On flavonoid accumulation in different plant parts: variation patterns among individuals and populations in the shore campion (Silene littorea)

Abstract

The presence of anthocyanins in flowers and fruits is frequently attributed to attracting pollinators and dispersers. In vegetative organs, anthocyanins and other non-pigmented flavonoids such as flavones and flavonols may serve protective functions against UV radiation, cold, heat, drought, salinity, pathogens, and herbivores; thus, these compounds are usually produced as a plastic response to such stressors. Although, the independent accumulation of anthocyanins in reproductive and vegetative tissues is commonly postulated due to differential regulation, the accumulation of flavonoids within and among populations has never been thoroughly compared. Here, we investigated the shore campion (Silene littorea, Caryophyllaceae) which exhibits variation in anthocyanin accumulation in its floral and vegetative tissues. We examined the in-situ accumulation of flavonoids in floral (petals and calyxes) and vegetative organs (leaves) from 18 populations representing the species' geographic distribution. Each organ exhibited considerable variability in the content of anthocyanins and other flavonoids both within and among populations. In all organs, anthocyanin and other flavonoids were correlated. At the plant level, the flavonoid content in petals, calyxes, and leaves was not correlated in most of the populations. However, at the population level, the mean amount of anthocyanins in all organs was positively correlated, which suggests that the variable environmental conditions of populations may play a role in anthocyanin accumulation. These results are unexpected because the anthocyanins are usually constitutive in petals, yet contingent to environmental conditions in calyxes and leaves. Anthocyanin variation in petals may influence pollinator attraction and subsequent plant reproduction, yet the amount of anthocyanins may be a direct response to environmental factors. In populations on the west coast, a general pattern of increasing accumulation of flavonoids toward southern latitudes was observed in calyxes and leaves. This pattern corresponds to a gradual increase of UV-B radiation and temperature, and a decrease of rainfall toward the south. However, populations along the southern coast exposed to similar climatic stressors showed highly variable flavonoid contents, implying that other factors may play a role in flavonoid accumulation.

Geographic variation in pollen color is associated with temperature stress

“…For example, drought, ambient light conditions and temperature contribute to geographic variation in petal color phenotypes within multiple taxa (e.g. Schemske & Bierzychudek, ; Arista et al ., ; Koski & Ashman, ; del Valle et al ., ; Berardi et al ., ), and abiotic selection underlies diversification in petal‐color patterning phenotypes among species (Koski & Ashman, ). Such abiotic selection acts on petal phenotypes indirectly through selection on whole‐plant biochemistry (Wessinger & Rausher, ), or directly through the effects of petal color on the pollen and ovule environment (Lacey et al ., ; Koski & Ashman, ).…”

Digital photography provides a fast, reliable, and noninvasive method to estimate anthocyanin pigment concentration in reproductive and vegetative plant tissues

“…Conversely, in striped calyces of S. littorea , the digital image method fails to increase both r 2 and NMRSE compared to the spectral reflectance method. In petals of O. italica and M. sylvestris , anthocyanins accumulate in epidermal cells, whereas in S. littorea calyces, the anthocyanins are also stored in basal cells of the trichomes (Del Valle et al., ). The cylindrical structure of these cells could cause a discrepancy between the amount of anthocyanin estimated by digital images (in two dimensions) and the concentration analyzed with the biochemical method.…”

“…Thus, we only removed the transparent petals from the methanol extract before anthocyanin quantification. For complete anthocyanin extraction in pedicels, calyces, and stems samples, we used the methods described in Del Valle et al (2015). maximum absorbance (A max ) of anthocyanins; this wavelength was confirmed with the literature whenever possible (Table 1).…”

“…For complete anthocyanin extraction in pedicels, calyces, and stems samples, we used the methods described in Del Valle et al. ().…”

“…In reproductive organs, anthocyanins help attract pollinators or seed dispersers, whereas in vegetative organs, they provide protection against environmental stressors such as UV-B radiation, excess light, cold, drought, salinity, pathogens, and/or herbivores (Landi et al, 2015;Lee & Gould, 2002;Schaefer & Ruxton, 2011). Variation in floral and vegetative anthocyanin concentrations within and among populations is common and often adaptive (e.g., Del Valle, Buide, Casimiro-Soriguer, Whittall, & Narbona, 2015;Menzies et al, 2016). Therefore, it is undeniable that the quantification of anthocyanins has become fundamental in understanding many aspects of plant evolutionary ecology (Ortiz-Barrientos, 2013;Sobel & Streisfeld, 2013).…”