Root and leaf attributes accounting for the performance of fast- and slow-growing grasses at different nutrient supply

Despite their difference in potential growth rate, the slow-growing Brachypodium pinnatum and the fast-growing Dactylis glomerata co-occur in many nutrient-poor calcareous grasslands. They are known to respond differently to increasing levels of N and P. An experiment was designed to measure which characteristics are affected by nutrient supply and contribute to the ecological performance of these species. Nutrient acquisition and root and shoot traits of these grasses were studied in a garden experiment with nine nutrient treatments in a factorial design of 3 N and 3 P levels each. D. glomerata was superior to B. pinnatum in nutrient acquisition and growth in all treatments. B. pinnatum was especially poor in P acquisition. Both species responded to increasing N supply and to a lesser extent to increasing P supply by decreasing their root length and increasing their leaf area per total plant weight. D. glomerata showed a higher plasticity. In most treatments, the root length ratio (RLR) and the leaf area ratio (LAR) were higher for D. glomerata. A factorization of these parameters into components expressing biomass allocation, form (root fineness or leaf thickness) and density (dry matter content) shows that the low density of the biomass of D. glomerata was the main cause for the higher RLR and LAR. The biomass allocation to the roots showed a considerable plasticity but did not differ between the species. B. pinnatum had the highest leaf weight ratio. Root fineness was highly plastic in D. glomerata, the difference with B. pinnatum being mainly due to the thick roots of D. glomerata at high nutrient supply. The leaf area/leaf fresh weight ratio did not show any plasticity and was slightly higher for B. pinnatum. It is concluded, that the low density of the biomass of D. glomerata is the pivotal trait responsible for its faster growth at all nutrient levels. It enables simultaneously a good nutrient acquisition capacity by the roots as well as a superior carbon acquisition by the leaves. The high biomass density of B. pinnatum will then result in a lower nutrient requirement due to a slower turnover, which in the long term is advantageous under nutrient-poor conditions.     

Relationship between collagen fibril diameters and body size

Summary Suspensions of collagen fibrils obtained from derma of Elasmobranchia and Actinopterygia of different body sizes and developmental stages were examined by transmission electron microscopy. Fibril diameters were measured and classified into groups comprising a 20 nm diameter interval. Diagrams showing fibril populations of each fish were made. The measurements were averaged and their confidence intervals and standard errors determined. For each species other diagrams were plotted in which the mean diameters were correlated to the body length of each sample. The results show that: 1) a correlation exists between an increase in diameter of collagen fibrils and somatic growth until sexual maturity is reached; 2) fibril populations are subsequently spread over a wider range due to the presence in the derma of classes of newly formed and therefore thinner fibrils. The deposition of new fibrils is possibly influenced by individual factors; 3) no relationship exists between mean fibril diameter and body size; 4) no relationship exists between phylogenetic position and pattern of diameter distribution.Research supported by a grant from C.N.R. Roma (69.02087.0115.1150)     

Influence of root diameter on the penetration of seminal roots into a compacted subsoil

A field experiment was conducted to evaluate the influence of root diameter on the ability of roots of eight plant species to penetrate a compacted subsoil below a tilled layer. The soil was a fine sandy loam red-brown earth with a soil strength of about 3.0 MPa (at water content of 0.13 kg kg^-1, corresponding to 0.81 plastic limit) at the base of a tilled layer. Relative root diameter (RRD), which was calculated as the ratio of the mean diameters of roots of plants grown in compacted soil to the mean diameters of those from uncompacted soil, was used to compare the sensitivity of roots to thicken under mechanical stress.Diameters of root tips of plants grown in soil with a compacted layer were consistently larger than those from uncompacted soil. Tap-rooted species generally had bigger diameters and RRDs than fibrous-rooted species. A higher proportion of thicker roots penetrated the strong layer at the interface than thinner roots. There were differences between plant species in the extent to which root diameter increased in response to the compaction. The roots which had larger RRD also tended to have higher penetration percentage.The results suggest that the size of a root has a significant influence on its ability to penetrate strong soil layers. It is suggested that this could be related to the effects which root diameter may have on root growth pressure and on the mode of soil deformation during penetration.     

