Abstract
OF THE DISSERTATION Availability and Uptake of Iron: Effect of pH Changes During Uptake of Macronutrient Ions by Adu Asabere Opoku Doctor of Philosophy, Graduate Program in Soil Science University of California, Riverside, June 1970 Professor Jakob J. Oertli, Chairman Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium. A mechanism was proposed to describe how uptake of macronutrient ions may in turn influence avail ability and uptake of Fe and other elements from their chelated and sparingly soluble compounds. It was hypothesized that since differen tial accumulation of cations is accompanied by a net release of H ions, and excess anion accumulation accompanied by a net release of OH ions, uptake of Fe, for example, will be enhanced by increasing supply of salts favoring differential accumulation of cations: The released H ions will acidify the root free space, root surfaces, and the immediate root environment; minerals on root surfaces will be dissolved and chelated molecules will be dissociated; both reactions will liberate ions most of which will diffuse.through a relatively high H ion environ ment to absorption sites in the roots. The hypothesis was tested in short-term absorption experiments in which corn seedlings were allowed to absorb Fe from FeEDDHA or Fehydroxide sols in the presence of increasing concentrations of salts of K, Na, Li, Mg, or Ca. Uptake of Fe was highest in the presence of salts from which excess cation accumulation is known to occur and in which the largest pH drop was observed. Increasing the concentration of K, as KC1 or K 2 SO4 , from 0.0 to 5.0 or 10.0 mM K in unbuffered solutions or exchange resin suspensions at pH >_ 6.9 resulted in considerable pH decline and increased Fe uptake. The pH decline correlated with the enhancement of Fe uptake. However, acidification to below pH of about 4.7 tended to reduce further Fe uptake. No detectable pH changes occurred in CaC0 3 plus Fe-hydroxide suspensions containing increasing supply of K, yet Fe uptake was enhanced during accumulation of K. Since essentially all Fe supplied as Fe-hydroxide occurred as colloidal parti cles or precipitates, enhancement of Fe uptake was attributed to a three-ion-contact effect: Plants accumulating excess cations released H ions which decomposed or dissolved the Fe sols or precipitates on root surfaces, thus freeing Fe ions for absorption. Theoretical calculations indicated that increasing H-ion concentration in the immediate root environment will significantly enhance liberation of Fe+^ from the stable chelate FeEDDHA. Old hypotheses claiming that potassium ions in plants are directly involved in reactions favoring translocation and utilization of Fe were replaced with one relating K uptake to subsequent reactions in the substrate.
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Claims 11
Claim · model-written summary
Increasing potassium supply enhanced Fe uptake from nutrient solutions by corn in long-term greenhouse experiments.
- Taxon
- corn
Zea mays subsp. mayse0 - Treatment
- increasing the supply of potassiume0
- Outcome
- uptake of Fee0
- Direction
- enhancede0
- Qualifier
- may be significantlye0
- Setting
- greenhouse experimentse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
Claim · model-written summary
Increasing K concentration in solution decreased pH in corn short-term absorption experiments.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- Increasing the concentration of Ke1
- Outcome
- pHe1
- Direction
- declinee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e1“Increasing the concentration of K, as KC1 or K 2 SO4 , from 0.0 to 5.0 or 10.0 mM K in unbuffered solutions or exchange resin suspensions at pH >_ 6.9 resulted in considerable pH decline and increased Fe uptake”
Claim · model-written summary
Increasing K concentration in solution increased Fe uptake by corn seedlings.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- Increasing the concentration of Ke1
- Outcome
- Fe uptakee1
- Direction
- increasede1
- Qualifier
- from 0.0 to 5.0 or 10.0 mM Ke1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e1“Increasing the concentration of K, as KC1 or K 2 SO4 , from 0.0 to 5.0 or 10.0 mM K in unbuffered solutions or exchange resin suspensions at pH >_ 6.9 resulted in considerable pH decline and increased Fe uptake”
Claim · model-written summary
The pH decline was correlated with enhanced Fe uptake by corn.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- pH declinee2
- Outcome
- Fe uptakee2
- Direction
- enhancemente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e2“The pH decline correlated with the enhancement of Fe uptake”
Claim · model-written summary
Acidification to below pH 4.7 tended to reduce Fe uptake by corn further.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- acidification to below pH of about 4.7e3
- Outcome
- Fe uptakee3
- Direction
- reducee3
- Qualifier
- tended toe3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e3“acidification to below pH of about 4.7 tended to reduce further Fe uptake”
Claim · model-written summary
In CaCO3 plus Fe-hydroxide suspensions, increasing K supply produced no detectable pH change.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- increasing supply of Ke4
- Outcome
- pH changese4
- Direction
- No detectablee4
- Setting
- CaC0 3 plus Fe-hydroxide suspensionse4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e4“No detectable pH changes occurred in CaC0 3 plus Fe-hydroxide suspensions containing increasing supply of K, yet Fe uptake was enhanced during accumulation of K”
Claim · model-written summary
In CaCO3 plus Fe-hydroxide suspensions, increasing K supply enhanced Fe uptake by corn.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- increasing supply of Ke4
- Outcome
- Fe uptakee4
- Direction
- enhancede4
- Setting
- CaC0 3 plus Fe-hydroxide suspensionse4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e4“No detectable pH changes occurred in CaC0 3 plus Fe-hydroxide suspensions containing increasing supply of K, yet Fe uptake was enhanced during accumulation of K”
Claim · model-written summary
Fe uptake by corn was highest with salts that cause large cation accumulation and pH drop.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- salts from which excess cation accumulation is known to occure5
- Outcome
- Uptake of Fee5
- Direction
- higheste5
- Qualifier
- largest pH drope5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e5“Uptake of Fe was highest in the presence of salts from which excess cation accumulation is known to occur and in which the largest pH drop was observed”
Claim · model-written summary
Theoretical calculations indicate that increasing H-ion concentration in the root environment enhances liberation of Fe from FeEDDHA.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- increasing H-ion concentration in the immediate root environmente6
- Outcome
- liberation of Fee6
- Direction
- enhancee6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e6“Theoretical calculations indicated that increasing H-ion concentration in the immediate root environment will significantly enhance liberation of Fe+^ from the stable chelate FeEDDHA”
Claim · model-written summary
Enhanced Fe uptake by corn is attributed to a three-ion-contact effect with H ions released by accumulating plants.
- Taxon
- cornZea mays subsp. mayse0
- Compound
- H ionse1
- Outcome
- Fe uptakee7
- Qualifier
- three-ion-contact effecte7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e7“enhancement of Fe uptake was attributed to a three-ion-contact effect”
e1“Plants accumulating excess cations released H ions which decomposed or dissolved the Fe sols or precipitates on root surfaces, thus freeing Fe ions for absorption”
Claim · model-written summary
Old hypotheses on potassium and Fe translocation were replaced by a model relating K uptake to subsequent substrate reactions.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- translocation and utilization of Fee1
- Qualifier
- relating K uptake to subsequent reactions in the substratee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term greenhouse experiments with corn (Zea mays) established that uptake of Fe from nutrient solutions may be significantly enhanced by increasing the supply of potassium”
e1“Old hypotheses claiming that potassium ions in plants are directly involved in reactions favoring translocation and utilization of Fe were replaced with one relating K uptake to subsequent reactions in the substrate”
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