In-Chang Son

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.

Relationship between cold hardiness and dehydrin gene expression in peach shoot tissues under field conditions

The relationship between cold hardiness and expression of dehydrin genes in the shoots of four peach cultivars (Prunus persica ‘Daewol’, ‘Aikawanakajima’, ‘Fukuyokabijin’, and ‘Kiraranokiwami’) was quantitatively evaluated during seasonal cold acclimation and deacclimation. Cold hardiness was determined by electrolyte leakage analysis, which increased gradually during fall, reached a maximum level in midwinter, and decreased again in spring. According to the temperatures at which 50% injury occurred (LT50), differences in cold hardiness of ‘Daewol’ and ‘Kiraranokiwami’ were the most obvious during deacclimation, with the exception of April 2012. The expression patterns of PpDhn1 and PpDhn3 showed parallel fluctuations in cold hardiness in the four cultivars, whereas PpDhn2 did not show any seasonal changes in any of the cultivars.

Photosynthesis of Chinese cabbage and radish in response to rising leaf temperature during spring

Photosynthesis in leaves, exposed to temperature change, was measured during spring to provide information for modeling of cropping systems for Chinese cabbage (Brassica campestris subsp. napus var. pekinensis) and radish (Raphanus sativus) in Jeju Island. The net photosynthetic rates (A) of Chinese cabbage and radish were depressed at temperatures above approximately 25°C (corresponding to the optimum temperature for photosynthesis), due in part to high rates of respiration above 25 or 30°C. Chinese cabbage was more sensitive to high temperature than radish. Above 25°C, stomatal conductance (gs) declined steeply with a sharp increase in the vapor pressure deficit (VPD) and transpiration rate (E), suggesting that stomatal closure could not be associated with transpiration rate, particularly in Chinese cabbage. Dramatic declines in water use efficiency (WUE), instantaneous transpiration efficiency (ITE), and carboxylation efficiency (CE) above 30°C indicated that the plants could be severely affected negatively by high temperatures above 30°C. However, compared to Chinese cabbage, radish had high light use efficiency and potential to assimilate CO2, judged by their high quantum yield (φ) and maximum photosynthetic rate (Amax). Radish utilized high levels of photosynthetic photon flux and strongly acclimated to the light environment, considering their high light saturation point (Qsat) and low light compensation point (Qcomp). These results suggested that rising temperature might substantially alter water availability of plants by itself and/or through effects on the rate of water loss from leaves of Chinese cabbage and radish under diurnal and/or seasonal fluctuations of temperature, and/or global temperature change. To maintain the high productivity and quality of these crop species, it may be necessary to harvest them until early June, when the daily maximum temperature is below 25°C in Jeju Island.

Estimation of Duration of Low-temperature in Winter Season Using Minimum Air Temperature on January

The duration of low temperature in winter season is one of the important agrometeorological characteristics in crop growing fields. This study was conducted to develop a method to estimate the duration of low-temperature with monthly meteorological data. Using daily meteorological data from 61 observation sites from 1981 to 2010, we analyzed the relationships between the averages of monthly temperature minima and the durations of low-temperature ranging from -15 to , The monthly mean of the January minimum air temperature was appropriate for theestimation of the durations of lowtemperature below . We tested a simple second order equation to predict durations of low-temperature. To apply the equation to various temperature ranges, we suggested two different equations for the estimation of coefficients a and b, which are dependent on the base temperatures from -15 to . Thevalidation of the equations using other daily meteorological datasets from 1971 to 2000 showed that they were appropriate for the range from -10 to , but underestimated at .

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

To analyze quantitatively environmental characteristics of cultivation area of citrus, Satsuma mandarin (Citrus unshiu Marc.), we made digital maps of environmental elements such as topography and climate. Elevation, degree of slope, and slope aspect were selected as elements of topological environment, and the annual mean air temperature, annual total precipitation, mean air temperature on January, extreme value of daily minimum air temperature, and the number of days below -5 o C were selected as elements of climatic environments. The grid values of 8 environmental elements were extracted by shape of citrus farm area and analyzed distribution patterns. We can determine 3 agroclimatic criteria for growing Satsuma mandarin as over 14.5 o C of annual mean air temperature, over -10.0 o C of extreme value of daily minimum air temperature, and less 5 days of below -5 o C of

Photosynthetic and Growth Responses of Chinese Cabbage to Rising Atmospheric CO2

The effects of elevated atmospheric CO2 on photosynthesis and growth of Chinese cabbage (Brassica campestris subsp. napus var. pekinensis) were investigated to predict productivity in highland cropping in an environment where CO2 levels are increasing. Vegetative growth, based on fresh weight of the aerial part, and leaf characteristics (number, area, length, and width) of Chinese cabbage grown for 5 weeks, increased significantly under elevated CO2 (800 μmol⋅mol-1) compared to ambient CO2 (400 μmol⋅mol-1). The photosynthetic rate (A), stomatal conductance (gs), and water use efficiency (WUE) increased, although the transpiration rate (E) decreased, under elevated atmospheric CO2. The photosynthetic light-response parameters, the maximum photosynthetic rate (Amax) and apparent quantum yield (φ), were higher at elevated CO2 than at ambient CO2, while the light compensation point (Qcomp) was lower at elevated CO2. In particular, the maximum photosynthetic rate (Amax) was higher at elevated CO2 by 2.2-fold than at ambient CO2. However, the photosynthetic CO2-response parameters such as light respiration rate (Rp), maximum Rubisco carboxylation efficiency (Vcmax), and CO2 compensation point (CCP) were less responsive to elevated CO2 relative to the light-response parameters. The photochemical efficiency parameters (Fv/Fm, Fv/Fo) of PSII were not significantly affected by elevated CO2, suggesting that elevated atmospheric CO2 will not reduce the photosynthetic efficiency of Chinese cabbage in highland cropping. The optimal temperature for photosynthesis shifted significantly by about 2C under elevated CO2. Above the optimal temperature, the photosynthetic rate (A) decreased and the dark respiration rate (Rd) increased as the temperature increased. These findings indicate that future increases in CO2 will favor the growth of Chinese cabbage on highland cropping, and its productivity will increase due to the increase in photosynthetic affinity for light rather than CO2.