• Journal of Bio-Environment Control
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• v.16 no.4
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• pp.303-308
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• 2007

An accumulation levels of osmolytes in chilling-tolerant and chilling-sensitive cultivar of Cucurbits against chilling stress were determined during chilling stress. Total soluble sugar contents in tolerant cultivar did not changes fur 10 days after chilling stress, but then slightly increased 20 days after chilling stress. In sensitive cultivar, it was increased rapidly in the beginning of chilling stress, and increased 3.4 times as much 20 days after chilling stress as compared with unstressed plants. Proline contents in tolerant cultivar was rapidly increased by the beginning of chilling stress, and then increased 26.6 times 20 days after chilling stress as compared with unstressed plants. In sensitive cultivar, it was increased 22.0 times 20 days after chilling stress as compared with unstressed plants. A levels of glycine betaine (GB) in tolerant cultivar increased 1.9 times as much during the 20 days of chilling stress. However, concentration of GB in sensitive cultivar did not change during the chilling stress. When plants were treated exogenous GB as a foliar spray, chilling tolerance was significantly enhanced in both cultivars. The foliar application of exogenous GB was induced chilling tolerance by accumulation of GB in the plant organs. However, it does not accumulate endogenous proline.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.2
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• pp.171-175
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• 1999

Morphological alteration of floral organ development in rice affected by chilling stress was examined. Three varieties of rice were grown under natural conditions and subjected to 12$^{\circ}C$ for 3 or 6 days starting from the ineffective tillering stage, before heading stage and returned to natural condition. Headings were delayed by a 6 day chilling treatment. After heading the panicles were collected and examined for any possible alteration in floral organ development. It appears that there were some differences in sensitivity to chilling stress and degree of injury depending on treatment stages and variety. Chuchungbyeo was the most frequent in producing abnormal flowers among the three varieties examined. Meiosis stage was shown to be the most vulnerable to chilling stress in both Chuchungbyeo and Ilpumbyeo and young panicle differentiation stage was the frequent stage to alter flower development in response to chilling stress only in Chuchungbyeo. It was confirmed that abnormalities occurred in pollen due to chilling stress is a major factor leading to low yield, but to some extent the alterations in carpel development may playa certain role in determining a total yield in response to chilling stress at the reproduction stage in rice. There were abnormalities like extra stigmata, extra lemma, double ovary as well as abnormal anther formation in response to chilling stress. Further studies of the phenocopy observed in rice floral development may be useful for an understanding of the resistance against chilling injury during reproductive stages in rice.

• Journal of Bio-Environment Control
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• v.16 no.1
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• pp.54-61
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• 2007

To determine whether antioxidant enzyme systems are related to chilling tolerance, changes of antioxidant enzyme activities during the chilling stress were determined in the leaves of a chilling-tolerant cultivar (Cucurbita ficifolia, cv. Heukjong) and a chilling-sensitive cultivar (Cucurbita moschata, cv. Jaerae 13). Leaves of chilling-tolerant plant have two major isoforms, Fe-SOD and Mn-SOD, at the Rm values of 0.20 and 0.52, respectively. In leaves of chilling-sensitive plant, two major isozymes of SOD was observed, one isoform is Mn-SOD at the Rm value of 0.20, and the other isoform is Cu/zn-SOD at the nm value of 0.58. When plants were treated with chilling stress, Cu/zn-SOD at the Rm value of 0.58 was newly expressed at 10 days after chilling stress in the chilling-tolerant plants, and density of this band increased at five days after chilling stress in the chilling-sensitive plants. One APX isozyme band was observed in unstressed plants of both cultivars. Under the chilling stress one APX isozyme band was newly expressed at 10 days after chilling stress in the chilling-tolerant cultivar. Significant genotype differences were observed fnr POD isozyme banding patterns such as few main isozyme bands in chilling-tolerant plants, and one band in chilling-sensitive plants. Densities of three POD isozyme bands at the Rm of 0.36, 0.40 and 0.54 increased at 10 days after chilling stress in the chilling-tolerant plants, while two bands at the nm of 0.36 and 0.54 increased at 10 days and 20 days after chilling stress in the chilling-sensitive plants, respectively. Activities of SOD, APX and POD significantly increased during five days after chilling stress in both cultivars. In the chilling-tolerant cultivar, activities of these enzymes were higher in chilling-stressed plant than in unstressed plants. However, activities of these enzymes in the chilling-sensitive cultivar decreased rapidly after five days of chilling stress, and were lower in chilling stressed plants than in unstressed plants.

