• Journal of Photoscience
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• v.7 no.2
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• pp.39-44
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• 2000

To examine the chilling tolerance lipids, we compared the chilling susceptibility of photosystem II of wild type tobacco plants with that of transgenic tobacco plants, in which the sensitivity to chilling had been enhanced by genetic modification of fatty acid unsaturation of chloroplast membrane lipids. The transgenic tobacco plants were found to contain reduced levels of unsaturated membrane fatty acids by being tansformed with cDNA for glycerol-3-phosphate acyltransferase from squash. For the purpose of studying on the functional integrity of photosystem II during low-temperature photoinhibition, the photochemical efficiency was measured as the ration of the maximun fluorescence of chlorophyll (Fv/Fm) of photosystem II. In parallel with an investigation on the transgenic plants, susceptibility of chilling-resistant species, such as spinah and pea, and of chilling-sensitive ones, such as squash and sweet potato, to low-temperature photoinhibition was also compared in terms of room temperature-induced chlorophyll fluorescence from photosystem II. When leaf disks from the two genotypes of tobacco plants were exposed to light at 5$^{\circ}C$, the transgenic plants showed more rapid decline in photochemical activity of photosysytme II than wild-type plants. When they were pretreated with lincomycin, an inhibitor of chloroplast-encoded protein synthesis, the extent of photoinhibition was even more accelerated. More impottantly, they showed a comparable extent of photoinhibition in the presence of lincomycin, making a clear contrast to the discrepancy observed in the discrepancy observed in the absence of lincomycin. Restoration of Fv/Fm during recovery from low-temperature photoinhibition occurred more slowly in the transgenic tobacco plants than the wild-type. These findings are discussed in relation to fatty acid unsaturation of membrane phosphatidylglycerol. It appears that the ability of plants to rapidly regenerate the active photosystem II complex from might explain, in part, why chilling-resistant plants can toleratlow-temperature photoinhibition.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.3
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• pp.356-360
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• 1986

The potential of the chlorophyll fluorescence technique in screening eleven rice varieties for chill-sensitivity was assessed by measuring the change in the rate of rise of variable fluorescence (FR) and the maximum yield of variable fluorescence, F$\_$VAR/ (F$\_$MAX/-F$\_$0/) after 8 days chilling at 10$^{\circ}C$. The changes in both fluorescence parameters with chilling agreed well with visual assessments of injury carried out at the end of the chilling period. Furthermore, it was found that in the majority of the rice cultivars tested their chilling sensitivity agreed well with the rate of rise of chlorophyll fluorescence (F$\_$R/) measured at 25$^{\circ}C$. The method of chlorophyll fluorescence was rapid, reproducible, sensitive and non-destructive and it should be a valuable new tool in screening large numbers of closely related rice varieties for chilling sensitivity.

• Journal of Photoscience
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• v.3 no.1
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• pp.9-14
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• 1996

For three cultivars of chilling-sensitive cucumber plants, chilling sensitivity was evaluated in terms of photosynthetic activity using Chl fluorescence techniques. Low-temperature treatment caused a decrease in photosynthetic activities of cucumber leaves, measured as CO$_2$ exchange, as well as the decrease in the stomatal conductance. FR of the three cultivars decreased after chilling for 24 h in light and the extent of decline of F$_R$ was the greatest in 'Chosaeng' cultivar. When these plants were recovered from light-chilling, 'Chosaeng' and 'Samchuk' cultivars did not fully restore the original value of F$_R$ after 24 h of recovery, in contrast to 'Ilmi' cultivar which showed a rather efficient recovery. The results of FR study showed that 'Chosaeng' was most susceptible, whereas Ilmi was most resistant, to chilling among the three cultivars of cucumber plants. When quenching coefficients for chlorophyll fluorescence was analyzed after chilling the cucumber plants for 24 h in light, 'Chosaeng' elicited more rapid declines in the coefficients for photochemical quenching (qQ), non-photochemical quenching (qNP) and energy-dependent quenching (qE) than 'Ilmi' and 'Samchuk'. The implications of these observations are discussed in relation to the growth habits of the respective cultivars in the field. The results showed that measurement of chlorophyll fluorescence was an effective means of screening chilling tolerance of cucumber plants. Furthermore, the study on the chlorophyll fluorescence induction and fluorescence quenching charactersitics showed that low temperature could accelerate inhibition of photosynthesis in chilling-sensitive plants, by limiting Calvin cycle activity and disrupting, in part, the energy dissipation mechanims of the photosystem II.

