Soonja Oh

Growth, photosynthesis and chlorophyll fluorescence of Chinese cabbage in response to high temperature.

In order to gain insight into the physiological responses of plants to high temperature stress, the effects of temperature on Chinese cabbage (Brassica campestris subsp. napus var. pekinensis cv. Detong) were investigated through analyses of photosynthesis and chlorophyll fluorescence under 3 different temperatures in the temperature gradient tunnel. Growth (leaf length and number of leaves) during the rosette stage was greater at ambient and ambient temperatures than at ambient temperature. Photosynthetic fixation rates of Chinese cabbage grown under the different temperatures did not differ significantly. However, dark respiration rate was significantly higher in the cabbage that developed under ambient temperature relative to elevated temperature. Furthermore, elevated growth temperature increased transpiration rate and stomatal conductance resulting in an overall decrease of water use efficiency. The chlorophyll a fluorescence transient was also considerably affected by high temperature stress; the fluorescence yield , , and decreased considerably at ambient and ambient temperatures, with induction of and decrease of . The values of RC/CS, ABS/CS, TRo/CS, and ETo/CS decreased considerably, while DIo/CS increased with increased growth temperature. The symptoms of soft-rot disease were observed in the inner part of the cabbage heads after 7, 9, and/or 10 weeks of cultivation at ambient and ambient temperatures, but not in the cabbage heads growing at ambient temperature. These results show that Chinese cabbage could be negatively affected by high temperature under a future climate change scenario. Therefore, to maintain the high productivity and quality of Chinese cabbage, it may be necessary to develop new high temperature tolerant cultivars or to markedly improve cropping systems. In addition, it would be possible to use the non-invasive fluorescence parameters , , and , as well as , , , RC/CS, ETo/CS, , and (which were selected in this study), to quantitatively determine the physiological status of plants in response to high temperature stresses.

Seasonal Photoprotective Responses in Needles of Korean Fir (Abies koreana) Over an Altitudinal Gradient on Mount Halla, Jeju Island, Korea

Abstract Chloroplast pigments and chlorophyll fluorescence were characterized in needles of Korean fir (Abies koreana) in summer, winter, and spring at three altitudes on Jeju Island, Korea. High light-harvesting efficiency (intrinsic photosystem II efficiency) and indirect evidence for high photosynthetic rates (high levels of&bgr;-carotene and chlorophyll b) during the growing season contrasted with mid-winter downregulation of light-harvesting efficiency involving retention of high zeaxanthin levels and locked-in photoprotective thermal dissipation (from low chlorophyll fluorescence emission). Neoxanthin levels were inversely correlated with sustained photoprotection in the winter, and lutein to xanthophyll cycle carotenoid levels decreased from summer to winter, suggesting that zeaxanthin plays the prominent role in winter photoprotection of Korean fir needles. Summer was apparently most conducive to photosynthesis, consistent with high levels of summer precipitation on Jeju Island, and in contrast to fir and other conifers in a climate with dry summers at high altitudes in Colorado, U.S.A., where studies have shown that the wet spring is the season most favorable for photosynthesis. Lastly, despite there being only 300 m difference in altitude among the three sites, there were discernible differences in (i) accumulation of zeaxanthin in winter (as an indicator for the severity of conditions, with highest levels at the highest altitude), (ii) apparent photosynthesis rates in summer (from &bgr;-carotene levels, with highest levels at the highest altitude), and (iii) transition to increased photosynthesis in spring (from fluorescence emission levels, slowest at the highest altitude).

Photosystem II photochemical efficiency and photosynthetic capacity in leaves of tea plant ( Camellia sinensis L.) under winter stress in the field

The effects of winter stress on photosynthesis of the tea plant (Camellia sinensis L.) were determined over the course of a year. Changes in gas exchange and chlorophyll fluorescence parameters largely tracked seasonal changes of temperature, precipitation, and atmospheric vapor pressure deficit. Intrinsic photosystem II (PSII) efficiency (estimated from the ratio of variable over maximal chlorophyll fluorescence, Fv/Fm) was at maximal levels (0.80–0.83) during the summer, then decreased in the fall and remained below 0.6 from January to March. The low levels of Fv/Fm in the winter were accompanied by the strongest quenching of maximal (Fm) and initial (Fo) fluorescence, presumably reflecting engagement of photoprotective thermal energy dissipation. Net photosynthetic rate, transpiration rate, and stomatal conductance were highest in the summer and lowest from late fall to early spring. These data suggested that PSII photochemical efficiencies and photosynthetic capacity of tea plant were limited under low temperature in the winter. On the other hand, a greater water use efficiency, lower light compensation point, and lower light intensity at which photosynthesis became saturated might be advantageous for tea plants acclimated to the lower precipitation levels and light intensities of winter. Analysis of the relationships between temperature or humidity and photosynthetic variables suggested that tea plants might benefit from irrigation in winter.

