Carbohydrate Changes and Leaf Blackening in Cut Flower Stems of Protea eximia

Bieleski, R. L.; Ripperda, J.; Newman, Julie; Reid, Michael S.

doi:10.21273/jashs.117.1.124

Cited by 26 publications

(30 citation statements)

References 11 publications

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“…Alternatively, considering that starch has minimal osmotic activity (Setter, 1990), the rapid rate of starch hydrolysis in response to sink demand may impose osmotic stress on leaf cells. It has been suggested that the sugar alcohol, polygalatol, may be involved in cellular osmotic adjustment during stress, since it does not decline under depleted carbohydrate conditions (Bieleski et al, 1992;McConchie and Lang, 1993b), as would be expected if it were involved in growth and maintenance metabolism (Cheeseman, 1988). Instead, concentrations either increase slightly or remain stable (Table 1) (Bieleski et al, 1992;McConchie and Lang, 1993b;McConchie et al, 1991).…”

Section: Discussionmentioning

confidence: 99%

“…Premature leaf blackening in many cut flower Protea species seriously reduces vase life and market value. When stems are held under dark postharvest conditions, blackening symptoms can appear within 3 days after harvest (Bieleski et al, 1992;McConchie et al, 1991). The current hypothesis suggests that postharvest leaf blackening in Protea is induced by a sequence of metabolic events associated closely with senescence, beginning with the total depletion of leaf carbohydrates and followed by subsequent hydrolysis of intercellular membranes to supply respiratory substrate for the developing inflorescence (Ferreria, 1986).…”

mentioning

confidence: 97%

“…We believe this hypothesis requires further investigation because of limited supporting evidence. Although strong correlative data exist between the postharvest reductions in sucrose and starch concentrations and leaf blackening (Bieleski et al 1992;Lang, 1993a, 1993b;McConchie et al, 1991), carbohydrates are not totally depleted in leaves of dark-held stems. McConchie and Lang (1993b) found no evidence of a sequential loss of membrane integrity that would facilitate contact of phenols with oxidative enzymes.…”

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confidence: 99%

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Reexamining Polyphenol Oxidase, Peroxidase, and Leaf-blackening Activity in Protea

McConchie¹,

Lang²,

Lax³

et al. 1994

jashs

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Premature leaf blackening in Protea severely reduces vase life and market value. The current hypothesis suggests that leaf blackening is induced by a sequence of events related to metabolic reactions associated with senescence, beginning with total depletion of leaf carbohydrates. It is thought that this carbohydrate depletion may induce hydrolysis of intercellular membranes to supply respiratory substrate, and subsequently allow vacuole-sequestered phenols to be oxidized by polyphenol oxidase (PPO) and peroxidase (POD) (Whitehead and de Swardt, 1982). To more thoroughly examine this hypothesis, leaf carbohydrate depletion and the activities of PPO and POD in cut flower Protea susannae × P. compacta stems held under light and dark conditions were examined in relationship to postharvest leaf blackening. Leaf blackening proceeded rapidly on dark-held stems, approaching 100% by day 8, and was temporally coincident with a rapid decline in starch concentration. Blackening of leaves on light-held stems did not occur until after day 7, and a higher concentration of starch was maintained earlier in the postharvest period for stems held in light than those held in dark. A large concentration of the sugar alcohol, polygalatol, was maintained in dark- and light-held stems over the postharvest period, suggesting that it is not involved in growth or maintenance metabolism. Polyphenol oxidase activity in light- and dark-held stems was not related to appearance of blackening symptoms. Activity of PPO at pH 7.2 in light-held stems resulted in a 10-fold increase over the 8-day period. Activity in dark-held stems increased initially, but declined at the onset of leaf blackening. There was no significant difference in POD activity for dark- or light-held stems during the postharvest period. Total chlorophyll and protein concentrations did not decline over the 8-day period or differ between light- and dark-held stems. Total phenolics in the dark-held stems increased to concentrations ≈30% higher than light-held stems. Consequently, the lack of association between membrane collapse, leaf senescence, or activities of oxidative enzymes (PPO or POD) with leaf blackening does not support the hypothesis currently accepted by many Protea researchers. An alternative scenario may be that the rapid rate of leaf starch hydrolysis imposes an osmotic stress resulting in cleavage of glycosylated phenolic compounds to release glucose for carbohydrate metabolism and coincidentally increase the pool of free phenolics available for nonenzymatic oxidation. The physiology of such a carbohydrate-related cellular stress and its manifestation in cellular blackening remains to be elucidated.