• Journal of Photoscience
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• v.3 no.1
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• pp.15-21
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• 1996

To investigate the chilling sensitivity related injuries in the photosynthetic apparatus of cucumber leaves, the light-chilling induced alterations of chlorophyll fluorescence transients in cucumber leaves were compared with those in pea leaves. As an early effect of light-chilling, an increase in Fp/Fm$^*$ was observed in both pea and cucumber leaves, which was saturated by about 6 h chilling. However, the saturated value of Fp/Fm was almost 1.0 in cucumber, in contrast to about 0.8 in pea. During the recovery period after 24 h chilling, the light-chilling induced changes in pea seemed to be reversed, but those in cucumber leaves were thought to be irreversible, because Fo was increased significantly. Light-chilling caused significant decreases in qQ and qE in cucumber leaves, but qR was increased until 6 h, and decreased thereafter. In both pea and cucumber leaves, Fm was increased by 2 h dark treatment. The Fm from the predarkened pea leaf discs was higher than the value from the preilluminated ones during the whole period of light-chilling (500 $\mu$mol m$^{-2}$s$^{-1}$ PAR). However, the predarkened cucumber leaf discs showed a reduction in Fm and an increase in Fo during the 2 h chilling in the light. These results indicate that the causes of chilling sensitivities in photosynthetic apparatus of cucumber leaves are possibly related with the damage in PSI reaction center and the ability of acidification of lumen by PSII.

• 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.

• Proceedings of the Botanical Society of Korea Conference
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• 1999.08a
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• pp.68-82
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• 1999

CHilling tolereance of plants are closely correlated with the degree of fatty acid unsaturation of membrane lipids. We studied the effects of low-temperature photoinhibition on the photochemical efficiency of photosystem II in terms of fatty acid unsaturation of thylakoid membranes lipids isolated from chilling -sensitive plants and chilling -resistant ones. To directly test the chilling tolerance of photosynthetic machinery in relation to membrane lipids, we further compared wild type tobacco plants with that of transgenic tobacco plants, in which the sensitivity to chilling had been enhanced by genetic modification of fatty acid unsaturation of chloroplast membrane lipids. The transgenic tobacco plants were found to contain reduced levels of unsaturated membrane fatty acids after being transformed with cDNA for glycerol-3-phophate acyltransferase from squash. The functional integrity of photosystem II during and recovery of photosynthesis from low-temperature photoinhibition will be discussed in connection with the degree of fatty acid unsaturation of chlorophast membranes lipids.

• Journal of Photoscience
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• v.12 no.1
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• pp.33-39
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• 2005

Plants possess the ability to dissipate the excitation energy for the protection of photosynthetic apparatus from absorbed excess light. Heat dissipation is regulated by xanthophyll cycle in thylakoid membranes of chloroplasts. We investigated the mechanistic aspects of xanthophyll cycle-dependent photoprotection against low-temperature photoinhibition in plants. Using barley and rice as chilling-resistant species and sensitive ones, respectively, chilling-induced chlorophyll fluorescence quenching, composition of xanthophyll cycle pigments and mRNA expression of the zeaxanthin epoxidase were examined. Chilled barley plants exhibited little changes in chlorophyll fluorescence quenching either of photochemical or non-photochemical nature and in the photosynthetic electron transport, indicating low reduction state of PS II primary electron acceptor. In contrast to the barley, chilled rice showed a marked decline in those parameters mentioned above, indicating the increased reduction state of PS II primary electron acceptor. In addition, barley plants were shown to have a higher capacity to elevate the pool size of xanthophyll cycle pigments in response to cold stress compared to rice plants. Such species-dependent regulation of xanthophyll cycle activity was correlated with the gene expression level of cold-induced zeaxanthin epoxidase. Chilled rice plants depressed the gene expression of zeaxanthin epoxidase, whereas barley increased its expression in response to cold stress. We suggest that chilling-induced alterations in the pool size of xanthophyll cycle pigments related to its capacity would play an important role in regulating plant's sensitivity to chilling stress.

• Horticultural Science & Technology
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• v.32 no.2
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• pp.227-234
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• 2014

The responses to chilling temperature of 12 Korean cucumber varieties was compared to those of two U.S.A. (previously determined cold tolerant NC76 and 'Chipper'), and Chinese and Japanese germplasms. Seedlings of each entry were exposed to $4^{\circ}C$ (Experiment 1) and $1^{\circ}C$ (Experiments 2 and 3) at the first-true leaf stage for eight and nine hours, respectively, under 80% relative humidity (RH) and $149{\mu}moles{\cdot}m^{-2}{\cdot}s^{-1}$ photosynthetic photon flux (PPF). The chilling response [damage rating (DR)] of each accession was based on visual ratings (1 to 5) after treatment, where 1 = no damage, 2 = slight, 3 = moderate, 4 = advanced, and 5 = severe damage. Predictably the cumulative average DR of chilling tolerant line NC76 and 'Chipper' after chilling w as 1 and 1.1, respectively. Korean 'Nacdongchungjang' was most sensitive to chilling temperatures [DR = 2.3] when compared to the other entries examined. The sensitivity to chilling of 'Nacdongchungjang' was followed by Chinese 'Dongguan' [DR = 1.7]. In contrast, 'Saeronchungjang' (DR = 1) and 'Janghyungnachap' (DR = 1) were the most chilling tolerant of the Korean accessions examined and equivalent to the response of line NC76 and 'Chipper'. Nevertheless, chloroplast type genotyping of these accessions with known chilling-linked sdCAPS genomic markers revealed genotypic differences between chilling tolerant lines (NC76 and 'Chipper') and all Korean lines examined.

• Proceedings of the Botanical Society of Korea Conference
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• 1993.07a
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• pp.107-112
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• 1993

• Proceedings of the Korean Society of Potoscience Conference
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• spring
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• pp.110-111
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• 1999