• Plant Biotechnology Reports
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• v.3 no.4
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• pp.301-307
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• 2009

To understand the adaptability of alfalfa (Medicago sativa L.) to chilling stress, we analyzed the antioxidative mechanism during seed germination. The germination rates of six alfalfa cultivars were studied comparatively at $10^{\circ}C$. Xinmu No. 1 and Northstar were selected as chilling stress-tolerant and stress-sensitive cultivars for further characterization. After chilling treatment, Xinmu No. 1 showed higher seedling growth than Northstar. Xinmu No. 1 exhibited low levels of hydrogen peroxide and lipid peroxidation compared with Northstar. In addition, shoots in Xinmu No. 1 treated with chilling showed higher activities of the superoxide dismutase, ascorbate peroxidase (APX), and catalase than those of Northstar, whereas Xinmu No. 1 showed higher APX activity in roots that Northstar. These results indicated that high antioxidation activity in Xinmu No. 1 under chilling stress is well associated with tolerance to chilling condition during germination.

• Journal of Bio-Environment Control
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• v.16 no.2
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• pp.121-129
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• 2007

Responses of antioxidant enzymes on chilling and drought stress in tomato seedlings were investigated. Growing patterns of tomato based on fresh weight of tomato seedlings were severely affected by chilling and drought stress. Fresh weight of tomato seedlings were reduced by 69.5% in chilling stress and 50.6% in drought stress compared to those in the unstressed control seedlings after 12 days of stress. The specific and gel activity of SOD and POD in the leaves, shoots, and roots of tomato seedlings were significantly increased by chilling and drought stress. Activation of SOD and POD activity by chilling stress were higher in the roots than those of drought stress. However, activation of SOD and POD activity by drought stress were higher in the leaves and shoots than those of chilling stress. The specific and gel activity of GR in the leaves, shoots, and roots of tomato seedlings were also significantly increased by chilling and drought stress. When the seedlings were treated with chilling or drought stress, one GR isozyme band (GR-3) was newly expressed in the leaves of tomato seedlings. The specific and gel activity of PPO was significantly increased in the roots and shoots of tomato seedlings by chilling and drought stress, respectively. However, the specific and gel activity of PPO in the leaves is no difference between stressed and controlled tomato seedlings.

• The Korean Journal of Ecology
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• v.19 no.2
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• pp.151-163
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• 1996

To investigate the early symptoms of light-chilling, alterations of chlorophyll fluorescence transients were monitored in cucumber (Cucumis sativus L. cv. Ilmichungjang) leaves. During 24 h chilling, decreases in (Fv)m/Fm, qE and qQ, and an increase in Fo were observed. The chilling effects were not recovered at room temperature, and a significant increase in Fo was observed during the recovery period. After 6 h chilling, ‘dip’(D) level of the transients became obscure, and the negative slope after ‘peak’(P) disappeared. The first derivative (dFv/dt) of the fast fluorescence rise curve was used to obtain more accurate information about the changes in the transients. The maximal rate of the fluorescence increase in the D-p rise curve (Fr) has been the most frequently used chilling stress indicator. However, a correct value of Fr could not be measured when the D level became obscure. This problem was overcome by introducing a new indicator, HFr (dFv/dt at Fv = 1/2 (Fv)m), and HFr gave very similar values to Fr. To monitor the changes in curvature around D level, another new parameter, ${\Delta}S$(D-Fr), was also introduced. These three parameters decreased very sensitively during light-chilling. In addition, increases in these parameters were observed during the first 2 h chilling, but this increase in Fr was also observed in pea leaf discs dark-chilled for 15 min, suggesting that this very early change is a common response to chilling in both pea and cucumber leaves. Quenching coefficients were also very sensitive to chilling, especially qE. Discussion on the usage of these parameters as chilling stress indicators is given in the text.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.3
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• pp.288-298
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• 1992

