• Journal of Plant Biology
• /
• v.31 no.3
• /
• pp.227-237
• /
• 1988

Effects of putrescine on senescence in detached leaves of Chinese cabbage (Brassica campestris L.) in the light were investigated. The putrescine as a potent antisenescence substane markedly inhibited chlorophyll and protein loss at the 10mM concentraton in the detached leaves during the dark incubation. In the light, however, putrescine showed the opposite effects to dark incubation. The chlorphyll loss by putrescine in the light was stopped with darktransfer, and inhibited competitively by a divalent cation Ca2+. In the light, putrescine reduced the protease activity. Putrescine, in the light, increased H2O2 content and reduced the activities of enzymes -superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6-involved in inhibiting the accumulation of free radicals. These results suggest that the effects of puterscine on chlorophyll and protein loss in detached leaves of Chinese cabbage in the light are related to the cationic nature of putrescine and the accumulation of free radicals.

• Journal of Plant Biology
• /
• v.31 no.4
• /
• pp.299-307
• /
• 1988

The electron transport activities of choloroplasts isolated from hte detached rise (Oryza sativa L. cv. Chucheong) leave stored under low temperature(4$^{\circ}C$) with light illumination were investigated to understand the role of light in the low temperature inhibition of photosynthesis in the chilling-sensitive plants. Chlorophyll content of the detached leaves upon incubation at 28$^{\circ}C$ and 4$^{\circ}C$ in the dark was also measured. The rice seedlings were grown with Hoagland medium in the growth chamber of 28$^{\circ}C$ temperature and 400 ft.c fluorescent light with the photoperiod of 16 h. Although chlorophyll content of the detached leaves stored in the dark declined by 61.7% after 28$^{\circ}C$ treatement, there occurred only 5.2% decrease of chlorophyll with 4$^{\circ}C$ treatment. Low temperature treatment(4$^{\circ}C$) for 6 days brought about decreases in total photosystem(PS II＋PS I) activities by 35.2% and 73.6% in te presence and absence of light, respectively, while after 28$^{\circ}C$ treatment of the detached leaves for 6 days in the dark there was only 27.6% decrease in PS II＋PS I activity. PS II activities were also decreased by 35.6% and 72.2% in the light and dark, respectively. PS I activities were decreased slightly, however, by 7.6% and 16.2% in the light and dark, respectively. Investigations into DPClongrightarrowDCPIP and NH2OHlongrightarrowDCPIP activities revealed that low temperature inhibition of PS II activities was not due to the inactivation of the water oxidation capacity at low temperature. It was concluded that light protects the electron transport activities of isolated rice chloroplasts from the inhibitory effect of low temperature in the detached leaves.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.4 no.4
• /
• pp.231-240
• /
• 2000

Effects of Jasmonic Acid and Wounding on Polyphenol Oxidase Activity in Senescing Tomato Leaves The effects of jasmonic acid(JA) and wounding on polyphenol oxidase(PPO) during leaf senescence was investigated by measuring the PPO activity in detached tomato(Lycopersicon esculentum Mill.) leaves of two-week-old seedlings. The PPO activity in the detached senescing leaves increased significantly in the dark. The leaf segments responded to the application of JA with accelerated senescence, as indicated by the loss of chlorophyll and rapid increase in the PPO activity. The senescence-promoting action of JA differed in the light and dark. Wounding the detached senescing leaves by scraping surface segments or making punctures with needles considerably delayed the loss of chlorophyll and had a significant effect on the PPO activity, the amounts of which were roughly proportional to the intensity of the wounding. In the dark, the combination of wounding plus JA resulted in stable levels of chlorophyll and PPO. JA and ABA acted similarly in both unwounded and wounded leaves, however, the amount of chlorophyll and PPO in the wounded segments was always higher than in the respective controls. JA was found to eliminate the senescence-retarding action of benzyladenine. In a histochemical localization test, the PPO activity was found to be localized in the cell walls of the parenchyma tissue, thereby indicating moderate cytoplasmic reactions. In the JA-treated plants, the PPO activity was intense in the cells of the cortex and phloem parenchyma. Accordingly, based on these observations it would appear that PPO is a component of a defense response maker, whereas JA plays an integral role in the intracellular signal transduction involved in inducible defense mechanisms.

