PATTERNS OF C2H4 PRODUCTION DURING GERMINATION AND SEEDLING GROWTH OFPEA AND WHEAT AS INDICATED BY A LASER-DRIVEN PHOTOACOUSTIC SYSTEM

Highly sensitive kinetic studies of ethylene evolution in germinating seeds of pea (Pisum sativum L. cv Frijaune) and wheat (Triticum durum L. cv Appulo) using a laser-photoacoustic system indicated that C2H4 p roduction started early after imbibition, and reached a maximum before mitotic activity, thus simultaneously with early radicle elongation. Most of this initial gas evolution originated from the embryonic tissu e. Thereafter, a major increase in ethylene production occurred during early coleoptile growth in wheat whereas the rate of ethylene evoluti on tended to decrease in pea. Seed decoating, after previous imbibitio n at 5 degrees C for 8 hr, accelerated germination and early root elon gation of peas. Moreover, decoated peas exhibited a faster and synchro nous increase in ethylene production. The results support the view tha t ethylene plays a regulatory role in seed germination and seedling gr owth pattern.