Changes In Chlorophyll Fluorescence Research Articles

Изменения в хлорофилната флуоресценция на симна обикновена пшеница в зависимост от заплевеляването и срока на внасянето на набор от хербициди

Изменения в хлорофилната флуоресценция на симна обикновена пшеница в зависимост от заплевеляването и срока на внасянето на набор от хербициди

Drought- and frost-induced accumulation of soluble carbohydrates during accelerated senescence in Quercus pubescens

Different environmental conditions affect tree senescence by different patterns of carbohydrate concentrations and have specific impact on the dissection of the photosynthetic apparatus. A proactive cultivation of Mediterranean broadleaf species, including oaks, has been suggested to fill possible temporal and spatial gaps in forestry created by Climate Change in Central Europe in the future. Climate can affect trees in several different ways, e.g., by modulating the course of leaf senescence. Senescence-associated processes, like regulation of carbohydrates and changes in chlorophyll fluorescence under drought stress conditions were studied with leaf tissue of drought-tolerant downy oak (Quercus pubescens). Two months of consistent drought stress in a frost-free greenhouse led to significantly earlier senescence and significant increased amounts of soluble sugars in the leaves of the drought-stressed group in comparison to a well-watered control group. Similar sugar accumulation was observed in trees outdoors, after exposure to frost. In contrast to monocarpic plants the accumulation of free sugars is neither triggering leaf senescence, nor is it a side effect of age-depending changes in Q. pubescens. Instead, sugar accumulation is induced by abiotical factors, like drought and frost. Furthermore, we suggest that the senescence process in the absence of drought stress or frost depends on the source status of the leaf, which, in term, is a function of light (through photosynthesis) and night temperature (through respiration). Contents of the storage metabolite starch decreased during late summer in all three groups. Drought-stressed plants showed a decline of the connectivity of photosystem II antenna, reflected as the L-band in the chlorophyll fluorescence induction curves, and stronger correlations between the declines in the capacity of photosynthetic dark reactions and electron transport-associated chlorophyll fluorescence parameters. We conclude that the disassembly of single parts of the photosynthetic apparatus during leaf senescence is a uniform process, but the onset of this process depends on abiotical environmental factors.

Dynamics of leaf gas exchange, chlorophyll fluorescence and stem diameter changes during freezing and thawing of Scots pine seedlings.

Boreal trees experience repeated freeze-thaw cycles annually. While freezing has been extensively studied in trees, the dynamic responses occurring during the freezing and thawing remain poorly understood. At freezing and thawing, rapid changes take place in the water relations of living cells in needles and in stem. While freezing is mostly limited to extracellular spaces, living cells dehydrate, shrink and their osmotic concentration increases. We studied how the freezing-thawing dynamics reflected on leaf gas exchange, chlorophyll fluorescence and xylem and living bark diameter changes of Scots pine (Pinus sylvestris L.) saplings in controlled experiments. Photosynthetic rate quickly declined following ice nucleation and extracellular freezing in xylem and needles, almost parallel to a rapid shrinking of xylem diameter, while that of living bark followed with a slightly longer delay. While xylem and living bark diameters responded well to decreasing temperature and water potential of ice, the relationship was less consistent in the case of increasing temperature. Xylem showed strong temporal swelling at thawing suggesting water movement from bark. After thawing xylem diameter recovered to a pre-freezing level but living bark remained shrunk. We found that freezing affected photosynthesis at multiple levels. The distinct dynamics of photosynthetic rate and stomatal conductance reveals that the decreased photosynthetic rate reflects impaired dark reactions rather than stomatal closure. Freezing also inhibited the capacity of the light reactions to dissipate excess energy as heat, via non-photochemical quenching, whereas photochemical quenching of excitation energy decreased gradually with temperature in agreement with the gas exchange data.

Ce3+ induces flavonoids accumulation by regulation of pigments, ions, chlorophyll fluorescence and antioxidant enzymes in suspension cells of Ginkgo biloba L.

