The Effects of Aluminum on the Influx of Calcium, Potassium, Ammonium, Nitrate, and Phosphate in an Aluminum-Sensitive Cultivar of Barley (Hordeum vulgare L.)

Abstract

The mechanism by which aluminum interferes with ion influx is not known. In this study, the effects of aluminum on the influx of the cations calcium, potassium, and ammonium and the anions nitrate and phosphate were measured in an aluminum-sensitive cultivar of barley (Hordeum vdgare 1.). Aluminum (100 PM) was found to inhibit the influx of the cations calcium (69%), ammonium (40%), and potassium (13%) and enhancing the influx of the anions nitrate (44%) and phosphate (17%). Aluminum interfered with the binding of the cations in the cell wall by the same order of magnitude as their respective influxes, whereas phosphate binding was strongly enhanced. The results are consistent with a mechanism whereby aluminum binds to the plasma membrane phospholipids, forming a positively charged layer that influences ion movement to the binding sites of the transport proteins. A positive charge layer would retard the movement of cations and increase the movement of anions to the plasma membrane in proportion to the charges carried by these ions. transport proteins, thereby impairing their function (Schroeder, 1988).Most of the studies on the effects of A1 on mineral nutrition have been long-term studies, lasting for a period of 1 or more d (Taylor, 1988). In the present study, to ensure that the inhibition of ion influx was the result of the impairment of membrane function rather than due to impairment of root function through general Al-induced toxicity, plants were grown in the absence of A1 and measurements of the effects of AI were camed out over a time period of 20 min or less. These conditions allowed us (a) to examine the effects of AI on short-term cation (Ca, K, ammonium) and anion (nitrate, phosphate) influx to reveal any patterns of discrimination between cation and anion transport, and (b) to critically evaluate the proposed basis of AI inhibition of ion uptake.

Effect of aluminium on ion uptake and H+ release by maize

“…However, other authors such as Klotz & Horst (1988) in soybean and Nichol et al (1993) in barley showed that Al enhances the NO3" uptake. Rufty et al (1995) noted that these two studies were made in conditions of acidity stress, i.e.…”

Alterações morfológicas e acúmulo de compostos fenólicos em plantas de sorgo sob estresse de alumínio

“…As alterações simultâneas no alongamento e na espessura celular sugerem que os efeitos do Al +3 , direta ou indiretamente, afetam diversos processos relacionados à expansão celular (NICHOL et al, 1993). LENOBLE et al (1996) (SASAKI et al, 1996).…”

Induction of Hexose-Phosphate Translocator Activity in Spinach Chloroplasts

“…A1 has profound effects on membrane structure, altering membrane permeability (Zhao et al, 1987), fluidity (Haug, 1984), protein-lipid interactions (Caldwell, 1989), and surface potential (Haug, 1984;Kinraide et al, 1992). These changes may lead to alterations in membrane function and ion transport (Suhayda and Haug, 1986;Caldwell, 1989;Nicho1 et al, 1993). Much of the recent work with A1 has focused on its effect on Ca2+ fluxes (Huang et al, 1992;Delhaize et al, 1993b;Ryan and Kochian, 1993;, although a causative relationship with A1 toxicity has not been established .…”