Evaluating the Effect of Abiotic and Biotic Factors on Physiology and Phytochemicals in Culinary Herbs

Culinary herbs are used in culinary dishes for their natural flavor, aroma, and visual appearance. Not only do they provide an enhanced visual appearance to the dishes, but they are also rich sources of nutrients, vitamins, and fiber as well as phytochemicals. Phytochemicals are the bioactive compounds found in plant products possessing antioxidant properties. These antioxidant properties provide health benefits when consumed regularly in balanced diets. A large number of natural phytochemicals, including polyphenols, found in different culinary herbs are affected by different abiotic and abiotic factors. Furthermore, different production systems can influence the phytochemical production of culinary herbs. Salinity, a major abiotic stressor, is known to affect the polyphenol production of culinary herbs. Soil salinity is often comprised of a complex mixture of ions, yet most salinity research focuses on sodium chloride. These studies aimed to determine if the polyphenol production of culinary herbs could be increased by the application of complex salt solutions at different salinity levels for different culinary herbs like cilantro (Coriandrum sativum), parsley (Petroselinum crispum), basil (Ocimum basilicum) and shiso (Perilla frutescens). The use of endophytic arbuscular mycorrhizal fungi (AMF) is a promising technique to mitigate crop salinity effects. AMF colonizes the roots of host plants to enhance productivity under stressed conditions. In order to determine if AMF could mitigate salinity stress in herbs and affect polyphenol concentrations in the plants, we subjected several herbs to AMF inoculation and salinity stress. In addition to management strategies used to mitigate stress and increase phytochemicals, production systems have been used to optimize yields and also increase the nutritional quality of plants. Here, we explored the use of both conventional production systems and hydroponic systems to grow the herbs and determine what factors impact phytochemical production. Results showed that higher salinity comprised of complex salts reduced morphological and phenolic constituents of all culinary herbs. However, proline content increased with an increase in salinity level. We saw cultivar-dependent responses to salinity on the polyphenol production of culinary herbs. Furthermore, AMF inoculation could not mitigate the effect of salinity because of unsuccessful colonization. The microscopic evaluation of roots further determined that AMF could not colonize the roots of culinary herbs. In the hydroponic study, we found that intermittent nutrient flow can be used instead of continuous without reducing yield in hydroponic culinary herbs. Furthermore, electric consumption can be lowered as well. The phytochemical production of culinary herbs can be influenced by different production systems, and optimum production systems with high phytochemical content can be achieved by evaluating different production systems. However, the effects of AMF in mitigating salinity and resulting changes in phytochemicals are unclear, and further in-depth research is necessary to elucidate their relationship.