Bio-stimulatory properties in seeds of plants from the families Caryophyllaceae and Fabaceae with application potential in agriculture

Abstract

A comparative investigation into the bio-stimulatory activity of seed suspensions from two South African plant species belonging to each of the families Caryophyllaceae and Fabaceae were conducted using ComCat®, a commercially available bio-stimulant, as a positive control. These included Acacia erioloba and Acacia karroo from the family Fabaceae and Dianthus basuticus and Pollichia campestris from the family Caryophyllaceae. Three different bio-assays were applied to screen for possible bio-stimulatory activity in the seed suspensions. These included the effect on the respiration rate of monoculture yeast cells, germination of seeds from five vegetable crops and subsequent root growth in seedlings. The study confirmed that seed suspensions of A. eri-oloba and P . c a m p e s tr is were consistently most active in terms of all three bio-assays used to test for bio-stimulatory activity. Following liquid-solid extraction of crude extracts from these two species by using organic solvents with increasing polarity, a very small amount of active extract was recovered from P. campestris seeds. Subsequently, only the semi-purified and active ethyl acetate fraction of an A. erioloba crude extract was purified further. By means of column- and preparative thin layer chromatography the active compound was isolated, purified and identified as 2-ethyl-hexyl phthalate by means of nuclear magnetic resonance (NMR) spectroscopy. The latter was proven not to be an artefact of the extraction process. It is concluded that sufficient evidence in terms of the application potential of an A. erioloba extract in agriculture has been produced to warrant further investigation under field conditions.