Figure 1.

Kinetic studies of gravitropic curvature, hexose and K⁺ accumulation, acid invertase activity, and Ivr2 transcript abundance in maize stem pulvini. Vertical maize plants were gravistimulated for the time indicated by displacing to a horizontal position. At each time point, angle of gravitropic curvature was measured (A) and pulvini was harvested into upper (⋄) and lower (♦) halves. Hexose sugars (B), K⁺ content (C), and acid invertase activity (D) were determined and values are expressed as a fold increase over the vertical control value (set to 1). Mean values (±se) from three independent experiments are shown. E, Total RNA was isolated and hybridized with an Ivr2 cDNA probe, radioactivity stripped, and the membrane was rehybridized with an 18S rRNA probe. Ivr2 and 18S hybridization signals were quantified using a densitometer, and Ivr2 expression levels in each treatment were normalized to the 18S loading control. Transcript accumulation in gravistimulated samples is expressed relative to the vertical control (set to 1). Mean values (±se) from three independent experiments are shown.