Evidence for Anoxic Zones in 2-3 mm Tips of Aerenchymatous Maize Roots Under Low O2 Supply

1995 ◽  
Vol 22 (5) ◽  
pp. 723 ◽  
Author(s):  
J Gibbs ◽  
GD Bruxelle ◽  
W Armstrong ◽  
H Greenway
Keyword(s):  
Fold Increase ◽  
Growth Reduction ◽  
Root Tips ◽  
Cortical Cells ◽  
Aerenchyma Formation ◽  
Metabolic Cooperation ◽  
Primary Roots ◽  
Maize Roots ◽  
O2 Supply ◽  
Anoxic Zones

Root elongation and the production of the end-products of anaerobic catabolism, ethanol, alanine and lactate, were measured in intact maize roots and excised tips exposed to a variety of oxygen regimes. Elongation was retarded by 56 and 44% respectively in intact aerenchymatous primary roots of maize incubated in 0.1% stagnant agar, or exposed to 0.06 mol m-3 external O2 in gas-sparged solution. This growth reduction was accompanied by a 3-5-fold increase in alanine as a percentage of total soluble amino acids in the 0-2 mm root tips. The increase in this value was not in response to ethylene or translocation of alanine from other parts of the root. Moreover, in excised tips exposed to 0.06 mol O2 m-3, net production of ethanol, alanine and lactate occurred. Even so, these root tips continued to elongate at 30% of the rate observed in aerated excised root tips. It appears that adaptation of maize to O2 deficiency may involve a combination of aerenchyma formation and tolerance to anoxia. We suggest that metabolic cooperation, in the form of symplastic transport of energy-rich compounds, might exist between cortical cells receiving adequate oxygen supply and cells in anoxic zones.

scholarly journals A Role for Auxin in Ethylene-Dependent Inducible Aerenchyma Formation in Rice Roots

Plants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 610 ◽  
Author(s):  
Takaki Yamauchi ◽  
Akihiro Tanaka ◽  
Nobuhiro Tsutsumi ◽  
Yoshiaki Inukai ◽  
Mikio Nakazono
Keyword(s):  
Oxygen Deficiency ◽  
Ethylene Biosynthesis ◽  
Auxin Signaling ◽  
Root Tips ◽  
Cortical Cells ◽  
Aerenchyma Formation ◽  
Rice Roots ◽  
Rice Mutant ◽  
Gas Space ◽  
The Relationship

Internal oxygen diffusion from shoot to root tips is enhanced by the formation of aerenchyma (gas space) in waterlogged soils. Lysigenous aerenchyma is created by programmed cell death and subsequent lysis of the root cortical cells. Rice (Oryza sativa) forms aerenchyma constitutively under aerobic conditions and increases its formation under oxygen-deficient conditions. Recently, we have demonstrated that constitutive aerenchyma formation is regulated by auxin signaling mediated by Auxin/indole-3-acetic acid protein (AUX/IAA; IAA). While ethylene is involved in inducible aerenchyma formation, the relationship of auxin and ethylene during aerenchyma formation remains unclear. Here, we examined the effects of oxygen deficiency and ethylene on aerenchyma formation in the roots of a rice mutant (iaa13) in which auxin signaling is suppressed by a mutation in the degradation domain of IAA13 protein. The results showed that AUX/IAA-mediated auxin signaling contributes to ethylene-dependent inducible aerenchyma formation in rice roots. An auxin transport inhibitor abolished aerenchyma formation under oxygen-deficient conditions and reduced the expression of genes encoding ethylene biosynthesis enzymes, further supporting the idea that auxin is involved in ethylene-dependent inducible aerenchyma formation. Based on these studies, we propose a mechanism that underlies the relationship between auxin and ethylene during inducible aerenchyma formation in rice roots.

