Mapping the Functional Roles of Cap Cells in the Response of Arabidopsis Primary Roots to Gravity

摘要: The cap is widely accepted to be the site of gravity sensing in roots because removal abolishes root curvature. Circumstantial evidence favors columella cells as gravisensory amyloplasts (and often other cellular components) are polarized with respect vector. However, there has been no functional confirmation their role. To address this problem, we used laser ablation remove defined Arabidopsis primary and quantified response using three parameters: time course curvature, presentation time, deviation from vertical growth. Ablation peripheral tip did not alter innermost caused strongest inhibitory effect on curvature without affecting growth rates. Many these deviated significantly had a 6-fold longer than controls. Among two inner stories, central story 2 contributed most gravitropism. These also exhibited largest amyloplast sedimentation velocities. Therefore, results consistent starch-statolith hypothesis for sensing.