Plant material.

Cut stems of lilies and gladiolus were received from The Sun Valley Group, Arcata, CA, and Glad-A-Way Gardens, Santa Maria, CA, respectively, during Oct. to Nov. 2013 at the Postharvest Laboratory, Department of Horticultural Science, North Carolina State University (NCSU), Raleigh. Stems of ‘Cobra’ oriental hybrid lily, ‘Cappuccino’, ‘Dot Com’, and ‘Orange Art’ asiatic hybrid lily, and ‘Alice’, ‘Mammoth’, ‘Passion’, and ‘Scarlet’ gladiolus were harvested in California in the morning when no flowers/florets were opened, hydrated in water, packed dry in standard floral boxes without any further treatment, and transported to the NCSU laboratory within 4 d of harvest. On arrival, stems were sorted into uniform groups on the basis of number of opened florets and stem caliper, labeled, recut to 60 or 80 cm lengths for lilies or gladioli, respectively, and placed in respective pulsing solutions. Solutions included GA₄₊₇ + BA at 2.5, 5.0, or 10.0 mg·L⁻¹ or commercial preservatives, GA₄₊₇ + BA + preservative at 2 mL·L⁻¹ or floral bulb preservative at 10.0 g·L⁻¹. GA₄₊₇ + BA + preservative was not tested on ‘Scarlet’ gladiolus. All solutions were prepared using tap water [pH 7.3, electrical conductivity (EC) 0.26 dS·m⁻¹], which was also used as control without any added compound. All solutions and stems were placed at 3 ± 1 °C in dark for 20 h. Thereafter, stem ends were rinsed in water and stems were placed in vases containing 700 mL tap water (pH 7.4, EC 0.25 dS·m⁻¹), with three stems per vase at 21 ± 1 °C with 40% to 60% relative humidity and a 12 h photoperiod provided by cool-white fluorescent lamps with a photosynthetic photon flux of about 20 μmol·m⁻²·s⁻¹ as measured at bench level with a quantum light meter (1078 QMSW; Apogee Instruments, Logan, UT).

Measurements.

Data were collected daily for vase life (duration from placement of stems in vases in the postharvest evaluation room to the time when individual stems ended), change in fresh weight (on day 6 of vase life), stem quality (rated on a scale of 1–10 on day 6 of vase life, where 1 = 0% to 10% wilting, chlorosis, or discoloration, and 10 = 91% to 100% wilting, chlorosis, or discoloration), water uptake (up until when first stem was ended in entire experiment), number of opened flowers during vase period, number of yellow leaves at termination, and termination symptoms. Symptoms for terminations were recorded as either present or not, and included leaf or petal abscission, necrosis, or wilting for lilies, and bent stem, bluing, leaf tip chlorosis, petal necrosis or wilting, or sepal chlorosis for gladiolus. The condition was recorded as present if it occurred on at least one petal/floret, bud, leaf, or stem, and stems were ended when they developed one or more of the aforementioned symptoms on ≥50% of the flowers/inflorescence, foliage, or stem (Ahmad et al., 2013).

Statistical analyses.

All experiments were completely randomized designs with five replicate vases of three stems each. Data were subjected to analysis of variance procedures using General Linear Models procedures of SAS (version 9.3; SAS Institute, Cary, NC) and means were separated using Fisher’s least significant difference at P ≤ 0.05. Experiments were also repeated for ‘Cobra’ and ‘Orange Art’ lily and for ‘Mammoth’, ‘Passion’, and ‘Scarlet’ gladiolus for confirmation of results. However, data were presented for only one experiment for each cultivar due to similar results among experiments.

Lily.

Stems of ‘Cobra’ oriental hybrid lily and ‘Cappuccino’ and ‘Dot Com’ asiatic hybrid lily had longest vase lives when pulsed with 5 or 10 mg·L⁻¹ GA₄₊₇ + BA or GA₄₊₇ + BA + preservative (Table 1). For ‘Orange Art’ asiatic hybrid lily, use of GA₄₊₇ + BA at 10 mg·L⁻¹ or GA₄₊₇ + BA + preservative resulted in longest vase life. Moreover, both compounds effectively controlled leaf yellowing of ‘Cobra’, ‘Dot Com’, and ‘Orange Art’ lily, and considerably reduced leaf yellowing of ‘Cappuccino’ lily. Results highlighted the efficacy of pulsing with GA₄₊₇ + BA + preservative or GA₄₊₇ + BA for maintaining stem quality and reducing loss of stem fresh weight during vase period. Use of gibberellins and benzyladenine is reported to control leaf chlorosis in easter lily (Han, 1997; Whitman et al., 2001), potted oriental lily (Çelikel et al., 2002; Ranwala and Miller, 2000), and cut lilies (Han, 2001; van Doorn and Han, 2011). However, continuous vase application at 0.5 or 2.5 mg·L⁻¹ or pulse at 25 mg·L⁻¹ for 4 h increased bud abscission (Han, 2001). Therefore, use of lower concentration of 5–10 mg·L⁻¹ for 20 h in this study provided a better option to control leaf chlorosis without any negative effects. In this study, GA₄₊₇ + BA and GA₄₊₇ + BA + preservative either increased or had no effect on the number of flowers opening. Leonard and Nell (2004) also noted that GA₄₊₇ + BA + preservative was effective for controlling leaf chlorosis and vase life extension of oriental lilies.

