Alcohol Dehydrogenase Activity In Roots Research Articles

Physiological relationship between oil tolerance and flooding tolerance in marsh plants

Coastal salt marshes are highly susceptible to accidental oil spills. Oil can cover root tissues, inhibiting gas exchange and increasing root oxygen stress. This is similar to flooding; both conditions reduce the availability of oxygen to a plant. Therefore, it was hypothesized that tolerance to both flooding and oil are related in plants, as both impede gas exchange between roots and their environment. We investigated effects of oil on respiration and photosynthesis in nine marsh species ranging from flooding sensitive (hypothesized oil sensitive) to flooding tolerant (hypothesized oil tolerant). Plants were subjected to 6Lm−2 light motor oil in greenhouse experiments for six weeks. Oil exposure caused root oxygen deficiency in all but the most flooding tolerant species. Alcohol dehydrogenase activities increased in roots of flooding sensitive species and moderately flooding tolerant plants under oil exposure, indicating oxygen stress. In contrast, flooding tolerant plants showed no sign of oxygen deficiency under oil treatment. Additionally, decreases in photosynthetic rates were measured in some species following oil exposure. Photosynthesis was reduced by non-stomatal limitations, suggesting toxic effects of oil. It was concluded that tolerance to oil relates to flooding tolerance when measured in terms of biochemical enzyme activity. Root alcohol dehydrogenase activity was a sensitive indicator of oil susceptibility, whereas leaf-level photosynthesis was less sensitive to oil. Relating flooding and oil tolerance based on physiological measures could help future efforts to protect marsh plants prior to an oil spill as well as manage coastal marshes following an oil spill.

Effects of flooding on photosynthesis and root respiration in saltcedar (Tamarix ramosissima), an invasive riparian shrub

The introduced shrub Tamarix ramosissima invades riparian zones, but loses competitiveness under flooding. Metabolic effects of flooding could be important for T. ramosissima, but have not been previously investigated. Photosynthesis rates, stomatal conductance, internal (intercellular) CO2, transpiration, and root alcohol dehydrogenase (ADH) activity were compared in T. ramosissima across soil types and under drained and flooded conditions in a greenhouse. Photosynthesis at 1500μmolquantam−2s−1 (A1500) in flooded plants ranged from 2.3 to 6.2μmolCO2m−2s−1 during the first week, but A1500 increased to 6.4–12.7μmolCO2m−2s−1 by the third week of flooding. Stomatal conductance (gs) at 1500μmolquantam−2s−1 also decreased initially during flooding, where gs was 0.018 to 0.099mol H2O m−2 s−1 during the first week, but gs increased to 0.113–0.248molH2Om−2s−1 by the third week of flooding. However, photosynthesis in flooded plants was reduced by non-stomatal limitations, and subsequent increases indicate metabolic acclimation to flooding. Root ADH activities were higher in flooded plants compared to drained plants, indicating oxygen stress. Lower photosynthesis and greater oxygen stress could account for the susceptibility of T. ramosissima at the onset of flooding. Soil type had no effect on photosynthesis or on root ADH activity. In the field, stomatal conductance, leaf water potential, transpiration, and leaf δ13C were compared between T. ramosissima and other flooded species. T. ramosissima had lower stomatal conductance and water potential compared to Populus deltoides and Phragmites australis. Differences in physiological responses for T. ramosissima could become important for ecological concerns.

Stress responses of spring rape plants to soil flooding

Abstract Stress responses of spring rape to soil hypoxia were investigated during 8-days flooding. Soil air-filled porosity decreased from 25-30% to 0%, oxygen diffusion rate - from 2.6-3.5 to 0.34 μmol O2 m-2 s-1, and redox potential - from 460 to 150mVwithin few hours. Alcohol dehydrogenase activity in roots increased up to 7-fold after one day of flooding and then decreased to 170% of control. Superoxide dismutase activity in roots increased by 27% during first 3 days and then dropped to 60% of control; in the leaves superoxide dismutase activity increased in average by 44%. Ascorbate peroxidase activity in leaves increased by 37% during first 3 days and then decreased to control value. Glutathione reductase activity increased by 45% in roots of flooded plants but did not change in leaves. Proline concentration in leaves increased up to 4-fold on the 3d day of flooding and then decreased to control value. Thus soil flooding induces increase of alcohol dehydrogenase activity and subsequent increase of superoxide dismutase and glutathione reductase activities in roots while the leaves display a few days increase of free proline concentration and ascorbate peroxidase activity, and a long-term increase of superoxide dismutase activity.

