• Journal of Plant Biology
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• v.33 no.2
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• pp.105-110
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• 1990

Physiological gradient of IAA-oxidizing enzyme activities was investigated in order to elucidate the mechanism of shoot differentiation in Cymbidium sp. (‘Jungfrau’) protocorms by using phenolic compounds (2, 4-dichlorophenol, catechol), auxin-inhibitors (PCIB, TIBA), and hormones (GA3, ABA, BA). The activity of IAA oxidase was decreased in protocorms treated with catechol decreased the catalytic activity of IAA oxidase or TIBA but this enzyme activity was increased after a temporary decrease at initial stages in the presence of 2, 4-dichlorophenol or PCIB. The activity of IAA oxidase in BA-treated protocorms (white and crown gall-like) was the highest of all. However, the catalytic activity of peroxidase increased after a temporary decrease at initial period. These results suggest that shoot differentiation and growth may be influenced by effective IAA levels in the protocorms causing IAA-oxidizing enzyme and phenolic compounds.

• Journal of Plant Biology
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• v.35 no.3
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• pp.265-271
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• 1992

Vie investigated the effect of indole acetic acid (IAA) on diamine oxidase (DAO; EC 1.4.3.6) in the seedling of soybean (Glycine max L. forma Paldalkong). DAO activity was not detected in the resting soybean seeds. During germination it appeared in the elongating zone on day 3, increased up to day 4 and decreased thereafter. Endogenous IAA content has been shown the same pattern as DAO activity. However, cadaverine content was reduced on day 4. To investigate the effect of IAA on DAO activity, the segments of hypocotyl on day 3 were soaked in various concentration of IAA. The activity increased at low concentrations ($10^{-7}-10^{-6}M$) of 1M as compared to that of control but not at high concentrations ($10^{-5}-10^{-4}M$) of IAA. Differing from DAO activity, cadaverine content increased as concentrations of IAA increased. On the other hand, ethylene was induced by IAA at high concentrations. To study the effect of ethylene on DAO activity, we cotreated IAA and 2,S-Norbonadiene (NDE). In this case, DAO activity was not affected.fected.

• Korean Journal of Plant Tissue Culture
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• v.25 no.2
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• pp.75-80
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• 1998

Disbudded epicotyl cuttings from light-grown 6-day-old seedings of Vigna angularis Owhi et Ohashi were preincubated in $2\;\times\;10^{-4}M$ IAA solution for 48 hr to promote adventitious root formation in upright or inverted direction and then incubated in upright direction for 96 hr. Adventitious root formation occurred only at the morphological base of the cuttings which were preincubated in upright direction, while at the both ends in inverted direction. IAA treatment enhanced the adventitious root formation in all cuttings regardless of their orientation during preincubation. To elucidate localized root development, the activity of enzymes involved in root initiation and development was measured 24 hr, 48 hr, and 148 hr after epicotyl incubation. IAA oxidase, peroxidase and catalase were assayed in the apical, middle and basal segment of the epicotyls, and their fresh weight and length were measured. Elongation occurred the most in the upper segment of the epicotyl while fresh weight gain was the most in the basal segment. At root initiation phase, 24 hr after incubation IAA peroxidase and catalase activities appeared high at rooting zone while IAA oxidase activity was low at both ends, IAA oxidase and peroxidase activities declined at the rooting zone during the adventitious root formation at 48 ht. Inversion of cuttings during preincubation caused a chrange of enzyme activities along their epicotyl cuttings. Only peroxidase activity showed a high correlation with root initiation. Therefore, the biochemical change is highly correlated with change in IAA level in the rooting zone of the epicotyl, resulting in root formation in unusual rooting zone of epicotyl.

