**1. Introduction**

268 Macro to Nano Spectroscopy

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180-186 (2010).

The pollination by honeybees is important to the best performance of several crops. In this interaction plant-insect there is a change of reward between both organisms, and the sugar concentration in the nectar is a keyword. The spectrophotometry allows analyzing the type and the quantities of sugar in the nectar of flowers, and identifying varieties that are more attractive for pollinators.

The nectar is the reward for several pollinators, and the principal is the honeybee *Apis mellifera*. The nectar is produced from sap of phloem by active secretion that results in a solution of sugars like sucrose, fructose and glucose in varied proportion depending on the vegetal.

Besides sugars, other compounds of the nectar has importance for the coevolution between plants and their pollinators like amino acids, proteins, lipids and alkaloids and these may be toxic for visitors and, however, these compounds may have a role of protection against animals that withdraw nectar of flowers without an efficient pollination.

Several researches are carried out to evaluate the effect of crop pollination using honeybees and consequently the increase of productivity in agriculture. The visit and hoarding of nectar and pollen allows rise in grain production, or tasteful fruit with symmetric format.

The study of sugar from floral nectary is important for identification if a rise or decrease in quantity or nectar quality. The plant may secret a little bit of nectar, but with high sugar concentration, or unlike, secret more quantities, but with low sugar concentration. These differences in nectar may vary depend on pollinator visitation. However, the frequency of honeybees that visit flowers may contribute for rising nectar production like change the sugar proportion.

<sup>\*</sup> Corresponding Author

Spectrophotometry as a Tool for Dosage Sugars in Nectar of Crops Pollinated by Honeybees 271

– pollen is loaded in this structure in association with nectar or oil, absence of ventral scopa

Each group among animals that visit flowers is associated to some particular type of floral reward, that is the morphological traits of flowers reflect adaptation to diversified pollinators. The contemporaneous interactions between plants with flowers and insects can be because of long and closer coevolutionary relation (Backer & Hurd, 1968; Prince, 1997). This process of coevolution or the interaction between plants and pollinators is based on a system of mutual dependence. This system was detailed by the first time by Christian Konrad Spengel (1750-1816), in which plants show their rewards like nectar, pollen, oil and resins by floral arrangement, colour, size and odour of flowers, while the pollinators in change of provided resources by plants transfer pollen between flowers increasing the gene flow and promoting the diversification of the species, named by this as key mutualism

Plants, year by year, specialized in attract more efficient pollinators and make transportation of their reproductive cells, and therewith could be benefited with cross pollination. The disposition of flowers is an important factor that can be isolated in the branches or grouped in the same floral axis forming inflorescence, colour, odour, size, nectar, oil, pollen and

The floral rewards provided by Angiosperms are required to attract pollinators, nectar seems the most searched in crop cultivated commercially, however, in searching by this reward many animals, mainly worker honeybees *Apis mellifera* have pollen adhered to their body, and so, later deposit accidentally their loads on the stigma of other flower of the same

Assays carried out in Marechal Cândido Rondon, Paraná, Brazil, with sunflower make clear worker honeybees that hoarding nectar are more frequent (mean 2.28 honeybees/capitulum) than pollen foragers (0.40 honeybees by capitulum) in anthesis period and schedule of higher visitation in the crop (Chambó et al., 2011). Other experimental results make clear more frequency of nectar foragers than pollen foragers in

Moreover, it must be considered that quantity of honeybee visitors to different species of superior vegetal can be related to concentration and volume of nectar in the flowers during all day (Pham-Delegue et al., 1990). Experiments with attractiveness sunflower genotypes show significative difference in relation to the number of honeybee visitation, mean of 3.40 (genotypes Helio 360 and Aguará) and 1.60 (genotype Multissol) visits of *A. mellifera* by capitulum in third day of anthesis (Chambó et al., 2011, in press). The researchers did not tested the concentration and volume secreted during all day, but assign to these causes the difference of sunflower genotypes assayed. In hybrid of ornamental coloured sunflower BRS-OASIS had an increase (*p* < 0.05) in four times in number of honeybee visitors using sucrose solution in two concentrations 5% and 7.5% as attractive. These solutions were pulverized on sunflower capitulum in relation to concentration of 2.5% (Martin et al., 2005). Despite of efficiency of pollination process, it depends on numerous received visits by pollinators (Schirmer, 1985). Vidal et al. (2010) studying the pollination and set fruit in *Cucurbita pepo* by honyebees reported that percentage of set fruit was maximum (100%)

and long tongue (Teixeira & Zampieron, 2008).

specie, performing indirectly the cross pollination.

sunflower crop (Paiva et al., 2002; Teixeira & Zampieron, 2008).

(Morgado et al., 2002).

resins.

Other factors that must be considered are secreted sugars: sucrose, glucose and fructose. The quantities of them may vary depending on variety and type of vegetal. Honeybees have preference for nectar with more sucrose concentration. Sugars present in nectar are related with honey quality that will be produced by honeybees and, finally will be commercialized.

The association of beekeeping and agriculture provide a rise in profits as for farmer as for beekeeper. However, the quantity and/or quality of the sugars in floral nectar like the pollination of cultivated crops by honeybees have an economic and social role wellestablished and significant currently.

The proposal of this chapter is perform a review about spectrophotometry in sugar dosages of nectar of the main cultivated crops and show the importance of this tool (spectrophotometry) to improve crop production by honeybee pollination contributing as for agriculture as for beekeeping.
