J. Van Overbeek

Dormin (Abscisin II), Inhibitor of Plant DNA Synthesis?

Dormin (abscisin II), inhibits growth of Lemna minor cultures. At 1 part per million (3.8x10-6M), the culture appears nearly completely dormant but can be revived readily by transferring it to fresh medium free of dormin. The cytokinin benzyladenine, but not auxin or gibberellin, will counteract the dormin effect. Quantitative restoration of normal growth by cytokinin, however, can be achieved only if the dormin concentration does not exceed a critical level. Separation, after phenol-detergent extraction, of nucleic acids on methylated albumin kieselguhr columns showed suppression of nucleic acid synthesis by dormin in all fractions. Inhibition of the synthesis of the DNA fraction seems to precede that of RNA. Cytokinins reverse the process. They promote synthesis of all nucleic acid fractions, but again DNA seems to lead. Further work on the interaction of dormin with growth-promoting hormones might be facilitated by adopting the Monod model of allosteric transition, with, for example, DNA polymerase as the protein, dormin as the inhibitor, and cytokinin or other growth promoters as activators.

Kinin-Induced Parthenocarpy in the Fig, Ficus carica L.

Parthenocarpic Calimyrna fig fruits induced with a kinin were identical morphologically to those previously produced parthenocarpically with auxin or gibberellin. Thus, the three types of endogenous hormones thought to originate in the seeds and to stimulate directly fruit growth can be supplied by plant parts other than seeds.

Acrolein for the control of water weeds and disease-carrying water snails.

Injection of the biocide acrolein into irrigation canals killed submersed weeds, thereby reducing flow resistance and increasing capacity. In a 20-mile canal, 150 gallons raised throughput from 311 to 552 ft2/sec. Acrolein also effectively eradicated aquatic snails; it promises to become a useful tool in the battle against Schistosoma blood flukes.