DIATOM MINERALIZATION OF SILICIC ACID. VII. INFLUENCE OF MICROTUBULE DRUGS ON SYMMETRY AND PATTERN FORMATION IN VALVES OF NAVICULA SAPROPHILA DURING MORPHOGENESIS1

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Abstract
Microtubule involvement in diatom valve symmetry and pattern formation was investigated using cells synchronized subsequent to mitosis and cytokinesis but prior to cell wall formation. Two analog drug pairs, each consisting of an active and an inactive microtubule drug, were used to distinguish inhibitory effects related or unrelated to microtubule disruption. The active anti‐microtubule drug of each analog pair produced significantly higher percentages of aberrant valves than did the respective inactive analogs. High frequencies of aberrant valves also were caused by N‐isophenlpropylcarbamate, which disorganizes rather than disrupts microtubules. Valves could be placed into different classes based upon characteristic aberrations. Formation of these classes was not random but was instead a function of both the drug and the drug concentration. The central nodule and the raphe were the principal valve components affected by anti‐microtubule drugs. Stria alterations appeared as a secondary result of alterations in the central nodule/raphe. Valve aberrations occurred at very low drug concentrations in the range 1 × 10−6 to 1 × 10−9M.