Concentrations of CO₂ and O₂ in floodwater and in internodal lacunae of floating rice growing at 1–2 metre water depths

Abstract

Environment and plant measurements were made to determine what factors may limit gr-owth of deepwater and floating rice plants dur-ing par-tial or complete submergence. Field surveys included measurements of temperature, pH, light, Oj and CO, in floodwater in Thailand. In addition, measurements were made of Oj and CO, concentrations inside internodal laeunae of deepwater and floating tiee growing at 0.5-2.0 rn water depths.The bulk of measurements wet-e taken during periods when the changes in water level were less than 50 mm d~'. In the 0-0.02 rn surface layer of floodwater at any location there wer-e lar-ge changes in oxygen concentrations over diurnal eyeles: there were decreases during the nighl down to 0,02-0,18 mol m"^ Oj at 0600 h and increases during the day to 0.13-0.28 mol rn~-^ O, at 1500 h (0,28 mol rn"'' being 120% ofthe O, concentration of air satur-ated water at 30 "C). Dur-ing Ihe day oxygen concentrations deereased with inereasing water depth; coneentr-ations just above the soil surface were occasionally zero. Most of this gradient disappear-ed during the night, and at dawn the 0.6 rn surface layer of water had uniform low O, concentr-ations.O2 concentrations were also measured during flash floods in Thailand. In contrast to the conditions with only small inct-eases in water level, the O, eoncentrations in the water during flash floods were more unifor-m with depth and changed little over a diurnal cycle, the O2 ranging between 0.14-0,19 mol rn"-'.In most locations floodwater contained 0.2-1,9 mol m •' CO, and 0.7-1.6 rnol rn"-' bicarbonate; however, in a location with aeid sulphate soil COj was only 0.05 0.2 rnol rn"', and bicarbonate concentrations were several fold lower. Concentrations of COj in floodwater increased with increasing water depth.O2 and CO2 concentrations inside internodal lacunae of riee were determined in the field when waler depth were 12 rn. Concentrations of O2 in internodes at the water surfaee wete 16-20%, and •Present address: Rice Research Inslirure. Deparrnienr of Agriculture, Bangkhen, Bangkok, Thailand 10900.decr-eased to 10% and 5% at 0.8 and 1.8 rn water depth respectively. There was no diurnal cycle in O, concentr-ations inside internodes. In contrast, CO2 concentrations in the lacunae incr-eased with water depth and ranged fr-om 1-3% in internodes at the water sur-face to 5-10% in internodes at 1.8 rn water depth. There was evidence for a diurnal eyele in CO, concentr-ations in the basal internode near the soil surface, CO2 incr-eased during the day and decreased during the night.The above data are used to show that there is little or no r-elationship between gas concentrations in floodwater and internodal lacunae of t-ice plants.Results at-e diseussed in relation to O, supply to subtnerged portions of rice and tnetabolism of" these tissues at low O2 concentrations.

Resistance to complete submergence in Rumex species with different life histories: the influence of plant size and light

“…In rice fields light levels at a depth of 0.5 m can be as low as 1-16% of those above the water (Setter et al, 1987a). The light level in the river Waal at 0.5 m depth is approx.…”

“…1). Most probably, this effect of light on survival is related to photosynthesis under water, which can provide both oxygen (Gaynard & Armstrong, 1987 ;Setter et al, 1987a ;Waters et al, 1989 ;Voesenek et al, 1993) and carbohydrates Clevering et al, 1995). This can lead to increased resistance to prolonged flooding, either by a higher and more efficient production of energy by aerobic respiration with photosynthetically derived oxygen or by the provision of readily respirable carbohydrates.…”

“…The formation of phytotoxic compounds as a result of oxidation of anaerobic metabolites, for instance the production of acetaldehyde by oxidation of ethanol (Monk et al, 1987), might also be involved in post-anoxic injury. It has been shown that oxygen concentrations in the floodwater and in submerged shoots of rice can become very low (Setter et al, 1987a) and there are indications that oxidative stress occurs after submergence in rice (Ushimaru et al, 1992) and maize (Yan et al, 1996), even if the tissues were not completely anoxic during submergence. Moreover, in R. palustris the conversion of ethanol into acetaldehyde takes place if plants are exposed to 21% of oxygen after a period of anoxia (Te Lintel Hekkert et al, 1998).…”

Ethylene-Mediated Acclimations to Flooding Stress

“…The flow of oxygen from the shoot to the root is, in turn, influenced by source to sink strength, tissue porosity, and root respiratory demand. Submerged shoots are surrounded by water that is relatively more oxygen replete , especially upper layers that are in contact with the atmosphere (Setter et al, 1987). Internal oxygen levels in the shoot are determined by light availability, presence of leaf gas films, and leaf traits that facilitate underwater photosynthesis and inward diffusion of oxygen, even under restricted conditions of the aquatic environment (Mommer et al, 2004;Pedersen et al, 2009).…”

1-Aminocyclopropane-1-Carboxylate Oxidase Activity Limits Ethylene Biosynthesis in Rumex palustrisduring Submergence

“…The oxygen concentration is 30 times lower in water than in air (Armstrong et al, 1994), and reduced photosynthesis due to the restricted availability of carbon dioxide and light causes a further decrease (Setter et al, 1987;Stü nzi and Kende, 1989).…”