Abstract
This study was conducted to investigate the effect of Trichoderma harzianum (T22) on the growth and development of maize (Zea mays) plants. T. harzianum was applied to the grains in two different treatments, either by inoculating the soil with air-dried mycelia of T. harzianum or by treating the seeds with different concentrations of the metabolic solution (as the culture supernatant of T. harzianum) before sowing. Comparisons were made between the two treatments to determine if any beneficial effects for improving the growth of maize plants occurred. Results revealed that application of the highest concentration of air-dried mycelia and all concentrations of the metabolic solution of T. harzianum caused increases in all measured parameters which include growth parameters, chlorophyll content, starch content, nucleic acids content, total protein content and phytohormone content of maize plants but the magnitude of these increases was much more pronounced in case of treating the seeds with the metabolic solution of T. harzianum.