• Title, Summary, Keyword: photosynthesis

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Analysis of Concept's Proximity of 7th Grade Students' Photosynthesis Concepts by the Level of Science Attitude (7학년 학생의 과학 태도 수준에 따른 광합성 관련 개념의 근접성 변화 분석)

  • Lee, Hee-Jeong;Kim, Youngshin
    • Journal of The Korean Association For Science Education
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    • v.32 no.10
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    • pp.1524-1536
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    • 2012
  • Science attitudes affect the quality of learning, and they are considered as one of the major concerns in science education. It is necessary to analyze the proximity between concepts with science attitudes. Accordingly, this study was designed to analyze the proximity of the concept related to photosynthesis as it changed after class according to the levels of science attitudes. A survey on the concept of photosynthesis and science attitudes before and after class was conducted on 270 7th-grade students. The concept of photosynthesis was composed of 'the place of photosynthesis,' 'products of photosynthesis,' 'reactants of photosynthesis,' and 'environmental factors.' The proximity of the concept of photosynthesis was analyzed through the utilization of multidimensional scaling (MDS). The research results were as follows: (1) Students changed the proximity between concepts by acquiring concrete concepts through class. (2) The upper group in science attitudes tends to be closer to the proximity between scientific concepts through class, compared to the intermediate and lower groups. (3) In all students with entire levels of science attitudes, non-scientific concepts continued to exist even after class, and the non-scientific concepts were deemed to interfere with the proximity between scientific concepts related to photosynthesis. (4) Students turned out to be aware of the concepts related to each other in four areas associated with photosynthesis. That is, it can be said that students are closely aware of the place where photosynthesis can occur and the materials needed as well as materials generated as a result of photosynthesis and the materials needed in terms of concepts related to photosynthesis.

Alteration of Gas Exchange in Rice Leaves Infected with Magnaporthe grisea

  • Yun, Sung-Chul;Kim, Pan-Gi;Park, Eun-Woo
    • The Plant Pathology Journal
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    • v.16 no.5
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    • pp.257-263
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    • 2000
  • Infection with rice blast fungus (Magnaporthe grisea) significantly reduced foliar net photosynthesis (A) of rice cultivars: Ilpoom, Hwasung, and Choochung in greenhouse experiments. By measuring the amount of diseased leaf area with a computer image analysis system, the relation between disease severity (DS) and net photosynthetic rate was curvilinearly correlated (r=0.679). Diseased leaves with 35% blast symptom can be predicted to have a 50% reduction of photosynthesis. The disease severity was linearly correlated (r=0.478) with total chlorophyll (chlorophyll a and chlorophyll b) per unit leaf area(TC). Light use efficiency was reduced by the fungal infection according to the light response curves. However, dark respiration (Rd) did not change after the fungal infection (p=0.526). Since the percent of reduction in photosynthesis greatly exceeded the percent of leaf area covered by blast lesions, loss of photosynthetic tissue on an area basis could not by itself account for the reduced photosynthesis. Quantitative photosynthetic reduction can be partially explained by decreasing TC, but cannot be explained by decreasing Rd. By photosynthesis (A)-internal CO$_2$ concentration (C$_i$ curve analysis, it was suggested that the fungal infection reduced ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity, ribulose-1,5-bisphosphate (RuBP) regeneration, and inorganic phosphate regeneration. Thus, the reduction of photosynthesis by blast infection was associated with decreased TC and biochemical capacity, which comprises all carbon metabolism after CO$_2$ enters through the stomata.

