Are Ros Involved In The Inhibition of Maize Root Tip Growth by Both Osmotic and Ionic Stresses?

BUSTOS, DOLORES; LASCANO, RAMIRO; CÓRDOBA, ALICIA; TALEISNIK, EDITH

Recife, Brasil

Congreso; XII Reunión Latinoamericana de Fisiología Vegetal; 2005

Sociedad Brasileña de Fisiología Vegetal

Reactive oxygen species (ROS) generation under abiotic stress has usually been associated to oxidative damage generation and protection. ROS also participate in signal tranduction chains and also in cell wall softening during fruit maturation and elongation growth. Juvenile maize root cells generate oOH, and respond to oOH by wall loosening, and in water-stressed root tips it has been hypothesed that ROS production is high. However, in salt-treated maize plants, salinity causes decreased ROS production that contributes to the reduction in leaf elongation. The purpose of this work was to compare the effects of salt and osmotic stress on root tip growth and ROS production, and to assess the contribution of ROS to root elongation under salinity. Root elongation was measured in maize seedlings grown in nutritive solution with or without the addition of 150 mM NaCl or 300 mM sorbitol. ROS presence was determined with 0.1 % nitro blue tetrazolium (NBT), which produces blue staining. Growth was depressed to a similar extent when plants were grown in modified Hoagland solution with the addition of 150 mM NaCl or 300 mM sorbitol, ROS production was high in the growing root region, it was conspicuous in both control and sorbitol-treated plants, but it was depressed by NaCl. Growth was stimulated in salt-treated plants by increasing the water potential in the growth media. Such treatment also produced an increase in ROS production. Both growth and ROS production were depressed by superoxide radical scavengers. Nevertheless, the addition of ascorbate, a mild ROS scavenger, promoted growth It is proposed that salinity may induce both increased and depressed ROS production, possibly in different cell compartments, and that the combination of these effects may affect root elongation under salinity by different mechanisms.