In this study, the induced responses of Kabuli and Desi chickpea (Cicer arietinum L. ) genotypes to cold stress physio-biochemical and molecular indices have been assayed. Cold acclimation established more readiness in facing up cold stress in Kabuli genotype compared to Desi one so that the minimum damage indices and the maximum enzyme activities were observed under these conditions. Simultaneous change of antioxidative activities related with damage indices electrolyte leakage index (ELI) and hydrogen peroxide (H2O2) showed that these enzymes accompanied with other defense mechanisms increased cold tolerance in chickpea. Results indicated that there were significant differences in catalase (CAT) and ascorbate peroxidase (APX) genes expression under thermal treatments. A significant increase of genes expression in Kabuli genotype compared to Desi one showed global patterns programmed cell responses along with increases in antioxidative activities, accompanying with a significant decrease particularly in Kabuli genotype. The short-term cold acclimation increased genetic capacity in chickpea genotypes so that the degree of tolerance in Kabuli genotype was higher than that of Desi one. Such defense and damage indices may be used as cold tolerance marker in evaluation of genotypes in a short-term cold stress profitably in a short time and low cost.

Insects can increase their survival at subzero temperatures, prior to long or short term exposure, to non-lethal cold temperatures by cold acclimation (ACC) or rapid cold hardiness (RCH). In this research, the effect of rapid or gradual decrease in temperature on cold tolerance of adults of the greenbug, Schizaphis graminum (Rondani) was investigated. LT50 (lower lethal temperature for 50% mortality) of aphids acclimated at 10°C for one week showed no significant differences with control (aphids reared at 20°C). In addition to the cold acclimation, adults of S. graminum showed RCH response too. When the rearing aphids at 20°C were transferred directly to a range of sub-zero temperatures for 2 h, LT80 (lower lethal temperature for 80% mortality) was -11.6 °C, but acclimation at 0°C for 5 h before transfer to -11.6 °C, induced maximum RCH, led to increase of survival to 73%. RCH was induced by cooling of the insects at 0°C for different rates. Maximum survival (66%) was achieved by cooling at 0.05°C/min. Accumulation of sugars and polyols is one of the major mechanisms underlying ACC and RCH. In this study, trehalose and glucose increased considerably through ACC and RCH treatments, suggesting the role of these compounds in increasing cold tolerance of S. graminum.

This study was conducted to investigate the changes in the levels of soluble carbohydrate, antioxidant capacity, total phenolic acid and fatty acid composition of olive during cold acclimation and deacclimation related with freezing tolerance (FT). Three olive cultivars, Amphisis, Gorgan and Manzanilla were selected and leaf samples were prepared from field-grown trees from autumn to summer at six times (November, December, December, February, April and July). The FT was measured by exposure to artificial freezing (0ºC to –25ºC). Result showed that there was a significant difference between the olive cultivars in terms of FT at each stage of sampling. The FT of cultivars increased during the cold acclimation stage and declined in deacclimation stage. Soluble carbohydrates, antioxidant capacity, total phenolic content, leaf dry matter, especially from the beginning of cold acclimation until full acclimation, in cold-tolerant –Amphisis– cultivar was more than the Gorgan and Manzanilla cultivars. The highest ratio of unsaturated to saturated fatty acids in both January and July was observed in Amphisis cultivar. Therefore, compounds such as soluble carbohydrates, total phenolic content, and fatty acids can be used as biochemical indicator of FT in screening of olive cultivars.

Sever coldness causes damage to the wheat and affect its growth and yield, thereby this experiment was conducted in controlled conditions to investigate freezing tolerance of 29 wheat genotypes. Acclimation treatments (in two levels: acclimation and non-acclimation) were considered in the main plot and combination of temperature (0, -4, -8, -12, -16oC) and genotypes as sub plot. Survival percentage, dry weight and plant height were measured four weeks after freezing in the glasshouse. All these traits were affected significantly by freezing treatments (P<0.001). Reducing temperature under -8 oC caused a significant reduction in the wheat survival percentage. Acclimation alleviated the effects of freezing, so that at -12oC in non-acclimation conditions, dry weight was 72.1 mgr, but it reached to 144.9 mgr in acclimation conditions. Lethal Temperature 50 (LT50) was lower than -15oC in 14 cultivars and higher than -15 oC in 15 cultivars. Among studied genotypes, Alamout, Bezostaja, Falat, Glenson and MV-17 were more cold tolerant than others. In order to determine the cold tolerance of genotypes, conducting complementary experiments in controlled and field conditions could be useful.

