Corn (Zea mays L.) is an important, strategic cereal crop that has a relatively short growing period and produces a high yield. Corn ranks third in world in terms of production after wheat and rice (Raji2003). Nanoparticles, which are 1–100 nm in diameter (Ruffini Castiglione and Cremonini2009) have a large specific surface area that can provides for a good level of reactivity and this character facilitates effective absorption of fertilizers and pesticides at nanoscale (Sheykhbaglou et al.,2010). Thus nano particles can be used to increase the supply of elements to plant shoots and foliage. Nano particles appropriate for such application are those of are nano Tio2, nano zinc, nano iron, nano aluminum and nano silver (Reynolds2002). Application of nanoparticles can also increase seed germination and seedling growth. Furthermore nanoparticles can facilitate enhanced ability of water and fertilizer absorption by roots, and increase antioxidant enzyme activity such as superoxide dismutase and catalase. Thus, nanoparticles can increase plant resistance against different stresses (Harrison1996). Many studies have reported that nano particles have favorable effects on plant growth and development. Titanium dioxide nanoparticles are used in agriculture to increase growth and can improve yield by approximately 30%; improve the rate of photosynthesis and reduce disease (Chao and Choi2005). Titanium dioxide is used commercially as the most appropriate catalyst for photo catalytic reactions; upon exposure to ultraviolet light it mineralizes the organic chemicals in rivers to water and carbon dioxide with the potential to destroy microorganisms (Owolade et al.,2008). Lei et al., (2007) found that, nano Tio2 increases photosynthesis and plant growth of spinach and enhances absorption and transmission of the sun’s energy to electron energy and activates chemical energy. Other research has reported that nano Tio2, could greatly improve whole chain electron transport, photo reduction activity of photosystem II, O2-evolving and photophosphorylation activity of spinach Chl, not only under visible light, but also energy-enriched electron from nanoanatase Tio2, which entered the Chl under ultraviolet light and was transferred in a photosynthetic electron transport chain and reduced NADP + be into NADPH, and coupled to photophosphorylation and stimulated the transformation of electron energy to ATP. In another experiment, Zheng et al. (2005), considered, germination rate and vigor index of spinach old seeds that treated with the nano Tio2 (concentrations of 0, 0.25, 0.5, 1, 1.5, 2, 2.5, 4, 6 and 8 percent) and Tio2 (concentrations of 0, 0.25, 0.5, 1, 1.5, 2, 2.5, 4, 6 and 8 percent) and observed that evaluations for these traits increased in seeds treated with concentrations of 0.25 to 4 percent of nano Tio2 in comparison with Tio2. Evaluations for chlorophyll levels, ribulose 1,5-bisphosphate carboxylase activity, dry weight and fresh weight in seedlings that had been treated with 2.5 percent were higher than evaluations for treatments at other concentrations of nano Tio2 and Tio2 (bulk). Lu et al., (2002) reported that evaluations for nitrate reductase, super oxide dismutase and catalase increased in germinated soybean seeds that had been treated with nano Tio2, and that levels of water water and fertilizer use efficiency increased. The research results of Moaveni et al., (2011) on effects of different nano titanium dioxide concentrations (0.01, 0.02, 0.03 percent) and titanium dioxide (bulk) spray treatment on barley plants showed that traits of grain yield, number of ears and harvest index in all treatments of nano titanium dioxide application were more effective than the control treatment. It was demonstrated that barley plants sprayed with nano titanium dioxide at concentrations of 0.03% was 21.32% produced higher evaluations for grain yield compared to the control. Also, Owolade et al., (2008) concluded that effects of nano Tio2 spray on evaluations for traits of seed number per pod, 1000 seed weight, grain yield, leaf area, pod number per plant and pod length of Vina unguiculata, were significant and evaluations of these traits significantly increased compared to the control. So, this study was done to examine changes of photosynthetic pigments in maize (Zea mays L.) sprayed with nano Tio2 at various stages of growth and development.