Abstract
Maize plants were grown in nutrient solution with or without 100 mg organic carbon L −1 of humic substances (HS) (MW > 12 000) extracted from a cambisol. To evaluate the effect of HS on leaf carbohydrate metabolism, after 14 d of growth apical and basal segments from the third leaf were collected and analyzed for sugar content and for the activities of enzymes involved in the synthesis and breakdown of starch and sucrose. Leaf starch content decreased in treated plants, whereas the level of soluble sugars increased. The decrease of starch was accompanied by an enhanced activity of amylase, whereas the activity of ADPglucose pyrophosphorylase was not affected. Activities of invertases and sucrose synthase were stimulated by HS treatment in apical tissue, and inhibited in basal one. Activities of enzymes involved in sucrose biosynthesis (sucrose phosphate synthase, cytoplasmic fructose-1,6- bisphosphatase, UDPglucose pyrophosphorylase) were stimulated or inhibited depending on the enzyme and on the tissue examined. Our results show that HS may affect both the level and percent distribution of sugars of maize leaves; these effects seem to be mediated by changes in the activities of enzymes involved in carbohydrate metabolism. Key words: Humic substances, enzymes, carbohydrate metabolism, maize
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Claims 8
Claim · model-written summary
Humic substances decreased starch content in maize leaves.
- Treatment
- 100 mg organic carbon L −1 of humic substances (HS)e1
- Outcome
- Leaf starch contente0
- Direction
- decreasede0
- Comparator
- withoute1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf starch content decreased in treated plants”
e1“with or without 100 mg organic carbon L −1 of humic substances (HS)”
t0“Effects of humic substances on carbohydrate metabolism of maize leaves”
Claim · model-written summary
Humic substances increased soluble sugar levels in maize leaves.
- Treatment
- 100 mg organic carbon L −1 of humic substances (HS)e1
- Outcome
- level of soluble sugarse0
- Direction
- increasede0
- Comparator
- withoute1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of soluble sugars increased”
e1“with or without 100 mg organic carbon L −1 of humic substances (HS)”
t0“Effects of humic substances on carbohydrate metabolism of maize leaves”
Claim · model-written summary
The starch decline under humic substances accompanied enhanced amylase activity.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease of starch was accompanied by an enhanced activity of amylase”
e1“humic substances (HS)”
t0“Effects of humic substances on carbohydrate metabolism of maize leaves”
Claim · model-written summary
ADPglucose pyrophosphorylase activity was unaffected.
- Treatment
- humic substances (HS)e1
- Gene
- ADPglucose pyrophosphorylasee0
- Outcome
- activity of ADPglucose pyrophosphorylasee0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the activity of ADPglucose pyrophosphorylase was not affected”
e1“humic substances (HS)”
t0“Effects of humic substances on carbohydrate metabolism of maize leaves”
Claim · model-written summary
Humic substances stimulated invertase and sucrose synthase activities in apical tissue.
- Organ / stage
- apical tissuee0
- Treatment
- HS treatmente0
- Outcome
- Activities of invertases and sucrose synthasee0
- Direction
- stimulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Activities of invertases and sucrose synthase were stimulated by HS treatment in apical tissue”
t0“Effects of humic substances on carbohydrate metabolism of maize leaves”
Claim · model-written summary
Humic substances inhibited invertase and sucrose synthase activities in basal tissue.
- Organ / stage
- basal onee0
- Treatment
- HS treatmente0
- Outcome
- Activities of invertases and sucrose synthasee0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Activities of invertases and sucrose synthase were stimulated by HS treatment in apical tissue, and inhibited in basal one”
t0“Effects of humic substances on carbohydrate metabolism of maize leaves”
Claim · model-written summary
Humic substances stimulated or inhibited sucrose biosynthesis enzymes depending on enzyme and tissue.
- Treatment
- humic substancest0
- Outcome
- Activities of enzymes involved in sucrose biosynthesise0
- Direction
- stimulated or inhibitede0
- Qualifier
- depending on the enzyme and on the tissue examinede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Activities of enzymes involved in sucrose biosynthesis (sucrose phosphate synthase, cytoplasmic fructose-1,6- bisphosphatase, UDPglucose pyrophosphorylase) were stimulated or inhibited depending on the enzyme and on the tissue examined”
t0“Effects of humic substances on carbohydrate metabolism of maize leaves”
Claim · model-written summary
The authors infer that enzyme activity changes mediate the effects of humic substances on maize leaf sugars.
- Outcome
- level and percent distribution of sugarse0
- Qualifier
- changes in the activities of enzymes involved in carbohydrate metabolisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“HS may affect both the level and percent distribution of sugars of maize leaves; these effects seem to be mediated by changes in the activities of enzymes involved in carbohydrate metabolism”
The same questions in other papers
other · molecular: metabolites · Zea mays (maize)Positive and negative results
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