Abstract
Plants cultivated with Cd can produce large amounts of phytochelatins. Since these compounds contain much cysteine, these plants should have an increased rate of assimilatory sulfate reduction, the biosynthetic pathway leading to cysteine. To test this prediction, the effect of Cd on growth, sulfate assimilation in vivo and extractable activity of two enzymes of sulfate reduction, ATP-sulfurylase (EC 2.7.7.4) and adenosine 5'-phosphosulfate sulfotransferase were measured in maize (Zea mays L.) seedlings. For comparison, nitrate reductase activity was determined. In 9-day-old cultures, the increase in fresh and dry weight was significantly inhibited by 50 micromolar and more Cd in the roots and by 100 and 200 micromolar in the shoots. Seedlings cultivated with 50 micromolar Cd for 5 days incorporated more label from (35)SO(4) (2-) into higher molecular weight compounds than did controls, indicating that the predicted increase in the rate of assimilatory sulfate reduction took place. Consistent with this finding, an increased level of the extractable activity of both ATP-sulfurylase and adenosine 5'-phosphosulfate sulfotransferase was measured in the roots of these plants at 50 micromolar Cd and at higher concentrations. This effect was reversible after removal of Cd from the nutrient solution. In the leaves, a significant positive effect of Cd was detected at 5 micromolar for ATP-sulfurylase and at 5 and 20 micromolar for adenosine 5'-phosphosulfate sulfotransferase. At higher Cd concentrations, both enzyme activities were at levels below the control. Nitrate reductase (EC 1.6.6.1) activity decreased at 50 micromolar or more Cd in the roots and was similarly affected as ATP-sulfurylase activity in the primary leaves.
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Claims 10
Claim · model-written summary
At 50 micromolar or more Cd, maize root fresh and dry weight gain was significantly inhibited.
- Organ / stage
- rootse0
- Treatment
- 50 micromolar and more Cde0
- Outcome
- increase in fresh and dry weighte0
- Direction
- inhibitede0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the increase in fresh and dry weight was significantly inhibited by 50 micromolar and more Cd in the roots”
t0“Zea mays L.”
Claim · model-written summary
At 100 and 200 micromolar Cd, maize shoot fresh and dry weight gain was significantly inhibited.
- Organ / stage
- shootse0
- Treatment
- 100 and 200 micromolare0
- Outcome
- increase in fresh and dry weighte0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the increase in fresh and dry weight was significantly inhibited by 50 micromolar and more Cd in the roots and by 100 and 200 micromolar in the shoots”
t0“Zea mays L.”
Claim · model-written summary
Seedlings exposed to 50 micromolar Cd incorporated more sulfate label into high molecular weight compounds than controls.
- Treatment
- 50 micromolar Cd for 5 dayse0
- Outcome
- label from (35)SO(4) (2-) into higher molecular weight compoundse0
- Direction
- moree0
- Comparator
- controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings cultivated with 50 micromolar Cd for 5 days incorporated more label from (35)SO(4) (2-) into higher molecular weight compounds than did controls”
t0“Zea mays L.”
Claim · model-written summary
Cadmium increased root ATP-sulfurylase activity.
- Organ / stage
- rootse0
- Treatment
- 50 micromolar Cd and at higher concentrationse0
- Outcome
- extractable activity of both ATP-sulfurylase and adenosine 5'-phosphosulfate sulfotransferasee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an increased level of the extractable activity of both ATP-sulfurylase and adenosine 5'-phosphosulfate sulfotransferase was measured in the roots of these plants at 50 micromolar Cd and at higher concentrations”
t0“Zea mays L.”
Claim · model-written summary
The cadmium effect on root sulfate-reduction enzyme activity was reversible after cadmium removal.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This effect was reversible after removal of Cd from the nutrient solution.”
t0“Zea mays L.”
Claim · model-written summary
Leaf ATP-sulfurylase activity increased significantly at 5 micromolar Cd.
- Organ / stage
- leavese0
- Treatment
- Cde0
- Outcome
- ATP-sulfurylasee0
- Direction
- positive effecte0
- Value
- 5 micromolare0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the leaves, a significant positive effect of Cd was detected at 5 micromolar for ATP-sulfurylase”
t0“Zea mays L.”
Claim · model-written summary
Leaf adenosine 5'-phosphosulfate sulfotransferase activity increased significantly at 5 and 20 micromolar Cd.
- Treatment
- Cde1
- Outcome
- adenosine 5'-phosphosulfate sulfotransferasee0
- Direction
- increaseinferrede0
- Value
- 5 and 20 micromolare0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at 5 and 20 micromolar for adenosine 5'-phosphosulfate sulfotransferase”
t0“Zea mays L.”
e1“the increase in fresh and dry weight was significantly inhibited by 50 micromolar and more Cd in the roots”
Claim · model-written summary
At higher Cd concentrations, both leaf sulfate-reduction enzyme activities fell below control.
- Treatment
- higher Cd concentrationse0
- Outcome
- both enzyme activitiese0
- Direction
- belowe0
- Comparator
- the controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At higher Cd concentrations, both enzyme activities were at levels below the control.”
t0“Zea mays L.”
Claim · model-written summary
Root nitrate reductase activity decreased at 50 micromolar or more Cd.
- Organ / stage
- rootse0
- Treatment
- 50 micromolar or more Cde0
- Outcome
- Nitrate reductase (EC 1.6.6.1) activitye0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate reductase (EC 1.6.6.1) activity decreased at 50 micromolar or more Cd in the roots”
t0“Zea mays L.”
Claim · model-written summary
Primary-leaf nitrate reductase activity responded similarly to ATP-sulfurylase activity.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“was similarly affected as ATP-sulfurylase activity in the primary leaves.”
t0“Zea mays L.”
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