POSTHARVEST PHYSIOLOGY | Xylem Structure and Function in Cut Roses

H.M.C. Put , A.C.M. Clerkx , in Encyclopedia of Rose Science, 2003

Introduction

As cut flowers lack roots, root-supplied hormones and dissolved materials are no longer available. As transpiration continues unabated, water moves upwards from the cut end and allows air to enter the vascular system. This makes it difficult to reestablish the supply of water to leaves and flowers. Additionally, when water uptake is established, dissolved materials, microbes and particulate matter carried into the vascular system restrict the flow of water and shorten postharvest life.

The vase-life of cut greenhouse roses is, above all, dependent on water balance, which is affected by the water uptake by the flower, water transport through the stem and transpiration. Although the maintenance of an optimal water status is the most important factor in cut-flower longevity, many of the underlying mechanisms leading to disturbed water balance are still unresolved.

This article summarizes methods of assessing the water status of the cut-rose flower, analysis of factors leading to a disturbed water status, the relation of a disturbed water status to the xylem structure and the consequences of disturbed water status for vase-life.

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Specialty Cut Flowers

Allan M. Armitage , in Introduction to Floriculture (Second Edition), 1992

V. SUMMARY

Specialty cut flowers have a huge potential in the United States market. At the present time, many specialty flowers are imported. There is no doubt that the market for specialty flowers will continue to rise, but the sites of production are still uncertain. American growers are capable of producing as large a variety of flowers equalling or surpassing the quality of imported production. If the American grower is to compete with international growers, competition must be based on the quality of the product and effective marketing. American growers must have pride in their product, and "Grown in the U.S.A." must mean that the flowers are true to name, color, and quality designation. Postproduction treatments must begin in the field, grading must be honest, and packing must be done with the contents in mind and not to see how many stems can be jammed together. "Grown in the U.S.A." must become a recognizable and proven symbol of quality to wholesalers, florists, and consumers or the specialty cut flower market will be turned over to lawyers and brokers, with no interest in quality, and to overseas producers.

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Snapdragons

Marlin N. Rogers , in Introduction to Floriculture (Second Edition), 1992

C. Postharvest Physiology

Few cut flower crops are more responsive to good postharvest treatment than snapdragons. Freshly cut flower spikes of most cultivars will have a vase life of about 1 week in tap water or distilled water. When the best combination of flower preservatives is used, vase life can be increased two or three times.

Larsen and Scholes (1966) and Raulston and Marousky (1971) found that longest vase life, greatest number of florets opening, and greatest increase in spike length after cutting occurred when flowers were held in a solution containing 300 ppm of 8-HQC + 1.5% sucrose. The former researchers also found the addition of 25 ppm Alar (n-dimethylaminosuccinamic acid) to be beneficial. Johnson (1972) got best results from a solution of 300 ppm 8-HQC + 0.5% sucrose. Both light and floral preservatives are crucial for proper development of floret color in florets that open after harvest (Marousky and Raulston, 1970). Regardless of the solution used, spikes held in darkness produced little anthocyanin and were poorly colored. In the light, those spikes held in 8-HQC + sucrose produced much more intensely colored florets than those held in tap water. Light (2.15 klx) incident on the developing floret at the time of opening was critical for anthocyanin production.

Self-generated ethylene gas can be a prime cause of early senescence in cut snapdragons. One of the reasons for excellent results with hypobaric storage is the constant removal of trace quantities of ethylene from the storage atmosphere. Pretreatment of cut snapdragon stems for 20 hours immediately after harvest in a solution containing silver thiosulfate (STS) and sucrose inhibits ethylene action and added about 6 days vase life compared to distilled water controls (Nowak, 1981 ). The highly toxic silver ion, however, has not yet been cleared for commercial use in postharvest treatment of cut flowers in the United States.

Another approach to control of ethylene problems has involved use of chemicals to suppress ethylene formation (Wang et al., 1977). In this study, two analogs of rhizobitoxine and sodium benzoate were tested to determine the relationships between their effects on ethylene production by flowers and keeping quality. Both ethoxy and methoxy analogs of rhizobitoxine significantly reduced ethylene production and increased vase life. Like hypobaric storage, however, this treatment has also not yet gained commercial acceptance.

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Orchids

Thomas J. Sheehan , in Introduction to Floriculture (Second Edition), 1992

D. Storage

Orchids, unlike many cut flowers, do not store for any length of time at 31°F. Flowers start turning brown in 3 days at this temperature and lose their salability very rapidly.

Because most orchid flowers are long-lived on the plants, up to 3 or 4 weeks, growers will often leave them on the plants until they are needed. If they must be cut and stored, they should be stored at 42° to 45°F. At this temperature, most orchids can be safely stored for a 10- to 14-day period. If orchids are not at their peak, then storage time will be less.

