Freezing is one of the weather phenomena which has a variety of effects on daily and developmental activities. In this research, the changes occurred in the Freezing period in the synoptic station of Rasht during the last fifty years (1960-2009) have been studied. The daily statistics along with the date of occurrence were obtained by the Excel software. Data analysis was done by statistical methods. The obtained results indicate that the annual absolute minimum Temperature (AMT) data shows greater fluctuations compared to other Temperature variables. The analysis of Rasht AMT data based on statistical distribution seems to be regressed appropriately with Gamble statistical distribution. In addition, the beginning of fall Freezing and the end of spring Freezing follow the normal statistical distribution function. The obtained results show that the Freezing period in the station under study has had a decreasing trend and has decreased from 100 days to less than 80 days. The annual absolute minimum Temperature increased from -7 to -40oc and the Freezing days fluctuated from 40 to less than 20 days. In conclusion, the decrease in the Freezing period along with the rise in minimum Temperature and decrease of the number of Freezing days represent the change in the minimum Temperature of Rasht in the past fifty years.

The present paper aims at Studying the changing trends of Temperature (mean, maximum, minimum, maximum and minimum absolute, Freezing days including) in order to find an easy and effective way to measure the similarity between Temperature time series on various stations.The cluster analysis was carried out in all stations of Tehran city, which led to classification: the following.1- Mehrabad Station and Doushan Tappeh.2- Chitgar Station.3- Ahminabad Station.4- Geophysics and Shomal Tehran Station.We recognised changing tempo-spatial patterns of Temperature. Tehran city, on a decadal scale, encountered with increasing Temperature trends.

Maintaining the nutritional quality and preserving pomegranate seeds is a major challenge due to the fast degradation of the texture, color and overall quality of pomegranate seeds. In order to investigate the Freezing of coated pomegranate seeds with chitosan and determine its quality during Freezing storage, an experiment was conducted, in a factorial arrangement in a completely randomized design with three replications. Factors were: chitosan at three levels (0, 1 and 2%), Freezing Temperature at two levels (-14 °-24 ° C) and time at 5 different storage times (14 days, 30 days, 60 days, 90 days, and 120 days). The highest tissue firmness was observed for 14 days of storage under both chitosan concentrations. Interaction of different levels of chitosan coating and time had an increasing effect on the color component changes, so that the most color changes in the brightness (L*), redness (a*), and yellowness (b*) was related to the use of chitosan coating 2%, were maintained at 60 days. The highest total soluble solids were related to 1% chitosan under 4 months of storage at-14° C. Maximum total acidity (1. 36 mg / L) was also attributed to coated pomegranate seeds during 120 days of storage under both Freezing Temperatures of-14° C and-24° C. The results of mean compares showed that the total phenol stability under Freezing Temperature was higher at-14° C and after 120 days of storage, more phenol content was observed in the seeds in-24 C. The overall results indicated a positive effect of chitosan on maintaining the quality of pomegranate seeds during Freezing, and the Freezing Temperature of-24 ° C with decreasing color changes during storage, played an important role in reducing metabolic activity and reducing anthocyanin degradation and was effective in maintaining fruit quality.

Liens tolerate environmental stresses utilizing is one of the applicable technologies in sustainable agriculture. Since occurrence of a suitable winter for studing and selection of cold/frost resistance on breeding materials is one year out of ten, therefore laboratory methods complementing field data provide a reasonable solution for this propose. This research was conducted in Khorasan Agri. Res. Center. Mashhad. Using RCBD in three replications during 1380-81. Treatments consisted of twenty promising genotypes of uniform regional yield trail (cold area). Genotypes suits low Temperature regions will be introduced based on generated results from this investigation. Using crown Freezing method, experimental genotypes were treated with -20. C Temperature under controlled conditions. Survival percentage was computed. Results indicated that genotypes No.9 (C-78-9) and No.7 (C-78-7) had highest (98.33%) and lowest (66.67%) survival percentage respectively. The minimum Crown Moisture Content was detected in line No. 9 (C-78-9) and there was no significant difference for the same trait between genotype No.7(C-78-7) and other superior genotypes. A high negative correlation (r=-0.701) was observed between survival percentage after exposing to frost and crown moisture content. Ear primordia development stage was one of the characters which had also a significant correlation with survival percentage (r=-0.619). Significant correlation between survival percentage and days to heading (r=-0.207) and days to physiological maturity (r =-0.028) was not observed. Correlation between survival percentage and collected cold damage data from experimental fields over five low Temperature regional stations was highly significant (r=0.416), therefore it may be concluded that Crown Freezing Method and subsequent computing of survival percentage is a reliable method for estimating wheat frost/cold tolerance in natural conditions.

The experiment was conducted in 1380-1381, on one year old olive plant cvs; "Zard", "Roghani" (native cvs.) and "Mission", "Koroneiki" (foreign cvs.) during two different growth status; cold and non-cold acclimated phase. Natural cold treatment was achieved by exposure plant to low Temperature during fall and winter in 1381. The influence of cold stress on plant growth, wet and dry weight, shoot tip bum and water content were studied. In order to determine ionic leakage leaf tissues were exposure to artificial Freezing Temperature; 0, -4, -8 and -12°C ranged by 4°C per hour. There was significant difference between cultivars with regards to vegetative growth index. The cv. "Koronieki" with more shoot growth, showed the more shoot tip bum damage. Based on ionic leakage study at non-acclimated phase, Olive cvs. were classified in distinct classes, includes: cold tolerance, semi tolerance and cold sensitive. However use of lower artificial Freezing Temperature especially during cold acclimated status will 'provide more reliable and certain results.