Growth Hormone and Mesocotyl Growth

If young maize seedlings are exposed to 48°C in air for about x/fm hour, the growth of the mesocotyl is markedly inhibited. The amount of growth hormone given off by the tips of the coleoptiles also is less in the heat treated plants than in the controls. By applying extra g.s. to the tips of the heat treated plants it could be proved that the inhibition of the mesocotyl growth is due to the decreased amount of growth hormone given off by the tip. If Avena seedlings are completely shielded from the darkroom illumination (yellow light) they develop very long mesocotyls in water and earth cultures alike.