Brassinosteroids in Vegetative Parts of Angiosperm Plants: A Survey of the Available Quantitative Data

Abstract Brassinosteroids (BRs) are important phytohormones naturally occurring in minute amounts in various plant species across the whole plant kingdom. Although the original quantitative analyses of these sterols were mostly done with plant organs/tissues related to reproduction, currently available methods enable us to work with plant vegetative parts which usually contain significantly lower BR amounts, and to determine not only total BR content but also differentiate between individual BRs. During the last two decades, the number of studies presenting quantitative data on various BRs has thus steeply increased. This allows for the compilation and sorting of the obtained information. This review summarises and describes the currently available quantitative data on contents of various BR types in vegetative parts of angiosperm plants, emphasizes/discusses some interesting aspects of the respective studies and their results (including factors that can influence endogenous BR contents, such as analytical methods, inter- and intraspecific variability, organ specificity, various aspects of plant development and external conditions plants are exposed to), and points out some directions that future quantitative analysis of BRs should focus on.