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PubMedDate not supplied

Vegetative propagation of Cecropia obtusifolia (Cecropiaceae).

Cecropia is a relatively well-known and well-studied genus in the Neotropics. Methods for the successful propagation of C. obtusifolia Bertoloni, 1840 from cuttings and air layering are described, and the results of an experiment to test the effect of two auxins, naphthalene acetic acid (NAA) and indole butyric acid (IBA), on adventitious root production in cuttings are presented. In general, C. obtusifolia cuttings respond well to adventitious root production (58.3% of cuttings survived to root), but air layering was the better method (93% of cuttings survived to root). The concentration of auxins used resulted in an overall significantly lower quality of roots produced compared with cuttings without auxin treatment. Future experiments using Cecropia could benefit from the use of isogenic plants produced by vegetative propagation.

Butyrates↗

PubMed2005

Plastic plants and patchy soils.

Soil nutrients are distributed in a non-uniform or 'patchy' manner. It is well established that the modular nature of root systems allows them to show both morphological and/or physiological plasticity upon encountering nutrient-rich patches. These plastic responses are widely believed to be foraging mechanisms by the plant to enhance nutrient resource capture. Although morphological plasticity has traditionally been viewed as the more expensive option as it requires new root construction, more recent evidence suggests this may not necessarily be the case. Moreover, plants may be able to recapture most of the initial outlay involved in new root construction, again lowering the overall cost to the plant. Under natural conditions the roots of most plant species have an additional nutrient acquisition mechanism namely mycorrhizal symbiosis. However, the impact of these important symbiotic associations upon the host plant's response to nutrient patches has received relatively little attention. The mycorrhizal fungal symbiont should, in theory, be better able to compete directly with the rest of the microbial community for the nutrients in the patch. This could potentially be important to the host plant, as generally, root proliferation responses are more important for interspecific plant, than plant-microbial, competition.

Acclimatization↗

PubMed1997

Evaluation of the three-dimensional clinostat as a simulator of weightlessness.

Concerns regarding the reliability of slow-and fast-rotating uni-axial clinostats in simulating weightlessness have induced the construction of devices considered to simulate weightlessness more adequately. A new three-dimensional (3-D) clinostat equipped with two rotation axes placed at right angles has been constructed. In the clinostat, the rotation achieved with two motors is computer-controlled and monitored with encoders attached to the motors. By rotating plants three-dimensionally at random rates on the clinostat, their dynamic stimulation by gravity in every direction can be eliminated. Some of the vegetative growth phases of plants dependent on the gravity vector, such as morphogenesis, are shown to be influenced by rotation on the 3-D clinostat. The validity of 3-D clinostatting has been evaluated by comparing structural parameters of cress roots and Chara rhizoids obtained under real microgravity with those obtained after 3-D clinostatting. The parameters analyzed up to now (organization of the root cap, integrity and polarity of statocytes, dislocation of statoliths, amount of starch and ER) demonstrate that the 3-D clinostat is a valuable device for simulating weightlessness.

Plant Physiological Phenomena↗

PubMed1992

Intraoperative monitoring of the dorsal sacral roots: minimizing the risk of iatrogenic micturition disorders.

In 31 children (age, 2-17 years) and 1 adult, individual dorsal root action potentials (DRAPs) from the S1-S3 roots were recorded intraoperatively after electrical stimulation of the dorsal penile or clitoral nerves, in preparation for surgery within the cauda equina. In most patients, pudendal afferent activity was present in S2 and S3 bilaterally; in some, the afferent activity was confined to a single root bilaterally, and in one, to a single root on one side. Dorsal root action potentials of small amplitude were recorded from S1 in 15 patients, although in no patient was S1 the primary carrier of these afferents. No lesion of the roots or rootlets carrying significant afferent activity was created during the rhizotomy, and no dysfunction in micturition resulted. We propose that the neurophysiological identification of roots and rootlets carrying afferent activity from the penile or clitoral nerves allows for rhizotomy of the S2 roots with the least possible risk of postoperative micturition and sexual dysfunction.

