Effect of biocides on postharvest vase life of Gypsophila cv. Star World

Introduction

Gypsophila (Gypsophila paniculata L.) is a flowering plant native to Central and Eastern Europe, widely cultivated in Eurasia, Africa, Australia, Turkey, and Pacific Islands, with Turkey boasting around 35 endemic species. Valued for its ornamental and cut flower purposes, Gypsophila is often used as a filler in flower bouquets, adding volume and texture. The Star World cultivar is a hardy plant, growing up to 1-2 meters tall, producing medium-sized white panicles, and exhibiting resistance to pests and diseases. Additionally, Gypsophila is a popular choice for floral arrangements due to its delicate, airy blooms and long vase life, making it an ideal selection for weddings, events, and everyday bouquets. Its versatility and beauty have also made it a favourite among florists and gardeners alike. Biocides are a crucial component in preservative solutions for cut flowers, controlling harmful bacteria and preventing bacterial embolism (Halevy and Mayak, 1981) [3] . Microbial blockage of xylem vessels is a primary cause of deterioration in cut flowers (Danaee et al., 2011) [2] . To address this, floral preservatives often include biocides, such as 8-Hydroxyquinoline Sulfate (8-HQS), a widely used germicide in the floral industry (Nowak and Rudnicki, 1990) [10] . 8-HQS acts as an antimicrobial agent, enhancing water uptake and promoting extended vase life (Ketsa et al., 1995; Reddy et al., 1996) [5,12] .

Materials and Methods

This study was conducted in the Floriculture and Landscape Architecture laboratory, College of Horticulture, Rajendranagar, under Sri Konda Laxman Telangana Horticulture University, Hyderabad. The experiment employed a CRD design with three replications and 14 treatments. Gypsophila cv. Star World flowers were obtained from the Floricultural Research Station, Rajendranagar, and harvested at a stage with 50% of overall flowers opened, after which leaves were removed. The flowers were then placed in 1000 ml beakers containing 14 different preservative solutions. Flowers were continuously held in the preservative solutions, and postharvest parameters were evaluated every two days throughout the vase life period.

Treatment details T1:

(Sucrose @ 2%), T2: (8HQS 100 @ ppm) T3: (8HQS 200 @ ppm) T4: [Sodium hypochlorite (SH) @ 25 ppm], T5: [Sodium hypochlorite (SH) @ 50 ppm], T6: [Calcium hypochlorite (Ca(OCl) 2 ) @ 25 ppm], T7: [Calcium hypochlorite (Ca(OCl) 2 ) @ 50 ppm], T8: (Sucrose @ 2% + 8HQS @ 100 ppm), T9: (Sucrose 2% + 8HQS @ 200 ppm), T10: (Sucrose 2% + SH @ 25 ppm), T11: (Sucrose 2% + SH @ 50 ppm) T12: (Sucrose 2% + Ca(OCl) 2 @ 25 ppm) T13: (Sucrose 2% + Ca(OCl) 2 @ 50 ppm) T14: [Control (Distilled water)] 1. Water uptake (WB) (g. flower -1 ) Water uptake was measured by recording the difference in weight of the container plus solution (without flowers) at alternate-day intervals, and expressed as grams per flower, following the method described by Venkatarayappa et al., 1980 [15] .

Transpirational loss of water was measured by recording the difference in weight of the container + solution + flowers at 2 days intervals, and expressed as grams per spike, following the method described by Venkatarayappa et al., 1980 [15] .

Optical density of vase solution (ODVS) (480 nm)

Optical density of the vase solution was measured using a spectrophotometer at a wavelength of 480 nm.

Vase life was recorded as the number of days taken for more than 50% of the flowers to wilt, and expressed in days.

Fresh weight of the flower spike was measured using an electronic balance and expressed in grams.

Results and Discussion

The collected data were subjected to statistical analysis, and the results are presented and discussed under relevant headings 1. Water uptake (WU) (g. flower -1 ) Significant differences were observed among biocide treatments for water uptake (WU) in Gypsophila cv. Star World. The highest WU was recorded in T 9 (27.42 g flower -1 ), comprising 2% sucrose and 200 ppm 8-HQS, it was on par with T 8 and T 11 , whereas the lowest WU was observed in the control treatment (T 14 ), with a value of 10.90 g flower -1 (Table 1). The highest water uptake recorded in T 9 treatment can be attributed to the enhanced and continuous water uptake facilitated by this treatment, which likely delayed senescence. Sucrose, acting as a respiratory substrate, maintained water balance and delayed turgidity loss, as reported by Sven and Jose (2004) [13] . Additionally, 8-HQS improved mineral salt uptake by influencing metal ions, leading to maximum solution uptake, as suggested by Hwang and Kim (1995) [4] . This finding is consistent with Pruthi et al., 2001 [11] , who observed enhanced solution uptake in Gladiolus at higher biocide concentrations. [1] .

Optical density of vase solution (ODVS) (nm)

The mean optical density of vase solution (ODVS) differed significantly among biocide treatments of Gypsophila cv. Star World. The lowest value of 0.045 nm was recorded in T 9 treatment (2% sucrose + 200 ppm 8-HQS), and was statistically at par with most other treatments. Conversely, the control treatment (T 14 ) showed the highest ODVS value of 0.173 nm (Table 3). The lowest ODVS observed in T 9 treatment is likely attributed to the reduced bacterial count, as this treatment also exhibited the highest water uptake and transpirational loss of water, indicating a cleaner vase solution with minimal microbial growth. The data in Table 4 indicates that T 9 treatment was the most effective in extending vase life, likely due to its superior performance in enhancing water uptake (WU), transpirational loss of water (TLW), and minimizing optical density of vase solution (ODVS). These findings are consistent with Laksminarayana and Prashath (2020a) [8] , who reported similar results in Gladiolus. The impact of biocide treatments on flower fresh weight of Gypsophila cv. Star World was shown in Table 5. A significant difference in fresh weight was observed among treatments. T 9 treatment (2% sucrose + 200 ppm 8-HQS) achieved the highest fresh weight (15.9 g flower -1 ), which was statistically at par with most other treatments except control. The control treatment (T 14 ) recorded the lowest fresh weight (11.07 g flower -1 ). The highest fresh weight observed in T 9 treatment can be attributed to its superior performance in water uptake, transpirational loss of water, and vase life compared to other treatments. The positive effect of 8-HQS on retaining fresh weight is likely due to enhanced water uptake, as reported by Uthaichay et al. (2007) [14] . Similar findings have been observed in rose by Martha et al. (2011) [9] and in Freesia by Kwon and Kim (2000) [7] , supporting the notion that 8-HQS plays a crucial role in maintaining fresh weight by promoting water uptake.

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