Structure and ontogeny of Betula alleghaniensis – Pisolithus tinctorius ectomycorrhizae

1990 ◽  
Vol 68 (3) ◽  
pp. 579-593 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
C. A. Ackerley ◽  
L. H. Melville
Keyword(s):  
Root Hairs ◽  
Root Surface ◽  
Pisolithus Tinctorius ◽  
Initial Contact ◽  
Broad Host Range ◽  
Betula Alleghaniensis ◽  
Cortical Cells ◽  
Structural Modifications ◽  
Hartig Net ◽  
Primary Roots

The ontogeny and ultrastructure of ectomycorrhizae synthesized between Betula alleghaniensis (yellow birch) and Pisolithus tinctorius, a broad host range fungus, were studied to determine the structural modifications in both symbionts during ectomycorrhiza establishment. A number of stages, including initial contact of hyphae with the root surface, early mantle formation, and mature mantle formation, were distinguished. Interactions between hyphae and root hairs were frequent. As a paraepidermal Hartig net developed, root epidermal cells elongated in a radial direction, but wall ingrowths were not formed. Repeated branching of Hartig net hyphae resulted in extensive fine branches and the compartmentalization of hyphal cytoplasm. Nuclei and elongated mitochondria were frequently located in the narrow cytoplasmic compartments, and [Formula: see text] thickenings developed along walls of cortical cells in primary roots.

Short-and long-term effects of cadmium on transmembrane electric potential (E m) in maize roots

Biologia ◽  
2006 ◽  
Vol 61 (1) ◽  
Author(s):  
Ján Pavlovkin ◽  
Miroslava Luxová ◽  
Ingrid Mistríková ◽  
Igor Mistrík
Keyword(s):  
Root Growth ◽  
Electric Potential ◽  
Time Course ◽  
Cumulative Effect ◽  
Significant Inhibition ◽  
Long Term Effects ◽  
Cortical Cells ◽  
Root Cells ◽  
Maize Roots ◽  
Atp Supply

AbstractIn this study, the effects of Cd on root growth, respiration, and transmembrane electric potential (E m) of the outer cortical cells in maize roots treated with various Cd concentrations (from 1 µM to 1 mM) for several hours to one week were studied. The E m values of root cells ranged between −120 and −140 mV and after addition of Cd they were depolarized immediately. The depolarization was concentration-dependent reaching the value of diffusion potential (E D) when the Cd concentration exceeded 100 µM. The values of E D ranged between −65 to −68 mV (−66 ± 1.42 mV). The maximum depolarization of E m was registered approx. 2.5 h after addition of Cd to the perfusion solution and in some cases, partial (Cd > 100 µM) or complete repolarization (Cd < 100 µM) was observed within 8–10 h of Cd treatment. In the time-dependent experiments (0 to 168 h) shortly after the maximum repolarization of E m a continuous concentration-dependent decrease of E m followed at all Cd concentrations. Depolarization of E m was accompanied by both increased electrolyte leakage and inhibition of respiration, especially in the range of 50 µM to 1 mM Cd, with the exception of root cells treated with 1 and 10 µM Cd for 24 and 48 h. Time course analysis of Cd impact on root respiration revealed that at higher Cd concentrations (> 50 µM) the respiration gradually declined (∼ 6 h) and then remained at this lowest level for up to 24 h.All the Cd concentrations used in this experiment induced significant inhibition of root elongation and concentrations higher than 100 µM stopped the root growth within the first day of Cd treatment. Our results suggest that Cd does not cause irreversible changes in the electrogenic plasma membrane H+ ATPase because fusicoccin, an H+ ATPase activator diminished the depolarizing effect of Cd on the E m. The depolarization of E m in the outer cortical cells of maize roots was the result of a cumulative effect of Cd on ATP supply, plasmalemma permeability, and activity of H+ ATPase.

Identification of genes expressed in maize root cortical cells during lysigenous aerenchyma formation using laser microdissection and microarray analyses

2010 ◽  
Vol 190 (2) ◽  
pp. 351-368 ◽  
Author(s):  
Imene Rajhi ◽  
Takaki Yamauchi ◽  
Hirokazu Takahashi ◽  
Shunsaku Nishiuchi ◽  
Katsuhiro Shiono ◽  
...  
Keyword(s):  
Laser Microdissection ◽  
Maize Root ◽  
Cortical Cells ◽  
Aerenchyma Formation ◽  
Microarray Analyses

scholarly journals RNA-Seq Transcriptome Analysis of Rice Primary Roots Reveals the Role of Flavonoids in Regulating the Rice Primary Root Growth

