الفهرس 
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Abstract
The study focuses on maximizing the β-carotene productivity from green halo-tolerant D. salina. In our study D. salina was exposed to different levels of N: 0.25, 0.5, 0.75 and 1 gL-1 KNO3 or Na+: 75, 100, 150, 200 and 250 g L-1. β-carotene production and accumulation were significantly better in nitrogen deficiency-treated D. salina than that in NaCl-treated cells, with a maximum increase of 5.5 mg g DW-1 at 0.25 gL-1 KNO3. Algal growth, in terms of cell number and the relative growth rate (RGR), was increased with the increase in the availability of nitrogen but decreased with NaCl stress.The ability of D. salina culture and/or β-carotene in alleviating salt stress on the Cucurbita pepo L was comparable to salicylic acid. After growing the squash (Cucurbita pepo L. Mabrouka) seeds in the greenhouse for 25 d, they were transplanted into pots, irrigated with graded dilutions of seawater and amended with a foliar spray of β-carotene extracted from D. salina and/or the culture of D. salina that added to the clay soil. The culture of D. salina exhibited a better beneficial effect than β-carotene and the combination of the two was better than either one alone, but the highest beneficial effect was assigned to salicylic acid. Therefore, the tolerance ability of the amendments to the salt stress was arranged as follows: the combination of the culture of D. salina and its extracted β-carotene ˃ the culture of D. salina˃ β-carotene ˃ non-amendments plants.