The germination and establishment of rice seed sown into water

Abstract

Observations have been made on the effects of varying water depth, temperature, aeration, and seeding rate on the germination and ear4 growth of rice seed sown into water. Under conditions of poor aeration, the coleoptile is extruded, but does not open, and there is little or no growth of the radicle. With better aeration, the coleoptile bursts and there is both shoot and root development. At low seeding rates, of the order used in field sowings, aeration of the water has little or no effect at temperatures below 27¦C, but does have an increasingly beneficial effect as temperatures rise above this, up to the level where temperature per se begins to retard growth. At 39¦C seedlings do not grow and aeration bas no effect. A t water temperatures below 25¦C, seedlings stay at the soil surface and roots freely enter the soil, giving rapid and good establishment, but at higher temperatures, seedlings float near the water surface, and roots show no general tendency to grow downwards. Such roots as do reach the soil surface show marked reluctance to penetrate into the soil. This appears due to insufficient aeration in the soil, for when air or fresh water is passed through the rooting medium, the roots enter freely. It is concluded that this is the major hazard to sowing in warm standing water.