The impact of nano copper on the biochemical and and growth characteristics of Moringa (Moringa oleifera L.) under salinity stress

Introduction

Moringa oleifera is a fast-growing tree that grows mainly in tropical or subtropical regions and in less fertile soils. Moringa owns anti-cancer and antioxidant properties. Moringa seedlings undergone saline water treatment (up to 8 dS/m) with a slight decrease in yield, chlorophyll, protein and antioxidant activity. But salt levels up to 12 dS/m associated with a significant decrease in yield, chlorophyll, peroxidase, superoxide dismutase activity, calcium, potassium, magnesium content, and an increase in catalase activity and phenol content. Since salinity is one of the destructive stresses on the growth of moringa, providing a suitable method to reduce its detrimental impacts can be effective. Nanomaterials, particles with dimensions between 1 and 100 nanometers, are of interest in agriculture mainly as nanofertilizers. Due to their small size, nanoparticles pass through biological barriers, enter the plant and are easily transferred to various tissues. Copper, as a micro element, presents in the structure of important plant enzymes and plays a role in electrons transfer. While in saline soils, the solubility of copper element is limited, solutions are of interest to supply this element to plants. There is no report on improved salinity tolerance through treatment with nano-Cu in Moringa. Therefore, the aim of this research is to survey the effects of salinity and Cu nano-fertilizer on biochemical, antioxidant and growth traits of Moringa plant.

Material and Methods

Six-month-old Moringa seedlings were cultivated in plastic pots. Sodium chloride (0, 3.9, 7.8 and 11.7 dS/m of salt) was considered as salinity treatment (through irrigation water, three times a week). Foliar treatment with nano- Cu (0, 10 and 20 ppm) was applied twice (three and five weeks after the initiation of salinity). Eight weeks after the end of salinity, leaf total chlorophyll and carotenoid content, relative water content, proline, protein, superoxide dismutase enzyme activity, shoot dry and fresh weight, leaf area and chlorophyll fluorescence were measured. The experiment was carried out as a factorial in completely random design in three repetitions (each repetition includes 3 pots). The factors were included irrigation with saline water (0, 3.9, 7.8 and 11.7 dS/m) and nano copper (0, 10 and 20 ml/L). Duncan's test was performed to compare the means.

Result and discussion

The lowest total chlorophyll was belonged to 11.7 dS/m salinity and 10 ppm nano-Cu. Foliar spraying of nano-Cu enhanced chlorophyll. 20 ppm of nano-Cu increased total chlorophyll compared to no nano-Cu treatment. 11.7 dS/m of salinity caused an 11% reduction of carotenoids compared to no-salt treatment. 20 ppm nano-Cu caused a 10% boost in carotenoid compared to no nano-Cu treatment. 11.7 dS/m caused a 30% decline in leaf relative water content compared to no-salt condition. Treatment with nano-Cu had no significant impact on leaf relative water content. Enhanced salt levels and foliar spray with nano-Cu, both caused an improvement in proline content. The highest proline content was assigned to the salinity of 11.7 decis/m and 20 ppm nano copper, and the lowest amount was assigned to no-salt treatment and no nano- Cu foliar application. According to findings, enhanced salt levels was accompanied by declined protein, but the usage of nano-Cu improved this trait. The results of SOD activity also indicated that boosted salt levels and the amount of nano-Cu foliar application, both increased SOD activity. In the absence of salt, foliar spraying with nano-Cu elevated shoot fresh weight by 9.4% compared to no nano-Cu treatment. Under 11.7 dS/m of salinity, the application of nano-Cu solution enhanced shoot fresh weight by 22%. Moreover, the treatment of plants with 20 ppm of nano-Cu caused a 26% increment in leaf area compared to no nano-Cu treatment. The highest Fv/Fm was also obtained in plants under the absence of salt and sprayed with 20 ppm nano-Cu. The lowest value of this ratio was also observed in of 11.7 dS/m salt and no nano-Cu foliar application.

Conclusion

Salinity led to declined shoot dry weight, leaf total chlorophyll content, relative water content, protein and incresed proline content and SOD activity. Among the nano-Cu treatments, under 11.7 dS/m salinity conditions, 20 mg/L nano-Cu had the most significant positive effect on the studied traits. Therefore, Nano-Cu foliar spraying (up to 20 mg/L) can play a fruitful role in reducing the adverse impacts of salinity stress in moringa plant.