Gas composition and respiration of water oak (Quercus nigra L.) and green ash (Fraxinus pennsylvanica Marsh.) roots after prolonged flooding

Abstract

We compared the effects of 9.5 months of a continuous flooding treatment with a drained control treatment on one year-old seedlings of green ash (Fraxinus pennsylvanica Marsh.) and water oak (Quercus nigra L.), two tree species common to the bottomland-hardwood forests of eastern North America. The internal root gas composition of the more flood tolerant species, green ash, maintained higher oxygen and lower carbon dioxide concentrations under the flooding treatment than water oak. This apparently resulted in differences in rhizosphere oxidation. The amounts of Fe and Mn and the Fe/Mn ratio of the root coating extracted from trees in reduced soil conditions were much higher for the green ash than the water oak. It is argued that this reflects differences in the ability of these two species to maintain rhizosphere oxidation under prolonged periods of flooding and to prevent the accumulation of reduced potentially phytotoxic compounds. Alcohol dehydrogenase activity increased in the green ash and decreased in the water oak in the flooded treatment. This indicated that the better adapted species was able to rely upon increased anaerobic respiration in order to compensate for the decreased root oxygen supply, but the water oak was unable to maintain previous levels of respiration, probably as the result of sulfide toxicity.

Efeitos da inundação no crescimento, trocas gasosas e porosidade radicular da carnaúba (Copernicia prunifera (Mill.) H.E. Moore)

“…A difusão de CO 2 foi menor nas raízes inundadas, o que era esperado, uma vez que a taxa de difusão de gases é mais lenta na água. Resultados semelhantes foram obtidos por Good & Patrick (1987), com raízes de Fraxinus pennsylvanica Marshall, onde a concentração de CO 2 foi 2,4% e a de O 2 20,0% em plantas drenadas e 10,4% e 14,1% respectivamente, em plantas inundadas. A concentração de O 2 , no entanto, não atingiu valores que pudessem resultar em hipoxia, indicando baixa resistência à difusão nas raízes mais grossas, o que foi causado pela alta porosidade (Tab.…”

Review: Mechanisms of anoxia tolerance in plants. I. Growth, survival and anaerobic catabolism

“…For example, in root gas extracted from two tree species that had been flooded for 9.5 months (Quercus nigra and Fraxinus pennsylvanica respectively), partial pressure of CO 2 (pCO 2 ) was about 2-5-fold higher than in drained treatments. In flooded treatments of both species, partial pressure of O 2 (pO 2 ) of root gas was greater than 8% (Good and Patrick 1987), implying flow of O 2 from shoot to root during flooding. Given the likelihood of elevated CO 2 concentrations in roots of plants with shoots in air, adverse effects of high CO 2 might occur in anoxic zones, in zones receiving sufficient O 2 for oxidative phosphorylation, or in both.…”

Soil O2 and CO2 effects on root respiration of cacti

“…In this regard, roots of O. ficus-indica are more tolerant of elevated CO2 than are those of F. acanthodes; 5000/ILL-~ CO2 inhibited respiration of established roots by 46 % for F. acanthodes but by 33-36 % for O.ficus-indica. Yet root respiration of both cacti as well as another CAM plant (Agave deserti; Palta and Nobel, 1989c) was substantially inhibited at 10,000#LL ~ CO2, a soil CO2 concentration that occurs in the rooting zone of many species (Good and Patrick, 1987;Kucera and Kirkham, 1971;Nakayama and Kimball, 1988). Although the restriction to porous, well-drained soils has been attributed to the necessity of maintaining a high 02 concentration for the roots of CAM plants (Cannon, 1911;1925), just as for desert shrubs (Lunt et al, 1973), the present results suggest that this restriction may rather be a consequence of the great sensitivity of the roots to even moderately high soil CO2 concentrations.…”

“…At shallow depths (0.I0 m) in Avondale clay loam in regions without plants, the COs concentration in the air phase of the soil can be about 1000/~LL -I (0.1% by volume; Nakayama and Kimball, 1988). The CO2 concentration in the rooting zone of various plant species is often near 1% (Good and Patrick, 1987;Kucera and Kirkham, 1971;Nakayama and Kimball, 1988), and it can be 5 % in certain clays (Jeffrey, 1987). Although useful for understanding root function, the responses of root respiration to such a range in 05 and CO2 concentrations have received little research attention (Lambers, 1985).…”

“…Oxygen concentrations in the air phase of wellaerated soils are generally about 20 % by volume, but they can be 1% or lower in flooded soils (Good and Patrick, 1987;Smit and Stachowiak, 1988;Trought and Drew, 1980). At shallow depths (0.I0 m) in Avondale clay loam in regions without plants, the COs concentration in the air phase of the soil can be about 1000/~LL -I (0.1% by volume; Nakayama and Kimball, 1988).…”