Genes ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 213
Author(s):  
Yu Xu ◽  
Junjie Zou ◽  
Hongyan Zheng ◽  
Miaoyun Xu ◽  
Xuefeng Zong ◽  
...  
Keyword(s):  
Cell Wall ◽  
Root Growth ◽  
Primary Root ◽  
Glutathione Metabolism ◽  
Auxin Signaling ◽  
Antioxidant Enzyme Activities ◽  
Rna Seq ◽  
Root Tips ◽  
Primary Roots ◽  
Quercetin Treatment

Flavonoids play important roles in root development and in its tropic responses, whereas the flavonoids-mediated changes of the global transcription levels during root growth remain unclear. Here, the global transcription changes in quercetin-treated rice primary roots were analyzed. Quercetin treatment significantly induced the inhibition of root growth and the reduction of H2O2 and O2− levels. In addition, the RNA-seq analysis revealed that there are 1243 differentially expressed genes (DEGs) identified in quercetin-treated roots, including 1032 up-regulated and 211 down-regulated genes. A gene ontology (GO) enrichment analysis showed that the enriched GO terms are mainly associated with the cell wall organization, response to oxidative stress, and response to hormone stimulus. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis showed that the enriched DEGs are involved in phenylpropanoid biosynthesis, glutathione metabolism, and plant hormone signal transduction. Moreover, the quercetin treatment led to an increase of the antioxidant enzyme activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) in rice roots. Also, the quercetin treatment altered the DR5:GUS expression pattern in the root tips. All of these data indicated that the flavonoids-mediated transcription changes of genes are related to the genes involved in cell wall remodeling, redox homeostasis, and auxin signaling, leading to a reduced cell division in the meristem zone and cell elongation in the elongation zone of roots.

scholarly journals Histological Observation of Primary and Secondary Aerenchyma Formation in Adventitious Roots of Syzygium kunstleri (King) Bahadur and R.C.Gaur Grown in Hypoxic Medium

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 137 ◽  
Author(s):  
Hong-Duck Sou ◽  
Masaya Masumori ◽  
Hiroyuki Kurokochi ◽  
Takeshi Tange
Keyword(s):  
Formation Process ◽  
Rainy Season ◽  
Adventitious Roots ◽  
Root Tip ◽  
Histological Observation ◽  
Root Tips ◽  
Aerenchyma Formation

Trees growing in wetlands develop adventitious roots from the trunk during the rainy season and adapt to the flooded environment by forming primary (schizogenous or lysigenous) and secondary aerenchyma in the roots. Therefore, it is necessary to clarify the formation process of each type of aerenchyma in these adventitious roots. In this study, saplings of Syzygium kunstleri (King) Bahadur and R.C.Gaur were grown under four different treatments, and a total of 12 adventitious roots generated from trunks were used to clarify the distribution of each aerenchyma type in the roots using light or epi-florescence microscopy. Schizogenous aerenchyma was observed in the root tips where the root color was white or light brown, whereas lysigenous aerenchyma was found at some distance from the root tip where the root color gradually changed from light to dark brown. The secondary aerenchyma and periderm were observed in dark brown parts near the root base. None or only one layer of phellem cells was detected in the white roots near the root tip, but dark brown roots near the root base had at least three layers of phellem cells. Considering these results, oxygen transportation may occur between primary and secondary aerenchyma at the point where two or more layers of phellem cells are formed.

The influence of nitrate on the induction of nitrate reductase in maize roots

1973 ◽  
Vol 51 (6) ◽  
pp. 1255-1258 ◽  
Author(s):  
D. L. Stevens ◽  
Ann Oaks
Keyword(s):  
Nitrate Reductase ◽  
Maize Root ◽  
Lag Phase ◽  
Root Tips ◽  
Final Level ◽  
Maize Roots ◽  
Mature Root

A concentration of 10 mM NO3 saturates the induction of nitrate reductase in maize root tips whereas concentrations up to 100 mM do not saturate the induction in mature root sections. Increasing concentrations of nitrate from 1 to 25 mM have no effect on either the lag phase, or the phase of rapid increase of the enzyme. They do influence the final level of enzyme obtained at 8 h.