Adolescent↗

PubMedDate not supplied

[Effect of extractive substances and total glycoside fraction from Panax ginseng C. A. Meyer on root growth of Cucumis sativus L. seedlings].

We studied the effect of extractive substances (ES) and total glycoside fraction (TGF) from Panax ginseng on plant cell growth. The seeds of cucumber Cucumis sativus L., KIT variety, were used for the biological assay. The tested substances inhibited the primary root growth in Cucumis sativus seedlings. Actively growing seedlings were most sensitive to this effect.

Cucumis sativus↗

PubMed2003

Plant meristems: a merry-go-round of signals.

Recent studies have provided significant new insights into the gene actions that specify and maintain stem cells in plant shoots and roots. New layers of genetic control and potential signalling pathways and effector mechanisms have emerged from these new studies and will be reviewed here. These new findings refine the current model in which stem cells in plant meristems are regulated by negative feedback loops and uncover a fundamental mechanism for stem cell maintenance that might be common to shoots and roots.

Arabidopsis Proteins↗

PubMed2004

Influence of nutrient application rate on growth and rooting potential of the West African hardwood Triplochiton scleroxylon.

Effects of stock plant nutrition on growth and subsequent rooting of leafy stem cuttings of the commercially important west African tree Triplochiton scleroxylon K. Schum. were investigated to identify the primary morphological variables influencing adventitious root formation. Potted plants were watered as required with one of four balanced nutrient solutions (0, 15, 63 or 125 mg N l(-1)). Increasing the nutrient supply to stock plants increased growth rate and rate of adventitious root production of subsequently harvested cuttings, but an optimum nutrient regime was not identified. Rooting percentage increased from 27% in cuttings harvested from stock plants receiving a low nutrient supply to 64% for cuttings harvested from stock plants receiving eight times the amount of nutrients extractable from plants under typical field conditions in West Africa. The ability of a cutting to retain its leaf during propagation and the length of the cutting were the primary measured characteristics associated with rooting and accounted for 43% of the variance fitted in the model. The length of the new shoot, total leaf area and within-shoot position (node position) were also significantly associated with rooting. After these characteristics were fitted to the model, the genetic origin (clone) was not statistically significant. We conclude that genetic variation in rooting potential is mediated through variations in morphological and physiological traits, rather than through genetic variation in cell differentiation or related aspects of root initiation.

Malvaceae↗

PubMed2000

Mechanism of plant growth promotion by rhizobacteria.

Plant growth results from interaction of roots and shoots with the environment. The environment for roots is the soil or planting medium which provide structural support as well as water and nutrients to the plant. Roots also support the growth and functions of a complex of microorganisms that can have a profound effect on the growth anti survival of plants. These microorganisms constitute rhizosphere microflora and can be categorized as deleterious, beneficial, or neutral with respect to root/plant health. Beneficial interactions between roots and microbes do occur in rhizosphere and can be enhanced. Increased plant growth and crop yield can be obtained upon inoculating seeds or roots with certain specific root-colonizing bacteria- 'plant growth promoting rhizobacteria'. In this review, we discuss the mechanisms by which plant growth promoting rhizobacteria may stimulate plant growth.

Gram-Negative Aerobic Bacteria↗

PubMed2003

Agrobacterium rhizogenes vs auxinic induction for in vitro rhizogenesis of Prosopis chilensis and Nothofagus alpina.

