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Effects of Light Availability on Attached Rhinanthus minor(L.), an Angiospermatic Root Hemiparasite
Hwangbo, Jun-Kwon,Seel, Wendy E 한국식물학회 2002 Journal of Plant Biology Vol.45 No.2
We studied the effect of light availability on the growth of an angiospermatic root hemiparasite, Rhinanthus minor. When attached to its host, height growth increased in response to shading, demonstrating that ft. minor was able to detect alterations in light quality and/or quantity. However, this reduced illumination did not affect its biomass, number of haustoria, or the amount of ^15N transferred from the hosts, compared with its performance under non-shaded conditions. Therefore, R. minor is unlikely to have difficulty in extracting host resources under shading. This result may have been mediated by a lowered R, minor transpiration rate in response to fluctuations in external conditions, including shading and water stress, compared with non-parasitic plants. Therefore, we suggest that, as long as the extent of resources diverted from host to parasite is not significantly altered by shading, growth of the attached R. minor will be unaffected by reduced light availability per se.
Tolerance of Several Woody Plants to Sulphur Dioxide
Hwangbo, Jun-Kwon,Lee, Chang-Seok,Kim, Joon-Ho The Korean Society for Integrative Biology 2000 Korean journal of biological sciences Vol.4 No.4
The photosynthetic and stomatal responses of several woody plants (Powlonia coreana, Firmiana simplex, Quercus acutissima Q. variabilis and Q. serrata) to SO$_2$ were investigated in order to understand their ecophysiological tolerance to $SO_2$ Of the plants, P, coreana showed the largest reduction in its photosynthesis in response to exposure of 0.4 ppm $SO_2$ for 20 h. Fumigation of 0.7 ppm $SO_2$ for 20 h caused complete leaf necrosis of P. coreana and f simplex, which made them unavailable for the measurement of photosynthesis. Q. variabilis exhibited the smallest reduction in photosynthesis following exposure of 0.7 ppm $SO_2$ for 20 h. Both stomatal- and non-stomatal inhibition of the plants by $SO_2$ were determined according to equations by lkeda et at. (1992). When exposed to 0.4 ppm $SO_2$ for 20 h, F. simplex and P. coreana showed the lowest stomatal and non-stomatal inhibition, respectively, while Q. variabilis and Q. serrata exhibited the lowest stomatal and non-stomatal inhibition, respectively, in response to 0.7 ppm $SO_2$ for 20 h. The data are discussed with regard to resistance mechanisms of other plants to $SO_2$ exposure and implications for restoration of declined Korean forests.
( Jun Kwon Hwangbo ),( Jae Sung Kim ),( Ji Hyeok Lim ),( Myung Hwa Baek ),( Byung Yeoup Chung ),( Jin Hong Kim ) 한국환경생물학회 2003 환경생물 : 환경생물학회지 Vol.21 No.4
N/A This study was to evaluate the effects of gamma irradiation on the germination, nutrient concentrations and growth of spinach and radish. Both the spinach and radish seeds exhibited relatively higher germination rates in response to the low doses of gamma irradiation compared to the non-irradiated control. Leaf DW of the radish did not respond to gamma irradiation hut that of the spinach increased significantly in response to a gamma radiation of 4 Gy (P< 0.05). Leaf growth parameters of the spinach including the leaf area and SLA (leaf aredeaf dry weight) also demonstrated increased responses to gamma irradiation. USL (root dry weightkhoot dry weight), root DW and root length of the spinach exhibited a positive response to gamma irradiation while those of the radish did not. In contrast, SRL (root IengtWroot dry weight) significantly decreased with gamma irradiation at 8 Gy for the spinach, hut not for the radish. The tissue nitrogen concentrations of the spinach showed an increased response to gamma irradiation while that of the radish did not. Furthermore, higher concentrations of phosphorus, potassium, calcium and magnesium were found in the irradiated spinach, hut not in the irradiated radish. It seems that the non-specific physiological and/ or biochemical activities of spinach might he accelerated by gamma irradiation, possibly accounting for the stimulation of nutrient uptake from the root media and early bio-mass accumulation in the current study.
