Gravitropism in Phycomyces: threshold determination on a clinostat centrifuge.
The absolute sensitivity of sporangiophores of Phycomyces blakesleeanus to centrifugal acceleration was determined on a clinostat centrifuge. The centrifuge provides centrifugal accelerations ranging from 10(-4) to 6 x g. The rotor of the centrifuge, which accommodates 96 culture vials with single sporangiophores, is clinostatted, that is, turning "head over", at slow speed (1 rev min(-1)) while it is running. The negative gravitropism of sporangiophores is characterized by two components: a polar angle, which is measured in the plane of bending, and an aiming-error angle, which indicates the deviation of the plane of bending from the vector of the centrifugal acceleration. Dose-response curves were generated for both angles with centrifugations lasting 3, 5, and 8 h. The threshold for the polar angle depends on the presence of statoliths, so-called octahedral protein crystals in the vacuoles. The albino strain C171 carAcarR (with crystals) has a threshold near 10(-2) x g while the albino strain C2 carAgeo-3 (without crystals) has a threshold of about 2 x 10(-1) x g. The threshold for the aiming error angle is ill defined and is between 10(-2) and 10(-1) x g. The threshold for the polar angle of the wild type NRRL 1555 (with crystals) is near 8 x 10(-2) x g.
Galland
Paul
P
Fachbereich Biologie, Philipps-Universität, Lahnberge, D-35032 Marburg, Germany. galland@staff.uni-marburg.de
Finger
Heike
H
Wallacher
Yvonne
Y
D002498:Centrifugation / Q000295:instrumentation / Q000379:methods; D004867:Equipment Design; D018522:Gravitropism / Q000502:physiology*; D010800:Phycomyces / Q000502:physiology*