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Role of Lipoxygenase During Flower Bud Opening in Roses (Rosa hybrida L.)
Naveen Kumar,Girish Chand Srivastava,Kiran Dixit 한국원예학회 2008 Horticulture, Environment, and Biotechnology Vol.49 No.3
The adverse effect of lipid peroxidation during flower bud opening in roses was investigated. Experiments were conducted from 2005 to 2007 on two cultivars of cut-roses (Rosa hybrida L.), ‘Grand Gala’ and ‘First Red’ obtained from a commercial grower. Flower stems were harvested at different developmental stages. Petals were separated from seven different petal whorls in flowers (outermost to innermost) of ‘Grand Gala’ and ‘First Red’ at all developmental stages. During the first three stages of flower bud development (S1 - S3) petal membrane remained stable for a considerable period of time. However, at subsequent stages (S4 - S6) membrane leakage increased considerably in both cultivars showing membrane stability index of 48 percent and 38 percent in flower petals of ‘First Red’ and ‘Grand Gala’ respectively. TBARS (Thiobarbiturate reactive substances) content was very low during the first two stages of flower bud development; thereafter, a steep rise was noted in different petal whorls of both cultivars. Lipoxygenase activity showed a progressive rise from stage 1 to stage 6 of flower bud development. Differential LOX (Lipoxygenase) activity was noticed during flower bud opening, a progressive rise during the first three phases, but at a slower pace and a two-fold rise at later stages of development.
Cell wall hydrolases: Expansion or Senescence in Roses (Rosa hybrida L.)
Naveen Kumar,Girish Chand Srivastava,Kiran Dixit 한국원예학회 2008 Horticulture, Environment, and Biotechnology Vol.49 No.6
Roles of cell wall hydrolases in relation to petal expansion and subsequent senescence in roses were studied. Experiments were conducted in a laboratory at the Indian Agricultural Research Institute, New Delhi, during the year 2005-07. Two cultivars of cut- roses (Rosa hybrida L.), ‘Grandgala’ and ‘First Red’ were obtained from a commercial grower (German Garden), Dharuheda, Haryana, India. Flower stems were harvested at six different developmental stages. Petals were separated from different petal whorls of the flower, outermost to innermost [7 whorls each in both ‘Grandgala’ and ‘First Red’] from all the developmental stages. Opening of the flower bud was accompanied by increased activity of cell wall hydrolases. Activities of polygalactouronase (PG) and pectin methyl esterase (PME) increased up to stage 5 in flower bud development in all the petal whorls and declined thereafter. Higher levels of PME and PG activity were correlated with the flower bud development and petal expansion. The highest level of ethylene production coincided with the peak activity of both enzymes in expanding petals. The PME activity appeared to create an acidic environment within the cell wall that promoted the action of PG, which might cause cell wall loosening and allow turgor driven petal expansion. It seems that both ethylene dependent (S3-S6) and ethylene independent (S1-S2) activities of PME and PG are parts of a highly coordinated cell death program, which follows initial cell wall loosening, expansion, and finally termination of petal life.