Auxin content in Air and Water Grown Rice Coleoptiles

Summary Rice coleoptiles of 2, 3 and 4 days were divided into segments of 3 and 10 mm in length, respectively, for experiments measuring the elongation of coleoptiles kept in air or water. Their growth - in terms of both elongation and fresh mass - was found to be much lower when they were maintained in air than when they were submerged in water. IAA levels were analysed with gas chromatography (GC) and mass spectrometry (MS. A significant IAA gradient was obtained for coleoptiles kept in air: segments from the tip have a higher IAA content compared with those from the base. In contrast, for coleoptiles maintained in water no significant differences were noticed between apical and basal segments. When IAA level was expressed for the whole coleoptiles maintained in air, it was significantly raised with increasing time of incubation (2 to 4 days), while for coleoptiles growing in water, the IAA level (constantly lower when compared with that in air) showed no real changes throughout the duration of the culture.