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PRODUCTION SYSTEMS AND AGRONOMY | Commercial Flower Production Methodology

W.B. Miller , in Encyclopedia of Applied Plant Sciences, 2003

Objectives of Commercial Flower Production

The basic objective in commercial flower production is to produce high-quality products for consumption by the flower- and plant-loving public. This very often involves manipulation of floral induction, initiation and development, as in "out-of-season" production of flowers such as chrysanthemums (Dendranthema×grandiflora), poinsettia (Euphorbia pulcherrima), Easter lily (Lilium longiflorum), or other bulbous crops such as tulip or hyacinth. Central to this objective is distinguishing between plant growth (essentially dry weight gain) and plant development (processes leading to alterations in the vegetative body of the plant and manipulation of floral development). Very simplistically, the life of a commercial flower crop may be divided into four phases: (1) propagation, (2) vegetative development, leading to a plant with sufficient structure and stature to support floral development, (3) floral induction, initiation, and development to anthesis (or marketing), and (4) the postharvest phase that encompasses packaging, transportation, marketing, and use by the final consumer.

Products under consideration include cut flowers and foliage that are used in floral arrangements, flowering or nonflowering pot plants as used for indoor decoration, and "bedding plants" that are mainly destined for use in gardens and for outdoor decoration in the warmer months. A key concept in commercial flower production is that greenhouses are expensive to operate (e.g., winter heating); thus the area a crop occupies and time it takes to grow are both crucially important to the floriculturist. Thus, adoption of techniques based on plant physiology must be economically feasible, for example by:

•

reducing time to grow the flower or plant to maturity

•

reducing labor by improving uniformity, and allowing adoption of automation

•

improving quality and thereby allowing a higher price (and hopefully profit) to be earned.

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Crop Systems

W.B. Miller , in Encyclopedia of Applied Plant Sciences (Second Edition), 2017

Overview and Objectives of Commercial Flower Production

The basic objective in commercial flower production is to produce high-quality products for consumption by the flower- and plant-loving public. This very often involves manipulation of floral induction, initiation, and development, as in 'out-of-season' production of flowers such as chrysanthemums (Dendranthema × grandiflora), poinsettia (Euphorbia pulcherrima), Easter lily (Lilium longiflorum), or other bulbous crops such as tulip or hyacinth. Central to this objective is distinguishing between plant growth (essentially dry weight gain) and plant development (processes leading to alterations in the vegetative body of the plant and manipulation of floral development). Very simplistically, the life of a commercial flower crop may be divided into four phases: (1) propagation, (2) vegetative development, leading to a plant with sufficient vegetative structure and 'machinery' to support floral development, (3) floral induction, initiation, and development to anthesis (or marketing), and (4) the postharvest phase that encompasses packaging, transportation, marketing, and use by the final consumer.

Products under consideration include cut flowers and foliage that are used in floral arrangements, flowering or nonflowering pot plants as used for indoor decoration, and 'bedding plants' that are mainly destined for use in gardens and for outdoor decoration in the warmer months. A key concept in commercial flower production is that greenhouses are expensive to operate (e.g., winter heating); thus the area a crop occupies and time it takes to grow are both crucially important to the greenhouse producer, regardless of crop (flower, vegetable, fruit). Thus, adoption of techniques based on plant physiology must be economically feasible, for example, by

•

reducing time to grow the flower or plant to maturity

•

reducing labor by improving uniformity and allowing adoption of automation

•

improving quality and thereby allowing a higher price (and hopefully profit) to be earned

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GENETICS | Cloned Genes

Y. Tanaka , ... J.G. Mason , in Encyclopedia of Rose Science, 2003

Ethylene-related Genes

Rose flowers, especially cut flowers, have a limited life. Longer flower life is beneficial to consumers, retailers and growers. Flower life is partly controlled by a gaseous plant hormone, ethylene. Ethylene is not a critical factor in regulating the vase-life of rose cut flowers. Practically speaking, blockage of the flower stem by microbial growth and subsequent inhibition of water uptake shorten the vase-life. The ethylene biosynthetic pathway and its signal transduction triggering senescence have been well-characterized ( Figure 4 ). Suppression of ethylene biosynthesis genes (ACC synthase and ACC oxidase) successfully extends the vase-life of carnation and the shelf-life of some fruits, including tomato, melon and banana.

Figure 4. A simplified ethylene biosynthesis and signalling model. Ethylene is biosynthesized from S-adenosyl-methionine by 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. When ethylene binds a receptor, negative regulation of CTR1 is released, and ethylene responses then start.

