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.     

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.     

Mineral characteristics of leaves of plants from different phylogeny grown in various soil types in the temperate region

The objective of this research was to analyze selected minerals in leavesof plants, belonging to 166 species growing in alluvial, low pH, brownforest and serpentine soils. Mineral characteristics of the soils involved werealso determined.For the macronutrients, in trees grown in alluvial soil, N, P, Ca, and Mgconcentrations of leaves were higher in recently evolved plants than inplants with a longer period of evolution; K concentration remained constantregardless of evolution. In grasses grown in alluvial soil, it was difficult todetect the general tendency of mineral concentration. N, P, and Kconcentrations in alluvial soil were closely related to those in low pH andserpentine soils. Ca concentration in alluvial soil was lower than that in lowpH and serpentine soils. Mg concentration in alluvial soils was higher thanthat in low pH soils, while lower than that in serpentine soil. Therefore, N,P, and K accumulated according to the plant characteristics for theseelements, while Ca and Mg accumulation was strongly affected by the soilproperties.For the micronutrients, in trees, Fe and Mn remained constant regardlessof evolution; Zn concentration was lower in recently-evolved plants than inplants with a longer period of evolution. In grasses, Fe, Mn, and Znconcentrations in Caryophyllids were high. Except for Caryophyllids, Fe andCu concentrations remained constant, Mn concentration decreased withevolution, Zn concentration was higher in recently-evolved plants than inplants with a longer period of evolution.     

Variations in cryptic assemblages in coral-rubble interstices at a reef slope in Ishigaki Island,Japan

The interstices of coral rubble provide a good refuge for cryptic small crustaceans and molluscs, which are important prey items for reef fishes. In this study, we focused on the assemblage composition of cryptic mobile species along the depth gradient at an outer reef slope. Traps with coral rubble (22 × 18 × 6 cm) were set at three sites at different depths, and mobile animals that colonized the traps were sorted. In total, 117 species of larger animals (mainly Decapoda and Gastropoda) were recorded: 71 species at the 3 m point, 53 species at the 11 m point, and 37 species at the 22 m point. On average, 260.3 individuals were captured in the traps at 3 m, while 95.3 and 57.8 individuals were captured at 11 and 22 m, respectively. MDS ordination showed that assemblage composition differed among the three sites. The most abundant species at the 3 m was the galathean crab Galathea mauritiana, followed by the gastropod Diala albugo. At 11 and 22 m, the galathean crab Sadayoshia edwardsii was most abundant. Thus, at the reef slope, the benthic assemblage was most diverse at the shallow site, and specific communities occurred at the three sites.     

Gas chromatography–mass spectrometry associated global analysis of rice root exudates under aseptical conditions

Components of rice root exudates were surveyed by gas chromatography–mass spectrometry (GC-MS) and the effect of phosphate (P) starvation was investigated. Rice seedlings were aseptically grown in controlled environments under P-supplied (+P) or P-deficient (–P) conditions. Root exudates were collected from the culture solution 4 and 8 days after treatment (D4 and D8, respectively), which contain the first and second 4-day intervals. The collected solution was lyophilized and then eluted with methanol. In the present study, primary metabolites, such as sugars, amino acids, organic acids and fatty acids, were mainly targeted. After derivatization with methoxyamine hydrochloride and N-methyl-N-trifluoroacetamide, the samples were analyzed by GC-MS. Sugars and various amino acids (such as aspartic acid and l -isoleucine) were mainly detected and the components changed with the growth stage rather than the P content in the culture solution. The relative amount of sugars (such as glucose and fructose) and amino acids (such as aspartic acid and l -isoleucine) decreased in the D8 samples. Of the 78 detected compounds, orthogonal partial least-squares discrimination analysis (O-PLS-DA) showed that four compounds were related to the P content of the nutrient solution and 58 were related to the sampling date (days after treatment). The results suggest that the physiological change during seedling development was unexpectedly large and that the response to the environment was rather small.     

