# Diversity of Potential (Bio)Technological Applications of Amino Acid-Based Ionic Liquids
## 2 Bioapplications of AA ILs: An Overview
### Biomass Production and Potency in Crop Protection  
_Haematococcus pluvialis_ is the major source of astaxanthin, a carotenoid used in cosmetics and as a food and health supplement for its potent antioxidant, immunostimulatory, anti-inflammatory, and anti-cancer properties [63]. Although these microalgae can be cultivated in a relatively simple process, they face several challenges, including low biomass production and high sensitivity to stress, resulting in increased microalgal mortality and reduced astaxanthin yield [64]. In a pilot study, [PERSON] et al. demonstrated that the biomass production and cell number of Haematococcus pluvialis increased by 38% and 34%, respectively, in the presence of [N\({}_{2222}\)][Arg] [64]. The study also showed an increase in carbohydrate, protein, and chlorophyll content. A concentration dependence of the increase in biomass production with increasing IL concentration was observed during plant development.  
On the contrary, AA-based ILs have a negative effect on the growth of cereal seedlings. For example, [N\({}_{2}\)Py][Ala], [P\({}_{2222}\)][Ala], [Emim][Ala], and [N\({}_{2222}\)][Ala], tested at concentrations ranging from 200 to 1200 mg/L, significantly inhibited the growth, chlorophyll content, and nutrient uptake of wheat seedlings, with the effect decreasing in the following order: [N\({}_{2}\)Py][Ala] > [N\({}_{2222}\)][Ala] > [P\({}_{2222}\)][Ala] > [Emim][Ala] [65]. A similar negative effect on rice growth was observed by [PERSON] et al. in the presence of ILs containing 1-methyl-3-alkyl imidazolium cations and bromide anions. The inhibitory effect increased with the increasing alkyl chain length of the cation [66].  
Interestingly, a stimulatory effect on phytohormone production in lettuce (Lactuca sativa L.) has been reported for a wide range of tetraalkylammonium tryptophohanates and dialkyldimethylammonium tryptophohanates [67]. [PERSON] et al. found a significant increase in auxin activity in the presence of all ILs tested, regardless of the alkyl chain length or the presence of aromatic substituents.  
A wide range of tested dicationic ILs containing bis-ammonium or bis-phosphonium cations with short (butyl) to medium (octyl, dodecyl) alkyl chains, or an ester linker, and His or Pro anions stimulate the germination of white mustard (_Sinapis alba_) seeds [68]. Interestingly, those with an alkyl linker in the cation promote root length, whereas all ILs with an ester linker negatively affect root length. On the other hand, all bis-ammonium and bis-phosphonium Pro- and His-based ILs inhibit shoot length during white mustard development [68]. Additionally, all ILs with short-chain substituents, both alkyl and ester, exhibited very good to excellent protection and repellent activity against two common storage pests: granary weevil beetles (_Sitophilus granarius_) and khapra beetle larvae (_Trogoderma granarium_) [68].  
Similarly, [Ch][AA] ILs have a stimulatory effect on maize germination and root and shoot growth [69]. The highest increase in the germination index, compared to controls, was observed in [Ch][Trp]-treated seeds. These ILs promote the production of growth-promoting phytohormones, such as gibberell acid and zeatin, in maize shoot tips, and stimulate the production of AAs essential for plant development, including Glu, Gly, and Arg [69].  
What germination is highly sensitive to environmental conditions and is often used as an assay to evaluate the cytotoxicity of ILs. For a series of 1-ethyl-3-methylpyrrolidinium (EmPy) ILs containing AA anions, it was found that [EmPy][Gly] had no effect on wheat germination at the concentrations tested, while those containing anions such as Pro, Ala, Val, and Leu suppressed wheat growth less compared to methanol (control) [70].