Physiological changes of Larix principis-rupprechtii seedlings inoculated with Trichoderma spp. under drought stress.

Tree regeneration is significantly affected by water deficiency, which could be alleviated by the inoculation of Trichoderma spp. In this study, the effects of rhizosphere inoculation with Trichoderma spp. on the antioxidant system and osmotic substances in the seedlings of Larix principis-rupprechtii was investigated under experimental drought stresses, with the relative water content 50%-60%, 35%-50%, and 20%-35% as the light, moderate and severe drought stress, respectively. The results showed that, with increasing drought stress, the activities of protective enzymes, SOD and POD in the needles of seedlings were significantly promoted, the contents of MDA and proline were remarkably increased, whereas the contents of soluble protein and starch showed a decreasing trend. Inoculation with Trichoderma spp. promoted much stronger increase in the activities of SOD and POD in the needles, yet the MDA content showed a lower level of increase. Under moderate drought, the activity of POD in the seedling inoculated with Trichoderma spp. was 1.8 folds of that in the control, while the content of MDA was 62.9% of the control. The contents of proline, soluble protein, soluble sugar, and starch in the inoculated seedlings were higher than that in the uninoculated seedlings. Drought-resistance of L. principis-rupprechtii seedlings inoculated by Trichoderma spp. was significantly enhanced due to the augmenting regulation of antioxidant system and osmotic adjustment substances. Therefore, under the trend of warming and drying in North China, the technique of rhizosphere inoculation of Trichoderma spp. could be popularized for forest plantation or understory tending.