Phytohormones
are chemical substances that regulate plants growth,
reproductive processes, longevity, development, and even death. One
of the most common representatives of this group is indole-3-butyric
acid (IBA), which is widely applied in various branches of agriculture.
Taking into consideration that the conversion of conventional herbicides
into ionic liquids leads to the enhancement of their biological activity,
we decided to implement the same strategy for selected phytohormone.
Hence, we synthesized a homologous series comprising alkylated choline
cations and indole-3-butyrate anions. The new biobased ionic liquids
(ILs) were characterized in terms of physicochemical properties (thermal
stability, phase transitions, solubility, surface activity, density,
and viscosity) and susceptibility to biodegradation according to the
OECD 301 F test. Subsequently, their activity as a growth stimulator
was evaluated for butterhead lettuce (Lactuca sativa L.) as a test plant. Additionally, the nutrient assimilation by
the test plants was analyzed. The study revealed that the IL containing
cations with octyl groups, at the optimal concentration of 0.5 ppm,
enhanced lettuce biomass production by approximately 21% compared
to that of the control. Moreover, the lettuce was enriched with valuable
micro- and macroelements, such as P, K, Ca, Mg, Na, and Mn. These
findings comply well with the concept of sustainable agriculture focused
on utilizing environmentally friendly compounds derived from sources
of natural origin while exhibiting enhanced efficacy.