ENERGY METABOLISM OF IMBIBING KALANCHOË SEEDS. RESPONSE TO GIBBERELLIC ACID AND CONTRIBUTION OF RESPIRATION AND FERMENTATION TO ATP PRODUCTION

Abstract

In Kalanchoe blossfeldiana seeds imbibed in the dark for 10 days at 20°C, very similar energy charge ( EC ) values were measured in the presence and absence of gibberellic acid (GA 3 ). This demonstrates that GA 3 does not prevent or strongly delay the induction of secondary dormancy in Kalanchoe seeds by elevating EC levels. However, GA 3 clearly increased the ATP and AMP content of the seeds. During the first hours of anoxic imbibition, the sodium-fluoride sensitive ATP production still represents 25 to 30% of the ATP amount produced in the air, indicating that in Kalanchoe seeds the fermentative pathway can partly contribute to ATP production. As the oxygen uptake by the seeds is cyanide-sensitive and a severe inhibition of the increase in ATP content by cyanide can be demonstrated during the first hours of aerobic imbibition, our results indicate the participation of the normal cytochromic pathway in ATP synthesis.