Cross-acclimation of mild drought stress and cold acclimation may additionally increase the chickpea’s cold tolerance due to transferring sowing date from spring to winter in Mediterranean high lands. Two weeks after sowing in greenhouse, chickpea seedlings were subjected to the following treatments in a controlled environment: (i) Well-Watered under an optimum temperature regime (WW); (ii) Well-Watered under a Cold temperature regime (WWC); (iii) Drought Preconditioned under an optimum temperature regime (DP); and (iv) Drought Preconditioned under a Cold temperature regime (DPC). After three-week acclimation period, plants were frozen on the thermogradient freezer, then, recovered for three weeks in a greenhouse. In the acclimation period, with decreasing temperatures, a clear decrease of the electrolyte leakage (EL) were observed for both genotypes: 51% for cold tolerant MCC252 and 36% for cold sensitive MCC505. Cold acclimation induced the greatest accumulation of proline and MDA contents (about 75% for both genotypes) and drought preconditioning most consistently induced an increase in soluble carbohydrate content (25% for MCC252 and 51.7% for MCC505) during the acclimation period. The survival percentage increased 9.3% for MCC252 and 21.25% for MCC505 by both cold and drought acclimation under freezing conditions. Generally, drought preconditioning had a synergistic effect on the cold acclimation period to improve freezing tolerance (as indicated by the lowest LT50el and LT50su) and leading to an increase in the freezing tolerance for the cold sensitive genotypes (MCC505). Thus, the greatest gains in freezing tolerance for both genotypes were associated with cross-acclimation treatment (DPC).

Background and Objectives Plant cells often increase cold tolerance by reprogramming their genes expression, which results in adjusted metabolic alternations, a process enhanced under cold acclimation (CA). In this study, responses of Carbohydrate alteration and delta12 and delta15 genes expression to cold stress (CS) phases were comparatively studied in three genotypes of bread and durum wheat differing in sensitivity. Two of them (Norstar, bread wheat and Gerdish, durum wheat) were tolerant to CS and the other one, SRN (durum wheat) was sensitive to CS. Materials and Methods Seeds of Norstar (hexaploid, bread wheat) and the two genotypes of Gerdish and SRN (tetraploid, durum wheat) provided by Dryland Agriculture Research Institute (DARI) of Iran were soaked in distilled water and then germinated in Petri dishes on filter paper for 72 h at 25 C in a thermostat. Subsequently, the seedlings were planted in pots. The cooling regime adopted in our experiments allowed us to differentiate the examined genotypes in terms of their tolerance to CS. In our experiment, the plants were moved from control conditions immediately into the acclimated temperature of 4– 5 º C for 14 days with the same photoperiod and irradiance. Leaf samples of genotypes were harvested and analyzed after 14 days under these conditions. After 14 days of CA, the plants were placed into a climatic chamber chilled preliminary to 0 º C. During further treatments, the temperature was lowered gradually to-5 C (at the rate of 0. 5 º C min-1 ), and the plants were incubated at this temperature for 12 and 24 h. Total cellular RNA was extracted by Biozol method (Fersion Pooyesh, Tehran, Iran) using 80 mg FM leaflets. Applying fermentase reverse transcriptase enzyme instruction, the first strand of cDNA was produced after DNase treatment. Primers were designed using primer 3 to obtain 18– 21 bp length. Carbohydrate extraction and determining the carbohydrate concentration were done by 80% ethanol and the AOAC method, respectively. Results These responses confirmed the existence of a wide range of genetic capacity in durum wheat to increase cold tolerance particularly in Gerdish. The findings of the present study showed that under experimental treatments, the carbohydrate content significantly changed so that cold stress in acclimated plants increased sucrose, glucose and fructose contents particularly in Norstar and Gerdish as compared to the SRN plants. Increasing expression of delta12 and delta15 genes under cold stress in Norstar and SRN genotypes in comparison with SRN indicates the capacity of cells in increasing cold stress. Discussion The results may be a sign for associating other metabolite or enzyme activities to create relative tolerance against cold-induced oxidative stress. Also, these responses showed high genetic diversity for cold tolerance in durum. Eventually, assessing the dynamics of cell responses after CS without CA phases could profitably be a novel path in plant stress response investigations in the short run.

