Plants are essential elements of the earth ecosystem. Despite the importance of plants to support the life on our world, our understanding of their developmental processes is still fragmentary. In nature, plants grow next to each other forming the different societies of the plant kingdom. Nature, in turn, affects the growth of these plants by applying different environmental factors that could limit the agricultural productivity. Duration, severity and rate of imposed stress are the factors underlying the plant response to stress (Munné-Bosch and Alegre, 2004; Omezzine et al., 2014). Under natural conditions, Plants and surrounding environment as well as their neighboring plants can interfere together during seed germination and seedling growth causing various morphological, physiological and biochemical responses (Tanveer and Rehman, 2010; Shanker and Venkateswarlu, 2011; Harun et al., 2014). However, plants, including weeds, grow in the same community are competing for moisture, nutrients, and light, they can also affect a neighboring crop growth and yield by releasing allelochemicals into the growing environment (Rice, 1984; Kim and Shin, 1998; Kadioglu et al., 2005; Tanveer and Rehman, 2010). Such plants, that negatively impact other plants through the production of secondary metabolites, are considered allelopathic.
Wheat (Triticum sativum L.) and pea (Pisum sativum) are of the most ancient crops known to man. They are providing staple food of the ever-burgeoning world