Effects of Plant Water and Carbohydrate Status on Cut Flower Quality in Eustoma
Date Issued
2010
Date
2010
Author(s)
Chuang, Ya-Ching
Abstract
Eustoma grandiflorum (Raf.) Shinn. is a cut flower crop with high economic potential in Taiwan. Before harvest, growers usually reduce irrigation, but there have been no studies on how this process affects cut flower quality in Eustoma. In this study we investigated the responses of Eustoma to preharvest water deficit and observed water and carbohydrate flow in cut flowers, to improve production and postharvest techniques.
When 0, 6, or 12 leaves were kept on stem per cut flower, water uptake rate increased along with number of leaves. However, 12 leaves on a cut flower caused excess transpiration, shortening vase life. Bud opening was the highest water consuming stage, with fresh weight increased up to 1.4 times from mature-bud stage to opened-flower stage. Uppermost immature buds did not open during the period cut flowers were in vase and had no impact on visual quality or water balance of cut flowers. Differences in regard of competition between florets were observed between cultivars. ‘Bolero White’ and ‘Bolero Blue Flash’ florets wilted when younger buds on the same inflorescence opened, resulting in longer inflorescence life. By contrast, bud opening of ‘Arena Pink’ and ‘Ex Rosa Pink Flash’ made no impact on keeping time of opened flowers, their inflorescence life was shortened by a decline in water uptake after bud opening. Hence vase life of ‘Ex Rosa Pink Flash’ is lengthened by additional number of mature buds, the removal of unopened buds did not increase life of originally opened flowers.
Maintaining medium water content above 30% or 40% after visible bud stage in Eustoma resulted in higher growth and plant water content. Keeping medium water content between 20% and 25% improved cut flower water balance in cultivars ‘Piccolo Lime Green’ and ‘Ex Rosa Green’. ‘Piccolo Lime Green’ had lower stomata conductance with lowered medium water content, while ‘Ex Rosa Green’ grown under 20% to 25% medium water conent had higher glucose concentration in leaves and stem. Yet cut flower vase life and floret life was lengthened by lower medium water content only in ‘Piccolo Lime Green’. Preharvest medium water content between 10% and 15% reduced growth of Eustoma such that harvestable quality was not reached.
Differences between preharvest irrigation treatments on Eustoma were less pronounced when growing plants in field than in pots. Due to lower water uptake rate, cultivar ‘Piccorosa Snow’ had shorter vase life when grown in water deficit field plots. Nevertheless cut flowers showed better recovering of a positive water balance after an hour of postharvest water stress. Vase life of flowers grown with doubled (16 L∙m-2/wk) irrigation was shortened by postharvest water stress treatment.
The most abundant soluble carbohydrate in Eustoma flowers is glucose, accounting for 7.8% flower dry weight. Glucose was consumed mainly during bud opening, after which glucose concentration dropped to 3.5%. Sugars originally supplied to vase solutions accumulated in flowers and vegetative parts during bud opening. Vase solution containing 20 g∙L-1 glucose or sucrose aided bud opening and fresh weight maintaining. Fructose in vase solution may also promote cut flower quality, especially when 8-hydroxyquinoline (8-HQS) is added.
Subjects
bud opening
water deficit
water balance
vase life
vase solution
Type
thesis
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