Table 1.

Effect of gibberellin plus benzyladenine (GA₄₊₇ + BA), a commercial proprietary floral preservative mixture of GA₄₊₇ plus BA (GA₄₊₇ + BA + preservative), or a commercial proprietary floral preservative mixture of sugar plus acidifier for bulbous flowers (floral bulb preservative) on vase life and postharvest parameters of ‘Cobra’ oriental lily and ‘Cappuccino’, ‘Dot Com’, and ‘Orange Art’ asiatic lily. Data for fresh weight change represent means of five replicate stems, for water uptake represent five replicate vases, whereas all other data represent means of 15 stems with three stems per vase.

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Pulsing with floral bulb preservative produced a similar vase life as with tap water, except for ‘Dot Com’ where vase life was 1.7 d longer for floral bulb preservative than tap water (Table 1). Stems for all cultivars in tap water gained the least fresh weight (FW) or lost the most FW at day 6. Pulsing with floral bulb preservative increased water uptake of ‘Orange Art’, but reduced uptake in ‘Cappuccino’ lily. Floral bulb preservative was intended as a final product to be used in vases and did not provide good results as a short-term pulsing solution.

Most common symptoms for termination of stems included abscission, necrosis, or wilting of leaves or petals with treatments significantly affecting leaf wilting and petal abscission for most cultivars (Table 1). Stems pulsed with tap water or floral bulb preservative resulted in the least petal abscission for all cultivars and the most leaf wilting with ‘Cappuccino’, ‘Dot Com’, and ‘Orange Art’. In addition, 5 or 10 mg·L⁻¹ GA₄₊₇ + BA or GA₄₊₇ + BA + preservative also resulted in higher leaf abscission in ‘Cobra’ (13% to 33%), higher leaf necrosis in ‘Dot Com’ (40% to 87%) and higher petal necrosis in ‘Dot Com’ (73% to 100%) compared with tap water (0%, 7%, and 13%, respectively) (data not presented). The higher rate of leaf and petal abscission and necrosis for GA₄₊₇ + BA or GA₄₊₇ + BA + preservative treated flowers is likely due to the longer vase life. Other reports indicated that cut lily stems generally senesce due to leaf chlorosis or petal wilting (van Doorn and Han, 2011). Additionally, bud abscission, petal abscission or browning, or failure of buds to open also result in rapid loss of quality in some cultivars. In the current studies, none of the cultivars had abscised buds. Incidence of leaf abscission was relatively low in the cultivars varying from 0% for ‘Cappuccino’, ‘Dot Com’, and ‘Orange Art’ to 11% for ‘Cobra’, while leaf necrosis incidence ranged from 0% for ‘Cobra’ to 55%, 31%, and 65% for ‘Cappuccino’, ‘Dot Com’, and ‘Orange Art’, respectively. Incidence of petal wilting was 100% in all of the cultivars.

Gladiolus.

Cut stems of ‘Alice’, ‘Mammoth’, ‘Passion’, and ‘Scarlet’ gladiolus had longest vase life, when pulsed with 5 or 10 mg·L⁻¹ GA₄₊₇ + BA (Table 2). Gladiolus stems had no or minor leaf yellowing with a significant difference found only for ‘Alice’ in which stems pulsed with GA₄₊₇ + BA had less leaf yellowing. Stems of ‘Alice’, ‘Passion’, and ‘Scarlet’ pulsed with GA₄₊₇ + BA had higher FW gain than stems pulsed with tap water. Quality was also higher for all cultivars and water uptake was higher for all cultivars, but Scarlet when pulsed with 5 or 10 mg·L⁻¹ GA₄₊₇ + BA compared with stems pulsed with tap water. More flowers opened on ‘Alice’, ‘Mammoth’, and ‘Passion’ when treated with 10 mg·L⁻¹ GA₄₊₇ + BA than with tap water. Vase life extension in gladiolus cultivars due to pulsing with GA₄₊₇ + BA was smaller than the increase in vase life of lilies tested and most of the gladiolus cultivars used in the study had no major postharvest leaf-yellowing problem. Pulsing with GA₄₊₇ + BA improved stem quality, water uptake, and flower opening, which may be further extended if stems would be pulsed immediately after harvest.

