Physiological characteristics of selenite uptake by maize roots in response to different pH levels

Abstract

In selenite solutions, H 2 SeO 3 , HSeO À 3 , and SeO 2À 3 are in equilibrium in proportions that vary with solution pH. The physiological characteristics of selenite uptake were studied with excised roots of maize (Zea mays L.) seedlings at pH 3.0, 5.0, and 8.0. The results showed that 0.10 mM 2,4-dinitrophenol (DNP), 1.0 mM sodium fluoride (NaF), and a temperature of 4°C inhibited selenite uptake by maize roots by 16%, 20%, and 23% at pH 3.0, by up to 80%, 79%, and 78% at pH 5.0, and by 5%, 9%, and 16% at pH 8.0. Hence, selenite may enter roots at pH 5.0 in an energy-dependent manner, in contrast to pH 3.0 and 8.0. The uptake kinetics for selenite were determined for excised roots of maize, and the curves were linear at pH 3.0 and 8.0, but saturated at pH 5.0, showing that carrier-mediated uptake of selenite occurred at pH 5.0, but not at pH 3.0 or 8.0. Further studies showed that HgCl 2 and AgNO 3 inhibited selenite uptake separately by 81% and 76% at pH 3.0 and indicated that selenite was absorbed by maize roots through aquaporins at pH 3.0. At pH 8.0, anion-channel inhibitors only inhibited a small fraction of selenite uptake, indicating that the major absorption pathway of SeO 2À 3 species into roots was not absorbed passively through anion channels, but might involve other processes. According to these results, it is proposed that selenite uptake occurs via different mechanisms depending on its species in solution in response to pH levels.

Inhibitor screen for limited-transpiration trait among maize hybrids

“…Silver interacts with the amino acid histidine in addition to cysteine (Table 1), but the reaction between silver and imidazole N of histidine is only supposed to occur at silver concentration of more than 200 M. Like mercury, use of silver nitrate in a recent citation was found to have toxic side effect on K + homeostasis and cellular integrity even in lower doses (Coskun et al, 2012). However, concentrations of silver of 10-50 M used in maize root studies showed no significant inhibition (Soós et al, 2010;Zhang et al, 2010). A silver concentration of 500 M used in this study was also used in studies of AQP in barley (Volkov et al, 2007) and in tomato (Kanai et al, 2011).…”

A possible new mechanism involved in ferro-cyanide metabolism by plants

“…LaCl 3 is a Ca 2+ channel blocker (Ebbs et al 2008). Na 3 VO 4 , HgCl 2 , and AgNO 3 are inhibitors of the ion transporting (Ebbs et al 2008;Zhang et al 2010). TEACl is an anion channel inhibitor (Zhang et al 2010).…”

“…Na 3 VO 4 , HgCl 2 , and AgNO 3 are inhibitors of the ion transporting (Ebbs et al 2008;Zhang et al 2010). TEACl is an anion channel inhibitor (Zhang et al 2010). The initial pH of spiked solution was adjusted to 7.5 with 0.1% NaOH.…”

Effects of inhibitors on ferricyanide uptake and assimilation by plants

“…channel blocker (Ebbs et al 2008). Na 3 VO 4 , HgCl 2 , and AgNO 3 are inhibitors of the ion transporting (Ebbs et al 2008;Zhang et al 2010). TEACl is an anion channel inhibitor (Zhang et al 2010).…”

“…Na 3 VO 4 , HgCl 2 , and AgNO 3 are inhibitors of the ion transporting (Ebbs et al 2008;Zhang et al 2010). TEACl is an anion channel inhibitor (Zhang et al 2010). The initial concentration of spiked solution was 10.50 (±0.225) mg CN/L.…”