Enhancement of gladiolus flower vase life with sodium nitroprusside treatment
Sharad Kumar Dwivedi
The importance of flowers in socio-cultural and religious life of the Indian people can hardly be exaggerated. Though flower cultivation has been practiced in India since time immemorial, floriculture has blossomed into a viable and profitable business only in recent years. Considering the potential of this sector in generating income and employment opportunities, promoting greater involvement of women and enhancement of exports, this has been identified as an extreme focus area for export by Government of India.
Flowers require sincere, patient, soft, affectionate as well as expert handling. All cut flowers are destined to die, and the challenge for postharvest researchers is to slow the processes controlling flower death to enable cut flowers to reach distant markets with a display life. Gladiolus (Gladiolus species) is very much liked for its majestic spikes containing attractive, elegant and delicate florets. Gladiolus have five stages of flower development viz., bud stage (colour visible), half-open stage, fully-open stage, incipient senescent stage and finally senescence stage. These florets open in sequence over a longer duration and hence have a good keeping quality of cut spikes. There is a wide range of colours- self or bicolour with or without central mark varying from white to dark. Normally, gladiolus floret spikes last for 4-6 days. Removal of petals through senescence and/or abscission could benefit the growth and development of reproductive structures. But in floriculture, delaying the onset of senescence is the focus of a great deal of research in an effort to extend the useful life of the product. Cut flower stems are removed from a source of nutrients, undergo water restrictions and may be held at undesirable temperatures in the dark for days prior to sale. Plant hormones, membrane stability, water availability, cellular proteolysis and carbohydrate metabolism act in concert to determine the differential rate of senescence for each floral organ. Currently, flowers can be grouped into several categories based on post harvest technologies that can extend their vase life (e.g., sensitivity to ethylene, chilling sensitivity, leafy stems, multiple/single flowers per stem, woody stems etc.,) Extended vase life of cut flowers depends upon their water relations and retarding the rate of senescence which can be achieved by using certain chemicals.
Chemicals used for vase life enhancement of Gladiolus cut flower
The chemicals which are usually used to delay senescence in gladiolus include sucrose, silver nitrate, silver thiosulphate, 8-hydroxy quinoline, trehalose, polyamines, 5-sulphosalicylic acid, sodium benzoate, α-lipoic acid, etc. Interest in the use of nitric oxide gas (NO) as a means of extending the postharvest life of horticultural commodities is of recent origin. NO was first characterised in plants in 1996. Subsequent investigations have linked its occurrence to a range of physiological processes including modulation of endogenous ethylene and vegetative stress, water loss, plant immunity, anthocyanin biosynthesis and chlorophyll production, root growth and fruit and flower formation. Postharvest application of NO has been shown to be effective in extending the shelf life of a range of flowers, fruits and vegetables when applied as a short term fumigation treatment at low concentrations.
Various nitric oxide (NO) donors compound like sodium nitroprusside (SNP) and DETA/NO, have been shown to protect a variety of cut flowers from ethylene and dramatically increase the vase life. Use of SNP instead of DETA/NO as a donar of NO is more profitable because of its cheaper price and availability.
How NO work to enhanced the vase life of Gladiolus cut flower
A significant loss in fresh weight of flower spikes occurred in gladiolus. Fresh weight, vase solution uptake and vase life of gladiolus flowers kept in Sodium Nitroprusside (SNP; 100 ppm), source of nitric oxide (NO) solution remained higher in compression to the control (without SNP). Vase solution having NO (100 ppm) maintained high membrans stability index MSI in comparison to control at all the stages of flower development.Treatment with NO (100 ppm) solution maintained lower protease activity, TBARS content and lipoxygenase activity in comparison to control at all the stages of flower development. The activities of antioxidant enzymes SOD, CAT, POX and AP responsible for scavenging various free radicals increased. The spikes treated with NO (100 ppm) solution maintained higher level of these enzyme activities in comparison to control at all the stages of flower development.The expression of senescence associated genes (SAGs) viz., GgCyP1, GgERS1a and GgERS1b were downregulated while GgDAD1 was upregulated by nitric oxide treatment during the course of flower development.
These findings have significant implications for post harvest research. As nitric oxide delays senescence, it can be used in floriculture to prolong the vase life of gladiolus. Farmers can earn more money due to enhanced vase life of cut flower and improve their standard of living by securing more income. Thus in nut shell vase life enhancement of gladiolous cut flower via nitric oxide treatment always an profitable business for the Indian farmers.
Dr. SHARAD KUMAR DWIVEDI
Division of Plant Physiology, IARI, New Delhi, India-110 012.