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Effects of Teaching Based on Driver's Conceptual Change Model on Rectifying High School Students' Misconception of Photosynthesis and Respiration (Driver의 개념변화 학습 모형을 적용한 수업이 고등학생들의 식물의 광합성과 호흡의 오개념 교정에 미치는 효과)

  • Kim, Dong-Ryeul
    • Journal of The Korean Association For Science Education
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    • v.29 no.6
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    • pp.712-729
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    • 2009
  • This study aims to research high school students' misconception of botanic photosynthesis and respiration, and as the measure of rectifying the misconception, to develop the teaching program based on Driver's conceptual change model, applying it to classes and observing the effect. Selected as the research subject was sixty-six students in 1st year of a highschool located in Busan who had chosen Biology Learning as discretionary subject, with their conceptual level on botanic photosynthesis and respiration researched through tests in drawing and descriptive writing. As a consequence of applying drawing as a way of classifying the levels of students' misconception on photosynthesis and respiration, many students' drawings included their misconception caused by textbooks or scientists, but after application of Driver's conceptual change model, they drew scientific drawings including the fundamental factors of botanic photosynthesis and respiration such as light, carbon dioxide, water, glucose, oxygen, leaf, chloroplast, mitochondria, stoma, and energy. Likewise, as a result of the descriptive writing test implemented for researching the students' conception on the various aspects of botanic photosynthesis and respiration, many students in the pretest showed misconception on the point of time and location at which botanic photosynthesis and respiration occur, botanic nutrient, the role of a leaf in photosynthesis, and the relation between botanic photosynthesis and respiration, but after teaching based on Driver's conceptual change model, their misconceptions on photosynthesis and respiration were rectified to a high degree.

Changes of Rutin Content and Photosynthesis Rate of Korean Buckwheat Cultivars under Various Environmental Stresses

  • Yoon, Byeong-Sung;Kwun, Hyok-Oun;Shin, Sang-Eun;Jin, Cheng-Wu;Yu, Chang-Yeon;Cho, Dong-Ha
    • Korean Journal of Medicinal Crop Science
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    • v.11 no.4
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    • pp.284-288
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    • 2003
  • This study was conducted to classify photosynthesis rate and changes of rutin content of Korean buckwheat (cv. Chunchon-jaerae and Yangjeul-memil) treated with salinity, UV-C and low temperature. In case of cv. Chunchon-jaerae and Yangjeul-memil, according to the salt stress, transpiration rate, stomatal conductance and photosynthesis rate were decreased. Both cultivars also showed decrease of transpiration rate and photosynthesis rate under the UV-C. Rutin contents within leaf and stem of cv. Yangjeul-memil were decreased when NaCl concentration was high. Rutin contents within leaf and stem of cv. Yangjeul-memil were generally decreased when the time laps under the UV-C stress. Rutin contents within leaf and stem of cv. Chunchon-jaerae was also generally decreased when the time laps under the low temperature stress.

Studies on the Leaf Photosynthesis of Salt-Stressed Rice Cultivars (염류처리에 따른 벼의 개엽광합성에 관한 연구)

  • 조동하
    • Korean Journal of Plant Resources
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    • v.7 no.1
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    • pp.97-101
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    • 1994
  • The effects of NaCl salinity on the leaf photosynthesis and water relation of two cultivars of rice(Oryza sativa L.) , the salt-tolerant cultivar Seohae and the salt-senstive cultivar Iri-380 were exam-ined. Two cultivars of rice were grown for 14 days in nutrient solution at SOmM NaCl. Comparing theieaf Na content of two cultlvars, Seohae showed high accumulation of Na content in the leaf blade, while Iri-380 showed low. The Na content in leaf blade reduced the rate of leaf photosynthesis. Salt-tolerant cultivar Seohae was less decreased the rate of leaf photosynthesis than salt- sensitive cultivarIri-380. And Seohae showed larger decreased the osmotic potential in the leaves than Iri-380. This in-dicates that in the salt-tolerant cultivar, osmotic adjustment is developed under saliniEation.

