Abstract
Aluminium (Al) toxicity is widely considered to be the most important growth-limiting factor for plants in strongly acid soils (pH<5.0). The inhibition of root elongation in three varieties of maize (Zea mays L. vars Clavito, HS701b and Sikuani) was followed over the first 48 h of Al treatment, and during the initial 10 h elongation was determined on an hourly basis. The silicon (Si)-induced amelioration of Al toxicity was investigated by pre-treating seedlings for 72 h in nutrient solutions with 1000 microM Si before transfer into solutions with 0, 20 or 50 microM Al (without Si). Plants were either grown in complete low ionic strength nutrient solutions (CNS) or in low salt solutions of 0.4 mM CaCl2 (LSS). In addition, the role of root exudation of organic compounds as a mechanism of Si-induced alleviation of Al toxicity was investigated. Aluminium-induced inhibition of root elongation in the maize var. HS701b was observed within 1 h of Al exposure. After a lag time of at least 8 h, Si-induced alleviation of Al toxicity was observed in this variety when grown in LSS. In the Al-resistant var. Sikuani, Al-resistance was only observed after exposure to 50 microM Al, and not after exposure to 20 microM Al, suggesting that there exists a threshold Al concentration before the mechanisms of Al resistance are activated. Aluminium stimulated root exudation of oxalic acid in all three varieties, but exudate concentrations did not increase with either Al resistance or with Si pretreatment. Aluminium and Si triggered release of catechol and of the flavonoid-type phenolics: catechin, and quercetin. In the Al-resistant variety, Sikuani, Al-exposed plants pretreated with Si exuded up to 15 times more phenolics than those plants not pretreated with Si. The flavonoid-type phenolics, to date unconsidered, appear to play a role in the mechanism(s) of Si-induced amelioration of Al toxicity.
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Claims 9
Claim · model-written summary
Aluminium inhibited root elongation in HS701b within one hour.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aluminium-induced inhibition of root elongation in the maize var. HS701b was observed within 1 h of Al exposure.”
Claim · model-written summary
Silicon alleviated aluminium toxicity in HS701b after at least eight hours in low salt solution.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After a lag time of at least 8 h, Si-induced alleviation of Al toxicity was observed in this variety when grown in LSS.”
t0“maize”
Claim · model-written summary
Sikuani aluminium resistance appeared at 50 microM Al but not 20 microM Al.
Verbatim
e0“In the Al-resistant var. Sikuani, Al-resistance was only observed after exposure to 50 microM Al, and not after exposure to 20 microM Al”
Claim · model-written summary
Aluminium stimulated oxalic acid root exudation in all three maize varieties.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aluminium stimulated root exudation of oxalic acid in all three varieties”
t0“maize”
Claim · model-written summary
Exudate concentrations did not increase with aluminium resistance or silicon pretreatment.
- Treatment
- Si pretreatmente0
- Outcome
- exudate concentrationse0
- Direction
- did not increasee0
- Qualifier
- Al resistancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exudate concentrations did not increase with either Al resistance or with Si pretreatment.”
t0“maize”
Claim · model-written summary
Aluminium and silicon triggered catechol release.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aluminium and Si triggered release of catechol”
t0“maize”
Claim · model-written summary
Aluminium and silicon triggered release of catechin and quercetin.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aluminium and Si triggered release of catechol and of the flavonoid-type phenolics: catechin, and quercetin.”
t0“maize”
Claim · model-written summary
Silicon-pretreated Sikuani exuded up to 15 times more phenolics after aluminium exposure than non-pretreated plants.
Verbatim
e0“In the Al-resistant variety, Sikuani, Al-exposed plants pretreated with Si exuded up to 15 times more phenolics than those plants not pretreated with Si.”
Claim · model-written summary
Flavonoid-type phenolics appear to contribute to silicon-mediated aluminium toxicity alleviation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The flavonoid-type phenolics, to date unconsidered, appear to play a role in the mechanism(s) of Si-induced amelioration of Al toxicity.”
t0“maize”
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