Production and characterization of interspecific hybrids between Asparagus kiusianus Makino and A. officinalis L.

Interspecific hybridization is a useful technique to introduce characteristics from wild species into crops. Garden asparagus (Asparagus officinalis, 2n = 2x = 20) is an economically important vegetable that is native to the Mediterranean region but widely cultivated in many countries. The genus Asparagus is comprised of over 100 species. Asparagus kiusianus (2n = 2x = 20) is a wild asparagus species endemic to Japan. This species occurs on the coast and is likely to be a salt-resistant species. Although the geographic distribution of these two species is not close, molecular phylogenetic analysis demonstrated that these two species are closely related. In this study, a reciprocal cross between A. officinalis and A. kiusianus was carried out by hand pollination, and progeny were obtained from both crossings. These progeny exhibited a morphologically intermediate phenotype in terms of flower shape, and restriction fragment length polymorphism analysis confirmed that these were indeed interspecific hybrids. The interspecific hybrids were fertile, and backcross progeny with garden asparagus was also generated. These interspecific hybrids are expected to supply novel traits to garden asparagus.     

Comparison of Characteristics of Acid Phosphatases Secreted from Roots of Lupin and Tomato

In this study we purified both acid phosphatases (Apase) secreted from tomato and lupin roots, and compared the properties of these two enzymes. The secretory Apases from tomato and lupin showed the following similar properties. 1) Both enzymes were homodimers consisting of two identical subunits, each with a molecular weight of approximately 68 kilodaltons (kD) in tomato and 72 kD in lupin. 2) The enzymes were stable in the pH range of 4–9. 3) The enzymes showed an optimum temperature of 37–40°C for their activity and were stable at temperatures below 60°C. 4) The enzymes exhibited a comparable affinity for p-nitrophenyl phosphate (the apparent K _m values were 2.7–3.0 × 10^-5 M). On the other hand, there were some slight differences in the isoelectric point, optimum pH, specific activity, substrate specificity, and inhibitory effect of metal ions between the two enzymes. Therefore, it was considered that the most important difference in the root ability of the two plants to hydrolyze organic phosphorus may depend mainly on the amount of Apase secreted from a unit amount of roots.     

Problems in the methods of estimation of growth and maintenance respiration

According to Thornley, J.H.M. (Nature, 227, 304-305, 1970) and McCree, K.J. (Crop Sci., 14, 509-514, 1974), respiratory substances are used only for maintenance respiration when plants are exposed to the dark conditions for a long period of time (more than 2 d). The maintenance respiration is also affected by the nitrogen status in plant, because protein turnover is one of the major energy consumption sources under maintenance process. Therefore, to determine whether respiratory substances are used only for maintenance, ¹⁴C- [U] -sucrose or a mixture of ¹⁴C- [U] -amino acids was introduced to rice and soybean plants from the tip of leaf. Plants were grown under natural light conditions and under dark conditions for 4 d with 2 nitrogen levels (0.2 and 0.02 g N L^-1 soil). After the introduction of the ¹⁴C-compounds, the ¹⁴CO₂ respiratory rate was monitored during 24 h, then the ¹⁴C distribution to organic acids, free amino acids, proteins, sugars, and polysaccharides was analyzed. Following results were obtained.

1. When ¹⁴C-[U]-sucrose or a mixture of ¹⁴C-[U]-amino acids was introduced to the leaf of rice and soybean plants, the ¹⁴C release rate by respiration was not affected by the nitrogen and light treatments except when ¹⁴C-sucrose was introduced to soybean in the low N plot. The ¹⁴C release rate from the ¹⁴C-compounds introduced into leaf in the low N plot of soybean was higher in the dark treatment than in the natural light treatment.

2. ¹⁴C-distribution ratio after introduction of ¹⁴C-sucrose and a mixture of ¹⁴C-amino acids to the leaf was not significantly affected by the nitrogen treatment. When ¹⁴C-sucrose was introduced to rice leaf, the ¹⁴C-distribution ratio to sugars and proteins was higher and that to polysaccharides was lower in the natural light treatment than in the dark treatment. The ¹⁴C-distribution ratio was less aifected by the light or nitrogen treatment in case of soybean leaf.

3. Although it was assumed that maintenance metabolism was dominant in the lower leaf (counted from the bottom), the ¹⁴C-distribution ratio was similar to that of upper leaf.

