Pages: 34-49

Abstract

Regarding different ultraviolet radiations (UV), UV-B plays the most effective role on the earth and bio-plant, which needs sunshine.  These radiations have a negative effect on plant growth while they mostly affect the processes such as genetic activities, cellular metabolism, plant anatomy and morphology, and ultimately the whole plant growth. The present study investigated the effects of UV-B stress on Aptenia cordifolia which is an ornamental and medicinal plant originated from  Aizoaceae family and it is resistant to some stress conditions. In this study the effect of UV-B with the intensity of 40 Lux was examined during germination and vegetative stages randomly with three replications in four intervals; 0, 45, 90,120 min and then the morphological, anatomical and phytochemical traits of the plant were examined. The results showed that when treatment level increaseed, the growth and morphological parameters such as: the percentage and rate of germination, seedling height, fresh and dry weight of root, aerial organ and leaf area decreased. Considering the anatomical traits, an increase was found in the stem thickness of the transverse wall vessel, the number of vascular bundles, the stem diameter of the vascular openings and the stem diameter. Also, in the roots under the root diameter stress, the number of vascular bundles, and diameter of their vascular opening decreased. The results of the biochemical section were consistent with the results in the morphological and anatomical sections, as any increase in the stress level led to the gradual decreases in the amount of phenolic and flavonoid compounds and photosynthetic pigments.