SEPARATING THE EFFECTS OF PARTIAL SUBMERGENCE AND SOIL OXYGEN DEMAND ON PLANT PHYSIOLOGY

In wetlands, a distinct zonation of plant species composition occurs along moisture gradients, due to differential flooding tolerance of the species involved. However, "flooding" comprises two important, distinct stressors (soil oxygen demand [SOD] and partial submergence) that affect plant survival and growth. To investigate how these two flooding stressors affect plant performance, we executed a factorial experiment (water depth x SOD) for six plant species of nutrient-rich and nutrient-poor conditions, occurring along a moisture gradient in Dutch dune slacks. Physiological, growth, and biomass responses to changed oxygen availability were quantified for all species. The responses were consistent with field zonation, but the two stressors affected species differently. Increased SOD increased root oxygen deprivation, as indicated by either raised porosity or increased alcohol dehydrogenase (ADH) activity in roots of flood-intolerant species (Calamagrostis epigejos and Carex arenaria). While SOD affected root functioning, partial submergence tended more to reduce photosynthesis (as shown both by gas exchange and 13C assimilation), leaf dark respiration, 13C partitioning from shoots to roots, and growth of these species. These processes were especially affected if the root oxygen supply was depleted by a combination of flooding and increased SOD. In contrast, the most flood-tolerant species (Juncus subnodulosus and Typha latifolia) were unaffected by any treatment and maintained high internal oxygen concentrations at the shoot : root junction and low root ADH activity in all treatments. For these species, the internal oxygen transport capacity was well in excess of what was needed to maintain aerobic metabolism across all treatments, although there was some evidence for effects of SOD on their nitrogen partitioning (as indicated by 865N values) and photosynthesis. Two species intermediate in flooding tolerance (Carex nigra and Schoenus nigricans) responded more idiosyncratically, with different parameters responding to different treatments. These results show that partial submergence and soil flooding are two very different stressors to which species respond in different ways, and that their effects on physiology, survival, and growth are interactive. Understanding species zonation with water regimes can be improved by a better appreciation of how these factors affect plant metabolism independently and interactively.

Fate of oxygen losses from Typha domingensis (Typhaceae) and Cladium jamaicense (Cyperaceae) and consequences for root metabolism

The objective of this work was to determine whether radial oxygen loss (ROL) from roots of Typha domingensis and Cladium jamaicense creates an internal oxygen deficiency or, conversely, indicates adequate internal aeration and leakage of excess oxygen to the rhizosphere. Methylene blue in agar was used to visualize the pattern of ROL from roots, and oxidation of a titanium-citrate solution was used to quantify rates of oxygen leakage. Typha's roots had a higher porosity than Cladium's and responded to flooding treatment by increasing cortical air space, particularly near the root tips. A greater oxygen release, which occurred along the subapical root axis, and an increase in rhizosphere redox potential (E(h)) over time were associated with the well-developed aerenchyma system in Typha. Typha roots, regardless of oxygen release pattern, showed low or undetectable alcohol dehydrogenase (ADH) activity or ethanol concentrations, indicating that ROL did not cause internal deficiencies. Cladium roots also released oxygen, but this loss primarily occurred at the root tips and was accompanied by increased root ADH activity and ethanol concentrations. These results support the hypothesis that oxygen release by Cladium is accompanied by internal deficiencies of oxygen sufficient to stimulate alcoholic fermentation and helps explain Cladium's lesser flood tolerance in comparison with Typha.

Changes in soluble sugar, starch, and alcohol dehydrogenase in Arabidopsis thaliana exposed to N2 diluted atmospheres.

Proper exchange of atmospheric gases is important for normal root and shoot metabolism in plants. This study was conducted to determine how restricted air supply affects foliar carbohydrates, while using the marker enzyme alcohol dehydrogenase (ADH) to report on the oxygenation status of the rootzone. Fourteen-day-old Arabidopsis thaliana (L.) Heynh. plants grown singly in 7-ml tubes containing agarified nutrient medium were placed in coupled Magenta vessels and exposed for six days to either ambient air or one of six different air/nitrogen dilutions. Redox potential of the agar medium was measured immediately after harvesting and freezing leaf tissue, and then root systems were quickly extracted from the agar and frozen for subsequent analyses. Redox potential measurements indicated that this series of gas mixtures produced a transition from hypoxia to anoxia in the root zones. Root ADH activity increased at higher rates as the redox potential neared anoxic levels. In contrast, ADH mRNA expression quickly neared its maximum as the medium became hypoxic and showed little further increase as it became anoxic. Foliar carbohydrate levels increased 1.5- to 2-fold with decreased availability of metabolic gases, with starch increasing at higher concentrations of air than soluble carbohydrate. The results serve as a model for plant performance under microgravity conditions, where absence of convective air movement prevents replenishment of metabolic gases.

Leaf gas exchange and growth of flood-tolerant and flood-sensitive tree species under low soil redox conditions.

