Nectar sugars

Wliile the corolla tube of S. divinorum suggests a co-evolved pollinator with long mouthparts, information concerning nectar sugar concentration and the volume of nectar secreted can help resolve further the identity of this long-tongued pollinator. Nectars sampled by Cm den et al. (1981) from a spectrum of Mexican plants below 2400 m showed that bee flowers produce more concentrated nectars (34.7%) than hawkmoth- (22.6%) and... 

Baker, H.G., and I. Baker. 1983. Floral nectar sugar constituents in relation to pollinator type. In, C.E. Jones and R.J. Little, eds.. Handbook of experimental pollination biology. Scientific and Academic Editions. New York. 

Abrol, D.P. Kapil, R.P. (1991). Foraging strategies of honeybees and solitary bees as determined by nectar sugar components. Proceedings of the Indian National Academy of Sciences, Vol. 57-B, p. 127-132, ISSN 0019-5588... 

Canto, A. Herrera, C.M. Medrano, M. Perez, R. Garcia, I.M. (2008). Pollinator foraging modifies nectar sugar composition in Helleborus fbetidus (Ranunculaceae) an experimental test. American Journal cf Botany, Vol. 95, No. 3, pp. 315-320, ISSN 1537-2197... 

Freeman, C.E. Worthington, R.D. Corral, R.D. (1985). Some floral nectar-sugar compositions from Durango and Sinaloa, Mexico. Biotropica, Vol. 17, p. 309-313, ISSN 0006-3606... 

In most markets fmit juice must be 100% juice and contain no additives. Fmit nectars consist of pulp, juice, sugar, and water, and contain from 25 to 50% juice, depending on the fmit used. In the EEC the minimum juice content is 50% for orange and apple, 40% for apricot, and 25% for passion fmit and guava (26). Other fmit juice drinks include cocktails, which usually contain at least 25% juice and a variety of juice drinks which can contain from 1.5—70% juice (Table 2). 

It has long been recognized that boron is required by higher plants [61, 62], and recent research indicates the involvement of boron in three main aspects of plant physiology cell wall structure, membrane function, and reproduction. In vascular plants, boron in solution moves in the transpiration stream from the roots and accumulates in the stems and leaves. Once in the leaves, the translocation of boron is limited and requires a phloem transport mechanism. The nature of this mechanism was only recently elucidated with the isolation of a number of borate polyol compounds from various plants [63-65]. These include sorbitol-borate ester complexes isolated from the floral nectar of peaches and mannitol-borate ester complexes from the phloem sap of celery. The implication is that the movement of boron in plants depends on borate-polyol ester formation with the particular sugar polyol compounds used as transport molecules in specific plants. 

As regards the occurrence of /3-D-linked disaccharides in the absence of a /3-D-linked substrate, one is tempted to conclude that these oligosaccharides are synthesized by the enzymic reversion of D-glucose by a /3-D-glucosidase. As White and Maher100 have found that their honey-invertase preparation had no /3-D-glucosidase activity, it would appear that these sugars are carried into the hive as constituents of nectar. 

Extrafloral nectaries include a wide range of nectar-excreting structures, which are distinguished from their floral counterparts by the fact that they are not involved in pollination. Extrafloral nectar is typically dominated by sucrose and its hexose components glucose and fructose. The fact that these common sugars are acceptable to the majority of insects, combined with the exposed nature of extrafloral nectaries, makes them suitable food sources for abroad range of insects. Compared with floral nectar, extrafloral nectar often has increased fructose and glucose levels (Tanowitz... 

A comparison of nectar- and honeydew sugars with respect to their utilization by the hymenopteran parasitoid Cotesia glomerata. Journal of Insect Physiology 47 1077-1084. 

Nectar studies included an analysis of constituents, a study of daily secretion patterns, and also total volumes produced per flower. Calibrated micropipettes were inserted into the pool of nectar that accumulates at the base of the corolla tube, with nectar extracted by capillary action. Sugar concentrations were measured with an Extech model 2132 pocket refractometer, with several nectar samples also analyzed for sugar constituents (ratio) by Irene Baker at UC Berkeley. 

The nectar was spotted on Whatman 2 filter paper, the diameter of the spot outlined with four pencil marks, and the volume and percent sugar for each spot provided to Dr. Baker. 

Honey. A natural syrup which vanes in composition and flavor, depending upon die plant source from which die nectar was collected by die honeybee, the amount of processing, and the duration of storage. The pnncipal sugars contained in honey are fructose and glucose, the same components as in table sugar. There are minute amounts of vitamins and minerals in honey, but these are not usually considered in terms of calculating minimum requirements. 

Although sugars are found in juices, the high-intensity sweeteners are not. However, they are often used in juice-based drinks or nectars, and here it is important to ensure that there is resolution of the sweeteners of interest from the compounds naturally present in fruit juices. This can be a particular problem in drinks with a high juice content as naturally occurring polyphenolic materials in the juice can disturb the analysis. 

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