Relationship between Lead Uptake by Lettuce and Water-Soluble Low-Molecular-Weight Organic Acids in Rhizosphere As Influenced by Transpiration

Abstract

The relationship between Pb uptake by leaf lettuce ( Lactuca sativa L.) and water-soluble low-molecular-weight organic acids (LMWOAs) in rhizosphere, as influenced by transpiration (high and low), has been studied. Studies were carried out by culturing lettuce plants grown for 2 weeks in pots filled with quartz sand mixed with anion-exchange resin and then for 30 days in a greenhouse. The potted lettuce plants were subjected to stress by the addition of Pb(NO 3) 2 solutions (100, 200, and 300 mg of Pb L (-1)) and by high and low transpiration treatments for another 10-day period. Blank experiments (without addition of Pb(NO 3) 2 solutions to the pots) were also run. There were no significant differences in the growth of the plants with the addition of Pb(NO 3) 2 solutions in either of the transpirations studies. Uptake of Pb by the shoots and roots of the plants was found to be proportional to the concentration of Pb solutions added, and more accumulation was observed in the roots than in the shoots at the end of days 3 and 10. High transpiration caused more Pb uptake than did low transpiration. One volatile acid (propionic acid) and nine nonvolatile acids (lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, d-tartaric, trans-aconitic, and citric acids) in rhizosphere quartz sand or anion-exchange resin were identified and quantified by gas chromatography analysis with a flame ionization detector. The amount of LMWOAs in rhizosphere quartz sand or anion-exchange resin increased with higher amounts of Pb in quartz sand solution and also with longer duration of the study. The total quantities of the LMWOAs in the rhizosphere quartz sand or anion-exchange resin were significantly higher under high and low transpiration with a 300 mg of Pb L (-1) solution addition at the end of day 10. Compared with our previous related studies (published work), the present study shows that the presence of LMWOAs in rhizosphere does not significantly affect Pb uptake by lettuce plants under high and low transpiration. A physiological mechanism of the roots of lettuce plants governing the relationship between Pb contamination level and quantity of water-soluble LMWOAs in rhizosphere quartz sand and resin, as influenced by transpiration, was proposed.

Testing and educating on urban soil lead: A case of Chicago community gardens

“…The mean shoot lead concentration was 7.00 parts per million and for roots was 11.8 parts per million. Finding higher concentrations in roots is consistent with other studies (Liao, Chien, Wang, Shen, & Seshaiah, 2007;Finster et al, 2004). No correlation existed between EPA or Mehlich-III soil lead and shoot lead concentrations in the lettuce, likely because individual plant uptake of metals can be complicated by factors like pH, organic matter, presence of compounds which can bind metals (like phosphates), and clay.…”

[Chromatographic auxanometry and GC-MS-auxanometry in forest plant species vegetation phenological monitoring based on flavor and gas chemistry principles with automatic pattern recognition (climatic, meteorological, taxonomic and phenospectral)]

“…Це частково корелює із газодинамічним моніторингом, оскільки кліматична конвекція, яка регулює фази осциляції вмісту вуглекислоти в атмосфері, регулює також і температуру повітряних мас, що впливає на випаровування/транспірацію рослин, з позиції гідравліки листка [54][55][56]. Елементний склад виділеного під час транспірації досліджується методами хроматографії як і тоді, коли мова йде про транспіраційні потоки на поверхні, так і тоді, коли мова йде про транспірацію коренів в конденсованому середовищі [57][58][59][60]. Ідеалізація під час вирішування відповідної модельної задачі in vitro в герметизованих умовах у термінології зарубіжної газової хроматографії може бути означена як відношення між sample phase і headspace (gas phase), де роль headspace виконує атмосфера або експериментальне середовище кліматичної камери, а sample phase -рідинна поверхня транспірації (по аналогії з [61]).…”