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Mohamed Rashwan
              lined by Jackson (1973).


                  2.2.3. Plant analysis:

                  2.2.3.1. Pretreatment


                  Segregation into different parts and corresponding parts from a
              few plant samples were composited; leaves were cleansed with gentle
              brushing with a stiff-bristled brush. Washing plant tissues with water

              was avoided, although roots were washed free of soil or sand (Ward

              and Johnston, 1962), removing of needles (leaves) from branch lets;
              air- drying leaves and all other plant material (branches, roots, etc.)
              were cut into small pieces. Before drying, pine needles and leaves

              were removed from the twigs; spruce needles were left to dry on the

              twigs (Kalra, 1971); plant samples were washed with tap water, and
              then oven dried at 70oC for 48 hours. Plant materials were ground
              and then mixed well according to Chapman and Pratt (1961). The

              mill was thoroughly cleansed between grinding individual samples.

              These samples were ground in an agate or porcelain mortar to avoid
              metallic contamination (Kalra, 1971). Also, samples were used for
              the determinations of proline, N, P, K and Na.


                  2.2.3.2. Accumulation percentage of proline and nutrient elements:

                  Proline % in plant was calorimetrically measured using non-hyrin

              reagent according to Bates et al., (1973). Nitrogen (N) of nitrates is
              fixed by combination with an aromatic compound, such as salicylic

              acid. The nitro groups are reduced and the total nitrogen is then lib-
              erated as ammonia by the usual kjeldahl digestion method followed

              by steam distillation (Jackson, 1973). Sodium (Na+) and potassium
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