Evaluation of growth, physiological and biochemichal responses of Alnus subcordata endemic seedling to drought stress

This study investigates the effect of drought stress on the morphological, physiological and biochemical parameters of Alnus subcordata C. A. Mey., an endemic wood species to Hyrcanian forests. The experimental design was completely randomized on one-year seedlings and four levels of drought stress (25% (severe stress), 50% (moderate stress), 75% (mild stress) and 100% (no stress) of crop capacity. The results showed that drought reduced the growth and biomass of seedlings. The decrease in severe stress treatment compared to the control in seedling height, basal diameter, total biomass, leaf area and specific leaf area were 41.8, 40, 72.4, 91.9 and 49.6% respectively. The root to shoot ratio showed an increase of 53.3%. With the increase of stress, total chlorophyll, chlorophyll a, chlorophyll b decreased by 50% and carotenoid decreased by 38.4%. The relative water content of the seedlings decreased by 33.50 and 24.9% in severe and moderate stress compared to the control treatment. The percentage increase of proline and malondealdehyde in the stress treatment compared to the control treatment was 169.8% and 142.7%, respectively. The activity of superoxide dismutase increased by 25% and 36% and peroxidase by 140% and 148% respectively in the mild and moderate stress treatment. The result showed that Caucasian alder seedling (a rather drought-sensitive species) could coped with drought in mild and moderate treatment by tolerance mechanisms such as reducing growth and biomass, increasing of the root to shoot ratio, reducing photosynthetic pigments and relative increasing in enzyme activities.