Temporal morphology and cap formation in Acetabularia--II. Effects of morphactin and auxin.
In order to support the hypothesis that circadian rhythms are implicated in cap formation, experiments were undertaken on the possible time-dependency of the effects of (a) a competitive inhibitor of auxins, morphactin and (b) of auxin (IAA). It was found that: (i) the inhibitory effect of morphactin varies dramatically with the time at which the several weeks' treatment was first begun; (ii) the maximum inhibition varies with development and decreases with time; (iii) IAA accelerates cap formation when the algae are submitted to IAA during the exponential growth phase; the effect is time dependent and decreases with time; (iv) IAA first applied on smaller algae has a transient inhibitory effect which is time dependent; (v) anucleate fragments also respond differentially to an IAA treatment begun at several times in the 24-hr cycle, most clearly when newly formed mRNA have been accumulated and (vi) the effect of iAA is not cumulative with that of a LD shift; that of morphactin is not, or only slightly, improved by a LD shift.
D000076:Acetabularia / Q000187:drug effects / Q000254:growth & development* / Q000528:radiation effects / Q000648:ultrastructure; D000460:Chlorophyta / Q000254:growth & development*; D002940:Circadian Rhythm / Q000187:drug effects*; D003624:Darkness; D005449:Fluorenes / Q000494:pharmacology*; D007210:Indoleacetic Acids / Q000494:pharmacology*; D008027:Light; D009024:Morphogenesis / Q000187:drug effects / Q000528:radiation effects; D012333:RNA, Messenger / Q000096:biosynthesis
D005449:Fluorenes; D007210:Indoleacetic Acids; D012333:RNA, Messenger; C005243:morphactins; C030737:indoleacetic acid