Quantity evaluation of rice plant in under cold stress at different growth stages

The main cold damage is take place in germination and seedling stages, but, some time it is observed in mountains area and lowland of north of country. To study of cold effect on different phonology of rice crop, three independent experiments were carried out in deputy of rice research institute of Iran-Amol in 2010.First experiment: the five cultivars (Tarom, fajr, shiroudi, Hybridriceand 843 line,) were used as main plot. temperature treatment as 10,13,16,32°c and temperature period in 5 levels( 1,2,3,4,5 days) was studied. Characters of germination percentage, germination speed, radicle and caulicle length, fresh and dry weight radicle and caulicle were recorded. The suitability index was calculated base on Feisher formula. Second experiment(seedling): the seedlings were planted in 32 oc until 2-3 leaves seedling stage and in growth chamber were treatment as 10,13,16,32°c and temperature period in 1,2,3,4,5 days. After each treatment, Characters of seedling height, leaf area, stem and root dry weight and leaf color in seedling test, were measured. Thrith experiment: treatment's included varieties in 5 levels (Tarom, Fajr, Shirudi, Hybrid rice and Line 843) as main factors and 2 levels of temperature treatment. (16 & 32 c°) along with 4 levels of growth (mid-tillering utile maximum tillering, stem elongation, booting-flowering and grain filling stages) were considered as two sub factors. After each stage, morphological characters of plant height, tiller number, leaf area, leaf dry weight, stem dry weight were measured. Yield and yield components of hill was measured in physiological maturity stage. Yield of each hill was calculated at 14% humidity and obtain data were analyzed with SAS program in form of split plot factorial, in the structure of completely randomized designs with three replications. The mean comparison of treatments was done with Mstatc program and the Duncan method. The results showed that low temperature in germination test, , the speed and percentage of germination and in seedling test, growth and stability of growing seedlings significantly decreased at low temperature. General, it's observed that the characters like speed and percentage of germination in germination test and the character of height of seedling stem in seedling test can be used as index in determining resistant cultivars to cold stress .Shirodi and Tarom as the most resistant cultivars in both germination and seedling test. The decrease of temperature from 32 to 16 c° causes the decrease of grain yield up to %16. The most amount of yield in one hill relates to the verity of hybrid (25/63grm in hill) that originates from more number of panicle, total number of grain and more full grain, and the least amount of yield obtioned in the variety of local Tarom (19/72 grm in hill) because of less number of panicle, the length of panicle and less number of grain in panicle. Among the levels of plant growth, mid-tillering utile maximum tillering, the least yield obtained because of weight of 1000 grain, the number of panicle in hill and the length of panicle were decaresed. The most sensitive variety in relation to temperature stress is the 843 line with the most percentage of decrease (% 20/64) and the most resistant in relation to temperature stress is the variety of Shirudi with the least percentage of decrease (% 11/01). The most amount of yield is in the variety of hybrid rice with temperature stress in grain filling stage (30/68 gr in hill) and the lowest amount in the variety was Tarom in the mid-tillering utile maximum tillering stage (16/57 gr in hill) because of decreasing the panicle number in hill and less number of grain in panicle.