Abstract
Heavy metals reduce the photosynthetic efficiency and disrupt metabolic reactions in a concentration-dependent manner. Moreover, by replacing the metal ions in metalloproteins that use essential metal ions, such as Cu, Zn, Mn, and Fe, as co-factors, heavy metals ultimately lead to the formation of reactive oxygen species (ROS). These, in turn, cause destruction of the cell membrane through lipid peroxidation, and eventually cause the plant to necrosis. Given the aforementioned factors, this study was aimed to understand the physiological responses of rice to cadmium (Cd) and arsenic (As) toxicity and the effect of essential metal ions on homeostasis. In order to confirm the level of physiological inhibition caused by heavy metal toxicity, hydroponically grown rice (Oryza sativa L. cv. Dongjin) plants were exposed with $0-50{\mu}M$ cadmium (Cd, $CdCl_2$) and arsenic (As, $NaAsO_2$) at 3-leaf stage, and then investigated malondialdehyde (MDA) contents after 7 days of the treatment. With increasing concentrations of Cd and As, the MDA content in leaf blade and root increased with a consistent trend. At 14 days after treatment with $30{\mu}M$ Cd and As, plant height showed no significant difference between Cd and As, with an identical reduction. However, As caused a greater decline than Cd for shoot fresh weight, dry weight, and water content. The largest amounts of Cd and As were found in the roots and also observed a large amount of transport to the leaf sheath. Interestingly, in terms of Cd transfer to the shoot parts of the plant, it was only transported to upper leaf blades, and we did not detect any Cd in lower leaf blades. However, As was transferred to a greater level in lower leaf blades than in upper leaf blades. In the roots, Cd inhibited Zn absorption, while As inhibited Cu uptake. Furthermore, in the leaf sheath, while Cd and As treatments caused no change in Cu homeostasis, they had an antagonist effect on the absorption of Zn. Finally, in both upper and lower leaf blades, Cd and As toxicity was found to inhibit absorption of both Cu and Zn. Based on these results, it would be considered that heavy metal toxicity causes an increase in lipid peroxidation. This, in turn, leads to damage to the conductive tissue connecting the roots, leaf sheath, and leaf blades, which results in a reduction in water content and causes several physiological alterations. Furthermore, by disrupting homeostasis of the essential metal ions, Cu and Zn, this causes complete heavy metal toxicity.
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Claims 14
Claim · model-written summary
Increasing Cd and As concentrations increased MDA content in rice leaf blades and roots.
- Taxon
- rice
Oryza sativae1 - Treatment
- Cd and Ase0
- Outcome
- MDA content in leaf blade and roote0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“With increasing concentrations of Cd and As, the MDA content in leaf blade and root increased with a consistent trend”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Cd and As caused an identical reduction in rice plant height at 14 days, without a significant difference between them.
- Taxon
- riceOryza sativae1
- Treatment
- Cd and Ase0
- Outcome
- plant heighte0
- Direction
- reductione0
- Value
- $30{\mu}M$e0
- Comparator
- Cd and Ase0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 14 days after treatment with $30{\mu}M$ Cd and As, plant height showed no significant difference between Cd and As, with an identical reduction”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Arsenic caused a greater reduction in rice shoot fresh weight than cadmium.
- Taxon
- riceOryza sativae1
- Treatment
- Ase0
- Outcome
- shoot fresh weighte0
- Direction
- greater declinee0
- Comparator
- Cde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As caused a greater decline than Cd for shoot fresh weight, dry weight, and water content”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Arsenic caused a greater reduction in rice shoot dry weight than cadmium.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As caused a greater decline than Cd for shoot fresh weight, dry weight, and water content”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Arsenic caused a greater reduction in rice water content than cadmium.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As caused a greater decline than Cd for shoot fresh weight, dry weight, and water content”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
The largest amounts of Cd and As occurred in rice roots, with substantial transport to leaf sheath.
- Taxon
- riceOryza sativae1
- Organ / stage
- rootse0
- Outcome
- amounts of Cd and Ase0
- Direction
- largeste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The largest amounts of Cd and As were found in the roots and also observed a large amount of transport to the leaf sheath”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Cadmium was detected in upper but not lower rice leaf blades.
- Taxon
- riceOryza sativae1
- Outcome
- Cd in lower leaf bladese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it was only transported to upper leaf blades, and we did not detect any Cd in lower leaf blades”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Arsenic transfer was greater in lower than upper rice leaf blades.
- Taxon
- riceOryza sativae1
- Organ / stage
- lower leaf bladese0
- Outcome
- As was transferrede0
- Direction
- greatere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As was transferred to a greater level in lower leaf blades than in upper leaf blades”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Cadmium inhibited zinc absorption in rice roots.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the roots, Cd inhibited Zn absorption, while As inhibited Cu uptake”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Arsenic inhibited copper uptake in rice roots.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the roots, Cd inhibited Zn absorption, while As inhibited Cu uptake”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Cd and As did not change copper homeostasis in rice leaf sheath.
- Taxon
- riceOryza sativae2
- Organ / stage
- leaf sheathe1
- Treatment
- Cd and Ase0
- Outcome
- Cu homeostasise0
- Direction
- no changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cd and As treatments caused no change in Cu homeostasis”
e1“in the leaf sheath”
e2“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Cd and As had antagonistic effects on zinc absorption in rice leaf sheath.
- Taxon
- riceOryza sativae2
- Treatment
- Cd and Ase1
- Outcome
- absorption of Zne0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they had an antagonist effect on the absorption of Zn”
e1“Cd and As treatments”
e2“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
Cd inhibited copper and zinc absorption in upper and lower rice leaf blades.
- Taxon
- riceOryza sativae1
- Organ / stage
- upper and lower leaf bladese0
- Treatment
- Cde0
- Outcome
- absorption of both Cu and Zne0
- Direction
- inhibite0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in both upper and lower leaf blades, Cd and As toxicity was found to inhibit absorption of both Cu and Zn”
e1“rice (Oryza sativa L. cv. Dongjin)”
Claim · model-written summary
As inhibited copper and zinc absorption in upper and lower rice leaf blades.
- Taxon
- riceOryza sativae1
- Organ / stage
- upper and lower leaf bladese0
- Treatment
- Ase0
- Outcome
- absorption of both Cu and Zne0
- Direction
- inhibite0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in both upper and lower leaf blades, Cd and As toxicity was found to inhibit absorption of both Cu and Zn”
e1“rice (Oryza sativa L. cv. Dongjin)”
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