Abstract
ABSTRACT Two solution studies were conducted a) to investigate the uptake of zinc (Zn) and cadmium (Cd) by rice plants (Oryza sativa L.) and interaction between these elements, and b) to determine experimental conditions for growing rice grain with desired Cd concentration for an animal feeding study. In both studies, free metal activities of cadmium and cationic microelements were buffered by an excess of chelating agents. The first study was a factorial design with two Zn levels (1.0 and 3.89 ÂμM) and four Cd levels (0.81, 1.44, 2.56 and 4.55 ÂμM) in the solution. In the second study, rice was grown in two solutions of different micro- and macro-element compositions and three Cd levels (0.0, 0.5, and 2.0 ÂμM). In the first study, solution Zn concentration of 3.89 ÂμM and corresponding free metal activity (pZn2+) of 6.00 was toxic to young rice plants. With time, Zn concentrations in rice plants decreased while Cd concentrations increased. Toxic concentration of Cd in roots (about 100 mg kg−1) associated with a 20% reduction in the root dry matter occurred at the free Cd2+ activities in the solution (pCd2+) in the range of 10.25–9.75. Sufficient Zn level in plants slightly stimulated Cd transfer from roots to shoots as opposed to barely sufficient or slightly deficient Zn concentration in shoots. However, the better Zn status in plants clearly diminished severity of Cd toxicity symptoms in shoots. The use of nutrient solutions adapted for rice growth allowed the rice grown in the second experiment to produce grain under controlled conditions. Cadmium in the brown rice grain was 0.1 to 0.8 mg kg−1, covering the range needed for feeding experiments relevant to rice Cd risk to humans. Composition of the nutrient solutions, in addition to solution Cd level, had a significant effect on Cd concentration in grain. Correlation of grain Cd concentration with solution Cd2+ activity was much stronger than with total solution Cd. Results of both experiments supported hypothesis that Cd uptake and transport within rice plants is an active process.
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Claims 10
Claim · model-written summary
High solution zinc was toxic to young rice plants.
- Taxon
- rice plants
Oryza sativae0 - Treatment
- solution Zn concentration of 3.89 ÂμMe0
- Outcome
- toxic to young rice plantse0
- Value
- 3.89 ÂμMe0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“solution Zn concentration of 3.89 ÂμM and corresponding free metal activity (pZn2+) of 6.00 was toxic to young rice plants”
Claim · model-written summary
Over time rice zinc concentration decreased and cadmium concentration increased.
- Taxon
- rice plantsOryza sativae0
- Outcome
- Zn concentrationse0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“With time, Zn concentrations in rice plants decreased while Cd concentrations increased”
Claim · model-written summary
Toxic root Cd near 100 mg kg−1 was associated with 20% less root dry matter.
Verbatim
e0“Toxic concentration of Cd in roots (about 100 mg kg−1) associated with a 20% reduction in the root dry matter occurred at the free Cd2+ activities in the solution (pCd2+) in the range of 10.25–9.75”
Claim · model-written summary
Sufficient plant zinc slightly stimulated root to shoot Cd transfer.
Verbatim
e0“Sufficient Zn level in plants slightly stimulated Cd transfer from roots to shoots as opposed to barely sufficient or slightly deficient Zn concentration in shoots”
Claim · model-written summary
Better zinc status diminished shoot cadmium toxicity symptoms.
- Taxon
- plantsViridiplantaee0
- Compound
- Zne0
- Outcome
- severity of Cd toxicity symptoms in shootse0
- Direction
- diminishede0
Verbatim
e0“better Zn status in plants clearly diminished severity of Cd toxicity symptoms in shoots”
Claim · model-written summary
Adapted nutrient solutions allowed rice to produce grain under controlled conditions.
- Taxon
- riceOryza sativae0
- Treatment
- nutrient solutions adapted for rice growthe0
- Outcome
- produce graine0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“use of nutrient solutions adapted for rice growth allowed the rice grown in the second experiment to produce grain under controlled conditions”
Claim · model-written summary
Brown rice grain Cd ranged from 0.1 to 0.8 mg kg−1.
- Taxon
- riceOryza sativae0
- Outcome
- Cadmium in the brown rice graine0
- Value
- 0.1 to 0.8 mg kg−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cadmium in the brown rice grain was 0.1 to 0.8 mg kg−1”
Claim · model-written summary
Nutrient solution composition significantly affected grain Cd.
- Taxon
- riceOryza sativat0
- Treatment
- Composition of the nutrient solutionse0
- Outcome
- Cd concentration in graine0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Composition of the nutrient solutions, in addition to solution Cd level, had a significant effect on Cd concentration in grain”
t0“RICE GRAIN”
Claim · model-written summary
Grain Cd correlated more strongly with free solution Cd activity than with total solution Cd.
- Taxon
- riceOryza sativat0
- Compound
- Cde0
- Outcome
- grain Cd concentratione0
- Direction
- much strongere0
- Comparator
- total solution Cde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Correlation of grain Cd concentration with solution Cd2+ activity was much stronger than with total solution Cd”
t0“RICE GRAIN”
Claim · model-written summary
The authors interpret both experiments as supporting active Cd uptake and transport in rice.
- Taxon
- rice plantsOryza sativae0
- Outcome
- Cd uptake and transporte0
- Qualifier
- an active processe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Results of both experiments supported hypothesis that Cd uptake and transport within rice plants is an active process”
The same questions in other papers
zinc atom · organism · Oryza sativa (rice)Results differ
3 papers in the same direction as this paper · 14 in the opposite direction
- positive
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See all 18 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.