Plant growth promoting N-alkyltropinium bromides enhance seed germination, biomass accumulation and photosynthesis parameters of maize (Zea mays)

Abstract

Tropane alkaloids have attracted increasing scientific attention as natural compounds which display interesting biological properties. Tropine, a common constituent of tropane alkaloids, is a relatively inexpensive and commonly available compound which can be transformed into the form of quaternary salt in order to increase its uptake by plants. The aim of this study was to assess the properties of quaternary N-alkyltropinium bromides with various alkyl substituents and their impact on a model crop plant (maize) in order to evaluate their applicability as potential plant growth regulators. The products were obtained with high yield (81–96%) and their structures were confirmed using NMR. Some of the obtained salts exhibited surface active properties (CMC ranging from 5.12 × 10⁻² to 2.33 × 10⁻³ mg L⁻¹). The conducted experiments confirmed the positive effect of the synthesized salts on maize, such as increased seed germination (up to 60%), higher fresh/dry biomass yield (up to 20%), enhanced electron transfer rate (up to 40%) as well as improved total chlorophyll content (up to 60%). Further studies revealed that the properties of N-alkyltropinium salts depended on the structure of the substituent introduced during quaternization. The substituent can be adjusted to either ensure rapid biodegradability (100% in case of ethylacetyl substituent) or antimicrobial properties (MIC ranging from 2 to 20 mg L⁻¹). The obtained result suggest that N-alkyltropinium bromides potentially constitute a promising group of novel plant growth promoting agents.