Impact of Invasive Weeds Lantana camara L. and Parthenium hysterophorus L. on the Secondary Metabolite Profiles of Okra (Abelmoschus esculentus L.).

Abstract

The impact of two invasive weed species, Lantana camara and Parthenium hysterophorus, on the development and secondary metabolism of okra (Abelmoschus esculentus) is the focus of this study. We explored the potential role of secondary metabolites as antioxidants to mitigate the stress induced by these common weeds on okra plants with special emphasis on chlorogenic acid (CGA). The study has been done with six experimental setups. One setup includes okra grown alone, and another set consists of okra co-cultivation with L. camara, P. hysterophorus, and a combination of both. Each setup consisted of 30 plants of each species. After these, biochemical assays were done to measure the production of secondary metabolites, which include polyphenols, flavonoids, and antioxidants. They are all measured in response to weed-induced stress. Total polyphenols, flavonoids, and antioxidants displayed a significant increment in okra when co-cultivated with Lantana or Parthenium. Co-cultivation with both weeds presented synergistic negative effects, like that interaction is characterized by elevated markers of stress, such as reactive oxygen species (ROS) and malondialdehyde (MDA) levels, indicating the compounded adverse effect on the okra plants. Moreover, it points out the effect of the weed's presence on secondary metabolism in okra. Gene expression analysis of two genes, phenylalanine ammonia lyase (PAL) and hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase (HQT), which are critical in the phenylpropanoid pathway, validated the role of secondary metabolites in weed-induced stress alleviation. High-performance liquid chromatography (HPLC) analysis shows that CGA has increased significantly in okra plants co-cultivated with weeds. It suggests a plant response to counteract weed-induced stress by enhancing CGA production. Therefore, the study shows the impact of weeds on stress indicators, such as ROS, RNS, and MDA. So, it is observed that stress levels are increased in okra in the weed's presence, as indicated by high lipid and proline content. These findings suggest practical strategies for weed management by enhancing secondary metabolism in crops to improve resilience and productivity under stress conditions caused by invasive weeds.