Physiologicaland molecular analysis of effect of spermine on senescing petals of gladiolus

Convincing evidences suggest the involvement of polyamines in the process of senescence. In order to unravel the mechanism underlying polyamines (spermine) regulated senescence in gladiolus, the present study was undertaken. Spermine at 5μM delayed flower senescence in ethylene-insensitive gladiolus by three days, along with increased fresh weight which was retained for longer period and increased vase solution uptake as compared to control. Activities of total SOD as well as that of its copper/zinc and iron isoforms were significantly enhanced by spermine. Qualitative analysis revealed one Fe SOD and two Cu/Zn isozymes, Cu/Zn SOD1 and Cu/Zn SOD2. Cu/Zn SOD1 appeared to be constitutively expressed but at a higher level than Cu/Zn SOD 2, though the later is more responsive to spermine treatment. Spermine reduced the expression of GgCyP while upregulating GgSOD. Spermine is thus effective in delaying senescence. It increased the activity of all the isoforms of SOD thereby, reducing oxidative stress and prolonging the vase life. Spermine affected gene expression of GgCyP and GgSOD without any impact on GgERS1a, while slightly affecting the expression of GgERS1b. The differential impact of spermine is related to the differential role of these genes in senescence.