• Research in Plant Disease
• /
• v.29 no.1
• /
• pp.82-87
• /
• 2023

Exogenous ferrous chloride (FeCl₂) suppressed in vitro growth of Ralstonia pseudosolanacearum, causing bacteria for tomato bacterial wilt. More than 50 μM of FeCl₂ reduced the in vitro bacterial growth in dosedependent manners. Two to 200 μM of FeCl₂ did not affect the fresh weight of detached tomato leaves at 3 and 5 days after the petiole dipping without the bacterial inoculation. The bacterial wilt of the detached tomato leaves was evaluated by inoculating two different inoculum densities of R. pseudosolanacearum (10⁵ and 10⁷ cfu/ml) in the presence of FeCl₂. Bacterial wilt in the detached leaves by 10⁵ cfu/ml was efficiently attenuated by 10-200 μM of FeCl₂ at 3 and 5 days post-inoculation (dpi), but bacterial wilt by 10⁷ cfu/ml was only reduced by 200 μM of FeCl₂ at 3 and 5 dpi. These results suggest that iron nutrients can be included in the integrated disease management of tomato bacterial wilt.

• Journal of Environmental Science International
• /
• v.1 no.2
• /
• pp.69-80
• /
• 1992

Effects of light on leaf senescence of Phseolus vulgaris were investigated by measuring the disassembly of chlorophyll-protein complexes in detached leaves which had been kept in the dark or under light. The loss of chlorophyll accompanied by degradation of chlorophyll- protein complexes. PSI (photosystem I) complex containing LHCI (light harvesting complex of PSI) apoproteins was rapidly decreased after the early stage of dark-induced senescence. RC(reaction center)-Cores was slightly increased until 4 d and slowly decreased thereafter. As disassembly of LHCII trimer progressed after the late stage of senescence, there was a steady increase in the relative amount of SC(small complex)-2 containing LHCII monomer. On the other hand, white and red light adaptation caused the structural stability of chlorophyll-protein complexes during dark-induced senescence. Particularly, red light was more effective in the retardation of LHCII breakdown than white light, whereas white light was slightly effect in protecting the disassembly of PSI complex compared to red light. These results suggest, therefore, that light may be a regulatory factor for stability of chlorophyll-protein complexes in the senescent leaves.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.2 no.1
• /
• pp.37-48
• /
• 1998

Effect of plant hormones on the leaf senescence of mung bean (Phaseolus radiatus) was investigated by measuring the changes of reducing sugar contents and invertase isozyme activities in detached leaves treated with NAA, $GA_3$ or BA. During dark-induced senescence, reducing sugar contents in the detached leaves increased temporarily at 4 d, thereafter decreased rapidly and reached minimum values within 7-14 d. The pattern of soluble acid invertase activity in the senescing leaves kept in the dark was similar to that of reducing sugar accumulation, whereas the activities of alkaline and extracellular invertases were not significantly changed during leaf senescence. Therefore, these results suggest that soluble acid invertase, but not alkaline and extracellular invertases, induces the accumulation of reducing sugar during leaf senescence of mung bean plants. Exogenous NAA application had little or no effect in the increase of soluble acid invertase activity during dark-induced senescence compared to the control. However, exogenous applications of $GA_3$ and BA led to the increase of soluble acid invertase activity in the senescing leaves. Particularly, BA application was very effective in enhancing the activity of soluble acid invertase as well as in delaying chlorophyll breakdown during dark-induced senescence. These results suggest, therefore, that BA regulates the activity of soluble acid invertase, which leads to the accumulation of reducing sugar, and the stability of photosynthetic apparatus to delay leaf senescence.

• Journal of Environmental Science International
• /
• v.2 no.1
• /
• pp.37-48
• /
• 1993

Effect of plant hormones on the leaf senescence of mung bean (Phseoln radiatus) was investigated by measuring the changes of reducing sugar contents and invertase isozyme activities in detached leaves treated with NAA, $GA_3$ or BA. During dark-induced senescence, reducing sugar contents in the detached leaves increased temporarily at 4 6, thereafter decreased rapidly and reached minimum values within 7-14 6. The pattern of soluble acid invertase activity in the senescing leaves kept in the dark was similar to that of reducing sugar accumulation, whereas the activities of alkaline and extracellular invertases were not significantly changed during leaf senescence. Therefore, these results suggest that soluble acid invertase, but not alkaline and extracellular invertases, induces the accumulation of reducing sugar during leaf senescence of Rung bean plants. Exogenous NAA application had little or no effect In the increase of soluble acid invertase activity during dark-induced senescence compared to the control. However, exogenous applications of $GA_3$ and BA led to the increase of soluble acid invertase activity in the senescing leaves. Particularly, BA application was very effective In enhancing the activity of soluble acid invertase as well as in delaying chlorophyll breakdown during dark-induced senescence. These results suggest, therefore, that BA regulates the activity of soluble acid invertase, which leads to the accumulation of reducing sugar, and the stability of photosynthetic apparatus to delay leaf senescence.

