Eleocharis sphacelata (Cyperaceae) is a common emergent hydrophyte in wetlands throughout Austral... more Eleocharis sphacelata (Cyperaceae) is a common emergent hydrophyte in wetlands throughout Australasia, and is notable as a particularly large member of its genus, able to grow in water up to 2 m deep (Sainty & Jacobs 1981). It is a perennial species, supporting live emergent shoots throughout the year, and grows only on flooded sediments. In Australia, the water temperature in E. sphacelata wetlands remains mild in winter (c. 6°C) but is high (25–30°C) during summer (Brix et al. 1992; Sorrell & Boon 1992). In this paper we present an analysis of the mechanisms of internal ventilation in this species and their ability to aerate the submerged tissue.
Abstract Hybrid Napier grass (Pennisetum purpureum Schumach × P. americanum (L.) Leeke cv. Pakcho... more Abstract Hybrid Napier grass (Pennisetum purpureum Schumach × P. americanum (L.) Leeke cv. Pakchong1) is a candidate species for use as a bio-energy crop in plant-based water treatment systems due to its high growth and biomass production rate, ease of propagation and harvesting, and the quality of the biomass. We conducted a 2 × 3 factorial mesocosm experiment with two levels of inorganic N (100 μM and 1000 μM) and 3 water levels (0, 10 and 20 cm depth) and monitored the plant responses in terms of growth and biomass allocation, root morphology and leaf pigment concentrations to assess how hybrid Napier grass responds to a combination of flooding and high N concentrations. Under non-flooded but saturated soil conditions, hybrid Napier grass grew well at both N concentrations, but the tissue contents of minerals and nutrients were higher when plants grew at high N concentration. At 20 cm water depth and at the low N concentration, hybrid Napier grass acclimated to the flooded conditions by producing 2.5 times longer adventitious roots from the stem nodes and containing 3 times more lysigeneous aerenchyma compared to the plants grown at non-flooded conditions. At the high N concentration, hybrid Napier grass was not able to acclimate to the flooded conditions and had chlorotic leaves and reduced growth. Hybrid Napier grass can grow both under water-saturated and flooded soil conditions (up to 20 cm water depth) while maintaining high biomass production. If N concentrations are moderate (
summaryThe ability of diffusive gas transport and pressurized, convective flow to satisfy interna... more summaryThe ability of diffusive gas transport and pressurized, convective flow to satisfy internal oxygen demands was examined for an aquatic sedge, Eleocharis sphacelata R. Br. Resistances to convection and diffusion through the plant were quantified from anatomical studies of the airspace dimensions, and these were used in mathematical models to calculate the fluxes required to satisfy oxygen demands measured in the tissue. The greatest resistance to diffusion in the underwater tissue was the submerged culm between the waterline and sediment surface (1560 Ms m−3 per m culm length). Resistances of the nodal intercalary meristem (52 Ms m−3) and rhizome internode (34 Ms m−3) were minor. In contrast, resistances to convection were low in the culms (38 MPa s m−3 per m culm length), and higher in the nodal meristems (93 MPa s m−3). The rhizome internodes had large cortical canals with a low convective resistance (0.75 MPa s m−3), and a parallel spongy pith with a very high resistance (518 MPa s m−3) that is probably short‐circuited by convection. The resistance of the submerged culm means that diffusion is inadequate to satisfy oxygen demands in plants growing in >10 cm of water, and that convection is therefore essential in the natural habitat of this species (water to c. 2 m depth). However, a convective oxygen influx as low as 28 × 10−8 mol s−1 per culm (equivalent to a gas flow rate of 3 μl s−1 per culm) could satisfy the entire oxygen demand of the underwater tissue; this value is well below actual rates. At this flow rate, the spongy pith in the rhizome would also remain aerobic: it has a low resistance to diffusion (73 Ms m−3) and could receive sufficient oxygen by diffusion from the node. The data agree well with previous empirical measurements of convection in this species and show that diffusion and convection are both important processes for its aeration.
1. Growth, photosynthesis and root adenine nucleotides were compared in two wetland plants, Phala... more 1. Growth, photosynthesis and root adenine nucleotides were compared in two wetland plants, Phalaris arundinacea and Glyceria maxima, grown in aerated, de-oxygenated or reduced (redox potential = -250 mV) nutrient ... Key-words: Adenylates, anoxia tolerance, aquatic, ...
... to the root-zone concept has gained important information about swamp plants, soil quality an... more ... to the root-zone concept has gained important information about swamp plants, soil quality and key processes in the removal of polluting agents in wastewater. ... prerequisite for future improvement in designing constructed wetlands with better treatment performance. ...
