ENERGY-CHARGE AND EMERGENCE OF THE COLEOPTILE AND RADICLE AT VARYING OXYGEN LEVELS IN ECHINOCHLOA-CRUS-GALLI

Energy charge, [(ATP + 1/2 ADP)/(ATP + ADP + AMP)], was measured in E. crus-galli (L.) Beauv. var. oryzicola seeds germinated in an aerobic or anaerobic environment. Within 24 h after the seeds were imbibed, total nucleotides increased and energy charge values went from 0.6 to at least 0.8 in both air and N2. Upon transfer from air to N2, the energy charge initially decreased, but subsequently (within 24 h) increased to at least 0.8. Total nucleotides also increased after an initial decline when transferred from air to N2. Emergence of the coleoptile and radicle were also examined at O2 levels ranging from 21% to less than 0.005%. At all O2levels, the time for 50% emergence of coleoptiles was less than for radicle emergence. This was most evident when the O2 concentration was 1% or less. One of the adaptations that allows E. crus-galli var. oryzicola to germinate and grow under anaerobic conditions is its ability to maintain a high level of energy. In its natural environment, this would permit coleptile growth and penetration of the shoot into a more aerobic zone.