Gating of aq  aporins by light and reactive XXXX species in leaf parenchyma cells of the midrib of @entity2829 .

@entity8798 @entity274 @entity2829 @entity26 @entity2041 @entity3282 @entity3917 @entity2145
Changes of the water permeability aq  aporin (AQP) activity of leaf cells were investigated in response to different light regimes (low versus high). Using a cell pressure probe, hydraulic properties (half-time of water exchange, T(1/2) infinity 1/water permeability) of parenchyma cells in the midrib tissue of @entity2829 ( @entity2829 .) leaves have been measured. A new perfusion technique was applied to excised leaves to keep turgor constant and to modify the environment around cells by perfusing solutions using a pressure chamber. In response to low light (LL) of 200 micromol m(-2) s(-1), T(1/2) decreased during the perfusion of a control solution of 0.5 mM @entity3282 by a factor of two. This was in line with earlier results from leaf cells of intact @entity2829 plants at a constant turgor. In contrast, @entity3917 ( @entity3917 ) at intensities of 800 micromol m(-2) s(-1) and 1800 micromol m(-2) s(-1) increased the T(1/2) in two-thirds of cells by factors of 14 and 35, respectively. The effects of @entity3917 on T(1/2) were similar to those caused by @entity274 treatment in the presence of @entity8798 , which produced * @entity2145 (Fenton reaction; reversible oxidative gating of aquaporins). Treatments with 20 mM @entity274 following @entity8798 pre-treatments increased the T(1/2) by a factor of 30. Those increased T(1/2) values could be partly recovered, either when the perfusion solution was changed back to the control solution or when LL was applied. 3mM of the antioxidant @entity2041 also reversed the effects of @entity3917 . The data suggest that @entity3917 could induce reactive @entity26 species (ROS) such as @entity2145 , and they affected water relations. The results provide evidence that the varying light climate adjusts water flow at the cell level; that is, water flow is maximized at a certain light intensity and then reduced again by @entity3917 . Light effects are discussed in terms of an oxidative gating of aquaporins by ROS.