The induction and improvement of in vitro rhizogenesis of microshoots of Prosopis chilensis (Mol.) Stuntz and Nothofagus alpina (Poep. et Endl. Oerst.) were compared using Agrobacterium rhizogenes (Ar) versus indole-3-butyric acid (IBA) in the culture media. Microshoots of P. chilensis (1-2 cm length), coming from in vitro grown seedlings, were cultivated in a modified Broadleaved Tree Medium (BTMm) containing half salt concentration of macronutrients and 0.05 mg x L(-1) benzilaminopurine (BAP). After 30 days, microshoots with 2-4 leaves were selected and cultured in BTMm-agar in presence or abscense of Ar and in combination with IBA. For N. alpina, the apical shoots with the first 2 true leaves, from 5 weeks old seedlings, were cultured in the abovementioned medium, but with 0.15 mg x L(-1) of BAP. After 2 months, microshoots with 2-3 leaves were selected and cultured in BTMm-agar, supplemented with 5 mg x L(-1) IBA or in liquid BTMm on perlite and, in the presence or absence of A. rhizogenes (Ar) and in combination with 3 mg x L(-1) IBA. Rooting in P. chilensis reached 100.0% when Ar infection was produced in the presence of IBA, increasing both, the number and dry weight of roots. In N. alpina, 90.0% of rooting efficiency was obtained when Ar infection was produced in liquid culture and in the absence of auxin.

Cell Differentiation↗

PubMed2002

Characterization of a family of IAA-amino acid conjugate hydrolases from Arabidopsis.

The mechanisms by which plants regulate levels of the phytohormone indole-3-acetic acid (IAA) are complex and not fully understood. One level of regulation appears to be the synthesis and hydrolysis of IAA conjugates, which function in both the permanent inactivation and temporary storage of auxin. Similar to free IAA, certain IAA-amino acid conjugates inhibit root elongation. We have tested the ability of 19 IAA-l-amino acid conjugates to inhibit Arabidopsis seedling root growth. We have also determined the ability of purified glutathione S-transferase (GST) fusions of four Arabidopsis IAA-amino acid hydrolases (ILR1, IAR3, ILL1, and ILL2) to release free IAA by cleaving these conjugates. Each hydrolase cleaves a subset of IAA-amino acid conjugates in vitro, and GST-ILR1, GST-IAR3, and GST-ILL2 have K(m) values that suggest physiological relevance. In vivo inhibition of root elongation correlates with in vitro hydrolysis rates for each conjugate, suggesting that the identified hydrolases generate the bioactivity of the conjugates.

Amidohydrolases↗

PubMed2005

Endocytosis and vesicle trafficking during tip growth of root hairs.

The directional elongation of root hairs, "tip growth", depends on the coordinated and highly regulated trafficking of vesicles which fill the tip cytoplasm and are active in secretion of cell wall material. So far, little is known about the dynamics of endocytosis in living root hairs. We analyzed the motile behaviour of vesicles in the apical region of living root hairs of Arabidopsis thaliana and of Triticum aestivum by live cell microscopy. For direct observation of endocytosis and of the fate of endocytic vesicles, we used the fluorescent endocytosis marker dyes FM 1-43 and FM 4-64. Rapid endocytosis was detected mainly in the tip, where it caused a bright fluorescence of the apical cytoplasm. The internalized membranes proceeded through highly dynamic putative early endosomes in the clear zone to larger endosomal compartments in the subapical region that are excluded from the clear zone. The internalized cargo ended up in the dynamic vacuole by fusion of large endosomal compartments with the tonoplast. Before export to these lytic compartments, putative early endosomes remained in the apical zone, where they most probably recycled to the plasma membrane and back into the cytoplasm for more than 30 min. Endoplasmic reticulum was not involved in trafficking pathways of endosomes. Actin cytoskeleton was needed for the endocytosis itself, as well as for further membrane trafficking. The actin-depolymerizing drug latrunculin B modified the dynamic properties of vesicles and endosomes; they became immobilized and aggregated in the tip. Treatment with brefeldin A inhibited membrane trafficking and caused the disappearance of FM-containing vesicles and putative early endosomes from the clear zone; labelled structures accumulated in motile brefeldin A-induced compartments. These large endocytic compartments redispersed upon removal of the drug. Our results hence prove that endocytosis occurs in growing root hairs. We show the localization of endocytosis in the tip and indicate specific endomembrane compartments and their recycling.

Arabidopsis↗

PubMed1999

Cell cycle synchronization in plant root meristems.