• Applied Biological Chemistry
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• v.33 no.2
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• pp.125-128
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• 1990

Previous work has shown that the levels of free and total IAA and tryptophan decrease on exposing etiolated pea (Pisum sativum L. var. Sparkle) seedlings grown at $25^{\circ}C$ to $5^{\circ}C$ for 3 days, suggesting that low temperature down-regulates the level of endogenous IAA, in part, by reducing tryptophan biosynthesis. To understand, in this study, the effect of low temperature on the regulation of IAA degradation system in etiolated pea seedlings, enzyme levels of IAA degradation system and hydrogen peroxide content were analyzed during and after chilling($5^{\circ}C$) 6-day-old pea seedlings grown at $25^{\circ}C$. The levels of IAA oxidase and peroxidase increased during chilling and gradually restored to the level of control on termination of chilling. Catalase levels decreased upon chilling and increased to the level of control on termination of chilling. $H_2O_2$ was accumulated during chilling up to the level of $5.5\;{\mu}mol/g$ fresh weight while at $25^{\circ}C$ maintained a relatively constant $H_2O_2$ level of $4\;{\mu}mol/g$ FW. All together, it appears that low temperature, in part, by increasing enzyme levels of IAA degradation system and accumulating $H_2O_2$, down-regulates endogenous level of IAA in etiolated pea shoots.

• Journal of Plant Biology
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• v.35 no.4
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• pp.409-414
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• 1992

Effect of quercetin, a kind of natural plant flavonoids, on auxin-induced ethylene production in barley coleoptiles was studied. Auxin-induced ethylene production was apparently stimulated by quercetin. This stimulatory effect of quercetin appeared after 4 h of incubation period. Ethylene production was stimulated 200% over the control after 8 h of incubation by $3{\times}10^{-5}\;M$ quercetin. The quercetin effect was most prominent at $10^{-4}\;M$ of IAA. Ethylene production induced by the synthetic auxin, 2,4-D and NAA, was not significantly affected by quercetin. Also ACC-based ethylene production was unaffected by the flavonoid. In an effort to elucidate mechanisms of quercetin action on auxin-induced ethylene production, the effect of quercetin on 1M metabolism was studied. Data obtained from these experiments indicate that quercetin treatment resulted in about 90% inhibition of IAA oxidase activity. IAA ($3{\times}10^{-5}\;M$) conjugation was found to be not affected by quercetin. This results suggest that the stimulatory effect of quercetin on auxin-induced ethylene production may be due to the fact that quercetin inhibits 1M oxidase activity, thus increasing the free IAA level.

• Journal of Plant Biology
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• v.32 no.2
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• pp.89-99
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• 1989

The effect of IAA on lysine decarboxylase(LDC)activity, diamine oxidase (DAO) activity and the polyamine level in seedlings of soybean were investigated. The seedlings of soybean were treated with IAA (10-8M, 10-6M, 10-4M) and LDC activity, DAO activity and polyamine levels of cotyledon, elongating hypocotyl, elongated hypocotyl and the root were measured after 4, 6, 8, 10 days. Increased concentration of IAA stimulated the LDC activity and increased the level of polyamine in the seedlings, which reducing the DAO activity and polyamine level was increased in the seedlings. The light also stimulated the IAA effect on polyamine level and DAO activity, and polyamine level was higher in the seedlings grown in the light than those in the dark. Cadaverine was the most abundant polyamine in the seedlings of soybean. The levels of diamines, cadaverine, putrescine were higher in the elongated hypocotyl and root than in the elongating hypocotyl, but the levels of spermidine and spermine were relatively higher in the cotyledon than in the other parts. Accumulation of diamines by high concentration of IAA is postulated to be a phenomenon of inhibition in seedlings growth.