• Mycobiology
• /
• v.32 no.4
• /
• pp.155-159
• /
• 2004

N-Methylhydrasteine hydroxylactam and 1-methoxyberberine chloride, both alkaloids, extracted from Corydalis longipes have been assayed for their activities against two powdery mildews. The spore germination of Erysiphe cichoracearum on detached leaf of balsam(Impatiens balsaminia) following pre- and post-inoculation treatments by their mixture has shown high efficacy against the pathogen at 100, 200 and 300 ${\mu}g/ml$. The mixture was also effective at both pre- and post-inoculation treatments at 500, 1000, 1500 ${\mu}g/ml$ doses against E. pisi causing pea powdery mildew in pea(Pisum sativum) under field conditions. The significant efficacy of the mixture of two compounds against spore germination on detached leaves of balsam and also under field conditions in pea warrants its inclusion in trials against some other diseases under field conditions.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.1 no.2
• /
• pp.69-80
• /
• 1997

Effects of light on leaf senescence of Phaseolus vulgaris were investigated by measuring the disassembly of chlorophyll-protein complexes in detached leaves which had been kept in the dark or under light. The loss of chlorophyll accompanied by degradation of chlorophyll-protein complexes. PSI (photosystem I) complex containing LHCI (light harvesting complex of PSI) apoproteins was rapidly decreased after the early stage of dark-induced senescence. RC(reaction center)-Core3 was slightly increased until 4 d and slowly decreased thereafter. As disassembly of LHCII trimer progressed after the late stage of senescence, there was a steady increase in the relative amount of SC(small complex)-2 containing LHCII monomer. On the other hand, white and red light adaptation caused the structural stability of chlorophyll-protein complexes during dark-induced senescence. Particularly, red light was more effective in the retardation of LHCII breakdown than white light, whereas white light was slightly effect in protecting the disassembly of PSI complex compared to red light. These results suggest, therefore, that light may be a regulatory factor for stability of chlorophyll-protein complexes in the senescent leaves.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2007.04a
• /
• pp.65-73
• /
• 2007

The objective of this study is to understand how regulatory mechanisms respond to sugar status for more efficient carbon utilization and source-sink regulation in plants. So, we need to identify and characterize many components of sugar-response pathways for a better understanding of sugar responses. For this end, genes responding change of sugar status were screened using Arabidpsis cDNA arrays, and confirmed thirty-six genes to be regulated by sucrose supply in detached leaves by RNA blot analysis. Eleven of them encoding proteins for amino acid metabolism and carbohydrate metabolism were repressed by sugars. The remaining genes induced by sugar supply were for protein synthesis including ribosomal proteins and elongation factors. Among them, I focused on three hydrolase genes encoding putative $\beta$-galactosidase, $\beta$-xylosidase, and $\beta$-glucosidase that were transcriptionally induced in sugar starvation. Homology search indicated that these enzymes were involved in hydrolysis of cell wall polysaccharides. In addition to my results, recent transcriptome analysis suggested multiple genes for cell wall degradation were induced by sugar starvation. Thus, I hypothesized that enzyme for cell wall degradation were synthesized and secreted to hydrolyze cell wall polysaccharides producing carbon source under sugar-starved conditions. In fact, the enzymatic activities of these three enzymes increased in culture medium of Arabidopsis suspension cells under sugar starvation. The $\beta$-galactosidase encoded by At5g56870 was identified as a secretory protein in culture medium of suspension cells by mass spectrometry analysis. This protein was specifically detected under sugar-starved condition with a specific antibody. Induction of these genes was repressed in suspension cells grown with galactose, xylose and glucose as well as with sucrose. In planta, expression of the genes and protein accumulation were detected when photosynthesis was inhibited. Glycosyl hydrolase activity against galactan also increased during sugar starvation. Further, contents of cell wall polysaccharides especially pectin and hemicellulose were markedly decreased associating with sugar starvation in detached leaves. The amount of monosaccharide in pectin and hemicellulose in detached leaves decreased in response to sugar starvation. These results supported my idea that cell wall has one of function to supply carbon source in addition to determination of cell shape and physical support of plant bodies.