The analysis of structure and metabolism of a cell at a defined phase of cell cycle is often difficult because cell cycle progression in somatic tissues is asynchronous and only a fraction of cells are cycling. An elegant solution to obtain populations of cells enriched for single stage of the cell cycle is to impose the synchrony artificially. Different systems have been used to obtain synchronized populations of plant cells, including suspension-cultured cells, leaf mesophyll protoplasts and root tip meristems. Root tips have been frequently used in a variety of studies ranging from chromosome analysis to cell cycle and its regulation. Seedlings with actively growing roots may be obtained in most plant species, they are easy to handle, the experimental system is well defined, reproducible and can be easily modified for different species. This paper describes a protocol for cell cycle synchronization in root tips of Vicia faba, which is based on the use of DNA synthesis inhibitor hydroxyurea [18]. Modifications of the protocol for Pisum sativum, Medicago sativa, Hordeum vulgare, Secale cereale, Triticum aestivum, and Zea mays are also given. Flow cytometric data indicate that about 90% of root tip cells are synchronized. On average, mitotic indices exceeding 50% are obtained with the method. Synchronized cells may be accumulated at metaphase using a mitotic spindle inhibitor to achieve metaphase indices exceeding 50%.

Genes, cdc↗

PubMed2000

Inhibitory role of root hairs on transport within root culture bioreactors.

An experimental system was developed to produce root cultures of Hyoscyamus muticus with and without the profuse root hairs. Growth in the presence of 7.6 microM pyrene butyric acid (PBA) and 2.2 mM phosphate virtually eliminated root hairs, whereas growth rate, general morphology and nutrient yields remained unchanged in well-mixed flask culture. These root cultures were used to demonstrate decreased flow resistance in a tubular reactor as a result of root hair removal. To assess the impact on bioreactor performance, hairy and hairless root cultures were grown in a highly characterized 15-L bubble column bioreactor. In the absence of root hairs, the mixing was greatly enhanced; mixing times became shorter for the hairless culture at roughly 100 g (fresh weight)/L. By the end of the 3-week culture period, the mixing time of the hairy culture was 29 times longer than that of the hairless culture. The growth rate of the hairless culture in the bioreactor was as much as 2.4 times greater than growth of the hairy culture under the same conditions. The improved reactor performance was reflected in greater biomass accumulation and respiratory activity. These results show that the root hairs-which facilitate nutrient uptake in a static soil environment-are detrimental to growth in a liquid environment as an effect of their stagnating fluid flow and limiting oxygen availability.

Biological Transport↗

PubMed1989

Differential growth resulting in the specification of different types of cellular architecture in root meristems.

Symplastic growth of plant organs may be described by a continuous growth tensor field. In tensorial analysis of meristems, the trajectories of periclinal and anticlinal cell walls represent trajectories of the principal directions of growth (PDGs); this follows from the maintenance of mutual orthogonality between periclinal and anticlinal wall trajectories during growth. Periclinal and anticlinal cell divisions are also oriented in the principal planes of growth. The growth tensor for the root apex is specified in such a way that the principal directions of the tensor fit the pattern of periclinal and anticlinal walls in the apex, and that the grid formed by material particles aligned along PDG trajectories preserve this alignment during growth. Two growth tensors are formulated--one giving a maximum and the other giving a minimum of the volumetric relative elemental growth rate at the region of the initial cell(s). Temporal sequences of deformation of a grid formed by lines coinciding with the principal directions of growth are shown. The formation of cellular patterns in root apices is simulated. Two types of patterns are obtained: one with an apical cell and merophytes, and another with files of cells converging towards a quiescent centre.

Biophysical Phenomena↗

PubMed2002

Involvement of polyamines in root development at low temperature in the subantarctic cruciferous species Pringlea antiscorbutica.

