Partial Reversion by 5-Aminouracil of the Inhibition of Coleoptile Growth in Hordeum vulgare by Large Volumes of Water

Barley seedlings show a differential response to an increasein the volume of water on which they are grown. On 20 ml, ascompared with 9 ml of water, germination of some seeds is delayedand growth of some coleoptiles is inhibited at 45 h. Both effectsincrease progressively from 9 to 20 ml. Treatment with 5-aminouracilcan reverse, in part, the effects of high volumes of water.With 12, 17, and 20 ml of solution 5-AU increases the frequencyof germination and coleoptile growth. Its effect is most markedon 20 ml of solution, i.e. the volume that produces the greatestover-all inhibition of growth when seeds are on water is theone at which 5-AU is most effective in stimulating growth. Ofthe three concentrations tested, 10^–4 M was most effectivewhen used at a volume of 20 ml.