RESPONSE OF THE CARBOHYDRATE-METABOLISM AND FRUCTOSE-2,6-BISPHOSPHATETO ENVIRONMENTAL-CHANGES - EFFECT OF DIFFERENT LIGHT TREATMENTS

Important and rapid variations of Fru-2,6-P-2 were observed during lig ht-on and light-off transitions in both spinach and mustard: Fru-2,6-P -2 undervent tremendous variations showing an 80% decrease within 13 m inutes in both plants. In mustard cotyledons, during both day and nigh t periods, Fru-2,6-P-2 showed a decrease during the first hour, follow ed by a regular 240% increase. In spinach, the same behavior of Fru-2, 6-P-2 was observed, except that once the concentration of the sugar ha d doubled, it remained constant. In contrast to mustard, spinach Fru-2 ,6-P-2 presented a much higher level during the night than during the light period. In 3 day old germinating oat, red light illumination for 5 min was accompanied by a 48 h halt of elongation and by a 180% incr ease of Fru-2,6-P-2 20 min after irradiation, followed by the total di sappearance of this sugar 80 minutes after light treatment. The presen t work shows the highly dynamic capacity of the regulatory sugar Fru-2 ,6-P-2 in plants with respect to short, mid and long term light treatm ents. This indicates an important cellular messenger role of Fru-2,6-P -2 in the regulation of carbohydrate metabolism in response to light c hanges.