Effect of foliar applications of aminolevulinic acid (bulk and nano-encapsulated) on bell pepper under heat stress

Abstract

Plant growth and production can be adversely affected by high temperature stress, which is defined as an increase in temperature over a threshold level. 5-aminolevulinic acid (ALA) can be used as a beneficial growth regulator in agriculture, particularly for plants experiencing abiotic stress. The efficacy of exogenous two form ALA application (bulk and nanoencapsulated) was investigated in a factorial experiment based on a completely randomized block design with 12 replications. In this study, different temperatures (optimal temperature 25 °C, and high temperature 35 °C) and different ALA treatments were used (control, 1 mM of ALA, and 1 mM Nano-encapsulated N-ALA). The study revealed that elevated temperatures of 35 °C had an adverse impact on the majority of bell pepper growth characteristics. Nevertheless, the application of ALA and N-ALA significantly enhanced the growth characteristics under these conditions. In contrast to the conditions at 25 °C, the concentrations of potassium (K), proline, electrolyte leakage (EL), glucose, and fructose exhibited an increase at 35 °C. However, both forms of ALA were effective in mitigating these adverse effects. Comparatively, the control treatment showed elevated levels of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) enzymes, along with increased malondialdehyde (MDA) levels compared to the ALA treatment. The treatment with ALA resulted in the highest fresh weight and shoot length at 35 °C compared to N-ALA. Conversely, at the same temperature, N-ALA led to a 17 % increase in chlorophyll fluorescence and a 32 % increase in DPPH compared to ALA. In summary, the application of both ALA and Nano-encapsulated N-ALA effectively mitigates the adverse effects of exposure to 35 °C on bell pepper growth and biochemical parameters.