Rare earth elements, a type of abiotic elicitor, were used to investigate the shift in the mechanism of flavonoid accumulation from primary metabolites in Ginkgo suspension cell culture. The changes in flavonoids, mineral ions, photosynthetic pigments, chlorophyll fluorescence and antioxidant enzymes with varying Ce3+ (Ce(NO3)3) doses (0.01–5.0 mM) were studied. Low doses of Ce3+ (0.01–0.1 mM) improved cell growth and the highest increased dry weight was 2.67 g L−1 medium at 0.1 mM Ce3+ dose. Moderate doses (0.5–1.0 mM) limited cell growth and initiated a self-protective mechanism through modulation of the pigments, ions and flavonoid content, chlorophyll fluorescence and antioxidant enzymes, while high doses (2.0–5.0 mM) inhibited the cell growth and even caused cell mortality. The chlorophyll content, K+, Zn2+ and growth mass peaked at 0.1 mM Ce3+. The Fv/Fm, and Fv′/Fm′ values, and the amounts of P, Ca2+, Fe2+ and Zn2+ reached a maximum at 0.5 mM Ce3+ while the flavonoids content was highest at 1.0 mM Ce3+ (11.1 mg L−1 medium). The antioxidant enzyme activities were high from 0.05 to 0.5 mM Ce3+. Moreover the changes of chlorophyll fluorescence images of the suspension cells were consistent with the cell growth, relative electrical conductivity (REC) and malondialdehyde (MDA) content with increasing Ce3+ doses. Our findings suggest doses of 0.1–0.5 mM Ce3+ in Ginkgo cells shifted the metabolism from primary to secondary processes, diverting the metabolism from growth to defense related pathways as a result of the flavonoids accumulation. The high ratio of Car/Chl t, high Car content and 0.5–1.0 mM Ce3+ were beneficial for the accumulation of flavonol glycosides in Ginkgo suspension cells.

Cold hardiness estimation of Pinus densiflora var. zhangwuensis based on changes in ionic leakage, chlorophyll fluorescence and other physiological activities under cold stress

Pinus densiflora var. zhangwuensis grows fast, and its drought and salinity resistance are better than Pinus sylvestris var. mongolica. We compared cold hardiness and mechanisms of cold hardiness between the two species, to provide a theoretical basis for promoting and applying P. densiflora var. zhangwuensis in cold regions. A cold stress experiment was carried out on 3-year-old plantlets of P. densiflora var. zhangwuensis and P. sylvestris var. mongolica after hardening at five temperature regimes, 5, −10, −20, −40, and −60 °C, respectively. Some indices of needle samples for both species were measured, such as relative conductivity (REL), maximum photochemical efficiency (Fv/Fm), malondialdehyde (MDA), catalase (CAT), proline (Pro), soluble sugar (SS), and stomata density. REL and MDA values of both species after hardening had the same trend of increasing, but the trend was opposite in Fv/Fm value with increasing cold stress. Compared with P. sylvestris var. mongolica, the P. densiflora var. zhangwuensis had smaller increases in REL and MDA, and a smaller decline in Fv/Fm during cold stress. Compared to the control, REL growth of P. densiflora var. zhangwuensis and P. sylvestris var. mongolica at −60 °C were 0.41 and 0.60, and MDA growth was 29.94 mol g−1 FW and 47.80 mol g−1 FW, and Fv/Fm declines were 0.08 and 0.27. Half-lethal temperatures (LT50) calculated by logistic equation for P. densiflora var. zhangwuensis and P. sylvestris var. mongolica were −58.23 and −50.34 °C, respectively. These data suggest that cold resistance of P. densiflora var. zhangwuensis is stronger than that of P. sylvestris var. mongolica. Cold-resistance mechanisms of the two species differed. In response to cold stress, P. sylvestris var. mongolica had strong osmotic adjustment ability because of higher Pro and SS content, while P. densiflora var. zhangwuensis had strong antioxidant ability due to stronger CAT activity. Stomata density and diameter of P. densiflora var. zhangwuensis were smaller, as were single leaf area and number of leaves per plant, both characteristics promoting survival in a cold environment. Greater shoot height and total biomass of seedlings of P. densiflora var. zhangwuensis might be another reason for its stronger cold tolerance.

Chlorophyll fluorescence and lipid peroxidation changes in rice somaclonal lines subjected to salt stress

The aim of the present work was to explore physiological changes provoked by somaclonal variation in response to salinity. Two parental cultivars (La Candelaria and Yerua) and their derived somaclones were used as a source for breeding new rice lines with improved salt tolerance. We studied the effect of NaCl salt stress on chlorophyll fluorescence-related parameters, such as the maximum quantum yield of primary PSII photochemistry (F v/F m) and the performance index for energy conservation from photon absorbed by PSII antenna (PIABS). In addition malondialdehyde (MDA) content and leaf temperature (LT) responses were also measured. In somaclonal lines, F v/F m, PIABS, MDA and LT showed coefficients of variation of 13.7, 39.3, 25.5, and 3 %, respectively, for La Candelaria and 1.4, 17.6, 34.4 and 3 % for Yerua. However, the fragrant character did not differ in the aromatic somaclonal lines with respect to their parentals. Our results suggest that the F v/F m ratio would not be as good marker of PSII vitality as PIABS for salinized rice somaclones, unless they are highly susceptible to salinity. On other hand, the MDA content showed a strong negative correlation with the PIABS content in somaclones of both rice cultivars, suggesting that MDA levels could also be used as an oxidative damage index in rice somaclones.

