Abstract
Cadmium (Cd) is a toxic heavy metal whose concentration in soils is rising. This study investigated the effect of transpiration on Cd uptake by plants using soil conditions akin to those experienced by field crops. Two experiments were performed using baby leaf spinach (Spinacia oleracea L.) grown in soil containing Chloride (Cl) at a typical concentration of 70 mg kg -1 . Experiment 1 explored plant response to Cd over the range ~0.04 to 10 mg kg -1 so that a non-toxic concentration could be selected for Experiment 2. Experiment 2 tested the hypothesis that transpiration and Cd uptake were related using soil amended to 70 mg Cl kg -1 and 0.24 mg Cd kg. Differences in transpiration were achieved by manipulating atmospheric CO 2 (~400 and ~640 L CO 2 L -1 ) and air temperature (22/14, 26/18 and 30/22C day/night). In Experiment 1, Cd in the foliage variedfrom ~2 to ~100 mg kg -1 DW, yet there was no evidence of Cd toxicity. In Experiment 2, temperature and [CO 2 ] caused large differences in plant growth. [Cd] was lower in chambers with increased temperature and higher in those with elevated CO 2 . Despite differences in growth, transpiration and foliar Cd uptake were positively and strongly correlated, even when both parameters were expressed on a DW basis. The data are consistent with Cd transport by mass flow towards the roots being a substantial contributor to Cd uptake. Higher [Cd] at elevated CO 2 raises concerns about future chronic dietary exposure to Cd. The findings challenge the interpretation of earlier studies on the effects of CO 2 and temperature on Cd uptake and may partly explain the inter-seasonal variation in Cd uptake by field crops.
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Claims 7
Claim · model-written summary
Foliar Cd in baby leaf spinach varied from about 2 to 100 mg/kg DW in Experiment 1, with no evidence of Cd toxicity.
Verbatim
e0“baby leaf spinach (Spinacia oleracea L.) grown in soil”
e1“Cd in the foliage variedfrom ~2 to ~100 mg kg -1 DW, yet there was no evidence of Cd toxicity”
Claim · model-written summary
No evidence of Cd toxicity was found in baby leaf spinach in Experiment 1.
Not reportedDirection
Verbatim
e0“baby leaf spinach (Spinacia oleracea L.) grown in soil”
e1“Cd in the foliage variedfrom ~2 to ~100 mg kg -1 DW, yet there was no evidence of Cd toxicity”
Claim · model-written summary
Temperature and CO2 manipulation caused large differences in plant growth of baby leaf spinach in Experiment 2.
- Taxon
- baby leaf spinache0
- Treatment
- temperature and [CO 2 ]e2
- Outcome
- plant growthe2
- Qualifier
- large differencese2
Not reportedComparatorDirection
Verbatim
e0“baby leaf spinach (Spinacia oleracea L.) grown in soil”
e2“In Experiment 2, temperature and [CO 2 ] caused large differences in plant growth”
Claim · model-written summary
Foliar Cd was lower in chambers with increased temperature.
Not reportedComparator
Verbatim
e0“baby leaf spinach (Spinacia oleracea L.) grown in soil”
e3“[Cd] was lower in chambers with increased temperature and higher in those with elevated CO 2”
Claim · model-written summary
Foliar Cd was higher in chambers with elevated CO2, which raises concern about dietary Cd exposure.
Not reportedComparator
Verbatim
e0“baby leaf spinach (Spinacia oleracea L.) grown in soil”
e3“[Cd] was lower in chambers with increased temperature and higher in those with elevated CO 2”
Claim · model-written summary
Transpiration and foliar Cd uptake of baby leaf spinach were positively and strongly correlated, also on a dry-weight basis.
Verbatim
e0“baby leaf spinach (Spinacia oleracea L.) grown in soil”
e4“transpiration and foliar Cd uptake were positively and strongly correlated, even when both parameters were expressed on a DW basis”
Claim · model-written summary
The data are consistent with Cd transport by mass flow towards the roots being a substantial contributor to Cd uptake by spinach.
Verbatim
e0“baby leaf spinach (Spinacia oleracea L.) grown in soil”
e5“The data are consistent with Cd transport by mass flow towards the roots being a substantial contributor to Cd uptake”
The same questions in other papers
co2 · nutrient: content · Spinacia oleracea (spinach)Results agree
3 papers in the same direction as this paper
- negative
- negative
- negative
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.