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At least 1,135 records · Page 63Linked to original sources
PubMed1986

Long-term evaluation of root surface caries in periodontally treated patients.

Caries development on exposed root surfaces was evaluated in 31 patients who had been subjected to surgical and/or nonsurgical periodontal treatment 8 years earlier due to advanced chronic periodontitis. Besides assessments for evaluation of the periodontal treatment, a number of examinations and tests were carried out in order to assess variables presumed to influence the root surface caries development. Both statistical and graphical analyses were carried out to test differences between groups of subjects and to evaluate the variables studied as possible risk factors for root surface caries. The variables studied were: salivary lactobacillus count, salivary Streptococcus mutans count, plaque score, salivary secretion rate, salivary buffer effect, oral sugar clearance time, dietary habits and the age of the subject. The final results support previous findings from an initial 4-year period that root surface caries occurs, though to a minor extent, in this patient category demonstrating good or excellent periodontal conditions after periodontal treatment. A positive correlation was found between the baseline and final root surface caries scores. After the second 4-year period, the salivary counts of S. mutans and lactobacilli, the plaque score and the dietary habits differed significantly between groups of subjects who had developed 0 or greater than 5 new DFS %. Root surface caries was far more prevalent when risk values of the variables studied were present than when they were absent. The important variables in this respect differed considerably between the subjects. No single variable was found to be discriminative in all subjects.

Adult↗
PubMed2002

Comparison of somatic embryogenesis-derived coffee (Coffea arabica L.) plantlets regenerated in vitro or ex vitro: morphological, mineral and water characteristics.

Coffea arabica L. plantlets obtained ex vitro after sowing somatic embryos produced in a bioreactor in horticultural substrate were compared with those obtained in vitro from the same embryo population under conventional culturing conditions on semi-solid media. The intensity and quality of aerial and root system development were compared. Shoot emergence was more efficient in vitro but rooting frequencies were low. In contrast, all ex vitro-regenerated embryos rooted. The cotyledon area of mature embryos produced in a bioreactor positively affected plantlet development when regeneration was carried out ex vitro. Embryos with an intermediate cotyledon area (0.86 cm2) had the highest rates of plant conversion ex vitro (63%), and also resulted in vigorous plantlets. Mortality was higher in nursery conditions, but better plant development was obtained. The quality of plantlets produced under ex vitro conditions was reflected in better growth of the aerial and root systems, and also by similar morphological, mineral and water status characteristics to seedlings. Unlike roots formed on semi-solid media, those produced in soil were branched, fine (30-50% had a diameter of less than 0-5 mm) and they bore root hairs. Leaves of plantlets regenerated ex vitro had a histological structure similar to that of seedling leaves, and a lower stomatal density (100 vs. 233 mm-2). Moreover, they were more turgid, as indicated by higher pressure potential (psiP) (0.91 s. 0.30 MPa) and relative water content values (97 vs. 93%). Furthermore, under in vitro conditions, leaves had larger stomata which were abnormally round and raised. Direct sowing of germinated somatic embryos resulted in the rapid production of vigorous plantlets under ex vitro conditions, whilst removing the need for problematical and costly conventional acclimatization procedures.

Coffea↗
PubMed2004

Genetic dissection of root formation in maize (Zea mays) reveals root-type specific developmental programmes.

BACKGROUND: Maize (Zea mays) forms a complex root system comprising embryonic and post-embryonic roots. The embryonically formed root system is made up of the primary root and a variable number of seminal roots. Later in development the post-embryonic shoot-borne root system becomes dominant and is responsible together with its lateral roots for the major portion of water and nutrient uptake. Although the anatomical structure of the different root-types is very similar they are initiated from different tissues during embryonic and post-embryonic development. Recently, a number of mutants specifically affected in maize root development have been identified. These mutants indicate that various root-type specific developmental programmes are involved in the establishment of the maize root stock. SCOPE: This review summarizes these genetic data in the context of the maize root morphology and anatomy and gives an outlook on possible perspectives of the molecular analysis of maize root formation.

Mutation↗
PubMed2006

Rates of root and organism growth, soil conditions, and temporal and spatial development of the rhizosphere.

