Exudate flavonoids are secondary metabolites (SMs) which are accumulated on aerial surfaces of plants, as a result of excretions mostly produced by glandular structures. Exudates often contain flavonoid aglycones, along with other lipophilic material such as terpenoid compounds. Amounts of excreted material and number of compounds present therein may vary between plant taxa and also between organs of the same plant. Larger amounts are mostly produced by plants occurring at higher altitudes or in xeric habitats. Conspicuous excretions may be found on Primulaceae, consisting of flavonoids in quasi-crystalline form, and on farinose ferns often as mix with terpenoids. Otherwise, exudate flavonoids are dissolved in the waxy material covering leaves, stems, and occasionally, fruits. Production of exudate flavonoids may be a way of protecting plants from increased UV-radiation. Generally, flavonoids (from tissues and exudates) are well known for their anti-oxidative properties, and therefore may also be protective in many ways – both for plants and for humans. Mind: flavonoids occur practically in all vegetables and fruits! Read more on “exudate flavonoids” by following this link.
SMs are the product of biosynthetic activities in plants (and fungi). Biogenetic trends within a given class of metabolites such as flavonoids may be observed when related taxa are analyzed against phylogenetic backgrounds (e.g. molecular systematic data). Taking natural variation and aspects influencing the metabolite profile of plants into account, obvious biosynthetic trends may serve as additional characters in systematic and phylogenetic studies (chemosystematics). At the infrageneric level, the composition of flavonoid exudate profiles provides additional characters. At this level, it may be assumed that chemical structural changes are the result of corresponding enzyme activity (homology). While chemical characters - if such are confirmed – may stimulate rethinking of current systematic groupings, they should never be used solely to rank taxa of any kind. For more information, please consult list of publications.
Editor’s comment to Special Volume: "Evolution of Chemodiversity: Cells-Plants-Communities" Vol. 3 (8), published August 2008 in Natural Product Communications (http://www.naturalproduct.us/). This introduction gives you some idea how broadly the concept “Chemodiversity” may be developed.
Aspects of chemodiversity are addressed in lectures, practicals and seminars in all major curricula (Bachelor in Biology; Master in Plant Sciences; Master in Botany; Master in Evolutionary Biology; Doctoral studies – PhD). Further information (in German) may be obtained by following the link on the left or by personal contact.
© Karin Vetschera