• Applied Biological Chemistry
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• v.28 no.1
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• pp.28-35
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• 1985

Potato tubers treated at $4^{\circ}C$ for 4 weeks were irradiated with a dose of 0.12 kGy from $^{60}Co$ source and stored at $20^{\circ}C,\;70{\sim}90%$ humidity for 5 weeks. Changes of ${\alpha}-amylase$, peroxidase, indole acetic acid oxidase, indole acetic acid synthesizing enzyme activities were determined. In addition, treatment of gibberellin or indole acetic acid to tubers irradiated were carried out to examine reversal of sprout-inhibition of tubers irradiated. Results are as follows; 1. Irradiation by ${\gamma}-ray$ at 0. 12 kGy dose inactivated easily the enzyme activities in vitro. $D_{37}$ values obtained were 0.94, 0.36 kGy for ${\alpha}-amylase$ and peroxidase, respectively 2. Complete inhibition of the toter sprouting was resulted by the irradiation of tubers with a dose of 0.12 kGy. 3. The indole acetic acid oxidase activity increased 2 times immediately after irradiation. Meanwhile, indole acetic acid synthesizing activity decreased about $50{\sim}75%$ for 5-week storage in irradiated potatoes, whereas the activity increased about 3.5 times along with sprouting in non-irradiated tubers. 4. In morphological aspects, deformed buds with necrosis in the meristmatic tissue were developed in irradiated tubers. Treatment of gibberellin or indole acetic acid at the concentration of 100 or 20 ppm to the irradiated tubers reversed the sprout-inhibition partially. Nevertheless, the deformed buds remained without change.

• Applied Biological Chemistry
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• v.26 no.2
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• pp.132-136
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• 1983

The indole-3-acetic acid(IAA) oxidase activity of shoot and root tips of etiolated pea seedlings (Pisum sativum L. var. Sparkle) during and after chilling was determined. The IAA oxidase level of root tips was 4 to 15 times as high as that of shoot tips. During chilling the seedlings apical and subapical 5 mm shoot sections increased in IAA oxidase activity but apical and subapical 5 mm root sections decreased. When chilled plants were returned to $25^{\circ}C$ to recover, the enzyme activity had a tendency to restore to the activity level of controlled plants.

• Journal of Life Science
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• v.20 no.5
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• pp.745-749
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• 2010

This study was conducted to examine the effect of cytokinin ($N^6$-benzyladenine; BA) and/or an IAA on ethylene production of maize (Zea mays) primary roots. When the two hormones were applied exogenously, both hormones synergistically increased ethylene production, which was greater than the sum of the level of each hormone's effect. For example, the ethylene production was stimulated between about 87% and 170% of the control by $10^{-4}\;M$ BA with $10^{-4}\;M$ IAA for 8 hours respectively, whereas the ethylene production was increased by about 480% of the control when the two hormones were treated simultaneously. Such a synergistic effect was also found in changes in the activity and gene expression level of ACC synthase. However, in the case of ACC oxidase did not show any observable effects. Based on our results, it is possible to conclude that BA and IAA stimulated the ethylene production synergistically by affecting the ACC synthase in maize roots.

• Journal of Life Science
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• v.24 no.12
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• pp.1364-1370
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• 2014

Ascorbic acid (AA) is a multifunctional metabolite in plants that is essential for plant development and growth. We examined the effect of AA, an antioxidant, on the gravitropic response of primary roots in maize. The application of $10^{-3}$ M AA to the elongation zone did not affect the gravitropic response and slightly inhibited the root growth. However, treatment with both $10^{-5}$ M and $10^{-3}$ M AA at the root tip increased the gravitropic response and inhibited root growth. Differences in indole-3- acetic acid (IAA) activity between the upper and lower hemispheres of the root resulted in differential elongation along the horizontal root. Roots are extremely sensitive to IAA, and increasing the amount of IAA in the lower hemisphere of the root inhibited elongation. Therefore, we examined the effect of IAA in the presence of AA. The inhibitory effect of AA on the gravitropic response was greater in combination with IAA. To understand the role of AA in the regulation of root growth and the gravitropic response, we measured ethylene production in the presence of AA in the primary roots of maize. AA stimulated ethylene production via the activation of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene, which regulates the conversion of ACC to ethylene. These results suggest that AA alters the gravitropic response of maize roots through modification of the action of ethylene.