English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

During a 7-day dark postharvest period, Protea neriifolia R.Br. leaf blackening was significantly reduced on floral stems treated with a 24-h 20% sucrose pulse compared with continuous holding in a 0.5% sucrose vase solution or removal of the flowerhead. Leaf blackening on vegetative stems was similar to that on the 20% sucrose-pulsed floral stems. Leaf starch and sucrose concentration profiles demonstrated that stems with reduced leaf blackening maintained higher levels of those carbohydrates during the early postharvest period. Conversely, leaf starch and sucrose reserves were quickly depleted in stem treatments that resulted in early blackening symptoms. Starch concentrations in all treatments of stems dropped 70% to 82% within 24 h of harvest, suggesting that leaf blackening may be initiated during shipping. Ethylene production was not associated with leaf blackening in any treatment. Lipid peroxidation did not differ among floral treatments nor did it increase over the postharvest interval. Oxidized glutathione (GSSG) concentration increased only with the 20% pulsed stems and was not related to leaf blackening. After an initial decrease, leaf respiration rate was generally maintained regardless of treatment. Collectively, these data are consistent with the hypothesis that carbohydrate depletion is the initiating factor in leaf blackening and is accelerated by inflorescence sink demand. We suggest that membrane degradation does not necessarily precede leaf blackening. A major postharvest problem of many cut flower Protea species is premature leaf blackening. Blackening symptoms in susceptible species can appear within 3 to 7 days after harvest, severely reducing market quality. The onset of leaf blackening has been associated with diminished carbohydrate concentrations in leaves during the postharvest period (Bieleski et al., 1992; McConchie et al., 1991). Leaf blackening can be delayed in cut stems of P. neriifolia by placing them in light (McConchie et al., 1991; Reid et al., 1989), due to the contribution of leaf photosynthetic activity to the carbohydrate pool (McConchie et al., 1991). After harvest, nonstructural carbohydrates appear to be mobilized from leaves to the floral sink for continuation of floral development. Postharvest leaf carbohydrate profiles under light show that during periods of rapid floral expansion, fixed C is preferentially partitioned into transport carbohydrates. In contrast, when the flower is fully expanded or senescing, photoassimilates are partitioned into starch and stored in the leaves. Leaf blackening in cut Protea stems has reportedly been reduced by placement in vase solutions containing 0.2% to 2% sucrose or by removal of the flowerhead (Brink and de Swardt, 1986; Paul1 et al., 1980; Reid et al., 1989). Collectively, these data suggest that when demand for stored or newly fixed carbohydrates is reduced, there is a corresponding reduction in leaf blackening.

Carbohydrate Metabolism and Possible Mechanisms of Leaf Blackening in Protea neriifolia under Dark Postharvest Conditions