الفهرس 
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Abstract
The Experiments of this study were conducted during 2012- 2013 and 2013- 2014 seasons at a private farm at 10th of Ramadan association, Ismaellia Governorate, (soil Ec 1.31 dSm) irrigated with saline water (water Ec 3.22 dSm), to study the effect of the following anti-stress treatments: salicylic acid (SA) at 200 and 400 ppm as growth regulator, glycine betaine ( GB) at 15 and 30 mM as osmolyte, in addition to two elements selenium (Se) at 16 and 32 µM and silicon (Si) at 1and 2 mM on the growth, chemical changes and productivity of two lettuce varieties (Balady and Great lakes).
The results were summarized as follows
1. Control plants (untreated plants) showed significant reduction in vegetative growth, yield and other plant characteristics in both cultivars and seasons compared to treated plants.
2. Plants treated with SA, GB, Se and Si significantly recorded an increase in the vegetative growth measurements of the two lettuce cultivars cultivated under saline conditions.
3. GB treatment at 30 mM obtained the highest significant increase in vegetative growth measurements, followed by Si treatment at 2 mM then GB at 15 mM compared to other treatments, as well as untreated plants in both cultivars and seasons at different sampling dates (35- 55- 75 days from planting) under saline conditions, Balady cultivar showed the best results with the exception of dry weight the preference was to Great lakes cultivar.
4. All treatments showed an increase in the leaf relative water content (LRWC) of two lettuce cultivars compared to untreated plants. The treatment of 30 GB mM gave the highest significant increase, followed by the treatment of Si at 2 mM then Si at 1 mM in both seasons.
5. All treatments led to reduce the permeability of membranes (MP) and reduce the negative impact of salinity on cellular membranes. Treatment of 30 mM GB showed the most significant reduction of the permeability of membranes in various ages and during two seasons under saline condition.
6. Treatments of growth regulator (SA) and osmolyte (GB) and the elements, Se and Si led to a significant increase in the concentration of chlorophylls a, b, carotenoids, phenols, free amino acids, proline and total soluble sugars in the leaves than in the plants non-treatment, and was treatment with a concentration of 30 GB mM the best treatment in both cultivars and seasons under saline condition.
7. Regarding the Malondialdehyde (MDA) concentration in leaves, treatment with (SA) and (GB) and the elements, Se and Si significantly decrease MDA concentration while, GB at 30 mM gave the most enzyme reduction in both cultivars and seasons under salinity condition.
8. Treatments of growth regulator (SA), osmolytes (GB) and elements (Se and Si) showed a significant activity increase of antioxidant enzymes: phenylalanine ammonia-lyase (PAL), peroxidase (POD), superoxide dismutase (SOD) and polyphenol oxidase (PPO) when compared with untreated plants under saline condition.
9. All treatment (SA, GB, Se and Si) significantly increase the concentration of Ca, K elements in treated plant leaves as compared to control plants under saline condition and almost increased K/Na ratio.
10. The treatments of (SA) and (GB) and the elements, (Se) and (Si) led to a significant decrease in plant concentration of Na element in the treated plants under saline conditions.
11. Treatments led to a significant increase in yield components compared with the control plants, in both cultivars and seasons.
12. Foliar application of GB at 30 mM on lettuce plants gave the best significant increase in yield compared to other treatments in both cultivars and seasons.
This study recommended using osmolytes (GB) and the elements, (Se) and (Si) foliar application on the leaves of lettuce plants suffering from salinity, as these treatments induced many physiological processes which reduce the adverse effect of salinity on the plants growing. The treatment of osmolyte (GB) at the concentration of 30 mM showed the best results in general followed with 2 mM concentration of silicon treatment.