Trichoderma spp. applied to rice plants reported in this research significantly increased rice root length compared to NPK treatment and control (Figure 3). Trichoderma sp. SL2 treated rice plants showed an impressive increase in root length compared to the plants treated with the other strains. Nawrocka and Malolepsza ([2013]) stated that the ability of Trichoderma spp. hyphae to release elicitors may contribute to signals being transmitted within the plant such as salicylic acid (SA), jasmonic acid (JA) and reactive oxygen species (ROS). Elicitors released by Trichoderma spp. are also involved in triggering expressions of defense protein within the plant (Thakur and Sohal, [2013]). In this way, plant immunity against pathogens is induced and in turn improves plant growth. Tchameni et al. ([2011]) showed that the inoculation of Trichoderma spp. in cacao plants may induce cacao plant resistance against Phytophthora megakarya and increase cacao root length. In addition, Cai et al. ([2013]) reported that harzianolide produced by Trichoderma spp. can improve the early stage of plant development through the enhancement of root length.