Summary

Phytohormone Determination Diagram

Plants play an indispensable role in human life. The growth and development of plants and their response to biotic and abiotic cues are highly dependent on a group of small molecules called plant hormones or phytohormones. Different types of phytohormones specifically influence different physiological processes in plants in minute amounts. For example, auxins, cytokinins, and gibberellins are responsible for plant growth and development, abscisic acid is associated with stress responses, and salicylic and jasmonic acids play a role in plant defense against herbivores and diseases. The importance of phytohormones in plant life is reflected in human efforts to manipulate their levels, e.g. genetically or chemically. In addition to naturally occurring phytohormones, there are a number of synthetic compounds widely used in agriculture that mimic the effects of natural phytohormones. Knowledge of phytohormone concentrations is essential for understanding the basic mechanisms of phytohormone action on plants, but also in agriculture to improve crop quality and yield.

Our approach

The quantification of phytohormones presents a number of challenges. Phytohormones are chemically diverse, ranging from bases to neutrals to weak acids; from polar to hydrophobic. Their natural abundances are very low, in the range of femtomolar to picomolar concentrations. Recent trends in phytohormone analysis have been to increase the number of compounds measured, including not only the active phytohormones but also their precursors and metabolites. This holistic approach of analyzing the "phytohormone metabolome" can give us a better understanding of the biochemical processes that phytohormones undergo. All these characteristics of phytohormones: chemical diversity, low concentrations and large number of compounds have to be addressed by the quantitative analytical approach. In our laboratory we use a combination of microextraction, purification by solid phase extraction (SPE) and instrumental analysis on ultra-high performance liquid chromatography (UHPLC) coupled to a triple quadrupole mass spectrometer (QQQ-MS) set in multiple reaction monitoring (MRM) mode. It allows the analysis of multiple compounds (100+) in a single sample with high specificity and sensitivity. The technique also allows the list of measured compounds to be expanded as needed to include new biologically relevant and interesting compounds.

List of measured compounds (pdf, 116 kB).