عنوان مقاله [English]
Salinity is one of the most important problems of abiotic stress in plants, which prevents seed germination, seedling growth and productivity reduction. Germination is a complex phenomenon that includes physiological and biochemical changes that are the result of embryo activity. Salinity is one of the most important environmental factors that reduce the growth and performance of plants and is a state of soil characterized by a high concentration of soluble salts. Studies on the effect of salinity have shown that in many plants, with an increase in salt concentration, germination indicators decrease and plant growth decreases. Germination is the first and most sensitive stage of plant growth and development, in addition to that, the uniformity of germination, the average time of germination and greening are also important parameters of seed quality. One of the studied species is woolly grass (Bromus tomenolus Boiss.), a perennial and stable plant, very palatable, strong and permanent with dense and many roots, which often grows in cold semi-arid climates and is one of the best mountain wheats for breeding and development. Summer meadows are considered. This plant prefers shallow to deep soils, light to medium texture, without salt and alkali. Persian clover (T. resupinatum) belonging to the genus Trifolium is one of the most important fodder plants of the Leguminous family in temperate and humid regions, which has great value as fodder and pasture and plays a significant role in livestock nutrition.
The main factor that effects on plant growth in arid and semiarid areas is salinity. In view of saline lands increasing in arid and semi-arid regions of Iran, is necessary finding the potential of plant species due to soil salinity changes in different climates
The first habitat is the north-eastern summer pastures of Harsin city, Kermanshah, whose average altitude is 2000 meters above sea level. The long-term average rainfall is 369 mm, and the climate of the semi-arid region is ultra-cold. The second habitat is a part of Golugah pastures located in Mazandaran province. Its maximum height is 2650 and minimum 2150 from the sea level and the average slope is about 25%. Its average annual rainfall is 383 mm, the highest amount in autumn and the lowest amount in summer. Its average annual temperature is 12.44 degrees Celsius. The climate of the semi-arid region is cold with mild summers and cold winters. In order to determine the resistance of the early growth stages of these species under different salinity stresses, an experiment was conducted in the form of a completely randomized design with 10 replications and 6 treatments. In order to create salinity stress, sodium chloride (NaCl) solution was used at zero (control), 50, 150, 25, 350 and 450 mM levels. Before placing the seeds in the Petri dish, they were disinfected by placing them in 5% sodium hypochlorite solution for 3 minutes and then washed with distilled water. 20 seeds were placed in each petri dish covered by filter paper. Salinity treatments were investigated for 20 days in laboratory conditions at 25°C with light conditions of 14 hours a day and 10 hours at night. During 20 days, the number of germinated seeds was counted every day, and at the end, characteristics such as the percentage and speed of germination, the length of root and plant were measured. In order to calculate the average length of roots and plants in each Petri dish, measurements were made and the average number was recorded
So, this research was studied the effect of salinity levels on germination properties of Bromus tomentellus and Trifolium resopinatom in two different habitats, Mazandaran and Kermanshah. For this, collected seeds of these species were grown in laboratory. 20 seeds were tested in Petri dish under salinity stress as control, 50, 150, 250, 350, 450 MM and germination percentage, germination speed, rootlet, seedling were measured.
The T-test was used for determination of mean difference between two species in SPSS 22 software. The result showed that seeds of Tr. resopinatom in Kermanshah have more resistant to this species in Mazandaran and the Br. tomentellus seeds were in the opposite. In the studied treatments Br. Tomentellus seeds of Mazandaran had more resistant and Tr. Resupinatum had less tolerance to salinity.
The results of the average of all three factors measured for Pashmeki grass and Iranian clover species in both regions showed that the highest amount of factors is present in the control treatment and with increasing salinity concentrations, germination percentage, germination speed and root length What is reduced? They stated that high salinity stops germination, growth of roots and stems. The reason for this is the physical and chemical effects or the toxic-osmotic effects of the solutes in the saline solution. In fact, with the increase in the salinity of the environment, the osmotic pressure (the osmotic potential becomes more negative) increases, which causes the disruption of the seed dehydration stage, and on the other hand, the presence of a high concentration of anions and cations (especially sodium and chlorine) in the environment, with Causing poisoning in seeds prevents seed germination. Considering that the climate of the two seed collection areas is different, it seems that plant seeds are affected by the climatic conditions of the origin region, he also stated that tolerance to salinity, in addition to the physiological complexities and structure of plants, depends on various factors such as temperature. It depends on the environment, plant growth stage, soil and water composition, environmental variables and plant variety. stated that the natural conditions of the habitat are effective on the growth and germination of different species, therefore, the different results of the studied parameters in different habitats can be justified.
Considering that some studies stated that the germination tolerance of plant species in saline environments under laboratory conditions is not necessarily the same as the response to salinity under field conditions; Therefore, it is suggested that the studied species should be cultivated under free environmental conditions to be able to introduce their seeds for the restoration of a specific area in principled decision-making.