بررسي اثر ملاتونين خارجي بر رشد، فتوسنتز و تنفس جلبك تك سلولي دونه‌ليه‌لا (Dunaliella)در پاسخ به تنش شوري

Dunaliella, classified as a green alga, is frequently utilized in physiological research due to its numerous distinctive characteristics. This unicellular microalga can live in saline habitats. Dunaliella serves as a significant reservoir of biological compounds, which find extensive applications across various sectors, including cosmetic, health, and pharmaceutical industries. Melatonin, a compound synthesized from tryptophan, is generated in both animal and plant systems. In the present study, we assessed the influence of varying concentrations (zero, 0.25, 0.5, 1, 2, 3, and 4mM melatonin)over three repetitions throughout a 14-day period on growth rate, total chlorophyll and total beta-carotene levels in cells. And we aimed to investigate its impact on salinity stress (1.5 to 2.5 M NaCl) by employing 0.25 and 0.5mM melatonin. salinity stress adversely impacts all growth parameters; however, melatonin at low concentrations enhances the cellular growth rate, and in Dunaliella salina, it additionally resulted in an elevation of chlorophyll content. The DPPH assay used to eva‎luate the free radical scavenging ability, utilizing melatonin concentrations of 0.25 mM and 0.5 mM with applying salt stress, which demonstrated that the antioxidant capacity of the cells in this condition was increase in comparison to stress conditions without using melatonin. Experiments result showed that the immediate application of this substance does not have much effect on the rate of photosynthesis and respiration of Dunaliella cells, but in the case of one-week treatment of cells with melatonin and the immediate application of salinity stress, it causes changes in the rate of photosynthesis and respiration of them. In general, the results indicate that melatonin, by affecting the amount of antioxidant that produced by cells and the other biological substances present in the microalgae Dunaliella, caused increases in growth and reduces some negatives effects that caused by salinity stress.

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