Seedlings of Taxodium distichum L., Quercus lyrata Walt. and Q. falcata var. pagodaefolia Ell. were grown for 22 days in a rhizotron system providing two soil redox potential regimes, +170 mV (low Eh) and +560 mV (high Eh). Leaf chlorophyll concentration and gas exchange, root alcohol dehydrogenase (ADH) activity, root and leaf ethylene production, and growth and biomass partitioning were measured. In response to the low Eh soil treatment, stomatal conductance was reduced in Q. falcata and Q. lyrata but not in T. distichum, whereas net photosynthesis was reduced significantly in all species; however, net photosynthesis in T. distichum began to recover within 2 weeks of treatment initiation. Within each treatment, mean stomatal conductance and net photosynthesis were significantly greater in T. distichum than in the oak species. Leaf chlorophyll concentration was not affected by the soil treatments. All species showed significant reductions in root and leaf dry weights in response to the low Eh soil condition. The low Eh soil treatment resulted in increased root ADH activity and ethylene production in T. distichum, but had no effect on root ADH activity and ethylene production in the oak species.

Mechanism for the hydrogen sulfide‐induced growth limitation in wetland macrophytes

Hydrogen sulfide, a phytotoxin that often accumulates in anoxic marine and freshwater marsh soils, suppressed the activity of alcohol dehydrogenase (ADH), the enzyme that catalyzes the terminal step in alcoholic fermentation, in the roots of two wetland macrophytes. This inhibition of root ADH activity with increasing sulfide concentration was associated with decreases in root total adenine nucleotide pool (ATP + ADP + AMP), the adenylate energy charge ratio (AEC), nitrogen uptake (percent recovery of 15NH4+‐N) and growth (leaf elongation). These responses were species‐specific with a greater negative impact in the freshwater marsh species that naturally inhabits low‐sulfide environments. These findings lend support to the hypotheses that ADH activity, as a measure of fermentative metabolism, is important in maintaining the root energy status of wetland plants under hypoxic‐anoxic conditions, that there is a significant negative effect of H2S on the anoxic production of energy in these roots, and that an important negative effect of H2S on plant growth is an inhibition of the energy‐dependent process of N uptake.

Relationship Between Anatomical and Metabolic Responses to Soil Waterlogging in the Coastal GrassSpartina patens

Flooding responses in Spartina patens propagated from plants collected in dune, swale, and marsh habitats were examined in a 63 d time-course experiment. Leaf growth rates and anatomical and metabolic responses did not depend upon plant population, suggesting that there were no physiologically significant differences in soil waterlogging responses among source populations. Flooding resulted in significant declines in soil redox potential and root specific gravity (indicating increased root aeration). Root alcohol dehydrogenase activity (ADH, a measure of the capacity to ferment ethanol) increased within 3 d of flooding, then exhibited a significant decline as root aeration increased (i.e. as root specific gravity decreased). However, maximal aerenchyma development (50% of the root volume after 29 d) reduced but did not eliminate hypoxic stress in the roots. When plants that were flooded for 63 d were drained, ADH activity fell to levels equivalent to drained controls. These results support the following inferences: (1) Soil waterlogging dramatically increases root ADH activity. (2) Impact of soil waterlogging on root metabolism diminishes once internal root aeration increases. (3) Under severe chemically-reducing soil conditions, root aerenchyma formation, which adjusts to the prevalent degree of soil waterlogging, cannot provide roots with sufficient oxygen to support aerobic respiration completely.

Hypoxic Induction of Anoxia Tolerance in Root Tips of Zea mays

When root tips of fully aerobic, intact maize (Zea mays L.) seedlings are made anaerobic, viability normally is only 24 hours or less at 25 degrees C. We find that viability can be extended to at least 96 hours if seedlings are given a hypoxic pretreatment for 18 hours by sparging the solution with 4% O(2) in nitrogen (v/v) before anoxia. Fully aerobic root tips (sparged with 40% O(2)) had very low alcohol dehydrogenase (ADH) activity (per gram root fresh weight), and the level remained low under anoxia. In hypoxically pretreated roots, however, high levels of ADH activity were induced, and activity rose further during the initial 24 hours of anoxia, and then remained high at about 20 times that of controls in 40% O(2). ADH activity in roots in solution sparged with air (21% O(2)) was about three times that in 40% O(2). Improved viability of hypoxically pretreated root tips was associated with maintenance of a high energy metabolism (ATP concentration, total adenylates, and adenylate energy charge). Roots that were not pretreated lost 94% of the total adenylates and ATP at 24 hours of anoxia. The relation between induced ADH activity, energy metabolism, and improved anoxia-tolerance in acclimated maize root tips is discussed.