Small diameter blood vessels with controllable micropore structure induced by centrifugal force for improved endothelialization

The micropore structure is prerequisite for fast and durable endothelialization of artificial small diameter blood vessels (ASDBVs). Although some methods, such as salt leaching, coagulation, and electrospinning, have been developed to construct micropores for ASDBVs, the uncontrollability of the structure and the complicated procedures of the process are still the issues to be concerned about. In this study, a compact device based on the principle of centrifugal force is established and used to prepare polyurethane (PU) ASDBVs with micropore structures by blasting different porogens. It is found that the glass beads could construct micropores with regular round shape, uniform distribution, and controllable size (60–350 µm), which significantly improves the endothelialization of PU‐based ASDBVs, especially when the pore size is about 60 µm. This method is easy‐accessible and wide‐applicable, which provides a new pathway for the research and development of ASDBVs.     

Patterns of morphological and genetic diversity of Valeriana jatamansi Jones in different habitats and altitudinal range of West Himalaya,India

Importance to know and understand diversity of Himalayan plants is increasingly recognized considering the fact that various natural and anthropogenic pressures might bring about serious influences to morphological and genetic diversity of the vegetation in the region. In this context, Valeriana jatamansi was investigated in detail, taking into account its importance in various Ayurvedic and modern medicines. Randomly selected mature plants from twenty five different populations (located between 1215 m to 2775 m asl) of V. jatamansi were analysed for their morphological attributes. Further, ISSR markers were used to detect genetic variation among 151 plants of selected 25 populations. Use of 20 primers yielded 125 reproducible polymorphic loci which were used to estimate different parameters of genetic diversity. These parameters were in turn applied to develop relationships with habitat types and altitude range. Significant variation (p < 0.05) in above ground dry weight (AGDW) and below ground dry weight (BGDW) across the populations was observed. Nei's genetic diversity index (He) ranged from 0.25 to 0.37 across the populations, with a mean of 0.31. Genetic diversity exhibited a decreasing trend with increasing altitude, and maximum diversity (He = 0.325) was observed in the range of 1201–1500 m asl. Among the different habitat conditions, highest genetic diversity (He = 0.334; Pp = 84.38) was observed in grassland habitats while minimum in mixed forest habitats (He = 0.285; Pp = 72.433). The genetic diversity (He) had significant negative relationships with AGDW, BGDW and rhizome diameter (Pearson r = −0.359, −0.424 and −0.317, respectively; p < 0.05). The genetic characterization of V. jatamansi from the western Himalaya by this study suggests influences of habitat types and the altitudinal range upon genetic diversity, and based on these proposals for conservation strategies in favour of the species are made.     

Apolipoprotein E gene polymorphism and the risk of left ventricular dysfunction among Egyptian β-thalassemia major

In Egypt, β-thalassemia is the most common hereditary hemolytic anemia. Cardiac dysfunction, secondary to iron overload with formation of oxygen free radicals, is the most common cause of death in β-thalassemia patients. This study was designed to determine whether the allelic genotype of apolipoprotein E (Apo E), which exhibits antioxidant properties, could represent a genetic risk factor for the development of left ventricular (LV) dysfunction in β-thalassemia major. Fifty Egyptian β-thalassemia major patients were subjected to echocardiography to assess LV function. Apo E genotyping by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) was done for all patients in addition to 50 age and sex matched healthy control subjects. Patients were classified into three groups. Group I and II were clinically asymptomatic. Group II subjects had evidence of LV dilatation, while Group III patients had clinical and echocardiographic findings of LV failure. Apo E4 allele was significantly higher among Group II and III than in controls. In conclusion, Apo E4 allele can be considered as a genetic risk factor for LV dysfunctions in β-thalassemic patients. It could be used as predictive indicator for additional risk of LV failure, particularly in asymptomatic patients with LV dilatation, requiring a closer follow-up, to prevent further disease progression.     

Locating QTLs controlling several adult root traits in an elite Chinese hybrid rice

This study aimed to elucidate the genetics of the adult root system in elite Chinese hybrid rice. Several adult root traits in a recombinant inbred line (RIL) population of Xieyou 9308 and two backcross F₁ (BCF₁) populations derived from the RILs were phenotyped under hydroponic culture at heading stage for quantitative trait locus (QTL) mapping and other statistical analysis. There a total of eight QTLs detected for the root traits. Among of them, a pleiotropic QTL was repeatedly flanked by RM180 and RM5436 on the short arm of chromosome 7 for multiple traits across RILs and its BCF₁ populations, accounting for 6.88% to 25.26% of the phenotypic variances. Only additive/dominant QTLs were detected for the root traits. These results can serve as a foundation for facilitating future cloning and molecular breeding.