Eleocharis sphacelata (Cyperaceae) is a common emergent hydrophyte in wetlands throughout Austral... more Eleocharis sphacelata (Cyperaceae) is a common emergent hydrophyte in wetlands throughout Australasia, and is notable as a particularly large member of its genus, able to grow in water up to 2 m deep (Sainty & Jacobs 1981). It is a perennial species, supporting live emergent shoots throughout the year, and grows only on flooded sediments. In Australia, the water temperature in E. sphacelata wetlands remains mild in winter (c. 6°C) but is high (25–30°C) during summer (Brix et al. 1992; Sorrell & Boon 1992). In this paper we present an analysis of the mechanisms of internal ventilation in this species and their ability to aerate the submerged tissue.
Abstract Hybrid Napier grass (Pennisetum purpureum Schumach × P. americanum (L.) Leeke cv. Pakcho... more Abstract Hybrid Napier grass (Pennisetum purpureum Schumach × P. americanum (L.) Leeke cv. Pakchong1) is a candidate species for use as a bio-energy crop in plant-based water treatment systems due to its high growth and biomass production rate, ease of propagation and harvesting, and the quality of the biomass. We conducted a 2 × 3 factorial mesocosm experiment with two levels of inorganic N (100 μM and 1000 μM) and 3 water levels (0, 10 and 20 cm depth) and monitored the plant responses in terms of growth and biomass allocation, root morphology and leaf pigment concentrations to assess how hybrid Napier grass responds to a combination of flooding and high N concentrations. Under non-flooded but saturated soil conditions, hybrid Napier grass grew well at both N concentrations, but the tissue contents of minerals and nutrients were higher when plants grew at high N concentration. At 20 cm water depth and at the low N concentration, hybrid Napier grass acclimated to the flooded conditions by producing 2.5 times longer adventitious roots from the stem nodes and containing 3 times more lysigeneous aerenchyma compared to the plants grown at non-flooded conditions. At the high N concentration, hybrid Napier grass was not able to acclimate to the flooded conditions and had chlorotic leaves and reduced growth. Hybrid Napier grass can grow both under water-saturated and flooded soil conditions (up to 20 cm water depth) while maintaining high biomass production. If N concentrations are moderate (
summaryThe ability of diffusive gas transport and pressurized, convective flow to satisfy interna... more summaryThe ability of diffusive gas transport and pressurized, convective flow to satisfy internal oxygen demands was examined for an aquatic sedge, Eleocharis sphacelata R. Br. Resistances to convection and diffusion through the plant were quantified from anatomical studies of the airspace dimensions, and these were used in mathematical models to calculate the fluxes required to satisfy oxygen demands measured in the tissue. The greatest resistance to diffusion in the underwater tissue was the submerged culm between the waterline and sediment surface (1560 Ms m−3 per m culm length). Resistances of the nodal intercalary meristem (52 Ms m−3) and rhizome internode (34 Ms m−3) were minor. In contrast, resistances to convection were low in the culms (38 MPa s m−3 per m culm length), and higher in the nodal meristems (93 MPa s m−3). The rhizome internodes had large cortical canals with a low convective resistance (0.75 MPa s m−3), and a parallel spongy pith with a very high resistance (518 MPa s m−3) that is probably short‐circuited by convection. The resistance of the submerged culm means that diffusion is inadequate to satisfy oxygen demands in plants growing in >10 cm of water, and that convection is therefore essential in the natural habitat of this species (water to c. 2 m depth). However, a convective oxygen influx as low as 28 × 10−8 mol s−1 per culm (equivalent to a gas flow rate of 3 μl s−1 per culm) could satisfy the entire oxygen demand of the underwater tissue; this value is well below actual rates. At this flow rate, the spongy pith in the rhizome would also remain aerobic: it has a low resistance to diffusion (73 Ms m−3) and could receive sufficient oxygen by diffusion from the node. The data agree well with previous empirical measurements of convection in this species and show that diffusion and convection are both important processes for its aeration.
1. Growth, photosynthesis and root adenine nucleotides were compared in two wetland plants, Phala... more 1. Growth, photosynthesis and root adenine nucleotides were compared in two wetland plants, Phalaris arundinacea and Glyceria maxima, grown in aerated, de-oxygenated or reduced (redox potential = -250 mV) nutrient ... Key-words: Adenylates, anoxia tolerance, aquatic, ...
... to the root-zone concept has gained important information about swamp plants, soil quality an... more ... to the root-zone concept has gained important information about swamp plants, soil quality and key processes in the removal of polluting agents in wastewater. ... prerequisite for future improvement in designing constructed wetlands with better treatment performance. ...
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Papers by Hans Brix