4. Nitrogen content of leaf was not different between rice and soybean in the high N treatment, unlike the ¹⁴C-distribution ratio. In rice, the nitrogen content of leaf was about twice as high in the high N treatment compared with the low N treatment, while the ¹⁴C-distribution ratio in leaf was stable regardless of nitrogen treatment.

Based on the above results, it is suggested that since the ¹⁴C-distribution ratio into each chemical component did not change regardless of light treatment, nitrogen treatment, or leaf age, It was impossible to separate respiration into two components, such as growth and maintenance respiration. The results also indicated that current photosynthates and storage substances were not used only for growth and maintenance, respectively.     

Distribution of exudates of lupin roots in the rhizosphere under phosphorus deficient conditions

Abstract

The distribution of secretory acid phosphatase and organic acids enhanced by phosphorus deficiency in lupin rhizosphere was investigated using a rhizobox system which separated the rhizosphere soil into 0.5 mm fractions. In the soil fraction closest to the root surface, the lupin exudates displayed an acid phosphatase activity of 0.73 u g^?1 dry soil and citrate concentration of 85.2 μmol g^?1 dry soil, respectively. The increase of the acid phosphatase activity-induced an appreciable depletion of organic P in the rhizosphere, indicating that lupin efficiently utilized the organic P from soil through the enzyme activitye The sterile treatments demonstrated that the acid phosphatase in the rhizosphere was mainly derived from lupin root secretions. The secretory organic acids enhanced considerably the solubility of the inorganic P in three types of soil and a sludge. However, the secretory acid phosphatase and organic acids from lupin roots were only detected in a considerable amount in 0-2.5 mm soil fractions from root surface.     

Beneficial effect of aluminum on growth of plants adapted to low pH soils

Plants in which growth was reduced by low and high Al applications were designated as Al-sensitive plant (Hordeum vulgare) and Al-medium tolerant plants (Leucaena leucocephala, Ischaemum barbatum, Stylosanthes guianensis, and Fagopyrum esculentum), respectively, while plants in which growth was not affected or was stimulated by Al application were designated as Al-tolerant plant (Brachiaria ruziziensis) and Al-stimulated plants (Melastoma malabathricum, Melaleuca cajuputi, Acacia mangium, Hydrangea macrophyila, Vaccinium macrocarpon, Polygonum sachalinense, and Oryza sativa), respectively. Plants tolerant to or stimulated by Al were further classified based on the criteria of Al accumulation: 1) Al-excluders such as M. cajuputi, A. mangium, L. leucocephala, I. barbatum, S. guianensis, and O. sativa, 2) Al root-accumulators such as V. màcrocarpon, B. ruziziensis, and P. sachalinense, and 3) Al-accumulators such as M. malabathricum, H. macrophylla, and F. esculentum. The growth and N, P, and K uptake in M. malabathricum, M. cajuputi, A. mangium, L. leucocephala, H. macrophylla, V. macrocarpon, I. barbatum, P. sachalinense, F. esculentum, and O. sativa were stimulated by Al application, especially P uptake, while in H. vulgare (Al-sensitive plant) they were reduced by Al application. Ca and Mg uptake of many plants was inhibited by Al application, while that of some plants adapted to low pH soils was not affected at all (Ca and Mg: M. cajuputi, H. macrophylla, V. macrocarpon, I. barbatum, and S. guianensis; Mg: B. ruziziensis and P. sachalinense). In M. malabathricum, the relationship between Al and Ca (or Mg) was antagonistic because the Ca and Mg contents decreased by Al application even though dry matter, N, P, and K accumulation was stimulated by Al application. Plants adapted to low pH soils grew poorly in the no-Al treatment. Since the effect of the pH on plant growth was less conspicuous than that of Al, growth stimulation by Al application was ascribed not only to the alleviation of H⁺ toxicity but also to the increase of root activity such as P uptake.     

