عنوان مقاله [English]
Introduction: Salinity stress impairs the absorption of elements such as potassium, leads to decrease in water and minerals, or due to an increase in Na+ effects the absorption of other elements. Salinity of water and soil is one of the obstacles to the expansion of agriculture in most part of the word. Salinity causes several physiological and morphological changes in plants and affects growth and photosynthesis. Salinity stress also affects the absorption of nutrients, and finally the plants sensitivity to stress increases. High concentrations of Nacl in rhizosphere reduce the water potential and cause physiological drought stress. Also, ion toxicity and imbalance due to salinity stress damage the plant. Salinity stress reduces plant biomass, which is related to the reduction of photosynthetic capacity, which occurs following a decrease in chlorophyll content. with increasing stress, stomatal conductance and co2 assimilation also decreased, both of which affect the rate of photosynthesis and lead to its decrease. Dianthus is an annual or perennial plant; it has velvety flower with various color. Due to the variety of colors and resistance to cold, this plant is widely grown in landscape and due to the fact that limited studies have been done in this field, so it is important to study the response of this plant to environmental stresses.
Material and method: This research was conducted in greenhouse of municipality of Khomein, Iran. The statistical design was used in the factorial experiment based on CRD. Experimental factors included salinity stress (0, 10, 20, 30, 40, 50, 60, 70, 80, 90 mM) and cultivars (Barbarin and Diana). After preparing the seeds, it is first disinfected using sodium hypochlorite and then planted in plastic pots containing soil, sand and manure. At the end of the experiment, morphological traits, stomatal conductance, photosynthesis rate, Na+, K+ and Na+/K+ was also examined. Gas exchanges were measured using an exchange measuring device (LCA4, ADC Bioscientific, Ltd., Hoddesdon, England). At the time of measuring gas exchanges, the temperature under chamber was 26-29 C and relative humidity was 58-62%. (stomatal conductivity is based on mmol/m2/s and photosynthesis in µmol/m2/s). To measure the concentration of Na+ and K+, the leaf first turned to ash (at 550 C). Then 5 ml of hydrochlorid was added to dissolve the sample and the volume of the filtered solution was reduced to 50 ml with distilled water and the concentration of Na+ and K+ was measured with flame meter. In order to measure the fresh weight of leaves and roots, plant components were separated. Fresh weight was recorded with a scale and then samples were placed in the oven (for 48 h) and weighted again to measure dry weight. Leaf area was measured with a leaf guuge device (A30325) and plant height and root length using a ruler. Statistical analysis of data was performed using Mini Tab and Excel software.
Results and discussion: the results showed that salinity stress generally affected the growth of both carnation cultivars and reduced vegetative and reproductive growth. According to the results obtained from the study, fresh and dry weight of shoot, root and leaves, root length, plant height, stem diameter, diameter and number of flower, lateral shoot number, stomatal conductance, photosynthesis rate, K+ concentration in Diana and Barbarin cultivars decreased with increasing salinity level. Na+ concentration and Na+/K+ increased with increasing salinity and these two traits were higher in Diana than Barbarin cultivar, which indicates lower resistance of Diana cultivar. the first reaction of the plant to stress is to reduce the leaf area, which reduces the supply of photo synthetics material to the growing parts and thus reduces growth and flowering. Photosynthesis highly sensitive to salinity stress and high osmotic potential in the rhizosphere causes the pore conductivity to decrease. Excessive absorption of Na+ interferes to the absorption of other elements and thus restricts plant growth. K+ plays an important role in increasing plant resistance to stress, as an inorganics smolite. Its plays a major role in maintaining turbidity and cell development as well as stomatal function. In this study, salinity stress affected the growth and yield of both carnation cultivars, and with increasing stress, all morphological traits decreased. This stress also reduce photosynthesis by reducing stomatal conductance and subsequently reduce other growth characteristics. Growth reduction was observed at high salinity stress concentrations in both cultivars. However, barbarin cultivar showed higher resistance than Diana.