BACKGROUND: Roots growing in soil encounter physical, chemical and biological environments that influence their rhizospheres and affect plant growth. Exudates from roots can stimulate or inhibit soil organisms that may release nutrients, infect the root, or modify plant growth via signals. These rhizosphere processes are poorly understood in field conditions. SCOPE AND AIMS: We characterize roots and their rhizospheres and rates of growth in units of distance and time so that interactions with soil organisms can be better understood in field conditions. We review: (1) distances between components of the soil, including dead roots remnant from previous plants, and the distances between new roots, their rhizospheres and soil components; (2) characteristic times (distance(2)/diffusivity) for solutes to travel distances between roots and responsive soil organisms; (3) rates of movement and growth of soil organisms; (4) rates of extension of roots, and how these relate to the rates of anatomical and biochemical ageing of root tissues and the development of the rhizosphere within the soil profile; and (5) numbers of micro-organisms in the rhizosphere and the dependence on the site of attachment to the growing tip. We consider temporal and spatial variation within the rhizosphere to understand the distribution of bacteria and fungi on roots in hard, unploughed soil, and the activities of organisms in the overlapping rhizospheres of living and dead roots clustered in gaps in most field soils. CONCLUSIONS: Rhizosphere distances, characteristic times for solute diffusion, and rates of root and organism growth must be considered to understand rhizosphere development. Many values used in our analysis were estimates. The paucity of reliable data underlines the rudimentary state of our knowledge of root-organism interactions in the field.

Diffusion↗
PubMed1969

Effect of light intensity and plant size on rate of development of early boron deficiency symptoms in tomato root tips.

Young tomato plants (Lycopersicon esculentum Miller, cultivar Rutgers) grown in solution culture at 27 degrees at 2 light intensities with adequate boron (0.1 mg/l) and treated with these 2 intensities in the absence of adequate boron developed root boron deficiency symptoms. The typical deficiency symptoms of decreased root elongation, increased depth of brown color and decreased RNA content of tips developed more rapidly at high than at low light intensity, and plant size influenced results. Plants supplied with adequate boron did not exhibit deficiency symptoms.

Journal Article↗
PubMed1978

The effect of ammonium nitrate on the synthesis of nitrogenase and the concentration of leghemoglobin in pea root nodules induced by Rhizobium leguminosarum.

The effects of NH4NO3 on the development of root nodules of Pisum sativum after infection with Rhizobium leguminosarum (strain PRE) and on the nitrogenase activity of the bacteroids in the nodule tissue were studied. The addition of NH4NO3 decreased the nitrogenase activity measured on intact nodules. This reduction of nitrogen fixation did not result from a reduced number of bacteroids or a decreased amount of bacteroid proteins per gram of nodule. The synthesis of nitrogenase, measured as the relative amount of incorporation of [35S]sulfate into the components I and II of nitrogenase was similarly not affected. The addition of NH4NO3 decreased the amount of leghemoglobin in the nodules and there was a quantitative correlation between the leghemoglobin content and the nitrogen-fixing capacity of the nodules. The conclusion is that the decrease of nitrogen-fixing capacity is caused by a decrease of the leghemoglobin content of the root nodules and not by repression of the nitrogenase synthesis.

Enzyme Precursors↗
PubMed2001

Recovery of gravitropic response during regeneration of root caps does not require developed columella cells and sedimentation of amyloplasts.

Correlations between regeneration of the root cap and recovery of a gravitropic response were studied using primary roots of Phaseolus vulgaris. After removal of various lengths of the root tip a gravistimulus was continuously given to the root. The statistical analysis of data showed that recovery of the gravitropic response was gradually delayed as the length of the tips removed increased. This suggested that the columella cells of the root cap were involved in gravitropism. When the root cap was completely removed, the roots did not respond to gravistimuli for the first 15 h and began to reorient their growth direction at 20 h. At this time, the columella cells had just begun to regenerate and had immature amyloplasts which did not sufficiently form a sediment. These results suggest that other systems of perception exist in plant cells in addition to the amyloplast-based model of graviperception.

Fabaceae↗
PubMed2003

Effect of soil moisture on seed germination, plant growth and root rot severity of navy bean in Fusarium solani infested soil.

The development of root rot and its severity were affected by numerous factors which through their interaction could distort results. In this study, a single factor, soil moisture was considered. Using Fusarium solani infested root rot soil we investigated the effect of three available soil moisture (ASM) levels (i.e. 100%, 70% and 25%) on seed rot, germination, plant growth and root rot severity of navy bean in the greenhouse. Percent germination differed strikingly averaging of 58.5, 89.5 and 87.0% respectively to ASM levels. Apparently, high soil moisture promoted seed rot and impeded seed germination. Root rot incidence and severity were examined two months later. Percent plant with root rot averaged 89.5, 89.0 and 69.8% while root rot severity was 3.01, 2.3 and 1.1 (on a 0-9 scale), respectively to ASM levels. Plant growth was moderate, good and poor with respect to ASM levels. It was apparent that the final plant growth was a sum of seed rot, root rot incidence, disease severity and soil moisture adequacy. However, seed rot appeared to be the largest contributing factor to final plant yield.

Crops, Agricultural↗