Effect of heat stress on age at first calving of Japanese Black cows in Okinawa

Calving records from birth certificates of cows were analyzed to investigate the effect of heat stress on age at first calving (AFC) of Japanese Black cows. The data set covered 20 years (1990–2009) of calving records. Total number of records was 9279. Daily weather information from weather stations in the vicinity of the farms was used. Temperature‐humidity index (THI) fitted to a linear model covered 30 days pre‐insemination to 61 days post‐insemination. Statistical analysis was conducted with procedures of SAS/STAT. Preliminary analysis showed that THI of the lowest temperature and humidity was most conducive to AFC. Covariance analysis, including main effect of sire, farm and year of insemination and covariates of THI on days showed that regression coefficients of THI on day ‐7, day ‐2 and day +31 were statistically significant. The estimated piecewise regression line showed different responses of AFC to THI on days: roof‐shasped downward trend on day ‐7, hockey‐stick shaped upward trend on day ‐2 and day +31. The difference among the estimated regression lines may be caused by direct and indirect factors on reproduction: indirect effect of reduced feed intake, failure of conception at previous insemination, direct effect of heat stress on oocyte and embryo development.     

Comparison and relation among different estimates of residual feed intake for Japanese Black (Wagyu) bulls

Residual feed intake (RFI) was estimated by ordinary regression (RFI_ord), linear regression (RFI_reg), and genetic regression (RFI_gen) for Japanese Black bulls, and compared among them by the magnitude of correlations, heritabilities, and empirical mean squared errors. The estimations were made for a total test periods of 140 days (77 bulls) and 112 days (663 bulls) sub‐divided each into two equal stages: first half and second half of the test periods. The means of RFI_reg, RFI_ord, and RFI_gen for the total test periods were 1.09, ?0.05, and ?2.21 kg/day, respectively. The genetic variation exists for these estimates at different stages of the test period. High genetic and phenotypic correlations (>0.95) were found between RFI_ord and RFI_gen, confirming that these are regarded practically as the same traits. The phenotypic variance (0.714) and heritability (0.24) of RFI_ord were close to those of RFI_gen (0.726 and 0.25, respectively). According to the empirical mean squared errors from the result of the total test periods, RFI_gen yielded better estimates of RFI. The high to moderate heritabilities for RFI_ord were estimated for the three stages of the test periods, indicating that RFI_ord might be an alternative estimate for genetic improvement of feed utilization.     

Preparation of board-like moldings from composites of isolated lignins and waste paper II: effect of inorganic salt addition on board performance and evaluation of practical use of MDF

Board-shaped composites with medium density (MDF) were prepared from isolated lignins and waste newspaper, in addition to preparation of the composites with high density (HB). The board properties of both composites concerning bending strength and water resistance were improved by the addition of hardwood acetic acid lignin (HAL). The internal bond strength and water resistance of MDF, in particular the degree of thickness swelling (TS), were also improved by prolonged molding time. Adding inorganic salts contributed to the improvement of TS. The effect depended on the charge of the cation. Considering practical utilization of lignin-based MDF as a structural material, its performance was evaluated by combination of the single-shear test of nailed joints and the modulus of rigidity. As a result, this MDF had sufficient strength to be utilized as an internal shear wall material. Therefore, lignin can be considered as an alternative to conventional adhesives for the production of boards such as HB and MDF.     

Bearing properties of Shorea obtusa beneath a laterally loaded bolt

Empirical equations to determine the bearing strength have been proposed by many researchers and design standards. Because these equations have been developed mainly based on test results of softwood species, it is a matter of great importance (to ASEAN structural engineers) to verify the applicability of these equations for tropical hardwood species, which are commonly used in many ASEAN countries. In this study, wood specimens of Shorea obtusa (a tropical hardwood species) were used and the bearing test under full-hole confi guration was carried out for fi ve different loading angles to the grain. The bearing stress-embedment curve obtained from the test was approximated by a linear elastic-plastic diagram indicating the initial and fi nal stiffness of the curve. Testing showed that the average bearing strength parallel to the grain was 7.25% lower than the prediction given in Eurocode 5. The bearing strength perpendicular to the grain evaluated based on bearing load at initial cracking was substantially different from any predictions given by previous studies or design standards. It was also found that the bearing strength and initial stiffness from the bearing stress-embedment curve for loading at intermediate angles to the grain could be satisfactorily predicted with Hankinson’s formula.