The chemical nature of the green fraction of P type humic acid

P type humic acid has absorption bands near 615, 570 and 450mµ in the visible region, and is a common component of many soils in north temperate regions (1, 2, 3). Its unusual spectral characteristics are due to a green fraction (Pg), which can be separated from the humic acid dissolved in aqueous alkali by chromatography on Sephadex or cellulose powder, and is precipitated as a reddish-brown substance on acidification (2). In aqueous alkali, it has λmax at 613, 568, 448, 430 (infl.) and 281mµ. The distribution of Pg in different soils is probably related to the presence of fungal sclerotia. The highest content of Pg in p type humic acid is about 10%. We have now obtained evidence that the characteristic colour of Pg is due to the presence of a derivative of 4,9 - dihydroxyperylene - 3,10 - quinone.     

The muscle protein Dok-7 is essential for neuromuscular synaptogenesis

The formation of the neuromuscular synapse requires muscle-specific receptor kinase (MuSK) to orchestrate postsynaptic differentiation, including the clustering of receptors for the neurotransmitter acetylcholine. Upon innervation, neural agrin activates MuSK to establish the postsynaptic apparatus, although agrin-independent formation of neuromuscular synapses can also occur experimentally in the absence of neurotransmission. Dok-7, a MuSK-interacting cytoplasmic protein, is essential for MuSK activation in cultured myotubes; in particular, the Dok-7 phosphotyrosine-binding domain and its target in MuSK are indispensable. Mice lacking Dok-7 formed neither acetylcholine receptor clusters nor neuromuscular synapses. Thus, Dok-7 is essential for neuromuscular synaptogenesis through its interaction with MuSK.     

Chemical Characteristics and Acid Buffering Capacity of Surface Soils in Japanese Forests

To determine the geological distribution of acid buffering capacity and exchangeable Al of forest soils in Japan, surface soils under forest vegetation were collected nationwide from a total of 1,034 sites. Generally, surface soils in Japanese forests are mostly acidic and low in both exchangeable cation content and exchangeable Al. The median of soil pH(H₂O), total exchangeable cations, and exchangeable Al are 5.1, 76 mmol₍₊₎Kg^?1, and 19.6 mmol₍₊₎kg^?1, respectively. Acid buffering capacities of selected soils were determined using a soil column, which was comparable to the capacity that resulted from cation exchanges with protons. Soils with high buffering capacity and low exchangeable Al are widely distributed in Japan, and overlap with the areas of Andisol distribution. Volcanogenic materials seem to mask soil characteristics derived from underlying geology even though they are not Andisols. However, central to western Honshu Island, Shikoku Island, and northern Kyushu Island showed weak acid buffering capacities with high exchangeable Al potential in surface soils.     

The chemical nature of components of PG (Green fraction of P type humic acid)

P type humic acids showing characteristic absorption maxima at 615, 575, and 450 nm have been found in various types of soils around the world (3, 5, 7,8). P type humic acid was fractionated into a brown fraction (Pb) and a green fraction (Pg) by column chromatography using cellulose powder (4) or Sephadex gel (3). The Pg fraction which has a strong absorption maxima at 615, 575, and 450 nm causes the characteristic absorption pattern of P type humic acid.     

Amino acid metabolism in plant leaf

¹⁴C-labelled sodium bicarbonate and ¹⁵N-labelled ammonium sulfate were simultaneously vacuum-infiltrated into detached sunflower leaves, and the incorporation of ¹⁴C and ¹⁵N into free amino acids was chased during 60-min period in the light and in the dark.

In the light, the ue specific activity of aspartic acid, alanine, serine and glycine rapidly increased for 5 min and thereafter decreased. On the other hand, that of gultamic acid continued to increase slowly during the entire 60-min period. In the dark, aspartic acid most actively incorporated ¹⁴C. The difference of changes in ¹⁴C specific activity between glutamic acid and other amino acids was also observed in the dark as in the light. These results suggest that the carbon skeleton of glutamic acid is synthesized from aspartic acid, alanine, serine and glycine.

¹⁵N content of glutamine was the highest of all amino acids investigated in the light, and it was followed by glutamic acid. alanine, aspartic acid, serine and glycine, in this order. In the dark, ¹⁵N content of glutamic acid fell remarkably and was lower than that of alanine up to 5 min. From these ¹⁵N tracer experiments, it is suggested that the incorporation of ammonium into glutamic acid is strictly dependent on light and that alanine incorporates ammonium by the direct amination besides the transamination from glutamic acid.     

Soybean preference for Bradyrhizobium japonicum for nodulation

For examining the probability of increase in the occupation ratio of inoculated rhizobium in nodules, various Rj-soybean cultivars including the Rj ₂ Rj ₃ Rj ₄-lines of soybean were grown in a field of the Kyushu University Farm. Bradyrhizobium japonicum USDA110 that carries uptake hydrogenase (Hup⁺) was used as an inoculum. The relative efficiency of nitrogen fixation generally increased by the inoculation. However, there were no significant differences in the effects among the genotypes of the host plants. The occupation ratio of serogroup USDA110 in the nodules on the taproot of the inoculated plants was in the range of 77–100%, suggesting that the B. japonicum strain USDA110 infected taproots immediately after inoculation. The occupation ratios in the nodules on the lateral roots were 53–67, 40–86, 63–83, and 62–77% in inoculated plants of the non-Rj-, Rj ₂ Rj ₃-, Rj ₄-, and Rj ₂ Rj ₃ Rj ₄-genotypes, respectively, and they decreased in all the genotypes with the progression of growth. At the time of the first sampling, the occupation ratios on the lateral roots of these Rj ₂ Rj ₃ Rj ₄-genotypes showed values intermediate between those of IAC-2 (Rj ₂ Rj ₃) and Hill (Rj ₄) , which were the parent cultivars of the Rj ₂ Rj ₃ Rj ₄-lines, B340, B349, and C242. The reduction in the occupation ratio of the serogroup USDA110 for about 1 month after the first sampling was the lowest (0.13–0.16) in the Rj ₂ Rj ₃ Rj ₄-genotypes, excluding B349, followed by the non-Rj- and Rj ₂ Rj ₃-genotypes and highest (0.52–0.69) in the Rj ₄-genotypes, excluding Hill. Therefore, it was considered that the population of compatible rhizobia with host soybean plants increased in the rhizosphere with the progression of the development and growth. The results showed that with the expansion of the root area of host plants, the occupation ratio of type A rhizobia including the serogroup USDA110 was high. Therefore, the Rj ₂ Rj ₃ Rj ₄-genotypes were superior to other Rj-genotypes in terms of the inoculation effects of nodulation type A rhizobium, B. japonicum USDA110. However, the preference of the Rj ₂ Rj ₃ Rj ₄-genotype for serogroup USDA110 is not sufficient to rule out the competition with the other serogroups in this study. Therefore, the study should be centered on the isolation of more efficient (Hup⁺) and highly compatible rhizobial strains with the Rj ₂ Rj ₃ Rj ₄- genotypes.     

A kuroko-type polymetallic sulfide deposit in a submarine silicic caldera

Manned submersible studies have delineated a large and actively growing Kuroko-type volcanogenic massive sulfide deposit 400 kilometers south of Tokyo in Myojin Knoll submarine caldera. The sulfide body is located on the caldera floor at a depth of 1210 to 1360 meters, has an area of 400 by 400 by 30 meters, and is notably rich in gold and silver. The discovery of a large Kuroko-type polymetallic sulfide deposit in this arc-front caldera raises the possibility that the numerous unexplored submarine silicic calderas elsewhere might have similar deposits.