Comparison of aluminum tolerance and phosphate absorption between rape (Brassica napus L.) and Tomato (Lycopersicum esculentum Mill.) in relation to organic acid exudation

Aluminum (Al) tolerance and phosphate absorption in rape and tomato were compared under water culture and field conditions. The relative growth rate in the Al treatment compared with -A1 treatment was similar in the two crops under water culture conditions, while under field conditions, the growth rate was 2- to 3-fold higher in rape than in tomato in spite of the higher Al concentration in the soil solution than in the culture solution. The relative amount of phosphate absorbed in the Al treatment compared with - Al was not appreciably different between rape and tomato under water culture conditions, while under field conditions, it was 3- to 6-fold larger in rape than in tomato. The exudation rate of citric acid by roots was much higher in rape than in tomato. The plant growth, root elongation, and amount of phosphate absorbed in rape were inhibited in the 150 µM Al in the culture solution. However, the inhibition was alleviated by the addition of 200 µM citric acid or 500 µM malic acid. The P concentration in the culture solution decreased by the presence of Al as aluminum phosphate. However, addition of citric and malic acids increased the amount of phosphate released from the precipitated aluminum phosphate. In conclusion, one of the mechanisms for the higher Al tolerance and larger phosphate absorption in rape than in tomato under field conditions was ascribed to the higher concentration of exuded citric acid by Al in the rhizosphere. It was suggested that the exudation of citric acid might contribute to the detoxification of Al and to the increase phosphate availability in the rhizosphere in rape.     

Two Cases of Metastatic Parathyroid Carcinoma in Male C3H Mice Following Irradiation

White nodules were observed in the thyroid in two male C3H mice (at 99 and 122 weeks of age) exposed to fast neutrons at the age of 8 weeks. Histopathologically, in both cases, tumors were developed in the region corresponding to the parathyroid gland, and the tumor cells were arranged in a solid sheet or nest-like structures. Necrosis, cell debris and/or hemorrhage were sometimes seen in the center of the tumor structures. Tumor cells were small and uniform with scanty cytoplasm, cell margins were indistinct, and basally located tumor cells were aligned along the vascular stroma. Mitotic figures were frequently observed. Metastasis to the renal cortex was observed in both cases. These cases were diagnosed as parathyroid carcinoma. A parathyroid tumor is an extremely rare endocrine tumor in mice, regardless of whether the tumor is spontaneous or experimentally induced. These cases may have been induced by neutron-exposure; however, how radiation induces parathyroid carcinoma in mice is not clear.     

Morphological analysis on comparison of organic and chemical fertilizers on grain quality of rice at different planting densities

ABSTRACT

Effects of organic (Italian ryegrass and Bokashi) and chemical fertilizer on growth, yield, and grain quality of rice (Oryza sativa L.) were compared under different planting densities in 2013/2014 and 2014/2015. Italian ryegrass was incorporated into the soil as green manure. Bokashi (a mixture of organic materials) was applied as basal dressing. To measure yield and its components, 30 hills were chosen for each treatment. Rice grains were harvested from each treatment to assess the grain quality and to evaluate accumulation structures using a scanning electron microscope. Bokashi treatment increased panicle number per hill, ripened grain percentage, panicle number per m², and grain yield compared to no fertilizer treatment at normal planting density. Chemical fertilizer treatment increased plant length at high planting density. Italian ryegrass and Bokashi treatments promoted the taste point (taste score as reference) by reduction of amylose and protein contents at normal planting density in contrast to chemical fertilizer. 1000-grain weight, panicle number per m², and grain yield were higher at high planting density than at normal planting density. However, high planting density decreased panicle number per hill and spikelet number per panicle. It also enhanced the amylose content of rice grain. Scanning electron microscopic observation revealed that chemical fertilizer treatment marked up protein bodies and their traces on amyloplasts. However, Bokashi treatment produced large amyloplasts, which included many starch granules. These results show that Italian ryegrass and Bokashi can offset reductions of chemical fertilizer and can lead to sufficient starch accumulation structures in rice grains.     

不同水分条件下麻疯树幼苗的光合生理适应性研究

通过研究干旱和复水对麻疯树幼苗叶片的相对含水量、气体交换特性和叶绿素荧光特性的影响,结果表明:随着基质含水量的减小,麻疯树叶片相对含水量、净光合速率、蒸腾速率、气孔导度持续下降,胞间CO₂浓度先下降后上升;最大荧光产量、PSII最大光量子产量、光化学猝灭系数和PSⅡ实际量子效率均呈现下降趋势,初始荧光有小幅上升。复水后,气体交换参数和荧光参数能很快恢复,植株可以成活,表明麻疯树有很强的自我调节能力,对基质干旱有极强的适应能力。当基质含水量从21.91%下降到15.22%时,各参数均无显著差异(P＞0.05);当基质含水量从8.70%下降到6.83%时,各参数均有显著变化(P<0.05)。基质含水量为8.70%以上时,麻疯树碳同化能力降低的原因主要是气孔限制;基质含水量在8.70%以下时,光合效率的降低主要受非气孔限制。