Colour of floral styles in the Banksia spinulosa Sm complex (Proteaceae) relates to the anthocyanin and flavonol profile, not soil pH. (December 2021)

• Record Type: Journal Article
• Authors: Stimpson, Margaret L.; Whalley, Ralph D.B.; McLean, Lynette; Sadgrove, Nicholas J.; Padilla-Gonzalez, Guillermo Federico; Van Wyk, Ben-Erik; Clay, Jonathon; Bruhl, Jeremy J.
• Is Part Of: Phytochemistry. Volume 192(2021)
• Publication Date: 2021-12
• Subjects: Abiotic factor -- Chelate -- Conflorescence -- Banksia -- Flavonoid -- Metal complex -- Proteaceae; Botanical chemistry -- Periodicals; Biochemistry -- Periodicals; Botany -- Periodicals; Chimie végétale -- Périodiques; 572.2
• DOI: 10.1016/j.phytochem.2021.112931
• Languages: English
• ISSNs: 0031-9422

Abstract

Abstract: The cylindrical conflorescences of the Banksia spinulosa Sm complex have several different colour types, i.e., black, red, maroon, lemon, and yellow. It is unknown if colour variation is due to extrinsic factors, importantly soil pH. Recent morphological observations have indicated that style colour are not contiguous, so follow-up chemical and soil analysis was conducted to further characterize the colour difference with respect to putative taxa and abiotic factors. Conflorescences of all known colours were sampled from across the eastern Australian distribution of B. spinulosa, and the respective soils were sampled and analysed for pH and total nitrogen. Regression analyses of this data demonstrated that pH and nitrogen gave nil and limited predictability for style colour respectively, i.e., only the taxa with black styles demonstrated a correlation, which was to a soil with slightly higher nitrogen content (p < 0.05). Furthermore, differences of pH were more often between taxa with conflorescences of the same colour. For chemical characterisation, the coloured styles were removed from conflorescences, extracted, and analysed by liquid chromatography-mass spectrometry (HPLC-MS/MS-DAD). Ten anthocyanin and twelve flavonol monoglycosides were identified by mass spectral fragmentation patterns (MS 1 and MS 2 ) and retention times. The data demonstrates that style colour differences are caused by the concentration of anthocyanins and their specific chemistry. It remains to be determined if the differences of anthocyanin expression are caused by other abiotic factors, or if it is intrinsic to the respective taxon. Graphical abstract: Image 1 Highlights: Styles from flowers of Banksia demonstrate high anthocyanin/flavonoid diversity. Diversity is within heterogeneous species aggregates. Black styles are highly concentrated with several major anthocyanins/flavonoids. Yellow styles contain flavonoids only. The colour of flower was not related to pH.