Developmental and phytochemical changes in pot marigold (Calendula officinalis L.) using exogenous application of polyamines.

Polyamines (PAs) are natural active compounds having more than two amino groups that play important roles in many physiological and developmental processes in plants. The purpose of this research was to see how foliar polyamine spray affected growth and photosynthetic indices, as well as secondary metabolites and antioxidant activity of the aqueous and methanolic extracts of pot marigold (Calendula officinalis L.). The experiment lasted for three months and was arranged in a randomized complete design with four replications. Three separate concentrations (0.5, 1 and 2.5 mM) of spermine (SPM), spermidine (SPD), and putrescine (PUT) were sprayed at four/five fully expanded leaf stage and some physiochemical attributes were evaluated. The treatments caused a significant increase in morphological and photosynthetic parameters and total oil. There were also significant variations in total phenolic and flavonoid content. Compared to other polyamines, 1 mM SPD foliar spraying showed the greatest effect. Furthermore, the highest antioxidant capacity (DPPH* scavenging assay, ferric reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC) and ß-carotene bleaching activity) was observed in the 1 mM SPD treatment. The results showed that the calendula essential oils (EOs) were rich in sesquiterpenes hydrocarbons (55.92-95.94%), with c-Cadinene and d-Cadinene as the major sesquiterpenes in the EOs. Also, the flowers were rich sources of carotenoids (lutein, flavoxanthin and luteoxanthin) following polyamines application. Hence, it can be inferred that polyamines specially spermidine would find a wide range of application in pharmaceutical industries due to its impact on antioxidant properties of phenolic and flavonoid compounds.

Potential Role of Foliar Application of Azotobacter on Growth, Nutritional Value and Quality of Lettuce under Different Nitrogen Levels.

Vegetables can be treated with biofertilizers as an alternative to chemical fertilizers because of their low toxicity. We investigated the effects of foliar spraying of Azotobacter under different levels of nitrogen (100, 150 and 200 mg/L in nutrient solution) on the growth, nutritional value, nitrate accumulation and antioxidant enzyme activities of hydroponically grown lettuce. The experiment was laid out in a completely randomized design with four replicates in a factorial combination. Plants treated with Azotobacter and 200 mg/L nitrogen had greater leaf area and photosynthetic pigments than plants treated with 200 mg/L nitrogen without spraying with Azotobacter. Increasing nitrogen levels increased leaf number, fresh and dry weights, leaf area and nitrate accumulation in lettuce plants. Peroxidase (POD) activity increased by 95.4% at a nitrogen level of 200 mg/L compared to a nitrogen level of 100 mg/L. Ascorbate peroxidase (APX) activity and leaf phosphorous (P) and potassium (K) concentrations were the highest in plants treated with a nitrogen source of 100 mg/L without foliar application of Azotobacter. As nitrogen levels increased in all treatments, nitrate reductase (NR) activity decreased and reached a minimum at the 200 mg/L nitrogen level. In general, foliar application of Azotobacter sp. can be used to promote plant growth and reduce nitrate accumulation in lettuce.