Dormancy in tulip (Tulipa gesneriana L.) bulbs and freesia (Freesia refracta Klatt.) corms: Changes in soluble proteins and APX activity

Abstract

The bulbs of tulip (Tulipa gesneriana L.) evs Negrita and Cassini and the corms of freesia (Freesia refracta Klatt.) cvs Polaris and Aladin were used in the study to investigate molecular changes during the storage and sprouting stage besides phenologic observations. One part of the bulbs and corms were directly planted (DP) into greenhouse without any treatment. Another part of the bulbs and corms were either stored in room condition (RC; 18-25 degrees C and 55-65% RH) or in normal atmosphere (NA; 5+/-1 degrees C and 70-85% RH) for 120 days before planting. In both storage treatments, the bulbs and corms were transplanted to the greenhouse in three periods with 40 days intervals. In every period, a part of the bulbs and corms were taken for the molecular analyses before planting. In addition, some of DP bulbs and corms were removed from soil at the same periods for molecular analyses. The storage of the bulbs and corms reduced the sprouting durations in comparison to the DP treatment. However, NA storage either reduced (in tulip) or inhibit (in freesia) to proportions of plant formation. The highest and the lowest ascorbate peroxidase (APX) activity were found during NA storage and DP treatment, respectively, in both species. In addition APX activity was higher in tulip than in freesia. Sharp decrease in total soluble protein (TSP) content particularly after 40 and 60 days of almost all treatments can be an evidence of breakdown of storage proteins. TSP profiles of tulip bulbs showed a major polypeptide, 18 kDa, with different band intensities according to the treatments. In freesia, 66 kDa protein accumulated especially in last two sampling periods of NA storage, whereas 58 kDa protein became invisible in last two sampling periods of NA storage. Since prolonged NA storage inhibits the sprouting and proportions of plant formation, 66 kDa and 58 kDa bands might be related to dormancy or sprouting in freesia.