Effect of Zinc Deficiency on Alcohol Dehydrogenase Activity and Nutrient Uptake in Rice

AbstractZinc deficiency in rice (Oryza sativa) usually occurs after flooding. A greenhouse experiment was conducted to determine if the metabolic disorders associated with Zn deficiency in flooded rice are due to decreases in alcohol dehydrogenase (ADH) or glutamate dehydrogenase (GDH) activities, or both, in the roots, since Zn is a cofactor in these enzymes. ‘Saturn’ rice, a variety characterized as being susceptible to Zn deficiency, was grown in 20 pots containing 3 kg of Crowley silt loam soil (fine, montmorillonitic, thermic Typic Albaqualf). Half of the pots received 1 mg Zn/kg as ZnEDTA; the other half served as controls. Five days after flooding the control plants showed signs of Zn deficiency. The plants were harvested 17 d after flooding. Aboveground dry matter production by the fertilized plants (x̄=0.91 g) was significantly greater than that of the Zn‐deficient control plants (x̄=0.24 g). Plant tissue analysis revealed that Zn‐deficient plants accumulated divalent cations at the expense of monovalent cations, possibly indicating the increased production of a divalent charge‐specific carrier. Root GDH activities of the control and fertilized plants were not significantly different. However, ADH activities in the roots of plants that had received Zn were more than twice as high as those in control plants. Root ADH activity was also correlated with Zn concentration in the leaves (r=0.78**). It is hypothesized that decreases in the ADH activity of Zn‐deficient flooded rice result in less ATP production, thereby reducing vital metabolic activities of the roots.

Spartina Alterniflora Die-Back in Louisiana: Time-Course Investigation of Soil Waterlogging Effects

SUMMARY (1) Transplantation of streamside Spartina alterniflora swards into the more waterlogged and less productive inland marsh caused rapid decreases in soil redox potential and increases in interstitial water sulphide and NH4 concentrations and root alcohol dehydrogenase activity. (2) One year later, standing crops in these transplanted swards were significantly reduced compared to their streamside controls. (3) Reciprocal transplantation from inland to streamside resulted in the amelioration of the detrimental conditions associated with the waterlogged inland marsh and in an increase in standing crop to levels equivalent to streamside controls. (4) Soil salinity and pH were not significant factors in causing reduced growth of S. alterniflora. (5) Sulphide toxicity, in combination with extended periods of anaerobic metabolism in the roots, appeared to be a major factor associated with reduced growth of S. alterniflora and may be a cause of dieback in these marshes.

Alcohol dehydrogenase activity in the roots of marsh plants in naturally waterlogged soils

The aim of this work was to discover whether oxygen tensions in the roots of marsh plants in flooded soils are high enough to allow fully acrobic metabolism. Activity of alcohol dehydrogenase (ADH), a protein synthesised in anoxic plants, was measured in roots of marsh plants growing in habitats where the availability of oxygen to the roots would be expected to differ. Roots of Carex riparia in standing water had ADH activities about 2.5 times higher than those of phosphofructokinase, and comparable to ADH activities of Poa trivialis, Urtica dioica and Ranunculus repens roots in dry soil. Removal of the oxygen supply via aerenchyma to Carex roots caused a 30-fold increase in ADH activity relative to that of phosphofructokinase. There was no change in ADH activity with depth in Carex roots in waterlogged soil, but in Filipendula ulmaria roots activity was 14 times higher below 10 cm depth than near the surface. Urtica roots in waterlogged soil had alcohol dehydrogenase activities 26 times higher than roots in dry soil, but for Poa and Ranunculus roots this figure was only 1.7 and 4.2, respectively. These results indicate that the oxygen tensions in the roots of marsh plants in waterlogged soil differ considerably among species. Ethanol was the major product of fermentation in roots of all species studied. There was no correlation between ADH activity and the rate of ethanol production under anoxia of Urtica roots. The physiological significance of high ADH activities in roots is thus unclear.

Effect of flooding on activities of soil dehydrogenases and alcohol dehydrogenase in rice (Oryza SativaL.) Roots

Dehydrogenase activity and redox potential were monitored over a period of 100 days in flooded and drained soils in which rice was grown. The activity of the enzyme alcohol dehydrogenase (ADH) was measured in the roots of the rice plants. The immediate decrease in soil redox potential and rapid increase in soil dehydrogenase activity upon flooding indicated a shift of microflora from aerobic to predominantly anaerobic microorganisms. Soil dehydrogenase activity remained elevated as long as the soil continued to be flooded, but was negligible in soils allowed free drainage. The rice roots only initially experienced anaerobiosis during flooding. Root ADH activity was stimulated upon flooding but declined by day 47 to levels similar to those measured in plants grown in a drained soil. The development of aerenchyma (air-space) tissue in the continuously flooded plants may have provided a pathway for oxygen movement to the roots which allowed aerobic metabolism to proceed in spite of the reduced amount of subs...