Nectar guides

Sasaki, K. and Takahashi, T., A flavonoid from Brassica rapa flower as the UV-absorbing nectar guide, Phytochemistry, 61, 339, 2002. 

Animals live in a world of chemical communication and receive both olfactory and visual cues that indicate appropriate host plants. When the animal has located the flower against the generally green background, it may be attracted to the nectar by nectar guides on the petals. These are derived from differential distribution of pigments within the flower tissue. The biochemistry of plant pollination mechanisms has not been studied extensively. 

Honey or nectar guides are part of the pigmentation of many flowers, but these features are particularly common in bee flowers. 

Thompson, W. R., J. Meinwald, D. Aneshansley, and T. Eisner, Flavonols Pigments responsible for ultraviolet absorption in nectar guide of flower, Science, 177, 528-530 (1972). 

All these examples focus on the temporal aspect of nectar induction. In addition, extrafloral nectaries are also especially suited for the study of spatial dynamics following induction. This aspect can be easily assessed because of the discrete distribution of nectaries, the possibility of non-destructive sampling, as well as the ease of nectar collection. With respect to the spatial pattern of induction, Wackers et al. (2001) showed that the impact of herbivory on extrafloral nectar induction is primarily localized (i.e., restricted to the damaged leaf). This local increase in nectar production can help in actively guiding ants to the site of attack. In addition, a weaker systemic response was found. This systemic induction was restricted to the younger leaves. 

Harbone, J.B. (1998). Phytochemical methods a guide to modern techniques of plant analysis, Chapman Hall, ISSN 0973-1296, New York, USA Heinrich, B. (1979). Resource heterogeneity and patterns of movement in foraging bumblebees. Oecologia, Vol. 40, p. 235-245, ISSN 00298549 Herrera, CM. Veja, C. Canto, A. Pozo, ML (2009). Yeasts in floral nectar a quantitative survey. Annals of Botany, Vol. 103, No. 9, p>p. 1425-1423, ISSN 1095-8290 James, RR. Pitts-Singer, T.L. (2008). The future of agricultural pollination. In ... 

Bees have a great sense of smell but their vision extends into the nltraviolet range. Flowers meant to attract bees are sweetly scented and soft in color. They are attractive nnder nltraviolet light, and have guides leading to their nectar sources. The yellow stripe (beard) on an iris s throat is an example of this (Figure 6.16.1). 

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