The Effects of Anoxia and Carbohydrates on the Growth and Viability of Rice, Pea and Pumpkin Roots

Webb, T.; Armstrong, W.

doi:10.1093/jxb/34.5.579

Cited by 121 publications

(70 citation statements)

References 37 publications

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Section: Resultsmentioning

confidence: 99%

“…Excised roots which are exposed to anaerobic conditions decrease in sugar content over time (20,28). The addition of glucose to either excised or attached roots enhance root viability (28). Additionally, the capacity which some roots have for the enhanced catabolism of starch grains, during flooding, suggests there is a shortage of available sugar in 02-stressed roots (18).…”

Section: Resultsmentioning

confidence: 99%

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Carbon Transport and Root Respiration of Split Root Systems of Phaseolus vulgaris Subjected to Short Term Localized Anoxia

Schumacher

Smucker²

1985

Plant Physiol.

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The influence of anoxia on carbon transport and root respiration was evaluated by applying [U-"Clsucrose to the foliage. Translocation patterns to the root systems of two dry edible bean genotypes (Phascolus vwlgaris L.) were examined after a 3-day exposure to aerated and nonaerated environments. Localized anoxia of root systems was simulated by growing roots in split configurations and exposing half of the system to anoxic conditions. Anoxia of the root system for 72 hours reduced the movement of "C label into the roots with concurrent accumulations in the hypocotyl region. The translocation of "C label to anoxic roots was less than 50% of the aerated controls of both genotypes. Most of the "C label translocated to anoxic root systems was excluded from respiratory metabolism during the 3-hour pulse/chase period and was an order of magnitude less than the aerated controls. These observations suggest that the bulk of "C label which entered the root during the anoxic period was unavailable for metabolism by the enzymes of glycolysis and/or was diluted by a relatively large metabolite pool. A higher percentage of "C label was translocated to the aerated half ofthe localized anoxia treatment relative to the half of the aerated controls. The proportion of "C label translocated to the root system in the aerated control was 20 and 16% compared to 28 and 25% in the aerated localized anoxia treatment for the genotypes Seafarer and line 31908, respectively. Line 31908 partitioned a greater percentage of "IC-labeled compounds to the actively growing fraction of the root system in the localized anoxia treatment than did Seafarer. This suggests a greater reliance on previously stored carbohydrate for immediate root growth in Seafarer than in line 31908.Root systems growing in heterogeneous soil environments may be exposed to both aerobic and anaerobic conditions (3). Several studies have demonstrated compensatory growth in nonstressed areas of the root environment when portions of a root system were subjected to anoxic conditions (2,23,27). In a previous study, we reported phenotypic differences in the growth patterns of dry edible bean root systems subjected to localized anoxia (23 necessarily reflect translocation patterns occurring at the conclusion of the treatment period, short term '4C labeling experiments were used to provide information on the pattern of carbon translocation within the plant at a particular point in time. Although a number of short term "1C labeling studies have been conducted on flooded plants (10,(14)(15)(16)26), there have been no reported measurements of the isotope losses to the root environment through exudation or respiration during the labeling period. Objectives of this study were: (a) to determine the translocation patterns for two dry edible bean genotypes whose root systems were subjected to short term (72 h) nonaerated, and localized anoxia treatments; and (b) to account for losses of 14C label within the root environment during the labeling period.MATERIALS AND METHODS Plant Cul...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Carbon Transport and Root Respiration of Split Root Systems of Phaseolus vulgaris Subjected to Short Term Localized Anoxia

Schumacher

Smucker²

1985

Plant Physiol.

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“…Submerged roots become dependent upon gas-phase transport from the shoot/atmosphere through the ground-tissue gas space of shoot and root. Such transport is essential to sustain root growth and root-tip viability in anaerobic media (Webb & Armstrong, 1983). Its effectiveness is dependent upon the physical resistance to diffusion and the oxygen demand along the diffusion path.…”