Early Germination Response of Soybean Seed to Accelerated Aging and Low Dose Gamma Irradiation
Hwangbo, Jun-Kwon,Kim, Jae-Sung,Lim, Ji-Hyeok,Baek, Myung-Hwa,Chung, Byung-Yeoup,Kim, Jin-Hong The Korean Society of Crop Science 2004 Korean journal of crop science Vol.49 No.1
The responses of soybean seeds were evaluated to accelerated aging and gamma irradiation with regard to germination, seed leakage, seed leachate component and dry weight of hypocotyl and primary root of the germinating seed. Accelerated aging significantly reduced the final germination rate while gamma irradiation increased the final germination rate. Furthermore, the interactive effects occurred that the final germination rate of 5-day aged seeds increased considerably in response to 4 Gy of gamma irradiation. The extent to which the electrolyte was leaked from the seeds (conductivity) was significantly affected by accelerated aging and showed a close negative correlation with the germination rate. Gamma irradiation, however, did not significantly affect the electrical conductivity of seed leachate. The accelerated aging significantly increased the concentrations of the particular electrolytes leaked from the seeds while the gamma irradiation did not affect those concentrations. Of the electrolytes leaked from the seeds, Ca and Mg showed relatively lower concentrations while K showed greater concentrations than others. Moreover, N and P showed similar responses to aging treatment. Aging treatment significantly affected dry weight (DW) of hypocotyls and primary root. Also, gamma irradiation decreased DW of hypocotyls and primary root, particularly for 8 Gy associated with 5 days aging treatment. The data were discussed in terms of the relationships of seed vigor with aging treatment and gamma irradiation.
Hwangbo, Jun-Kwon,Kim, Jae-Sung,Lim, Ji-Hyeok,Baek, Myung-Hwa,Chung, Byung-Yeoup The Korean Society of Crop Science 2003 Korean journal of crop science Vol.48 No.4
The objective of this study was to demonstrate whether or not the deleterious effects of accelerated aging on seed vigour and viability are alleviated by interaction with gamma irradiation. Seeds of soybean (Glycine max L.) were artificially aged and subsequently irradiated with 4 and 8 Gy of gamma irradiation. Germination rate was negatively affected by accelerated aging and positively by gamma irradiation, with a positive interaction of a 3day-seed aging treatment occurring with 4 Gy, possibly suggesting that 4 Gy of gamma irradiation partially offset the adverse effects of seed aging on germination. However, 5-day aged seeds did not gain any benefits from the gamma irradiation. Electrolyte leakage from the seeds increased with the duration in days aged. Irradiation, however, did not impose any effects on the leakage. Respiration rate of the seed with hypocotyl and primary root was significantly low for the aged seeds, but not for the seeds with both irradiation and aging treatments. Accelerated aging decreased the dry weight of the hypocotyl and primary root of the seeds without any measurable effects of irradiation. $\alpha$-Amylase activity decreased with seed aging and positively responded to gamma irradiation. The data is discussed with regard to the possible roles of gamma irradiation for improving the seed vigour and viability of aged seeds.
Effects of Elevated CO_2 and Nitrogen on Growth of Poa pratensis(L.)
Hwangbo, Jun-Kwon,Kwak, Young Se 한국식물학회 2001 Journal of Plant Biology Vol.44 No.1
The growth responses of a grass, Poa pratensis, to elevated CO_2 and nitrogen were investigated. Light-saturated photosynthetic rate per unit leaf area increased with exposure to elevated CO_2, while dry weight did not respond to increased CO_2. Patterns of biomass allocation within plants, including leaf area, leaf area ratio, specific leaf area, and root to shoot ratios, were not altered by elevated CO2, but changed considerably with N treatment Shoot and whole-plant tissue N concentrations were significantly diluted by elevated CO_2 (Tukey test, P < 0.05). Total N content did not differ significantly among CO_2 treatments. The absence of a concomitant increase in N uptake under elevated CO_2 may have caused a dilution in plant tissue [N], probably negating the positive effects of increased photosynthesis on biomass accumulation.