Exogenous triacontanol provides tolerance against arsenic-induced toxicity by scavenging ROS and improving morphology and physiological activities of Mentha arvensis L.

Arsenic (As), recognized as a toxic metalloid globally, has posed a serious threat to soil, plants and aquatic resources. Arsenic restrain fundamental processes of plant grown under the As-contaminated soil which are the worst sufferers for their sustenance. Thus, various scientific strategies are being continuously employed for reducing the soil As. In this regard, use of well-known plant growth regulators (PGRs) like triacontanol (TRIA) shown great efficiency towards heavy metals stress tolerance. TRIA is a plant growth promoter that has been proved effective for growth and development of plants under diverse environmental conditions for many decades. The research work was carried out to examine the toxic effects of As on various morphological, physio-biochemical, yield and quality parameters of Mentha arvensis L. and amelioration of the As toxicity through exogenous application of TRIA. Mentha plants were supplemented with various treatments (i) 0 (control), (ii) TRIA (10-6 M), (iii) As (60 mg kg-1), (iv) As (80 mg kg-1), (v) TRIA (10-6 M) + As (60 mg kg-1), and (vi) TRIA (10-6 M) + As (80 mg kg-1). Several parameters studied during the present investigation were plant height, fresh and dry weights, herbage yield, chlorophyll and carotenoid content, carbonic anhydrase (CA) activity, several chlorophyll fluorescence parameters, superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), proline (PRO), H2O2 content, TBARS content, electrolyte leakage (EL), essential oil content (EO) and yield and microscopic analyses as well as PCA analysis. Arsenic treatment exhibited deleterious effects on the overall growth, photosynthetic, and quality parameters of M. arvensis. However, the toxicity of As was mitigated by the leaf-applied TRIA to the plants, proved advantageous in combating the ROS generation.

Oligomers of carrageenan regulate functional activities and artemisinin production in Artemisia annua L. exposed to arsenic stress.

Recently, a promising technique has come forward in field of radiation-agriculture in which the natural polysaccharides are modified into useful oligomers after depolymerization. Ionizing radiation technology is a simple, pioneering, eco-friendly, and single step degradation process which is used in exploiting the efficiency of the natural polysaccharides as plant growth promoters. Arsenic (As) is a noxious and toxic to growth and development of medicinal plants. Artemisinin is obtained from the leaves of Artemisia annua L., which is effective in the treatment of malaria. The present study was undertaken to find out possible role of oligomers of irradiated carrageenan (IC) on two varieties viz. 'CIM-Arogya' (As-tolerant) and 'Jeevan Raksha' (As-sensitive) of A. annua exposed to As. The treatments applied were 0 (control), 40 IC (40 mg L-1 IC), 80 IC (80 mg L-1 IC), 45 As (45 mg kg-1 soil As), 40 IC + 45 As (40 mg L-1 IC + 45 mg kg-1 soil As), and 80 IC + 45 As (80 mg L-1 IC + 45 mg kg-1 soil As). The present study was based on various parameters namely plant fresh weight (FW), dry weight (DW), leaf area index (LAI), leaf yield (LY), chlorophyll and carotenoid content, net photosynthetic rate (PN), stomatal conductance (Gs), carbonic anhydrase activity (CA), proline content (PRO), lipid peroxidation (TBARS), endogenous ROS production (H2O2 content), catalase activity (CAT), peroxidase activity (POX), superoxide dismutase activity (SOD), ascorbate peroxidase activity (APX), As content, and artemisinin content in leaves. Plant growth and other physiological and biochemical parameters including enzymatic activities, photosynthetic activity, and its related pigments were negatively affected under As stress. Leaf-applied IC overcame oxidative stress generated due to As in plants by activating antioxidant machinery. Interestingly, leaf-applied IC enhanced the production (content and yield) of artemisinin under high As stress regardless of varieties. The oligomers of IC and As were found to be responsible for the production of endogenous H2O2 which has a pivotal role in the biosynthesis of artemisinin in A. annua.