodules. Under flooding conditions, the aerenchyma tissues contributed to about 40% of N2 transport to root nodules, and 60% was supplied through stem.

Growth characteristics of Sesbania species under adverse edaphic conditions in relation to use as green manure in Japan

Abstract Edaphic-stress tolerance of three Sesbania species, Sesbania rostrata, S. cannabina, and S. speciosa was evaluated in terms of growth. Plants exhibited the most vigorous growth in August, the hottest days in Japan, while in July and September, the growth decreased by 30 to 80%; S. speciosa showed the strictest requirement for temperature. When the medium pH was 3.5, S. cannabina was the most tolerant to low pH. At pH 8, growth was reduced to 60% for all the species. S. speciosa appeared to be less sensitive to Al (1 mol m-3). Copper (1.6 and 6.4 mmol m-3) damaged plants irrespective of species. S. speciosa was less sensitive and S. cannabina slightly sensitive to drought. S. rostrata yielded 16.8 Mg ha-1 dry matter in 13 weeks under field conditions, with 426 kg nitrogen ha-1 in the aerial parts. Timing of seed sowing was the determinant for a higher biomass production.