Stimulation Effects of Glutamic and 5-Aminolevulinic Acids On Photosynthetic Pigments, Physio-biochemical Constituents, Antioxidant Activity, and Yield of Peanut

Abstract

Soil not only represents the main supporter for root growth, but also is the supplier of water and nutrients. However, several soils, i.e. sandy soils, do not adequately fulfill the plant growth requirements of the environmental resources. Therefore, it is necessary to compensate, even partially, the lack of these required resources for better plant growth and development. Amino acids could introduce a substantial solution in this respect. Therefore, two field experiments under field conditions were carried out to investigate the effect of glutamic (GLA) and 5‑aminolevulinic (ALA) acids on photosynthesis pigments, oxidative defense indicators as well as yield and seed quality of peanut. Three concentrations of glutamic acid (10, 20 and 40 mg L⁻¹, denoted GLA10, GLA20, and GLA40, respectively) and three concentrations of 5‑aminolevulinic acid, (10, 20 and 40 mg L⁻¹, abbreviated to ALA10, ALA20, and ALA40, respectively), in addition to a check treatment (tap water) were applied. Treatments were arranged in a randomized complete block design with three replicates. Findings exhibited potentiality of GLA20 treatment for recording the highest values of chlorophyll a, chlorophyll b, chlorophyll a/b, carotenoids and total pigments compared to the other treatments. The increases in indole acetic acid, phenolics and free amino acids were 68.1, 58.9 and 19.6% as well as 64.6, 51.2 and 17.7%, due to application of GLA20 and ALA20, respectively. Substantial improvements in pod yield ha⁻¹, oil %, flavonoids and antioxidant activity were obtained with GLA20 or ALA20. In conclusion, since glutamic or 5‑aminolevulinic acids at concentration of 20 mg L⁻¹ showed promotive effect on physiological and biochemical status of peanut, such amino acids should be adopted as a promising practice in peanut cultivations.