عنوان مقاله [English]
In recent years, dust has recognized as the one of the main problems in the west and southwest of Iran which annually has adverse effects on environment and agriculture. Reducing light penetration, decreasing photosynthesis, changing stomatal performance, and reducing flowering are the some adverse effect of air pollution on plants. Strawberries have a shallow root system, high leaf area and is sensetive to drought stress. Kurdistan province is the most important producer of strawberries in Iran. Since the occurrence of dust in Kurdistan occurs more in the spring and during flowering and strawberry fruit production, we investigated the interaction effect of dust and drought stress on some physiological characteristics of two strawberry cultivars (cvs. Paros and Queen elisa) during 2013-2014.
Materials and Methods
The experiment was conducted based on a completely randomized design with four treatments (control, -1.2 MPa soil water potential as drought stress, dust and dust + drought stress) and three replications. In this experiment leaf relative water content (RWC), membrane stability index (MSI), proline, soluble carbohydrates, malondialdehyde (MDA), hydrogen peroxide, peroxidase (POD) and ascorbate peroxidase (APX) activity were evaluated.
Results showed that, RWC, MSI were decreased in response to dust and drought in both cultivars. Amount of malondialdehyde, hydrogen peroxide and activity of antioxidant enzymes were increased by dust and drought treatments. Most increase in the proline and total soluble carbohydrates, hydrogen peroxide, malondialdehyde, the activity of antioxidant enzymes were obtained by dust + drought stress. Drought stress + dust had the highest levels of POD and APX. There was a significant difference between two cultivars, so that Paros cultivar had higher activity of POD and APX compared to queen elisa. Dust and drought treatments reduced shoot and root dry weigth in both years and both cultivars.
Dust in the first year increased the total leaf soluble sugars, which is probably due to the stress caused by dust. In this condition, the plant can continue to absorb water from the soil by increasing the soluble carbohydrates through osmotic regulation. In the second year, the long-term reduction in photosynthesis led to a reduction in total soluble carbohydrates, due to prolonged exposure to dust or damage to light absorption pigments due to dust accumulation and its negative effects on stomatal function. Dust and drought stress decreased RWC by decreasing water absorption by the strawberry plants, and decreasing of water led to increasing of H2O2. With increasing of H2O2 in dust and drought stress, membrane lipid degradation increased and led to increasing of MDA. MDA increased in all treatments in Queen Eliza cultivar, which could indicate the higher sensitivity of this cultivar to dust and drought stress. In this study, Paros showed higher antioxidant enzyme activity that was accompanied with lower H2O2 content and consequently a lower MDA, therefore showed more resistance to drought and drought stress. Reducing the dry matter of the roots and the shoot can be due to increased free radicals, reduced leaf water content and, consequently, loss of photosynthesis of the leaf.