Abstract
Cadmium (Cd) contamination is a serious threat to plants and humans, which subsequently impairs sustainable agricultural production and ecosystem service. Silicon (Si) has been applied to mitigate Cd toxicity, but inevitably has direct and indirect impacts on nitrogen (N) behaviors in soil and plants. However, what role plants play in the N response to Si in soil–rice systems under Cd stress is not known. Therefore, the effects of Si on N migration through different pathways in the soil-rice system were systematically investigated in a rice-cultivation lysimeter experiment. The rice was planted in Cd-contaminated (5 mg kg−1) and uncontaminated soils with three levels of Si application (0, 100, and 200 kg SiO2 hm−2), and the contents of N and Cd in different forms in plants and soils were measured. The group without Cd and Si was set as CK. The study reported that Cd stress caused Cd accumulation in plants, inducing a decrease of 26.0~83.4% in plant dry weights and a decrease of 15.7~46.6% in N concentration compared with CK. Moreover, the leaching of N in soils was increased by Cd, in which the NO3−-N rather than the NH4+-N was leached out. These adverse effects on the plant growth and soil N loss were significantly alleviated by Si application in two ways: (1) the Cd availability in soils was reduced with the acid-extractable Cd (the Cd form with high mobility), decreasing from 1.07 to ~0 mg kg−1; (2) the Cd uptake and translocation in plants were restricted, with the Cd content decreasing by 59.1~96.4% and the translocation index decreasing from 17.7% to 2.2%. The combination of the two mechanisms consequently increased the N absorption of plants from 1.35 to 2.75~3.5 g. The results of the N mass balance calculation showed that, compared with soil N flux, plant-absorbed N contributed predominantly (43.9~55.6%) to the soil total N variation. Moreover, there is a significant trade-off between plant-absorbed N and soil N flux. The magnitude and direction of the soil N flux were greatly and negatively affected by plant-absorbed N during the flooding period. Hence, we conclude that Si application could reduce the leaching of N in soil–rice systems under Cd stress, mainly due to the promotion of the N absorption of plants rather than N immobilization in soils. This study provided new evidence that plants played a dominant role in N response to Si in soil-rice systems under Cd stress.
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Claims 12
Claim · model-written summary
Cd stress reduced rice plant dry weight by 26.0~83.4% compared with the Cd- and Si-free control (CK).
- Taxon
- rice
Oryza sativae3 - Treatment
- Cd stresse1
- Outcome
- plant dry weightse2
- Direction
- decreasee2
- Value
- 26.0~83.4%e2
- Comparator
- CKe4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Cd stress caused Cd accumulation in plants”
e2“a decrease of 26.0~83.4% in plant dry weights”
e3“rice-cultivation lysimeter experiment”
e4“The group without Cd and Si was set as CK”
Claim · model-written summary
Cd stress reduced the nitrogen concentration in rice plants by 15.7~46.6% compared with the control (CK).
- Taxon
- riceOryza sativae3
- Treatment
- Cd stresse1
- Outcome
- N concentratione2
- Direction
- decreasee2
- Value
- 15.7~46.6%e2
- Comparator
- CKe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Cd stress caused Cd accumulation in plants”
e2“a decrease of 15.7~46.6% in N concentration compared with CK”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
Cd increased nitrogen leaching from soils in the rice system, with nitrate-N rather than ammonium-N being leached out.
- Taxon
- riceOryza sativae3
- Treatment
- Cde1
- Outcome
- leaching of N in soilse1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“leaching of N in soils was increased by Cd, in which the NO3−-N rather than the NH4+-N was leached out”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
Silicon application significantly alleviated the adverse effects of Cd on rice plant growth and soil nitrogen loss.
- Taxon
- riceOryza sativae3
- Treatment
- Si applicatione1
- Outcome
- adverse effects on the plant growth and soil N losse1
- Direction
- alleviatede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“These adverse effects on the plant growth and soil N loss were significantly alleviated by Si application”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
Silicon application reduced acid-extractable Cd in the soil from 1.07 to about 0 mg kg-1.
- Taxon
- riceOryza sativae3
- Treatment
- Si applicatione2
- Outcome
- acid-extractable Cde1
- Direction
- decreasinge1
- Value
- from 1.07 to ~0 mg kg−1e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the acid-extractable Cd (the Cd form with high mobility), decreasing from 1.07 to ~0 mg kg−1”
e2“alleviated by Si application in two ways”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
Silicon application decreased the Cd content of rice plants by 59.1~96.4%.
- Taxon
- riceOryza sativae3
- Treatment
- Si applicatione2
- Outcome
- Cd contente1
- Direction
- decreasinge1
- Value
- 59.1~96.4%e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the Cd content decreasing by 59.1~96.4%”
e2“alleviated by Si application in two ways”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
Silicon application decreased the Cd translocation index in rice plants from 17.7% to 2.2%.
- Taxon
- riceOryza sativae3
- Treatment
- Si applicatione2
- Outcome
- translocation indexe1
- Direction
- decreasinge1
- Value
- from 17.7% to 2.2%e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the translocation index decreasing from 17.7% to 2.2%”
e2“alleviated by Si application in two ways”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
Silicon application increased nitrogen absorption by rice plants from 1.35 to 2.75~3.5 g.
- Taxon
- riceOryza sativae3
- Treatment
- Si applicatione2
- Outcome
- N absorption of plantse1
- Direction
- increasede1
- Value
- from 1.35 to 2.75~3.5 ge1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“increased the N absorption of plants from 1.35 to 2.75~3.5 g”
e2“alleviated by Si application in two ways”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
In the nitrogen mass balance, plant-absorbed N contributed predominantly (43.9~55.6%) to the variation in soil total N compared with soil N flux.
- Taxon
- riceOryza sativae3
- Outcome
- soil total N variatione1
- Value
- 43.9~55.6%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“plant-absorbed N contributed predominantly (43.9~55.6%) to the soil total N variation”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
There is a significant trade-off between plant-absorbed N and soil N flux.
- Taxon
- riceOryza sativae3
- Compound
- plant-absorbed Ne1
- Outcome
- soil N fluxe1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“there is a significant trade-off between plant-absorbed N and soil N flux”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
The magnitude and direction of the soil N flux were greatly and negatively affected by plant-absorbed N during the flooding period.
- Taxon
- riceOryza sativae3
- Compound
- plant-absorbed Ne1
- Outcome
- magnitude and direction of the soil N fluxe1
- Direction
- decreaseinferrede1
- Setting
- flooding periode1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The magnitude and direction of the soil N flux were greatly and negatively affected by plant-absorbed N during the flooding period”
e3“rice-cultivation lysimeter experiment”
Claim · model-written summary
The authors conclude that Si application reduced N leaching in soil-rice systems under Cd stress mainly through promoted plant N absorption rather than N immobilization in soils.
- Taxon
- riceOryza sativae1
- Treatment
- Si applicatione1
- Outcome
- leaching of Ne1
- Qualifier
- promotion of the N absorption of plants rather than N immobilization in soilse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Si application could reduce the leaching of N in soil–rice systems under Cd stress, mainly due to the promotion of the N absorption of plants rather than N immobilization in soils”
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