Table 2.

Effect of gibberellin plus benzyladenine (GA₄₊₇ + BA), a commercial proprietary floral preservative mixture of GA₄₊₇ plus BA (GA₄₊₇ + BA + preservative), or a commercial proprietary floral preservative mixture of sugar plus acidifier for bulbous flowers (floral bulb preservative) on vase life and postharvest parameters of ‘Alice’, ‘Mammoth’, ‘Passion’, and ‘Scarlet’ gladiolus. GA₄₊₇ + BA + preservative was not tested on ‘Scarlet’. Data for fresh weight change represent means of five replicate stems, for water uptake represent five replicate vases, whereas all other data represent means of 15 stems with three stems per vase.

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Use of GA₄₊₇ + BA + preservative also extended the vase life of ‘Alice’, ‘Mammoth’, and ‘Passion’, but floral bulb preservative had no effect on ‘Mammoth’, ‘Passion’, and ‘Scarlet’ compared with tap water (Table 2). GA₄₊₇ + BA + preservative had a positive effect on most other measures as well: greater fresh weight change for ‘Alice’, higher stem quality for Alice’ and ‘Passion’, higher water uptake for ‘Alice’, ‘Mammoth’, and ‘Passion’, greater flower opening for ‘Mammoth and ‘Passion’, and reduced leaf yellowing for ‘Alice’. Floral bulb preservative also had a positive effect, but less than GA₄₊₇ + BA + preservative: greater fresh weight change for ‘Alice’, ‘Passion’, and ‘Scarlet’, higher stem quality for ‘Passion’, higher water uptake for ‘Mammoth’, and reduced leaf yellowing for ‘Alice’ and ‘Passion’. GA₄₊₇ + BA + preservative was developed as a grower-applied treatment to prevent leaf yellowing and promote flower opening, while floral bulb preservative was intended as final product to be used in vases. It is clear that the grower-applied pulsing treatment worked as intended, while the floral bulb preservative is probably better suited as a final solution.

Major reasons of termination of cut gladiolus stems were stem bending, petal necrosis or wilting, or sepal chlorosis, but most of the termination criteria were unaffected by the treatments (data not presented). Incidence of stem bending for ‘Alice’, ‘Mammoth’, ‘Passion’, and ‘Scarlet’ averaged 16%, 20%, 35%, and 18%, respectively, and incidence of sepal chlorosis averaged 88%, 66%, 77%, and 0%, respectively. For petal necrosis and wilt, 98% to 100% of stems exhibited the condition across all four cultivars. On the other hand, pulsing of ‘Passion’ gladiolus stems with GA₄₊₇ + BA or GA₄₊₇ + BA + preservative increased petal bluing incidence (80% to 100%), which was not recorded for stems pulsed with tap water (0%) or for the other cultivars. Petal blueing may have been a byproduct of increased vase life from GA₄₊₇ + BA and GA₄₊₇ + BA + preservative. Pulsing with GA₄₊₇ + BA or GA₄₊₇ + BA + preservative lowered the leaf tip chlorosis of ‘Alice’ (13% to 33%) compared with tap water (93%), which might be due to mobilization of carbohydrates to the opening petals. Movement of soluble sugars like sucrose between cells has been reported during senescence (Chuang and Chang, 2013). Leaf tip chlorosis was not noted on the other cultivars.

In summary, cut stems of lilies and gladioli should be pulsed with 5.0–10.0 mg·L⁻¹ GA₄₊₇ + BA or 2 mL·L⁻¹ GA₄₊₇ + BA + preservative at 3 ± 1 °C in dark for 20 h before shipping for longest vase life and preventing leaf yellowing. However, floral bulb preservative was not effective as overnight pulse for vase life extension or controlling leaf yellowing. Commercial growers and wholesalers should consider maintaining postharvest quality of cut lilies and gladioli and increase financial returns by pulsing cut stems with GA₄₊₇ + BA or GA₄₊₇ + BA + preservative to control leaf yellowing in addition to vase life extension.

Units

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