Polyamine involvement in root development at low temperature was studied in seedlings of Pringlea antiscorbutica R. Br. This unique endemic cruciferous species from the subantarctic zone is subjected to strong environmental constraints and shows high polyamine contents. In the present study, free polyamine levels were modified by inhibitors of polyamine biosynthesis (D-arginine, difluoromethylornithine, cyclohexylammonium, and methylglyoxal-bis-guanylhydrazone) and variations of the endogenous pools were compared to changes in root growth. The arginine decarboxylase pathway, rather than that of ornithine decarboxylase, seemed to play a major role in polyamine synthesis in Pringlea antiscorbutica seedlings. Root, but not shoot, phenotypes were greatly affected by these treatments, which modified polyamine endogenous levels according to their expected effects. A positive correlation was found between agmatine level and growth rate of the primary root. Spermidine and spermine contents also showed positive correlations with primary root growth whereas the putrescine level showed neutral or negative effects on this trait. Free polyamines were therefore found to be differentially involved in the phenotypic plasticity of root architecture. A comparison of developmental effects and physiological concentrations suggested that agmatine and spermine in particular may play a significant role in the control of root development.

Acclimatization↗

PubMed2002

Evidence of association of salmonellae with tomato plants grown hydroponically in inoculated nutrient solution.

The possibility of uptake of salmonellae by roots of hydroponically grown tomato plants was investigated. Within 1 day of exposure of plant roots to Hoagland nutrient solution containing 4.46 to 4.65 log(10) CFU of salmonellae/ml, the sizes of the pathogen populations were 3.01 CFU/g of hypocotyls and cotyledons and 3.40 log(10) CFU/g of stems for plants with intact root systems (control) and 2.55 log(10) CFU/g of hypocotyls and cotyledons for plants from which portions of the roots had been removed. A population of > or =3.38 log(10) CFU/g of hypocotyls-cotyledons, stems, and leaves of plants grown for 9 days was detected regardless of the root condition. Additional studies need to be done to unequivocally demonstrate that salmonellae can exist as endophytes in tomato plants grown under conditions that simulate commonly used agronomic practices.

Culture Media↗

PubMed1996

Changes in D-aspartic acid in human deciduous teeth with age from 1-20 years.

The racemization ration (D/L ratio) of aspartic acid in the dentin (collagen) of deciduous teeth was studied, using dentin of permanent teeth as a reference. D-aspartic acid in deciduous teeth was found to increase almost linearly with aging. The reaction velocity constant of racemization (kyr-1) in deciduous teeth (1.1915 x 10(-3)yr-1) was approximately double the value for permanent teeth (6.2550 x 10(-4)yr-1). The velocity of the racemization reaction was similar between deciduous teeth and permanent teeth in a dry state. The D/L ratio determined using transverse sections of deciduous teeth tended to be high in the crown and low in the root. The reaction velocity of racemization is considered to be affected to some extent by the tooth material, ambient temperature and salivary pH, but most importantly by physiologic resorption of deciduous teeth at the root associated with age.

Adolescent↗

PubMed1997

Solving the puzzle of gravitropism--has a lost piece been found?

Attempts to devise models to account for the gravitropic behaviour of plant organs have been limited conceptually by the predominance of studies on the gravitropic behaviour of organs of young seedlings. The dramatic growth responses induced by gravitropic stimulation of young shoots or roots, which rapidly restore the elongating axes to vertical, are experimentally convenient but theoretically limiting because gravitropism needs not simply restore an organ to vertical. Evidence is reviewed that suggests that plant organs must possess a mechanism which will allow them to attain a stable gravitropic position at any angle and that each organ has a characteristic gravitropic set-point angle (GSA). The GSA can be changed developmentally and is also regulated in a reversible manner by environmental parameters such as light. It is speculated that gravity may itself influence the GSA of an organ. The recognition that plant organs can grow at angles other than vertically up or down is not new, but previously it has been accepted that angles other than vertical were the consequence of the vectorial resultant effect of two different, opposing mechanisms. The new GSA concept proposes that a single mechanism might be sufficient to account for all forms of gravitropism in roots and shoots. This unifying concept proposes that the ability to change the angle of an organ with respect to the vertical is part of the basic gravitropic mechanism and that models of gravitropism must be able to account for this important feature.

Gravitropism↗