Studies on Flora of Wetlands on Jeju City for Application as Nature Exploration Sites

This study was investigated on biodiversity and life forms of plants distributed in 28 wetlands on Jeju city, in order to apply wetlands to nature exploration sites for environmental education. The 131 kinds of the plants were found on 28 wetlands. The plant biodiversity was relatively high in Ban pond, Jeongmool, Mosanimool, Dolgaegi pond, Woot pond, and etc. The life forms of plants, relatively high in variousness to other wet lands, were distributed in Mosanimool, Dolgaegi pond, Woot pond, and Yeonhoa pond as well as Jeongmool and Yongsoo reservoir. The 71 kinds, which correspond to 54.2% of plants observed in this study, were identified as hydrophytes. The forms of hydrophytes were distributed on 23 wetlands, including Jeongmool, Mosanimool, Yongsoo reservoir, Ban pond, Dolgaegi pond, and etc. In conclusion, 5 wetlands such as Jeongmool, Yongsoo reservoir, Dolgaegi pond, Mosanimool and Woot pond were high in variousness of plant life forms as well as biodiversity of plants. These results suggest that 5 wetlands above could be applied as nature exploration sites. In addition, Korean rare and endangered plants such as Isoetes japonica, Nymphoides coreana, Utricularia japonica and Sparganium stoloniferum in this study need to be conserved.

Characterization of Chl a Fluorescence of Hydrophytes under Cadmium Stress

The effects of ions on the Chl a fluorescence of 5 hydrophytes (e.g. Lemna, Salvinia, Ricciocarp, Nymph, Typha plants) were investigated in order to select -sensitive plant species and to get informations on physiological responses of plants to stress. Lemna plants were most sensitive to cadmium stress, while Nymph plants were tolerant. However, in all -treated plants, Fv/Fm, the maximum photochemical efficiency of PS II, decreased in proportion to the increase of concentration and treatment time. The Chl a fluorescence transient O-J-I-P was also considerably affected by ions; the fluorescence yield decreased consid- erably in steps J, I and P in treated plants, although it followed a typical polyphasic rise in non-treated plants. In Lemna plants, the functional parameters, ABS/CS, TRo/CS와 ETo/CS and RC/CS, decreased in proportion to the increase of concentration, while N, Mo and Kn increased. The structural parameters, , /(), Plabs, SFlabs, Kp and RC/ABS, also decreased according to the increase of concentration. Consequently, Lemna plants will be useful as a experimental model system to investigate responses of plants. And several functional or structural parameters could be applied to determine quantitatively the physiological states of plants under stresses.

Impact of Elevating Temperature Based on Climate Change Scenarios on Growth and Fruit Quality of Red Pepper (Capsicum annuum L.)

This study was conducted to determine the impact of temperature elevated based on climate change scenario on growth and fruit quality of red pepper (Capsicum annuum L.) in walk-in plant growth chambers. The intraday temperatures of climate normal years (IT) were determined using intraday mean temperatures of climatic normal years (1971~2000) in the Andong Province during the growing season (May 1~July 30). Red pepper plants were cultivated under different temperatures (starting at IT rise by up to 6 o C, 2 o C increment). Plant height, stem diameter, branch number, leaf number, fresh weight and dry weight increased under the temperatures higher than IT. The number of flower was the greatest under IT+2 o C (mean temperature at 22.8 o C). The total number and the weight of fruits were the highest under IT+2 o C. While the fruit weight, fruit length and fruit diameter decreased more than IT+2 o C as the temperature increased gradually. These results concluded that in condition that the current diurnal temperature change cycle is maintained in Andong area, in accordance with climate change scenarios, when the temperature rise 2 o C higher than intraday temperature of Andong area the quantity of pepper fruits will increase while maintaining quality, but increases more than that degree yields are expected to decrease significantly. This result suggests that the fruit yield could increase under IT+2 o C and fruit quality could maintain great, but the fruit yield could decrease under the temperatures higher than IT+2 o C.

Chlorophyll a Fluorescence Response to Mercury Stress in the Freshwater Microalga Chlorella Vulgaris

【The response of the freshwater microalga Chlorella vulgaris to mercuric ion (

Quantification of Environmental Characteristics on Citrus Production Area of Jeju Island in Korea

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Impact of Elevated Temperature in Growing Season on Growth and Fruit Quality of Red Pepper (Capsicum annuum L.)

) stress was examined using chlorophyll a fluorescence image analysis and O-J-I-P analysis as a way to monitor the toxic effects of mercury on water ecosystems. The levels of photosynthetic pigments, such as chlorophyll a and b and carotenoids, decreased with increasing

Analysis of CO 2 Fixation Capacity in Leaves of Ten Species in the Family Fagaceae

Hg^{2+}