Background: During two consecutive winter seasons of 2019/2020 and 2020/2021, two experiments in the field were done at the Research and Production Station, National Research Centre, El-Nubaria Province, El-Behira Governorate, Egypt. This experiment aimed to evaluate the physiological effect of mannitol at 0, 10, 20 and 30 mM on growth, productivity, and nutritional value of faba bean plants (Misr 2 and Sakha 3).

Results: Results show that faba bean cv. Misr 2 was more adaptable to grow under sandy soil conditions than faba bean cv. Sakha 3, since it characterized by higher vegetative growth parameters, photosynthetic pigments, seed yield, yield components, and nutritive value. Mannitol treatments at 20 and 30 mM significantly increased plant fresh and dry weight, total photosynthetic pigments, seed number and weight/plant, seed yield(Kg/feddan),reducing sugar and starch accompanied by significant decreases in total phenolic content, tannins and vicine content. It is worthy to mention that mannitol treatments at 0, 10, 20 and 30 mM significantly increased seed yield (Kg/feddan) by 23.73, 31.88 and 40.15% respectively. Regarding interaction between cultivars and mannitol treatments, it was noted that 30 mM mannitol increased seed yield (Kg/feddan) by 56.37% in Misr 2 and by 22.21% in Sakha 3 relative to corresponding controls. It is obvious that response of faba bean cv. Misr 2 to mannitol treatments was more pronounced than that of faba bean cv. Sakha3.

Conclusion: It could be concluded that Misr 2 cultivar was more adaptable to grow under sandy soil conditions and show more effectively response to mannitol treatments than Sakha 3 cultivar. Mannitol treatments caused significant increases in most investigated parameters of both cultivars and its promotive effect increased by increasing mannitol levels. Mannitol at 30mM was the most pronounced treatment.