EXAMINATION OF GAS EXCHANGE PARAMETERS OF Abies balsamea (L) MILL. AND Abies concolor SAPLINGS, GROWN UNDER VARIOUS WATER REGIME, EXPOSED TO EXTREME DROUGHT STRESS AT THE END OF THE GROWING SEASON
İsmail Koç
Abstract
Two-year-old (plug+1) containerized Abies balsamea (L) Mill. and Abies concolor saplings were grown under various irrigation in the greenhouse to examine gas exchange parameters end of the growing period when they were exposed to extreme drought stress. Relative height growth (RHG) and relative root collar diameter (RRCD) were measured next to gas exchange parameters, such as net photosynthetic rate (Anet), stomatal conductance (gs), transpiration rate (E), intrinsic water use efficiency (iWUE=Anet/gs), and water use efficiency (WUE=Anet/E). As a result, Abies balsamea saplings had a higher RHG and RRCD than Abies concolor. Species had a significant effect on leaf gas exchange parameters that Abies balsamea had a higher Anet, gs, and a lower iWUE than Abies concolor. Increasing irrigation increased Anet and E. The interaction of species and time was statistically significant for gs and iWUE measurement. İncreasing prolonged drought decreased gs and did not change iWUE values for Abies balsamea, while increased gs and reduced iWUE for Abies concolor saplings. Even though Anet, E, and WUE were not statistically significant under the interaction of species and time, there is a decreasing trend for Abies balsamea on these parameters. In contrast, Abies concolor had a decreasing trend on Anet, and WUE and an increasing trend for gs when the saplings were exposed to extreme drought or extended the dehydration period were observed. Abies balsamea had a better performance and drought tolerance than Abies concolor when exposed to a prolonged drought.