The effects of ecological factors on physiological, anatomical and morphological adaptations of Alnus subcordata C.A.Mey. in the Hyrcanian Forests

The effects of ecological factors and their interaction on quantitative changes of 10 physiological, 12 anatomical and two morphological traits of leaves in six different populations of Caucasian alder (Alnus subcordata C.A.Mey.) in the west (Guilan province) and east (Golestan province) of Hyrcanian forests were examined and statistically compared in three altitudinal ranges of lowlands, midlands and highlands. Two-way analysis of variance was used to investigate the effect of ecological factors in the region (temperature and precipitation) and their interaction on the studied variables. The principal component analysis (PCA) was used for the correlation between leaf traits and the relationship between environmental factors. The activity of catalase, peroxidase enzymes and proline were significantly different between the two provinces and showed an increasing trend from west to east. In addition, the amount of phenol in the site located in Golestan province was about 1.5 times that of Guilan province. There was no significant difference between the levels of superoxide dismutase activity and the amount of soluble sugar between the two provinces. Superoxide dismutase showed an increasing trend from lowlands to highlands, but the amount of soluble sugar increased from low altitudes to midlands and decreased in the highlands. There was no significant difference in the amount of chlorophylls a and b, total chlorophyll and carotenoids between the two provinces and at different altitudes, as well as the effects of the interaction of ecological factors on them. The most important morphological and anatomical adaptations to drought included increased leaf thickness, stomata density and length, abaxial cuticle thickness, epidermal cell thickness, thickness of palisade cells, thickness of spongy cells, middle vein thickness, thickness of vein abaxial parenchyma cells and number of abaxial parenchyma layers of vein. There was a correlation between most leaf physiological as well as morphological traits and ecological factors. The results of analysis of variance and the interaction of ecological factors on some anatomical features of Caucasian alder leaves were significant. It seems that the anatomical adaptations that are formed in plants over a long period of time are more appropriate indicators for measuring drought stress in plants.