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Section: Discussionmentioning

confidence: 99%

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confidence: 97%

mentioning

confidence: 99%

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Reexamining Polyphenol Oxidase, Peroxidase, and Leaf-blackening Activity in Protea

McConchie¹,

Lang²,

Lax³

et al. 1994

jashs

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“…Simple carbohydrates can be distinguished by thin layer chromatography (Petrovic & Canic, 1969;Washuttl et al, 1973;Webb & Burley, 1962), gas chromatography (GC) (Makinen & Soderling, 1980;Megias-Perez et al, 2014;Sanz et al, 2004;Wrolstad, Culbertson, Nagaki, & Madero, 1980), and high performance liquid chromatography (HPLC) (Bieleski, Ripperda, Newman, & Reid, 1992;Cantin et al, 2009;Fan-Chiang & Wrolstad, 2010;Durst et al, 1995;Ellefson, 2005;Muir et al, 2009;Spanos & Wrolstad, 1987;Usenik, Fabcic, & Stampar, 2008;Zhou et al, 2012). These analyses and methods have been well summarised in Brummer and Cui (2005), De Goeij (2013), Ellefson (2005), Muir et al (2009), andMartinez-Castro (2007) regarding the specific advantages and pitfalls of each separation technique.…”

Section: Analysing For Simple Carbohydrate In Fruit and Fruit Productsmentioning

confidence: 99%

“…Their removal can be accomplished by several methods, including ion exchange or reversed phase sorbent mini-columns (Ballistreri et al, 2013;Cantin et al, 2009;Durst et al, 1995;Fan-Chiang & Wrolstad, 2010;Liu et al, 1999;Muir et al, 2009;Spanos & Wrolstad, 1987;van Gorsel et al, 1992), syringe filters containing nylon, PVP (polyvinylpyrrolidone), etc. (Ledbetter et al, 2006;Lee et al, 2009), or PVP and PVPP (polyvinylpolypyrrolidone) powders alone (added directly to sample; Bieleski et al, 1992;Cornwell et al, 1981). Sample preparations prior to carbohydrate analysis were well reviewed by Sanz and Martinez-Castro (2007).…”

Section: Analysing For Simple Carbohydrate In Fruit and Fruit Productsmentioning

confidence: 99%

Sorbitol, Rubus fruit, and misconception

Lee

2015

Food Chemistry

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It is unclear how the misunderstanding that Rubus fruits (e.g., blackberries, raspberries) are high in sugar alcohol began, or when it started circulating in the United States. In reality, they contain little sugar alcohol. Numerous research groups have reported zero detectable amounts of sugar alcohol in fully ripe Rubus fruit, with the exception of three out of 82 Rubus fruit samples (cloudberry 0.01 g/100 g, red raspberry 0.03 g/100 g, and blackberry 4.8 g/100 g(∗); (∗)highly unusual as 73 other blackberry samples contained no detectable sorbitol). Past findings on simple carbohydrate composition of Rubus fruit, other commonly consumed Rosaceae fruit, and additional fruits (24 genera and species) are summarised. We are hopeful that this review will clarify Rosaceae fruit sugar alcohol concentrations and individual sugar composition; examples of non-Rosaceae fruit and prepared foods containing sugar alcohol are included for comparison. A brief summary of sugar alcohol and health will also be presented.

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