الفهرس 
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Abstract
SUMMARY
This study was carried out at the Experimental Station of Agricultural Botany Department, Faculty of Agriculture, Moshtohor, Benha Branch, Zagazig University in the two successive seasons of 1993/1994 and 1994/1995 on two wheat cultivars (Giza 163 and Sakha 92) and two tomato cultivars (Castle Rock and Edkawi).
The study included two independent experiments: a laboratory experiment and a pot experiment.
I- The laboratory experiment:
The aim of this experiment was to study the effect of different salinity levels (0, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 and 10000 ppm) on the germination percentages and rates of wheat cvs. (Giza 163 and Sakha 92) and tomato cvs. (Castle Rock and Edkawi). Also aimed to detect the maximum tolerable salinity level of certain wheat and tomato cultivars.
The obtained results could be summarized as follows: 1.Wheat cvs.(Giza 163 and Sakha 92):
For wheat cv. Giza 163, it was noticed that increasing salinity level from 0 to 7000 ppm progressively decreased the germination percentages and increased the number of days required for germination. But for wheat cv. Sakha 92, it was noticed that increasing salinity level up to 6000 ppm did not show a clear effect on the germination percentages or rates. Meanwhile, salinity at 7000 ppm decreased the germination percentage and increased the number of days required for germination. Besides, salinity at the concentrations more than 7000 ppm(8000,9000 and 10000 ppm) completely inhibited seed germination in the two assigned wheat cultivars.
2. Tomato cvs. (Castle Rock and Edkawi):
The dominant effect of salinity on seed germination of these two tomato cultivars was the reduction in germination percentages and the increase in number of days required for germination. This effect was directly proportional to the applied concentration. Furthermore, salinity concentrations more than 5000 ppm (6000, 7000, 8000 and 10000 ppm)completely inhibited seed germination in Castle Rock cv. Although in Edkawi cv. all the seeds did not germinate at the high salinity concentrations (9000 and 10000
PPrn).
The obtained results indicated that the maximum level of tolerable salinity (i.e. the salinity level after which the germination percentage was less than 50% of the control) was 7000 ppm for the two wheat cultivars and the tomato cv. Edkawi as well. While, the maximum level of tolerable salinity was 5000 ppm for the tomato cv. Castle Rock. Also, the results indicated that wheat cv. Sakha 92 and tomato cv. Edkawi were more salt-tolerant than wheat cv. Giza 163 and tomato cv. Castle Rock.
II- The pot experiment:
The aim of this experiment was to study the response of wheat and tomato plants to saline conditions including the differences between the more salt-tolerant and the less salt-tolerant cultivars. Also, to investigate if it is possible to improve the endurability of wheat and tomato plants to salinity through the usage of paclobutrazol as a new and common growth regulator. Paclobutrazol was applied as soaking material in two concentrations of 10 and 50 ppm before the treatment with the untolerable salinity levels. The treatments were as follows:
206 For wheat cvs. Giza 163 and Sakha 92 as well as tomato cv.
Edkawi:
- Control (plants irrigated with tap water).
- Salinity at 7000 ppm (the maximum tolerable salinity level
during germination stage).
- Salinity at 8000 ppm preceded with paclobutrazol at 10 or 50
ppm.
- Salinity at 9000 ppm preceded with paclobutrazol at 10 or 50
ppm.
For tomato cv. Castle Rock:
- Control (plants irrigated with tap water).
- Salinity at 5000 ppm (the maximum tolerable salinity level
during germination stage).
- Salinity at 6000 ppm preceded with paclobutrazol at 10 or 50
ppm.
- Salinity at 7000 ppm preceded with paclobutrazol at 10 or 50 ppm.
In this pot experiment, some morphological characters, chloroplast pigments, flowering or heading, anatomical features, endogenous phytohormones, free proline accumulation, yield and yield components, nitrate reductase activity and nitrate accumulation and also the chemical contents of wheat grains and tomato fruits (total carbohydrates, sugars - reducing and non reducing sugars - and protein content and NPK) were measured and estimated. Besides, the content of ascorbic acid. and the percentage of total soluble solids in tomato fruits were also
estimated.