Carbohydrate Depletion and Leaf Blackening in Protea neriljiolia

McConchie, Robyn; Lang, N. Suzanne; Gross, Ken

doi:10.21273/jashs.116.6.1019

Cited by 20 publications

(33 citation statements)

References 16 publications

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“…In contrast, blackening symptoms in the light did not occur until after day 7. The rate of blackening in the dark was greater than in the light (b dark = 17.76, b light = 3.43; t 38 = 20.17; P < 0.001), which is consistent with previous results for other Protea species Lang, 1993a and1993b;McConchie et al, 1991). Leaf starch concentrations declined dramatically (≈58%) during the 24-h dark shipping period immediately after harvest (Table 1).…”

Section: Resultssupporting

confidence: 89%

“…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).…”

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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: Resultssupporting

confidence: 89%

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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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“…Starch stored in flower organs is usually synthesized from carbohydrates supplied by photosynthesis, which occurs in the green vegetative organs of the plant (Tirosh and Mayak 1988;McConchie et al 1991). These assimilates reach the flower bud and are distributed among the various floral organs.…”

Section: Discussionmentioning

confidence: 99%

Morphological and cytological development and starch accumulation in hermaphrodite and staminate flowers of olive (Olea europaea L.)

et al. 2009

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In olive (Olea europaea L.), the formation of functionally staminate flowers rather than fully functional hermaphrodites is one of the major factors limiting fruit set, as flowers with aborted pistils are incapable of producing fruit. Studies conducted on various angiosperm species have shown a correlation between flower abortion and starch content. Thus, it is important to know if starch content plays a role in regulating pistil development in olive and if so, what mechanism regulates starch distribution. Cyto-histological observations of staminate and hermaphrodite olive flowers show that pistil development in staminate flowers is interrupted after the differentiation of the megaspore mother cell. At that stage, starch grains were only detected in the ovary, style and stigma of the hermaphrodite flowers. No starch was observed in the pistils of the staminate flowers. This finding suggests a tight correlation between starch content and pistil development. The secondary origin of starch within the flower is indicated by low chlorophyll content in the gynoecium, undetectable Rubisco activity in the pistils of these two kinds of flowers and by the ultrastructure of the plastids observed by transmission electron microscope analysis. The plastids have few thylakoid membranes and grana and in the staminate flowers appeared very similar to proplastids. Considering differences in starch content between staminate and hermaphrodite flowers and the secondary origin of the starch, differences in pistil development in the staminate and hermaphrodite flowers could be related to differences in the sink strength of these two types of flowers.

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“…A deficiency in carbohydrate metabolism in the anther leads to abnormal pollen development (Sawhney and Bhadula, 1988;Bhadula and Sawhney, 1989;Sawhney, 1992) and is often correlated with male sterility (Banga, Labana, and Banga, 1984). Anthers are usually supplied with carbohydrates by photosynthesis, which occurs in the green organs of the plant (Tirosh and Mayak, 1988;McConchie, Lang, and Gross, 1991). These assimilates reach the flower bud and are distributed among the various floral organs.…”

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Floral Organ Growth and Carbohydrate Content During Pollen Development in Lilium

Clément

Burrus

Audran

1996

American Journal of Botany

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In order to understand floral sugar physiology, we correlated the growth of the organs with carbohydrate content in the flower of Lilium cv. “enchantment” during pollen development. In a previous work, we distinguished two phases in pollen ontogenesis: the anther growth phase, from the microspore mother cell until the vacuolated microspore, and the anther maturation phase, from the vacuolated microspore until anthesis. In the present work, we showed that during the growth phase, the anther underwent most of its size and dry weight growth, whereas the growth rate of nonanther organs was reduced. Anther and filament possessed the highest amounts of carbohydrates, which decreased progressively until the vacuolated microspore stage. During the maturation phase, sucrose and starch increased in all floral organs. Anther growth was completed at the Mi stage, whereas the nonanther organs began exponential growth. From these observations, we concluded that hierarchic nutritional correlations exist between the flower organs, in which the anther is the main actor: during the anther growth phase, the anther represents the highest sink strength floral organ, and mainly attracts assimilates through the filament. During the anther maturation phase, anther growth is achieved, its needs decrease, and assimilates are thus available for neighboring organs, which undergo intense growth until anthesis.

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Carbohydrate Depletion and Leaf Blackening in Protea neriljiolia

Cited by 20 publications

References 16 publications

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

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

Morphological and cytological development and starch accumulation in hermaphrodite and staminate flowers of olive (Olea europaea L.)

Floral Organ Growth and Carbohydrate Content During Pollen Development in Lilium

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