The ethylene signal is transduced to various physiological responses via a two-component regulatory-signal transduction system, which includes a kinase cascade. Ethylene receptors negatively regulate ethylene signal transduction ( Figure 4 ). There are at least five ethylene receptors in Arabidopsis: ETR1 (ethylene response 1), ETR2, ERS1 (ethylene response sensor), ERS2 and EIN4 (ethylene insensitive). Similar ethylene receptor genes have been obtained from many plants, such as tomato and melon. The CTR1 (constant triple response) gene, which is a negative regulator of ethylene signal transduction and is negatively regulated by ethylene receptors, has also been cloned from Arabidopsis and some other plants. EIN2, EIN3, EIN5 and EIN6 are known to be positive regulators of the ethylene response in Arabidopsis. Among them, EIN3 is a transcription factor that binds to the promoters of ethylene-response genes. Four rose homologues of ethylene receptor genes (partial cDNAs, ETR1 (AF394914, AF127221), ETR2 (AF127220), ETR3 (AF154119), ETR4 (AF159172)) and a rose homologue of a CTR1-like protein kinase consisting of 847 amino acid residues (AY032953) have been registered in the DNA databases. A partial sequence from R. hybrida encoding an EIN3-like transcriptional factor (AY025825) has also been registered.

The utility of these genes in strategies aimed at prolonging flower life is untested in rose. Not all rose varieties are sensitive to the application of ethylene, as measured by petal drop. However, the genes detailed above have been used in related strategies in other flower crops, as mentioned above. Two broad strategies could be considered for application in roses. The first involves blocking endogenous ethylene production in the flower, and the second involves interference with ethylene perception in the flower, as a result of which endogenous and exogenous ethylene has no impact on senescence. Blocking ethylene production in the flower can be achieved via sense- or antisense-mediated suppression of ACC oxidase or ACC synthase synthesis. These enzymes are involved in the final steps leading to ethylene biosynthesis. S-adenosyl-l-methionine (SAM) is converted by ACC synthase to ACC, which is converted to ethylene, carbon dioxide and cyanide by ACC oxidase ( Figure 4 ).

Through the introduction of an Etr1 gene carrying, for example, the Etr1–1 mutation of Arabidopsis, rose plants that would lack the ability to perceive ethylene could be generated and, thus, would not respond to endogenous or exogenous ethylene, a drawback of the first strategy. If the expression of such a mutation were confined to the flower, then interference with ethylene transduction, which is important to other plant processes, such as the defence response, would be avoided. Such a strategy has been successful in carnation. In petunia, a similar approach utilizing ERS has been used to a similar effect.

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Cloned Genes☆

Y. Tanaka , ... J.G. Mason , in Reference Module in Life Sciences, 2017

Ethylene-Related Genes

Rose flowers, especially cut flowers, have a limited life. Longer flower life is beneficial to consumers, retailers and growers. Flower life is partly controlled by a gaseous plant hormone, ethylene. Ethylene is not a critical factor in regulating the vase-life of rose cut flowers. Practically speaking, blockage of the flower stem by microbial growth and subsequent inhibition of water uptake shorten the vase-life. The ethylene biosynthetic pathway and its signal transduction triggering senescence have been well-characterized ( Fig. 4). Suppression of ethylene biosynthesis genes (ACC synthase and ACC oxidase) successfully extends the vase-life of carnation and the shelf-life of some fruits, including tomato, melon and banana.

Fig. 4

Fig. 4. A simplified ethylene biosynthesis and signaling model. Ethylene is biosynthesized from S-adenosyl-methionine by 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. When ethylene binds a receptor, negative regulation of CTR1 is released, and ethylene responses then start.

The ethylene signal is transduced to various physiological responses via a two-component regulatory-signal transduction system, which includes a kinase cascade. Ethylene receptors negatively regulate ethylene signal transduction (Fig. 4). There are at least five ethylene receptors in Arabidopsis: ETR1 (ethylene response 1), ETR2, ERS1 (ethylene response sensor), ERS2 and EIN4 (ethylene insensitive). Similar ethylene receptor genes have been obtained from many plants, such as tomato and melon. The CTR1 (constant triple response) gene, which is a negative regulator of ethylene signal transduction and is negatively regulated by ethylene receptors, has also been cloned from Arabidopsis and some other plants. EIN2, EIN3, EIN5 and EIN6 are known to be positive regulators of the ethylene response in Arabidopsis. Among them, EIN3 is a transcription factor that binds to the promoters of ethylene-response genes. Four rose homologs of ethylene receptor genes (partial cDNAs, ETR1 (AF394914, AF127221), ETR2 (AF127220), ETR3 (AF154119), ETR4 (AF159172)) and a rose homolog of a CTR1-like protein kinase consisting of 847 amino acid residues (AY032953) have been registered in the DNA databases. A partial sequence from R. hybrida encoding an EIN3-like transcriptional factor (AY025825) has also been registered.