The effect of cycloheximide on amide formation in maize roots

1973 ◽  
Vol 51 (1) ◽  
pp. 91-95 ◽  
Author(s):  
Ann Oaks ◽  
F. J. Johnson
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Root Tip ◽  
Minor Effect ◽  
Root Tips ◽  
Corn Root ◽  
Basic Amino Acids ◽  
Maize Roots ◽  
A Minor ◽  
Mature Root

Cycloheximide inhibits the incorporation of acetate-2-14C into protein and into asparagine in corn root tips. It also causes an accumulation of glutamine and, over a concentration range of 0.4 to 5.0 μg/ml, a transient accumulation of the neutral and basic amino acids. In mature sections, cycloheximide inhibits protein synthesis but causes an increase in the incorporation of radioactivity into both glutamine and asparagine. Azaserine, a glutamine analogue, also inhibits the formation of asparagine in root-tip sections but has only a minor effect on protein synthesis. In mature root sections, there is an accumulation of glutamine but no effect on asparagine formation when azaserine is used. Glutamine additions to root tips or mature root sections affect neither asparagine formation nor protein synthesis. We conclude that cycloheximide is behaving as a glutamine analogue in its effect on asparagine biosynthesis, and that its effect as a glutamine analogue is lost as cells mature.

Regeneration of whole plants from cultured root tips of Limnophila indica

1981 ◽  
Vol 59 (6) ◽  
pp. 969-973 ◽  
Author(s):  
Sunanda Rao ◽  
H. Y. Mohan Ram
Keyword(s):  
Liquid Medium ◽  
Root Tip ◽  
Root Tips ◽  
Cortical Cells ◽  
Starch Grains ◽  
Histological Studies ◽  
Shoot Buds ◽  
Whole Plants

Root tips (1 cm long) were excised from in vitro grown plants of Limnophila indica (L.) Druce and cultured in liquid medium with 2% sucrose. The explants floated horizontally on the surface of the medium; they became green, and their tips started to grow geotropically into the medium. Four to six shoot buds each were differentiated in 84.5% of the cultures in 4 weeks. Subsequently, shoot buds covered the surface of the bent part of the root and portions above and below it. No buds were formed at the cut end or near the growing root tip. Buds failed to differentiate in roots in which the apex was not growing. Histological studies of the roots showed that the buds originated from proliferating cortical cells, which had prominent chloroplasts and starch grains. The shoot buds grew into entire plants which flowered eventually.

Studies on the haustorium of Castilleja (Scrophulariaceae). I. The upper haustorium

1973 ◽  
Vol 51 (5) ◽  
pp. 917-922 ◽  
Author(s):  
David R. Dobbins ◽  
Job Kuijt
Keyword(s):  
Root Hairs ◽  
Surface Lipid ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Spherical Structure ◽  
Cortical Zone ◽  
Primary Roots ◽  
Distinct Cell ◽  
Parenchyma Cells ◽  
Host Tissues

The portion of the Castilleja secondary haustorium external to host tissues was investigated at the light- and electron-microscopic levels. One or more haustoria may be present along a single lateral root; however, primary roots of Castilleja may also have haustoria. A localized development of root hairs usually precedes haustorial formation. The first sign of haustorial formation is the swelling of root cortical cells which gives rise to a nearly spherical structure. Eventually, the haustorial epidermis is obliterated at the contact surface between parasite and host. The upper haustorium has a complex internal structure consisting of several distinct cell zones. The pericycle gives rise to a parenchymatous zone of cells adjacent to the plate xylem. Later, collenchyma differentiates in the center or core of the haustorium and is surrounded by a cortical zone of parenchyma cells. This is the first report of collenchyma tissue in a haustorium of any parasite. Thus, a mature Castilleja haustorium consists of a plate xylem zone, an adjacent parenchymatous zone, a centrally located collenchyma zone, and a peripheral cortical zone. The endophyte is initiated from hypodermal parenchymatous cells located between the collenchyma core and the haustorial surface. Lipid is abundant in the young endophyte and paramural bodies are common in many cells. Strands of vessel members differentiate at random and are sheathed by thin-walled densely cytoplasmic cells. Vessel members occur within the collenchyma zone as well, and frequently contain starch and other coarsely granular materials. No phloem was found in the upper haustorium of Castilleja. The upper haustorium of Castilleja and of other members of the Scrophulariaceae are compared.

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