 B. G. Pickard

B. G. Pickard coauthored a 1989 test of gravity sensing in Arabidopsis thaliana using a starchless mutant. With T. Caspar, B. G. Pickard combined microscopic observations of plastids with measurements of gravitropism in roots and other tissues.^[ref]

Normal starch-containing plastids settled toward the lower side of the tested cells after inversion. The mutant plastids did not behave similarly, yet mutant roots retained a substantial bending response. Comparing short gravity exposures followed by clinostat rotation connected an initial stimulus to later curvature.^[ref]

The work illustrates a useful two-part test of a proposed sensor: establish that the candidate physical process was disrupted, then ask whether the biological response remains. Observing only the mutant's shape would not demonstrate that plastid sedimentation had been altered.