Abstract
The growth of seedlings of Townsville sytlo (Stylosanthes humilis H.B.K.) is inhibited by aluminium (Al) ions, their elongation being re-covered with sodium selenate at 1.0 µM. Methyl viologen and hydrogen peroxide, reactive oxy-gen species (ROS)-generating compounds, also inhibited seedling elongation and again growth was relieved by selenate. Selenate, thus, seemed to be operating as a ROS quencher, since N-acetylcysteine (NAC), an antioxidant com-pound, also stimulated largely the growth of Al-inhibited seedlings. At a higher concentra-tion (0.1 mM), however, selenate inhibited seed-ling growth and elongation was recovered by NAC. Ethylene production by selenate plus NAC-treated seedlings was very higher and thus the gaseous hormone was not responsible for the seedling growth inhibition caused by sele-nate. Hence, it seems that at high levels sele-nate operates as a ROS-generating compound whose effects were counteracted by NAC. It can be deduced that, at low concentration, sele-nates behave as a ROS quencher and at high level as a ROS-promoting species.
Highlights
Plant growth is greatly affected by several environmental stresses such as drought, extreme temperatures and heavy metals
Selenium (Se) is interesting in this matter because in response to oxidative stresses, Se compounds at low concentrations, perform a protective function by scavenging free radicals [7,8]
Inhibition of growth of Al-treated seedling was alleviated by Na2SeO4, at the low concentration employed
Summary
Plant growth is greatly affected by several environmental stresses such as drought, extreme temperatures and heavy metals. Since the effects of reactive oxygen molecules at cellular level is mediated by their production and removal via antioxidant activity [6], the use of free radical quenchers may help to identify the role of ROS in plant systems. Selenium (Se) is interesting in this matter because in response to oxidative stresses, Se compounds at low concentrations, perform a protective function by scavenging free radicals [7,8]. Excess Se can cause damage to plants, likely by triggering ROS generation [9,10]. This antagonistic property makes Se unique in studies dealing with systems requiring ROS to elicit a physiological response. The species has been considered as a potential contributor for pasture improvement in tropical zones due to its high-quality forage for livestock, high seed production and wide adaptability to low fertility soils [17]
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