Gladiolus

Abstract: Gladiolus bud explants propagated in agitated liquid medium, in the presence of the growth retardants daminozide, ancymidol, paclobutrazol or Majic, proliferated into massive bud aggregates without leaves. The buds developed into protocorms and after subculture to agar-solidified medium formed cormlets 8–10 mm in diameter. The corms were not dormant and, after transplanting to pots in the greenhouse, developed into plantlets, 5–6 months after explant isolation.

Abstract: In vitro responses of twelve species of bulbs and corms were compared. Plantlets could be induced directly without intervening callus on stem tissue in nine species, on ovary tissue in five species, and on leaf tissue in four species. In Gladiolus, Hyacinthus, Muscari, Ornithogalum, and Scilla plantlets were formed without growth factors added to the Murashige and Skoog medium. In Hippeastrum, Schizostylis, Sparaxis, and Ipheion auxin was required. No plantlets could be induced directly on expiants of growing tissue of Freesia, Tulipa, or Narcissus. Adventitious plantlets could be induced on pieces of bulb or corm from ten species but such material was difficult to free from contamination. Callus was obtained from all species except Tulipa and Hippeastrum. Plantlets could be regenerated from callus except that of Gladiolus, Sparaxis, and Schizostylis. Differences in responses of the twelve species tend to cut across the three families and no simple relation is evident between the natural rate of vegetative increase and the in vitro behaviour.

Abstract: The opening and senescence of gladiolus ( Gladiolus sp.) florets was accompanied by climacteric or nonclimacteric patterns of respiration and ethylene production, depending on variety, and whether data were expressed on a fresh-weight or floret basis. A climacteric pattern of ethylene production by the youngest buds on the spike (which never opened) was stimulated by cool storage, and was not affected by holding the spikes in a preservative solution containing sucrose. Ethylene treatment had no effect on senescence of the florets of any of the cultivars tested. Pulse treatment of the spikes with silver thiosulfate (STS) improved floret opening but not the life of individual florets. Sucrose and STS had similar but not synergistic effects on floret opening, suggesting that STS improves flower opening in gladiolus by overcoming the effects of carbohydrate depletion. Gladiolus are prized by florists for their showy flower spikes, and by growers for their relative ease of production. Like other flowers with spike inflorescences, gladiolus are normally har- vested with relatively few open florets, and the life of the flower is a function both of the life of individual florets, and of the postharvest expansion and opening of the buds remaining on the spike. Ideally, many of the florets on the spike should open before the senescence of the bottom florets. Because the dead florets are unattractive, senescence of the bottom florets marks the end of the flower spike's commercial display life. The typical life of these florets on a spike placed in water is 4 to 6 days (Marousky, 1968; Mayak et al., 1973). Modest increases in the life of gladiolus flowers have been gained by pulsing with sucrose, or using vase preservatives containing sucrose (Marousky, 1971). Little has been done to examine the physiological basis of senescence in gladiolus, and no work has been reported on the physiology of individual florets. This is surprising, since gladiolus flower spikes offer an interesting model system for studies of flower senescence. Individual florets provide a graded series of stages of development and senescence in an identical genetic and environmental background. Many studies have examined the possible role of ethylene in gladiolus senescence. Woltering and van Doorn (1988) reported that treatment with ethylene (3 μl·liter - 1 ) for 24 h revealed little to no sensitivity as indicated by slight acceleration of petal wilting in only some cultivars. Pulse treat- ments with the silver thiosulfate anionic complex (STS) have likewise provided little (Farhoomand, 1978) or no (Mor et al., 1981) benefit. In contrast, Merodio and de la Plaza (1989) reported that ethylene removal during storage improved the subsequent vase life of 'pink' and 'white' gladiolus cultivars. Ethylene re- moval also resulted in reduced water and color loss, and improved stem 'rigidity'. Murali and Reddy (1993) used a range of metal salts (in combination with sucrose) and found a positive correla tion between the effects of their treatments on ethylene production and vase life of the flower spikes. Thus, the role of ethylene in senescence of gladiolus petals and the life of the flower spikes is unclear. In this study, we examined the role of ethylene in floret senescence of gladiolus flowers by determining ethylene produc- tion and respiration of individual florets during development and senescence, and by exploring the effects of exogenous ethylene, STS, and sucrose treatments on opening and senescence of florets in a range of commercial cultivars.