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KMID : 1024520160250081143
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Journal of the Environmental Sciences
2016 Volume.25 No. 8 p.1143 ~ p.1153
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Growth, Photosynthesis and Zinc Elimination Capacity of a Sorghum-Sudangrass Hybrid under Zinc Stress
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Oh Soon-Ja
Koh Seok-Chan
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Abstract
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Plant biomass, photosystem II (PSII) photochemical activity, photosynthetic function, and zinc (Zn) accumulation were
investigated in a sorghum-sudangrass hybrid (Sorghum bicolor × S. sudanense) exposed to various Zn concentrations to
determine the elimination capacity of Zn from soils. Plant growth and biomass of the sorghum-sudangrass hybrid decreased with increasing Zn concentration. Symptoms of Zn toxicity, i.e., withering and discoloration of old leaves, were found at Zn
concentrations over 800 ppm. PSII photochemical activity, as indicated by the values of Fv/Fm and Fv/Fo, decreased
significantly three days after exposure to Zn concentrations of 800 ppm or more. Photosynthetic CO2 fixation rate (A) was high between Zn concentrations of 100-200 ppm (22.5 μmol CO2?m?2?s?1), but it declined as Zn concentration increased. At Zn concentrations of 800 and 1600 ppm, A was 14.1 and 1.8 μmol CO2?m?2?s?1
, respectively. The patterns of stomatal conductance (gs), transpiration rate (E), and water use efficiency (WUE) were all similar to that of photosynthetic CO2 fixation rate, except for dark respiration (Rd), which showed an opposite pattern. Zn was accumulated in both above- and below-ground parts of plants, but was more in the below-ground parts. Magnesium (Mg) and iron (Fe) concentrations were significantly low in the leaves of plants, and symptoms of Mg or Fe deficiency, such as a decrease in the SPAD value, were found when plants were treated with Zn concentrations above 800 ppm. These results suggest that the sorghum-sudangrass hybrid is able to accumulate Zn to high level in plant body and eliminate it with its rapid growth and high biomass yield.
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KEYWORD
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Biomass, PSII photochemical activity, Photosynthetic CO2 fixation rate, Zinc accumulation, Zn toxicity
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