Since the major important factors limiting plant growth and crop productivity are environmental stresses, of which low temperature is the most serious. It has been well known that many physiological processes are alterant in response to the environmental stress. With regard to the relationship between plant hormones and the regulation of chilling tolerance in rice seedlings, the major physiological roles of plant hormones: abscisic acid, ethylene and polyamines are evaluated and discussed in this paper. Rice seedlings were grown in culture solution to examine the effect of such plant hormones on physiological characters related to chilling tolerance and also to compare the different responses among tested cultivars. Intact seedlings about 14 day-old were chilled at conditions of 5$^{\circ}C$ and 80% relative humidity for various period. Cis-(＋)-ABA content was measured by the indirect ELISA technique. Polyamine content and ethylene production in leaves were determined by means of HPLC and GC respectively. Chilling damage of seedlings was evaluated by electrolyte leakage, TTC viability assay or servival test. Our experiment results described here demonstrated the physiological functions of ABA, ethylene, and polyamines related to the regulation of chilling tolerance in rice seedlings. Levels of cis-(＋)-ABA in leaves or xylem sap of rice seedlings increased rapidly in response to 5$^{\circ}C$ treatment. The tolerant cultivars had significant higher level of endogenous ABA than the sensitive ones. The ($\pm$)-ABA pretreatment for 48 h increased the chilling tolerance of the sensitive indica cultivar. One possible function of abscisic acid is the adjustment of plants to avoid chilling-induced water stress. Accumulation of proline and other compatible solutes is assumed to be another factor in the prevention of chilling injuies by abscisic acid. In addition, the expression of ABA-responsive gene is reported in some plants and may be involving in the acclimation to low temperature. Ethylene and its immediate precusor, 1-amincyclopropane-1-carboxylic acid(ACC) increased significantly after 5$^{\circ}C$ treatment. The activity of ACC synthase which converts S-adenosylmethionine (SAM) to ACC enhanced earlier than the increase of ethylene and ACC. Low temperature increased ACC synthase activity, whereas prolonged chilling treatment damaged the conversion of ACC to ethylene. It was shown that application of Ethphon was beneficial to recovering from chilling injury in rice seedlings. However, the physiological functions of chilling-induced ethylene are still unclear. Polyamines are thought to be a potential plant hormone and may be involving in the regulation of chilling response. Results indicated that chilling treatment induced a remarkable increase of polyamines, especially putrescine content in rice seedlings. The relative higher putrescine content was found in chilling-tolerant cultivar and the maximal level of enhanced putrescine in shoot of chilling cultivar(TNG. 67) was about 8 folds of controls at two days after chilling. The accumulation of polyamines may protect membrane structure or buffer ionic imbalance from chilling damage. Stress physiology is a rapidly expanding field. Plant growth regulators that improve tolerance to low temperature may affect stress protein production. The molecular or gene approaches will help us to elucidate the functions of plant hormones related to the regulation of chilling tolerance in plants in the near future.

• Journal of Photoscience
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• v.9 no.2
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• pp.59-62
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• 2002

In chilling-sensitive plants, the donor side of Photosystem II is inhibited by the chilling treatment in the dark, while the acceptor side of Photosystem I is inhibited by the chilling under the moderate light. Since the addition of inhibitors of electron transfer from Photosystem II protects Photosystem I from chilling induced photoinhibition of Photosystem I, inhibition or down-regulation of Photosystem II activity in vivo may also protect Photosystem I from photoinhibition. It was revealed that dark-chilling pretreatment actually protected Photosystem I from photoinhibition. The results imply that down-regulation of Photosystem II under stress conditions may have a role to protect Photosystem I from photoinhibition.

• Journal of Bio-Environment Control
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• v.15 no.4
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• pp.390-395
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• 2006

Effects of exogenously foliar applied glycine betaine (GB) on the growth and contents of osmolyte in tomato seedling was investigated. Plants treated with exogenous glycine betaine induced better biomass production and plant height during chilling stress than the untreated plants. The total soluble sugar contents in GB foliar-applied plants lower than that of untreated plants 28 days after foliar application. Total water soluble protein contents in GB foliar-applied plants did not change 28 days after chilling stress. In untreated plant, it decreased rapidly in the beginning of chilling stress. Proline contents in untreated plants rapidly increased by the beginning of chilling stress, and then slightly decreased during the next 3 weeks. However proline contents in GB foliar-applied plants did not change during the 28 days chilling stress period. The results suggest that foliar application of GB is a effect methods to increase the chilling tolerance of tomato seedlings in protected cultivation system at low temperature season.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.4
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• pp.289-294
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• 2004

This study was carried out to investigate the antioxidative enzymes and isozymes between chilling-tolerant and -susceptible varieties at the booting stage under cold water stress $(13^{\circ}C)$ in japonica rice. Total SOD, CAT, POX, and GR activities on the basis of protein were found to be important factors to defend cold water stress. Especially, SOD and CAT activities showed distinctive differences between chilling-tolerant and -susceptible varieties. Chilling-tolerant varieties were higher than chilling-susceptible varieties for SOD and CAT activities. One of eight isozyme bands for SOD was a inducible isoform. Three isozymes for CAT and one isozyme for POX were closely correlated with defense to cold water stress. Total GR activities except Stejaree 45 on the basis fresh weight and POX were increased by cold water stress, but there was no difference between chilling-tolerant and -sus­ceptible varieties.