The beet armyworm, Spodoptera exigua (Hubner), is one of the most important pests of sugar beet that overwinter as mature larvae or pupae in the soil. In this research, the influence of cold acclimation in full-grown larvae and tolerance at temperatures below their body supercooling point (SCP) was studied. Moreover, the influence of soil humidity was investigated on temperature that pest may expose. After six different temperature treatments on lab-reared mature larvae, cold tolerance of the larvae was measured under two different programs executed on them. In the first program, larvae were acclimated by cooling rate of 1°C/min and reached to -5°C or -15 °C, for 24h then it was raised to +25°C. During second program the temperature was decreased with much lower cooling rate (0.01°C /min) to -15°C and kept for 2h then it was increased again to +25°C. These two temperature programs were also performed on different soil humidity (dry, humid and humid covered with an ice layer). The results showed that these pest larvae will only be able to tolerate -15°C when they were acclimated with slow cooling rate to reach below their SCP. These findings indicated that cold acclimation at sub-zero may induce expression of freezing tolerance in these larvae. It was shown that humid soils especially those covered with an ice layer, are more resistant against temperature decreasing rather than dry soils and could play an important role in the cold-hardiness strategy and mortality of this pest under low temperatures.

Among the different species of Pistacia genus, P. atlantica is more distributed in cold area than P. khinjuk. In this study, in order to illustrate the physiological mechanisms of cold tolerance under acclimation phenomenon, two experiments were established. First experiment was conducted to induction of acclimation on seedlings at two stages and each stage was done for two weeks with different photoperiods. Then chlorophyll and florescence's chlorophyll was measured. For second experiment, leaves and stems of seedlings were exposed to three levels of temperature, +4° C (control),-20° C in one hour and-20° C in two hours. For this purpose, we measure relative water content (RWC) and electrolyte leakage (EL). Results of first experiment showed that 44% electron transport rate and 46% photochemical quenching was significantly reduced. This reduction in P. atlantica was grater by 30% compared to P. khinjuk. Second experiment results revealed that leaf RWC and EL increased during cold acclimation to be 8 and 11%, respectively. In addition, stem EL increased only in P. khinjuk (44%). In fact, P. atlantica due to decreasing of RWC during acclimation was able to maintain the photosystem efficiency and showed more resistance to cold stress. According to our findings, we can identify cold-resistant species or genotypes by measuring the florescence's chlorophyll.

It is necessary to alter temperature gradually when we have an intention for screening of plants to freezing tolerance so that it allows us to make active acclimation mechanisms and reveal impression of efficient genes. In order to asses manners of applying these temperature alternations on chickpea in vitro, in this study seeds of two genotypes 'ILC533' and 'ILC482' and a variety of Qazvin were grown in the relatively steril condition and 1 cm explants from second and third nods of those plants were prepared and grown on an agar medium in vitro. Acclimation treatments were done 10 days and/or 20 days at 4°C. After acclimation, those cultures as well as control (no acclimation) were frozen at -4, -8, -12, -16 and -20°C for 1h and on the basis of present injury, probit analysis was accomplished to identify LT50 for each treatment. Evaluation of freezing tolerance by LT50showed that the cold acclimation increased freezing tolerance and 20 days cold acclimation had better effect on cold hardiness and viability. Freezing tolerance of 'ILC533' induced by cold acclimation was more than other cultivars. Also acclimation for 20 days allowed satisfactory discrimination between the hardy cultivars 'ILC482' and 'Qazvin' and less cold hardy 'ILC533'. The results suggest that acclimation treatment for 20 days at 4°C can be used for in vitro screening of chickpea to decline freezing injury. So it seems to prepare the possibility of autumn culture by screening of tolerant chickpea.