Gas exchanges and chlorophyll content of endemic Caspian locust (Gleditsia capsica) seedlings under flooding and flooding-recovery conditions

Caspian locust, native to Hyrcanian forests of Iran, is one of the pioneer species, which it distributed in the moist soils of these forests. So far, the response of its seedlings to permanent and temporary flooded beds has not been reported. This study was conducted with the objective to analyze the physiological responses of Caspian locust seedlings to flooding and flooding-recovery conditions.

Flooding conditions were examined for 90 days in the greenhouse of the Tarbiat Modares University. The study was carried out in a factorial experiment as a completely randomized design with 5 treatments and 4 replications. Treatments included: (1) continuous flooding for 90 days (F90), (2) flooding for 60 days followed by a 30-day recovery (F60+R30), (3) flooding for 45 days followed by a 45-day recovery (F45+R45), (4) flooding for 30 days followed by a 60-day recovery (F30+R60) and (5) Control.

Results showed that flooding for 90 days induced a significant decrease in net photosynthesis (-91%), stomatal conductance (-77%), transpiration (-81%), Chl a (-63%), Chl b (-67%) and Chl Tot (-64%) compared to the control (p<0.05). When flooding was removed for 30-60 days, plants were able to recover gas exchange activities from 30 to 90% and Chl content by 55-90%.

Based on our results, seedlings of G. caspica can survive and grow throughout a medium period of soil waterlogging. Therefore, Caspian locust appears to be a promising species for reforestation programs in the riverine areas and temporarily flooded wetlands.