Selenium (Se) is a necessary microele-ment for microalgae growth. Moreover, it might be directly act and cause a decrease in primary production in microalgae. Nowadays, there is a great focus on preparations of Se-enriched products. In the current study, the effects of various selenate concentrations on Spirulina evaluated as a primary stage to large-scale production of Se-enriched S. platensis. Zarrouk medium supplemented to investigate the stimulatory/inhibitory effects of selenate on the growth at various concentrations. Biomass dry weight and cell mass measured on OD550. Thereafter, inhibitory and algicidal concentrations were determined. Furthermore, its effects on morphology and changes of some important pigments in response to the metal challenge investigated, too. While the results showed that at 5 and 10 ppm concentrations growth was supported, the dry weight of microalgae decreased at selenate levels above 50 ppm. Besides, the inhibitory and lethal effects of selenate were at 100 ppm and 300 ppm, respectively. In addition, morphological changes observed at this concentration. Additionally, chlorophyll, carotenoid and phycobiliproteins, showed a stimulatory effect at 5-50 ppm, 10 ppm, and 10 ppm, respectively. Moreover, Spirulina uses for foods production because some chemicals are unique compounds. Simple cultivation method and high quality of its protein, and no toxic effects, cause its feasibility for large-scale production.

Potassium is a major nutrient which may play an important role in many processes such as ion homeostasis in plant cells and osmotic adjustment of guard cells during stomatal opening and closing. Pathumthani 1 (PT1) rice has been reported as being a salt sensitive cultivar and has been selected as a model plant in this study to investigate the possibility of improving the osmotic potential, pigment stabilization, photosynthetic efficiency and growth characteristics of this plant under salinity stress by potassium nitrate (KNO3) application. Sodium ion accumulation in root and leaves of KNO3 (11.8 mM) treated plants declined as compared to the control plants. In control plants, however, due to decline in potassium ion content, the Na+/K+ ratio increased significantly. A positive relation between Na+ accumulation and osmotic potential was found. Osmotic potential (Ys) in the root and leaf tissues of PT1 rice treated with 11.8 mM KNO3 was maintained at low levels, which was accompanied with the stabilization of photosynthetic pigments, high photosynthetic performance and better growth characters under 200 mM NaCl. The photosynthetic ability in plants with KNO3 application was positively related to plant dry weight. Exogenous KNO3 application to rice crops may play a vital role as a short-gun technique for the improvement of salt tolerance.

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The effects of UV-B radiation on the amount of chlorophyll a, b, carotenoids, flavonoids, anthocyanins, and polyphenols of three soybean cultivars was studied. After germination in the incubator, plants were put in pots of soil and during 3 weeks and irrigated with Hoagland solution every day. After 3 weeks, plants were exposed to UV-B for 20 min every day for a week. In each cultivar, UV-B reduced chlorophyll a, b, and carotenoids and increased anthocyanins, flavonoids, and polyphenols. The reduction of chlorophyll a and b content was significant between two cultivars Williames, Linfored and L17, Linfored. Carotenoids content showed significant decrease between cultivars Linfored, Williames and Linfored, L17. The anthocyanin and flavonoid contents were affected by UV-B and there was a significant difference in the increase between Williames and L17 and also between L17 and Linfored cultivars. Also increase in phenol content was significantly different between Williames and L17 and also between Williames and Linfored cultivars.