A comparative anatomical investigation of three taxa of Brassica L. from Bangladesh

In the present study, micromorphology and comparative anatomy of young root, stem and leaf of three economically important taxa of Brassica L. viz., B. rapa L. subsp. campestris (L.) Clapham, B. juncea (L.) Czern. and B. napus L. are investigated in detail for the first time in Bangladesh by using light microscopy (LM). In anatomical studies, cross sections of young root, stem and leaf have been examined and biometric measurement of cell and tissues are presented. The micromorphological studies are related to the epidermal surface. In addition, the stomatal index and stomatal index ratio of these taxa have been calculated and presence of simple, non-glandular, unicellular trichome on stems and leaves also been observed except on the stem of B. rapa L. subsp. campestris (L.) Clapham. The anatomical study reveals that the investigated taxa have primary growth in roots and stems as well as amphistomatic and bifacial leaves with anisocytic stomata have been noticed. Finally, presence of tetrarch or single strand exarch xylem in vascular bundle of root, the size, shape and presence or absence of trichome over stem, shape of midrib of leaf have been considered to provide reliable features for identification of the Brassica species. Bangladesh J. Plant Taxon. 27(1): 15-26, 2020 (June)

Antimicrobial Efficacy of Methanolic and Aqueous Extracts of Partially Purified Protein from Young and Matured Root of Guiera senegalensis (Moshi Medicine)

Background: Antibiotic resistance among pathogenic bacteria is increasing at an alarming rate leading to the need for traditional medicine as an alternative. Aim of the Study: The study aimed to evaluate the antimicrobial activity of methanolic and, aqueous extracts of partial purified protein of young and matured roots of Guiera senegalensis. Methodology: Antimicrobial activity was determined by disc diffusion and broth dilution techniques, Quantitative phytochemical analysis was carried out by standard procedure, the gel chromatography technique was used to fractionate the crude protein. The test isolates were Bacillus subtilis, Staphylococcus aureus, E. coli, Salmonella typhimurium and Candida albicans. Results: The antimicrobial activity showed all the extracts were quite effective against most of the test isolates except Candida albicans (fungus). The crude and partially purified proteins were active against Gram-positive bacteria. The maximum zone of inhibition (37.33±5.03b mm) was observed in methanolic extracts of young root against Staphylococcus aureus at 100 mg/ml. Most extracts of methanolic exhibited minimum inhibitory concentration (MIC) at the range of 6.25 mg/ml and 12.5 mg/ml and minimum bactericidal concentration (MBC) at 12.5 mg/ml and 25 mg/ml. The young root was more active than the matured root. Quantitative phytochemicals showed a high amount of saponins (9.98% and 6.42%) in matured and young roots respectively. Conclusion: Guiera senegalensis has broad-spectrum antimicrobial activity and a potential source of new antibiotics that could be useful for the treatment of infectious diseases.

Effect of Aging on Dentinal Crack Formation after Treatment and Retreatment Procedures: a Micro-CT Study

In order to evaluate the volume of dentinal cracks taking into account the age of the dentin and the type of file system used for endodontic procedures, forty freshly extracted single-rooted lower incisive teeth presenting similar root volume, were divided into two groups according to the age of the patient: Group Young (18 - 30 years old) and Group Old (60 years old or more). Each specimen was scanned by microcomputed tomography (micro-CT) in three stages: (i) before any treatment, (ii) after endodontic treatment with Reciproc files (REC), and (iii) after subsequent endodontic retreatment. Each group was subdivided into two subgroups, according to the retreatment technique used: retreatment with REC or with ProTaper Universal Retreatment (PUR) files. For each subgroup, the images were analyzed for differences in the volume of dentinal cracks in the middle and apical thirds of the teeth , according to the dentin age. In both stages (before and after instrumentation), the micro-CT images of the old root dentin presented with higher volume of cracks than those of the young root dentin, statistical significance notwithstanding (p>0.01). The use of REC files appeared to have no statistically significant differences in the generation of cracks in any type of root dentin when compared with PUR files (p>0.01). When retreated with PUR, the old root dentin presented with a significantly higher volume of cracks (p<0.01) when compared with the old root dentin initially.

Effect of parameter choice in root water uptake models – the arrangement of root hydraulic properties within the root architecture affects dynamics and efficiency of root water uptake

Detailed three-dimensional models of root water uptake have become increasingly popular for investigating the process of root water uptake. However, they suffer from a lack of information on important parameters, particularly on the spatial distribution of root axial and radial conductivities, which vary greatly along a root system. In this paper we explore how the arrangement of those root hydraulic properties and branching within the root system affects modelled uptake dynamics, xylem water potential and the efficiency of root water uptake. We first apply a simple model to illustrate the mechanisms at the scale of single roots. By using two efficiency indices based on (i) the collar xylem potential ("effort") and (ii) the integral amount of unstressed root water uptake ("water yield"), we show that an optimal root length emerges, depending on the ratio between roots axial and radial conductivity. Young roots with high capacity for radial uptake are only efficient when they are short. Branching, in combination with mature transport roots, enables soil exploration and substantially increases active young root length at low collar potentials. Second, we investigate how this shapes uptake dynamics at the plant scale using a comprehensive three-dimensional root water uptake model. Plant-scale dynamics, such as the average uptake depth of entire root systems, were only minimally influenced by the hydraulic parameterization. However, other factors such as hydraulic redistribution, collar potential, internal redistribution patterns and instantaneous uptake depth depended strongly on the arrangement on the arrangement of root hydraulic properties. Root systems were most efficient when assembled of different root types, allowing for separation of root function in uptake (numerous short apical young roots) and transport (longer mature roots). Modelling results became similar when this heterogeneity was accounted for to some degree (i.e. if the root systems contained between 40 and 80% of young uptake roots). The average collar potential was cut to half and unstressed transpiration increased by up to 25% in composed root systems, compared to homogenous ones. Also, the least efficient root system (homogenous young root system) was characterized by excessive bleeding (hydraulic lift), which seemed to be an artifact of the parameterization. We conclude that heterogeneity of root hydraulic properties is a critical component for efficient root systems that needs to be accounted for in complex three-dimensional root water uptake models.