Changes in endogenous polyamines during in vitro cormlet formation in Gladiolus hybridus Hort.

Abstract

Cormlet formation was achieved in the cultures of Gladiolus hybridus Hort. cv. ‘Her Majesty’ (an important bulbous cut flower) on plant growth regulator-free (PGR-free) Murashige and Skoog medium. Changes in the endogenous polyamines (PAs) were monitored during in vitro cormlet formation up to 140 days, at an interval of 20 days, following transfer of rooted shoots to PGR-free medium. The levels of total PAs as well as free and conjugated PAs showed an increase during the phase of cormlet development; the levels subsequently declined during cormlet maturation. While the levels of bound PAs were initially higher than free and conjugated PAs, the same were found to decline later on. The free and conjugated PAs, however, increased during the initial phase of the study (up to 80 days). Spermidine was found to be the major polyamine followed by spermine during cormlet formation. Maximum levels of free and conjugated spermidine were recorded after 80 and 60 days of incubation respectively. This time period coincided with the phase of cormlet development. While free spermine levels were higher after 40 day of incubation, levels of conjugated spermine were maximum at the beginning. In comparison to spermidine and spermine, putrescine levels were found to remain low throughout the culture period. The observed higher levels of free and conjugated spermidine and spermine in cultures grown on PGR-free medium are suggestive of their role in the process of cormlet formation in gladiolus.