Abstract
Abstract The Cadmium (Cd)‐polluted soils are is an increasing concern worldwide. Phytoextraction of Cd pollutants by high biomass plants, such as sweet sorghum, is considered an environmentally‐friendly, cost‐effective and sustainable strategy for remediating this problem. Nitrogen (N) is a macronutrient essential for plant growth, development and stress resistance. Nevertheless, how nitrate, as an important form of N, affects Cd uptake, translocation and accumulation in sweet sorghum is still unclear. In the present study, a series of nitrate levels (N1, 0.5 m m ; N2, 2 m m ; N3, 4 m m ; N4, 8 m m and N5, 16 m m ) with or without added 5 μ m CdCl 2 treatment in sweet sorghum was investigated hydroponically. The results indicate that Cd accumulation in the aboveground parts of sweet sorghum was enhanced by optimum nitrate supply, resulting from both increased dry weight and Cd concentration. Although root‐to‐shoot Cd translocation was not enhanced by increased nitrate, some Cd was transferred from cell walls to vacuoles in leaves. Intriguingly, expression levels of Cd uptake and transport genes, SbNramp1 , SbNramp5 and SbHMA3 , were not closely related to increased Cd as affected by nitrate supply. The expression of SbNRT1.1B in relation to nitrate transport showed an inverted ‘U’ shape with increasing nitrate levels under Cd stress, which was in agreement with trends in Cd concentration changes in aboveground tissues. Based on the aforementioned results, nitrate might regulate Cd uptake and accumulation through expression of SbNRT1.1B rather than SbNramp1 , SbNramp5 or SbHMA3 , the well‐documented genes related to Cd uptake and transport in sweet sorghum.
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Claims 8
Claim · model-written summary
Optimum nitrate supply enhanced aboveground cadmium accumulation in sweet sorghum.
- Taxon
- sweet sorghume0
- Treatment
- optimum nitrate supplye0
- Outcome
- Cd accumulation in the aboveground partse0
- Direction
- enhancede0
Not reportedComparator
Verbatim
e0“Cd accumulation in the aboveground parts of sweet sorghum was enhanced by optimum nitrate supply”
Claim · model-written summary
Optimum nitrate increased dry weight and Cd concentration.
- Taxon
- sweet sorghumt0
- Treatment
- optimum nitrate supplye1
- Outcome
- dry weight and Cd concentratione0
- Direction
- increasede0
Not reportedComparator
Verbatim
e0“resulting from both increased dry weight and Cd concentration”
e1“optimum nitrate supply”
t0“sweet sorghum”
Claim · model-written summary
Increasing nitrate did not enhance root-to-shoot Cd translocation.
- Taxon
- sweet sorghumt0
- Treatment
- increased nitratee0
- Outcome
- root‐to‐shoot Cd translocatione0
- Direction
- not enhancede0
Not reportedComparator
Verbatim
e0“root‐to‐shoot Cd translocation was not enhanced by increased nitrate”
t0“sweet sorghum”
Claim · model-written summary
Some Cd shifted from cell walls to leaf vacuoles.
Verbatim
e0“some Cd was transferred from cell walls to vacuoles in leaves”
t0“sweet sorghum”
Claim · model-written summary
SbNramp1, SbNramp5 and SbHMA3 expression was not closely related to nitrate-associated Cd increases.
- Taxon
- sweet sorghumt0
- Treatment
- nitrate supplye0
- Gene
- SbNramp1 , SbNramp5 and SbHMA3e0
- Outcome
- increased Cde0
Not reportedDirection
Verbatim
e0“expression levels of Cd uptake and transport genes, SbNramp1 , SbNramp5 and SbHMA3 , were not closely related to increased Cd as affected by nitrate supply”
t0“sweet sorghum”
Claim · model-written summary
SbNRT1.1B expression followed an inverted U shape with increasing nitrate under Cd stress.
- Taxon
- sweet sorghumt0
- Treatment
- increasing nitrate levelse0
- Gene
- SbNRT1.1Be0
- Outcome
- expression of SbNRT1.1Be0
- Qualifier
- under Cd stresse0
Not reportedDirection
Verbatim
e0“expression of SbNRT1.1B in relation to nitrate transport showed an inverted ‘U’ shape with increasing nitrate levels under Cd stress”
t0“sweet sorghum”
Claim · model-written summary
SbNRT1.1B expression tracked aboveground Cd concentration changes.
Not reportedDirection
Verbatim
e0“which was in agreement with trends in Cd concentration changes in aboveground tissues”
e1“expression of SbNRT1.1B in relation to nitrate transport”
t0“sweet sorghum”
Claim · model-written summary
The authors infer nitrate may regulate Cd uptake and accumulation through SbNRT1.1B rather than the other named transport genes.
Verbatim
e0“nitrate might regulate Cd uptake and accumulation through expression of SbNRT1.1B rather than SbNramp1 , SbNramp5 or SbHMA3”
t0“sweet sorghum”
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