Effects of seed priming and aging on some physiological characteristics of Milk thistle was studied in a factoral experiment based on Complete Randomized Design (CRD). Tratments were included hydro priming (using distilled water), halo priming (0, 1.5, 3, 4.5 and 6% KNO 3 ) and accelerated aging (0, 2, 4 and 6 days under 45°C and 95% humidity) in three replications. Determined parameters were germination charactristics including germination percentage, daily germination speed, mean time of germination, seed vigor index, hypocutile length and hypocutile dry weight. Activity of catalase, peroxidase and polyphenol oxidase were determined at 12 hours after imbibition and seedling stage. According to results of this experiment, germination percentage, seed vigor and seedling growth of seeds were increased under all priming treatments. Improving the catalase and peroxidase activity led to decrease the aging damages. Germination characteristics were improved under both priming treatments at the beginning of germination as well as seedling growth. Polyphenol oxidase activity was increased in the pre-treated seeds but decreased in seedling growth stage. Aging treatments led to reduce the germination percentage, daily germination speed, seed vigor and seedling growth while the germination time was increased. Accelerated aging caused to reduce the germination rate and seedling growth of milk thistle that is probably due to increasing the lipid peroxidation, free radical increment and decreasing the antioxidants activity. The greatest and lowest antioxidants activity, the germination percentage, germination speed and seed vigor were respectively observed under priming using 3% KNO 3 concentration and control seeds.

To evaluate the responses of canola seedlings to different levels of drought stress and nitrogen at different growth stages, a factorial experiment was conducted in a completely randomized design with three replications at the experimental greenhouse of Mohaghegh Ardabili University in 2013. Treatments included three levels of drought stress (30%, 50%, and 70% of FC) and five levels of nitrogen (control, based on soil test results; 25% less than the recommended level; 50% less than the recommended level; 25% more than the recommended level; and 50% more than the recommended level). The recommended level of nitrogen, based on soil test results, was 0.09 g of nitrogen per kilogram of soil. Results showed that drought stress, nitrogen, and their interaction significantly affected the enzymatic activity of antioxidant catalase (CAT), polyphenol oxidase (PPO), and peroxidase (PO) at various stages of growth. Proline was also affected by drought stress and nitrogen. Maximum CAT activity (794.04 OD mg protein min -1 ) was observed at the 4-6 leaf stage under mild drought stress conditions (50% of FC) and a nitrogen application rate 50% less than the recommended level. Increased rates of nitrogen enhanced the PPO activity at the 4-6 and 6-8 leaf stages. PO had a negative response to increased rates of nitrogen application. The highest rate of increase in proline was at the 8-10 leaf stage: 205% and 207% higher under mild drought stress (50% of FC) and severe drought stress (30% of FC) conditions, respectively, compared to favorable moisture conditions (70% of FC). Increased nitrogen application led to an increase in proline production at all stages of sampling (4-6, 6-8, and 8-10 leaf stages).

In order to study genetic diversity and some physiological features related to chilling stress using molecular markers, an experiment was conducted at University of Mohaghegh Ardabili. Treatments were set in a factorial experiment based on randomized complete block design with 3 replications and 3 stress levels (25, 15 and 5°C) between 20 cotton genotypes. The results showed that chilling stress influenced on some physiological features such as the activity of catalase, proline content, soluble carbohydrates and proteins. Cluster analysis carried out using WARD method in physiological features showed that genotypes located in three groups in the acclimation level and after acclimation, respectively. Nazilli, Ciakra, Avangard and B-557 were in the better group in studied levels. Also based on the results Avangard, Chegurava, Tashkand and Shirpan 603 were the most tolerant genotypes. In the ISSR marker analysis using of 12 primers produced 96 polymorphic bands. The mean of PIC, MI and EMR were 0.283, 1.065 and 3 respectively, for all primers. Some of markers had promising results that confirmed ISSR markers as powerful tool in any marker assisted program for plant breeders.