الفهرس 
Declaration
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Abstract
The current study was conducted in two main parts:
A- Effect of Nano- and Ord-TiO2 on seed germination of Helianthus annuus L. and Lupinus albus L.
1- In this experiment, seeds of H. annuus (sunflower) and L. albus (lupin) were germinated in Petri dishes containing different concentrations (50, 150, 300, 600 and 1000 ppm) of Nano- or Ord-TiO2 in addition to untreated control.
2- After 8th day, the total number of germinated seeds, and the lengths of epicotyl, hypocotyl and seedlings were estimated. Also, the following parameters were calculated: Germination percentage (GP), the sprouting or germination index (GI), the coefficient of velocity (CV) and actual elongation rate.
B- Effect of Nano- and Ord-TiO2 on growth and physiology of H. annuus and L. albus under water deficit stress
1- In pots experiment (120 pots), containing 3 kg 1 : 2 sand : clay soil, seeds of H. annuus and L. albus were cultivated separately in September and February, respectively, and irrigated regularly to the field capacity. After the plants were bearing 3 true leaves, the pots were divided randomly into 10 groups, 12 pots in each. The plants subjected to four water deficit levels (full, 75%, 50% and 25 % of field capacity) and the effect of foliar spraying with 50, 150, 300 and 600 ppm Nano- or Ord-TiO2 on each plant species under water stress levels were evaluated. There were a control group and another water-sprayed group.
2- After 70 and 60 days from cultivation of H. annuus and L. albus, respectivily, the plants were harvested and separated into shoots and roots. The RWC, WC%, osmotic potential, dry mass of shoots and roots, cell membrane injury and electrolyte leakage were estimated. In suitable extracts, the contents of pigments, primary metabolites (SS, TAA, SP), H2O2, MDA, proline, and activities of antioxidant enzymes (CAT, GPX and APX) were assayed.