Section: + + I ++ Imentioning

confidence: 99%

The Anatomical Characteristics of Roots and Plant Response to Soil Flooding

1987

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SUMMARYNinety-one plant species from wetland (WL), intermediate (INT) and non-wetland (NWL) habitats were grown in flooded and drained soils and responses to flooding were assessed in relation to root anatomy and fractional root porosity (FRP).Flooding response and tolerance were related to FRP. Rooting depth increased with FRP in accordance with diffusion model predictions and emphasized the ventilating efliciency of aerenchyma. Major determinants of FRP were cortical cell conflgurations, closeness of cell packing, the relative proportions of conflguration types, porous: non-porous tissue ratios, aerenchyma development and the type and degree of secondary growth. A classification of cortical types based on cell and aerenchyma patterns is presented.Aerenchyma, both schizogenous and lysigenous, developed preferentially where preaerenchymatous cortical cell configurations (in TS) were radial and particularly, cubic and radial typical of WL and INT species. Aerenchyma rarely formed from hexagonal non-radial arrays which occur chiefly in NWL and in the outer cortical zones of WL and INT plants. The ventilating potential in non-aerenchymatous tissue was shown to be greater for cubic (fractional porosity, FP, max. 0-2146) than for hexagonal arrays (FP max. 0-0931); closer packing greatly accentuated the differences. It is suggested that cubic: hexagonal zonal ratios in roots may reflect a balance between respiratory and mechanical needs.In a majority of WL and INT species, shoot weights were unaffected by or increased with flooding and maximum rooting depths usually much exceeded 50 mm. Cubic packing raised the FRPs, as did aerenchyma which was often much greater under flooding. In the dicotyledonous species, a suppression of secondary growth in some, and a highly porous phelloderm in others, helped maintain high FRP. A minority of species were anatomically and responsively similar to NWL plants; survival under flooding was attributed to shallow rooting.Under flooding, the FRP of almost all NWL species was < 0-055 due to hexagonal packing, a lack of aerenchyma and, in dicotyledonous plants, secondary growth with scanty phelloderm. Shoot weights were reduced in 50 % of cases, rooting depths were < 50 mm, and some species died. Some species were exceptional in having cubic and radial packings; a lack of aerenchyma was associated with continuing meristematic activity in the primary cortex.

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“…If oxygen remains available to sustain the unloading of sugars, a normal functioning of the phloem might help sustain not only the substrate demands of aerobic cortical respiration but also the requirements of anaerobic respiration in the anoxic parts of the stele and meristem. In this connection, it should be noted that there is considerable evidence that root-tip death occurs only when there is anoxia throughout the root apex, and that a trace of oxygen in the cortex is sufficient to ensure continuing viability (Webb & Armstrong, 1983;Armstrong & Webb, 1985). An aerated pericycle should help sustain the important meristematic function of this zone.…”

Section: Final Comments and Discussionmentioning

confidence: 99%

Internal Aeration and Development of Stela Anoxia in Submerged Roots

1987

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SUMMARYA case is presented for progressing from mathematical models of root aeration which assume complete radial homogeneity in respiratory demand and oxygen diffusivity to models which accommodate radial differences between the various tissue cylinders. The described model simulates aeration in submerged roots and allows for axial gas-phase diffusion in the cortex and radial liquid-phase diffusion elsewhere. It also accommodates diffusion into the rhizosphere and axial and radial differences in the root's properties on a tissue cylinder basis.The results, based on the characteristics of aerenchymatous graminean roots, highlight the potential for stelar anoxia and some wall-layer anoxia in submerged, and even non-submerged, roots. They show that, (1) stelar anoxia should raise oxygen levels elsewhere and enhance root extension; (2) with high and constant oxygen diffusivity in the stele, anoxia should first occur close to the apex and spread basally and laterally with further root extension; (3) there will be competition between the oxygen demands of the root and rhizosphere; (4) extension may be reduced by radial oxygen losses into the rhizosphere, but the subapical decline in root-wall permeability in wetland species safeguards against this effect; (5) differences in critical oxygen pressure for extension growth (COPE) and respiration (COPR) may arise; and (6) survival may be helped by the manner in which anoxia spreads with aerobic conditions persisting in the phloem and pericycle until only traces of oxygen remain in the cortex. Sectional profiles of the roots show how oxygen gradients in the stele and wall layers will increase with increasing subapical impedance in these zones and, in the case of the wall layers, by oxygen throughflux to the rhizosphere.Some of the results suggest that inner-stele anoxia might account for some of the hypoxic responses found in roots, and it is predicted that declining stelar oxygen diffusivity in subapical regions will raise COPR but not COPE, the inner-stele becoming anoxic subapically and the apical regions remaining wholly aerobic. This implies the possibility that where roots are described in the literature as hypoxic, because of ethanol production, raised alcohol dehydrogenase activity and reduced energy charge, the symptoms may be sometimes indicative only of some subapical stelar anoxia.The results also serve to illustrate how variable the occurrence and shape of anoxic stelar zones might be. With only a slight alteration in subapical stelar oxygen diffusivity, anoxia could arise simultaneously in two positions along the root, or the first site of anoxia in the growing root might be both subapical and hypobasal. The likelihood of the endodermis in subapical parts being a possible cause of anoxia in roots is also considered.

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The Effects of Anoxia and Carbohydrates on the Growth and Viability of Rice, Pea and Pumpkin Roots

Cited by 121 publications

References 37 publications

Carbon Transport and Root Respiration of Split Root Systems of Phaseolus vulgaris Subjected to Short Term Localized Anoxia

Carbon Transport and Root Respiration of Split Root Systems of Phaseolus vulgaris Subjected to Short Term Localized Anoxia

The Anatomical Characteristics of Roots and Plant Response to Soil Flooding

Internal Aeration and Development of Stela Anoxia in Submerged Roots

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