Inoculation of Gleditsia caspica seeds with arbuscular mycorrhiza to increase drought tolerance of saplings

In arid and semiarid regions, establishment, growth and development of trees, especially young saplings, are severely affected by water scarcity. Gleditsia caspica is one of the valuable forest species of Iran, which due to some of its unique features such as low-expectation, resistance to harsh environmental conditions, tolerance to polluted air and ability to symbiosis with some soil microorganisms, makes it a valuable plant and could be cultivated as a landscape plant. However, saplings are sensitive to drought and one of the main causes of damage to saplings after cultivation is lack of ability of adaptation to drought. In order to investigate the effect of mycorrhiza fungi on improvement growth of Gleditsia caspica saplings under drought stress, a factorial experiment was performed in completely randomized design.

After scarification, Gleditsia caspica seeds were inoculated with Funneliformis mosseae fungi and then were cultivated. For fungi colonization, saplings were kept in stress-free conditions for one year. Treatments were included drought stress (Well-watered and withholding water) and mycorrhiza (inoculation and uninoculated with Glomus moseae). Totally, were included four treatments: +H2O −AM, +H2O +AM, −H2O −AM and −H2O + AM. Drought treatment was stopped when 80% of saplings showed signs of leaf wilting (leaf rolling) at daydawn. Characteristics including RWC, electrolyte leakage, root and aboveground dry biomass, chlorophyll a and b, carotenoid content, total phenol content, total flavonoid content, proline content and total antioxidant capacity were measured.

Results showed that drought stress significantly reduced growth indices such as RWC (25.1%), cell membrane stability index (16.7%), content of chlorophyll a (46.1%) and b (47.8) and percentage of aboveground (8.7%) and root (12.4%) dry biomass. Inoculation of Caspian locust seeds with arbuscular mycorrhizal fungi improved cell membrane stability index (10.1%), RWC (9%), percentage of root dry biomass (6.2%), chlorophyll a and b content (53.5% and 50%, respectively), total phenol content (50.7%), total flavonoid content (43.3%) and total antioxidant capacity (82%) compared to uninoculated saplings. Also, percentage of aboveground dry biomass and total carotenoid content in inoculated saplings were higher and the proline content decreased than uninoculated saplings under both drought and normal irrigation conditions.

increased in aboveground dry biomass and carotenoid content and decreased in proline content under severe drought stress in inoculated saplings compared to non-inoculated saplings was may be due to reduction of drought stress effects caused by mycorrhiza. Therefore, inoculation of Gleditsia caspica saplings with mycorrhiza fungi before planting in urban landscape is recommended.