The utility of these genes in strategies aimed at prolonging flower life is untested in rose. Not all rose varieties are sensitive to the application of ethylene, as measured by petal drop. However, the genes detailed above have been used in related strategies in other flower crops, as mentioned above. Two broad strategies could be considered for application in roses. The first involves blocking endogenous ethylene production in the flower, and the second involves interference with ethylene perception in the flower, as a result of which endogenous and exogenous ethylene has no impact on senescence. Blocking ethylene production in the flower can be achieved via sense- or antisense-mediated suppression of ACC oxidase or ACC synthase synthesis. These enzymes are involved in the final steps leading to ethylene biosynthesis. S-adenosyl-l-methionine (SAM) is converted by ACC synthase to ACC, which is converted to ethylene, carbon dioxide and cyanide by ACC oxidase (Fig. 4).

Through the introduction of an Etr1 gene carrying, for example, the Etr1–1 mutation of Arabidopsis, rose plants that would lack the ability to perceive ethylene could be generated and, thus, would not respond to endogenous or exogenous ethylene, a drawback of the first strategy. If the expression of such a mutation were confined to the flower, then interference with ethylene transduction, which is important to other plant processes, such as the defense response, would be avoided. Such a strategy has been successful in carnation. In petunia, a similar approach utilizing ERS has been used to a similar effect.

More ethylene related genes have been isolated: ACC synthase (Rh-ACS1(AY061946), Rh-ACS2 (AY803737), Rh-ACS3 (AY803738), ACS4 (AY525068), ACS5 (AY525069), Rh-ACS1 promoter region (KP133132-KP133135)), ACC oxidase (Rh-ACO1 (AF441282), ethylene receptor (Rh-ETR1 (AY953869), Rh-ETR3 (AY953392), Rh-ETR5 (AF441283)), CTR1-like protein kinase (Rh-CTR2, AY029067), EIN3-like transcriptional factor ((Rh-EIN3–1 (AF443783) Rh-EIN3–2 (AY919867), RTE1/GR-like protein (HM246664)).

R. hybrida contains five ACC synthase genes (RhACS1–5) and five ethylene receptor genes (RhETR1–5). Among them, expression of RhACS1 and RhACS2 was induced by dehydration and rehydration in the gynoecia and sepals. Expression of RhETR3 is induced by dehydration and rehydration in the petals. Suppression of RhETR genes upregulated 10 genes and downregulated 11 genes in response to ethylene.

A rose aquaporin water channel protein (Rh-P1P2;1, EU572717), localized on the plasma membrane, highly expresses in petal epidermal cells in correlation to petal expansion. Ethylene downregulates its expression and inhibits petal expansion.

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Carnations

C. Anne Whealy , in Introduction to Floriculture (Second Edition), 1992

E. Kenya

The carnation is the primary cut flower crop in Kenya. In 1987, Kenyan producers exported 156 million stems worth $13.4 million. Most of this product was exported to Germany.

Spray carnations are grown outside at an altitude of 6000 feet and standard carnations are grown at 9000 feet under polyethylene (Cox, 1987). Night temperatures range from 40° to 57°F and day temperatures from 77° to 95°F. Total production in Kenya is 400 acres with sprays representing 350 acres. The majority of this production is concentrated at one operation.

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Flower Senescence: Present Status and Future Aspects

Maryam Sarwat , Narendra Tuteja , in Senescence Signalling and Control in Plants, 2019

3.3 Ethylene and Abscisic Acid

ABA accumulation promotes the senescence of cut flowers and flowering potted plants ( Ferrante et al., 2015). Müller et al. (1999) reported that ABA application increased the sensitivity of rose to ethylene. Some ethylene receptors were found to be upregulated by exogenous application of ABA. However, in H. rosa sinensis, the ABA negatively affects the tissue sensitivity of all floral tissues and reduced the transcript abundance of HrsACS, HrsACO, HrsETR, and HrsERS (Trivellini et al., 2011).

The application of ethylene and ABA in Petunia flowers caused increased expression of PhHD-Zip (Chang et al., 2014). Trivellini et al. (2015) reported that exogenous CKs (BA) treatment caused overexpression of various genes belonging to ABA biosynthesis, catabolism, and signaling pathways.

Chang et al. (2003) reported lower endogenous ABA levels in IPT overexpressing transgenic lines of Petunia. This is further confirmed by Trivellini et al. (2015), which found that BA treatment causes delayed senescence through reducing the ABA content and higher ethylene production. Both ethylene and CKs seem to regulate ABA biosynthesis and its degradation in flowers.

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