Potential ecological effect  of abiotic stress on flowers pollination system via changes in anthocyanin concentration Seminar Paper
1 .      Introduction Flowering plants exhibit enormously diverse floral traits (among them floral size, color, shape etc.), many of which are useful for animal pollination (Ollerton, Winfree et al. 2011). For example, showy perianths and odors can attract pollinators, and nectars, oils and other floral secretions can reward pollinators (Faegri and Van Der Pijl 1979). There are numerous studies about the relationship between floral traits to pollinators attraction- from hummingbirds and other birds to bees, flies and beetles (Baker 1961, Lars Chittka 1992, Menzel and Shmida
1 993, Chittka and Raine 2006, Handelman and Kohn 2014). Furthermore, pollinators, as major determinants of mating patterns in many plants, are one of the most primary drivers of plant diversification. For example, in comparative studies across angiosperms, animal-pollinated lineages have significantly more species than abiotically pollinated lineages (Dodd, Silvertown et al. 1999).
2.      Plant color and anthocyanin Plants produce more than 200,000 different types of compounds, including many colored (pigmented) ones (Fiehn 2002). There are 3 main classes of pigments for coloration in plants: flavonoids/anthocyanins, betalains and carotenoids, of which this review will focus on the first group.
Flavonoids, a group of secondary metabolites belonging to the class of phenylpropanoids have the widest color range, from pale-yellow to blue. In particular, anthocyanins, a class of flavonoids, are responsible for the orange-to-blue colors found in many flowers, leaves, fruits, seeds and other tissues. A total of 19 types of anthocyanidins or chromophores of anthocyanins are knows and their color greatly depends on the number of hydroxyl groups on the B-ring: the larger the number of groups, the bluer the color. The color of anthocyanins changes depending on the pH, co-existing colorless compounds (co-pigments) and metal ions. Biosynthesis of anthocyanins is part of the flavonoid biosynthetic pathway, a well understood pathway which is conserved among seed plants.
Flavonoids are synthesized in the cytosol (in a multi-enzyme processes which will not discussed here), can undergo various modifications and are then transported to the vacuole (in a mechanism less well understood than their biosynthesis). Inside the vacuole, the regulation of the vacuolar pH (again in partly understood mechanisms) greatly affects anthocyanin color- and thus the organ color. The only known structural gene that regulates vacuolar pH with relevance to color is the Japanese morning glory antiporter that is specifically expressed before flower opening and increases the vacuolar pH to generate blue flowers (Yamaguchi, Fukada-Tanaka et al. 2001). Petunia loci that regulate vacuolar pH have also been identified (Tanaka, Sasaki et al. 2008).
Since, as mentioned earlier, there are several factors affects anthocyanin synthesis, modifications and structure, the environment (biotic and abiotic factors) has a great effect on the plant's color as will be discussed in the following sections.
3.      Anthocyanin function in stress Anthocyanins display a variety of biological activities other than their role in pigmentation- antiflammotory (Carvalho, Gutierres et al. 2015), anticarciogenic, antimicrobial (Cisowska, Wojnicz et al. 2010) and lately it has been suggested that they play ….. context. The next sections of the paper will review some papers dealing with stress, change in anthocyanin concentration and flower color, some selection agents working on color and possible implications for potential effects of stress on the pollination system of flowering plants. a)      Heat and cold stress ….