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Effect of $TO_3$ and $NO_2$ on Net Photosynthesis, Transpiration and Accumulation of Nitrite in Sunflower Leaves

  • Park, Shin-Young;Lee, Sang-Chul
    • Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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    • v.3 no.2
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    • pp.121-129
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    • 1999
  • Photosynthesis and transpiration rates were simultaneously measured in attached sunflower leaves(Helianthus annuusL. cv. Russian Mammoth) during exposure to $NO_2$ and $O_3$ to determine the effect of mixed gan on photosynthesis and the stomatal aperture. The application of $O_3$ alone reduced both the net photosynthetic and transpiration rates. An analysis of the $CO_2$ diffusive resistances indicated that the main cause affecting photosynthesis reduction during $O_3$ exposure was not the internal gas phase of the leaf $(rCO_2^{liq})$ but rather the liquid phase or mesophyll diffusive resistance $(rCO_2^{liq})$, suggesting that there is a very concomitant relation between photosynthetic reduction and $rCO_2^{liq}$. The application of NO2 alone caused a marked reduction of the net photosynthesis yet no significant reduction of transpiration, indicating that NO2 affects the $CO_2$ fixation processes with no inluence on the stomatal aperture. A greter reduction in the photosynthesis of sunflower plants was caused by the application of $NO_2$ alone as compared to a combination of $NO_2$ and $O_3$. $NO_2$ alone reduced the photosynthetic rate by 90%, whereas a mixture of NO2 and O3 reduced it by 50%.

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Analysis of Concept's Diversity and Proximity for Photosynthesis in Grade 7 Students

  • Lim, Soo-Min;Jeong, Jae-Hoon;Kim, Youngshin
    • Journal of The Korean Association For Science Education
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    • v.32 no.6
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    • pp.1050-1062
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    • 2012
  • Concepts of science have been developed by occupying 'ecological niche' within conceptual ecology. The ecological niche is determined from the mutual effect between intellectual environmental of the learner and new concept, which few studies have been conducted. This study examined how the ecological niche of the concept of photosynthesis in $7^{th}$ grade is changed by instruction. The ecological niche was analyzed using 2 methods: (1) the change in the diversity of concepts, and (2) the change in the proximity of concepts based on the frequency and the relativeness score of the concepts. The concept of photosynthesis was analyzed in the 4 domains in the place of photosynthesis, products of photosynthesis, reactants of photosynthesis, and environmental factors. The results of this study are as follows: (1) reduced diversity of concepts, (2) increased frequency and relativeness score of the scientific concepts, and (3) increased proximity of the scientific concepts by instruction. With these results, the mutual effects of the concepts within the conceptual ecology have become active by class to differentiate the relationships between the concepts, which accordingly displayed their changes in status.

Hydrogen Evolution from Biological Protein Photosystem I and Semiconductor BiVO4 Driven by Z-Schematic Electron Transfer

  • Shin, Seonae;Kim, Younghye;Nam, Ki Tae
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.251.2-251.2
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    • 2013
  • Natural photosynthesis utilizes two proteins, photosystem I and photosystem II, to efficiently oxidize water and reduce NADP+ to NADPH. Artificial photosynthesis which mimics this process achieve water splitting through a two-step Z-schematic water splitting process using man-made synthetic materials for hydrogen fuel production. In this study, Z-scheme system was achieved from the hybrid materials which composed of hydrogen production part as photosystem I protein and water oxidizing part as semiconductor BiVO4. Utilizing photosystem I as the hydrogen evolving part overcomes the problems of existing hydrogen evolving p-type semiconductors such as water instability, expensive cost, few available choices and poor red light (>600 nm) absorbance. Some problems of photosystem II, oxygen evolving part of natural photosynthesis, such as demanding isolation process and D1 photo-damage can also be solved by utilizing BiVO4 as the oxygen evolving part. Preceding research has not suggested any protein-inorganic-hybrid Z-scheme composed of both materials from natural photosynthesis and artificial photosynthesis. In this study, to realize this Z-schematic electron transfer, diffusion step of electron carrier, which usually degrades natural photosynthesis efficiency, was eliminated. Instead, BiVO4 and Pt-photosystem I were all linked together by the mediator gold. Synthesized all-solid-state hybrid materials show enhanced hydrogen evolution ability directly from water when illuminated with visible light.

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