DIAGNOSING BITTER PIT IN APPLE DURING STORAGE BY CHLOROPHYLL FLUORESCENCE AS A NON-DESTRUCTIVE TOOL

Bitter pit is an important physiological disorder of apple that can develop on the tree but is most prevalent during storage. Delaying fruit maturation after harvest through controlled atmosphere storage and application of 1-MCP SmartFreshTM) can delay the onset of symptoms; however, significant losses may occur in long-term stored apples. It is hard to detect internal bitter pit using external examination alone. Current predictive methods are based on destructive internal quality assessments and mineral analysis. A non-destructive method to detect and predict the propensity of fruit to develop bitter pit at harvest and during the early stages of storage would improve store management practices. High risk ‘Bramley’ orchards were identified from over 100 orchards surveyed across the south east of UK in 2010/11. A subsample of susceptible orchards with fruit that consistently developed bitter pit in storage as well as orchards where fruit remained free from problems were selected. Trials were conducted over two consecutive seasons (2012/13 and 2013/14) to evaluate changes of chlorophyll fluorescence in SmartFreshTM treated and untreated ‘Bramley’ apples during storage. The relationship between chlorophyll fluorescence profiles and bitter pit incidence were similar in the presence or absence of SmartFreshTM. In the early stages of storage, the chlorophyll fluorescence profiles were able to distinguish between SmartFreshTM treated and untreated samples and correlated well with fruit maturity, rate of ethylene production and onset of bitter pit; however, they were less discriminatory in determining the severity of bitter pit in long-term storage. The most discriminant chlorophyll fluorescence characteristics correlated to bitter pit were identified. Models have been developed to predict the likely incidence and development of bitter pit during storage, although they are not capable of estimating severity of the disorder.

Non-destructive postharvest quality monitoring of different pear and sweet pepper cultivars

Postharvest quality changes of two pear and five sweet pepper varieties during cold storage (2±1 °C and 10±1 °C, respectively) and shelf-life (22±2 °C and 20±1 °C, respectively) by non-destructive optical methods (laser backscattering imaging, chlorophyll fluorescence analysis, surface colour measurement) and texture analysis methods (acoustic impulse-response technique, impact method) were determined and monitored. The rate of the change of ‘Conference’ pears’ Fv/Fm chlorophyll fluorescence parameter was lower than for ‘Bosc kobak’, referring to the cultivar characteristic and photosynthetically active chlorophyll content related maturity and colour change. Acoustic and impact stiffness decreased during shelf-life, referring clearly to temperature related textural change. Taking into account the seven different measuring wavelengths (650–1064 nm), laser scattering parameters showed significant and cultivar dependent changes versus time during cold storage and shelf-life. The used non-destructive methods were found to be suitable for objective sweet pepper quality determination. Cold storage combined shelf-life resulted in a relatively longer shelf-life, with a lower intensity and rate of quality decrease in time, based upon mass loss, stiffness, surface colour, and chlorophyll fluorescence changes. ‘Gigant’, ‘Carma’, and ‘Kárpia’ cultivars were found to be favourable, but ‘Kais’ and ‘Kun’ hot pepper samples were really sensitive to quality degradation.

Evaluation of yield and some physiological changes in corn and sorghum under irrigation regimes and application of barley residue, zeolite and superabsorbent polymer

In order to investigate the changes in chlorophyll fluorescence, chlorophyll, relative water content (RWC) and forage yield of corn and sorghum under various irrigation regimes and combination treatments of barley residue, zeolite and superabsorbent polymer, an experiment was conducted over 2 years in Kerman, Iran. A randomized complete block design arranged in a factorial split was used with three replications. Two irrigation regimes of normal and drought stress based on 70 and 140 mm cumulative pan evaporation, respectively, and two plant species (corn and sorghum) as factorial combinations were compared in the main plots. Five treatments, (1) 10 t ha−1 zeolite + 4.5 t ha−1 residue, (2) 60 kg ha−1 superabsorbent + 4.5 t ha−1 residue, (3) 5 t ha−1 zeolite + 30 kg ha−1 superabsorbent + 4.5 t ha−1 residue, (4) 4.5 t ha−1 residue and (5) – control, were compared in subplots. In both plants, forage yield, potential quantum yield (Fv/Fm), chlorophyll a, total chlorophyll and carotenoid contents decreased significantly under drought stress. Chlorophyll a content, SPAD index and Fv/Fm were higher in corn than in sorghum, but RWC was higher in sorghum. Corn produced higher forage yield (62.8 t ha−1) than sorghum (49.3 t ha−1). The application of 10 t ha−1 zeolite with 4.5 t ha−1 residue increased most traits more than any of the other treatments, but the superabsorbent had no significant effect on the studied traits.

Changes in cell density and chlorophyll fluorescence with salinity stress in two Isochrysis galbana strains (P rymnesiophyceae)

Changes in cell density and chlorophyll fluorescence with salinity stress in two Isochrysis galbana strains (P rymnesiophyceae)

Photosynthetic acclimation in shade-developed leaves of Euterpe edulis Mart (Arecaceae) after long-term exposure to high light

To analyze acclimation of Euterpe edulis seedlings to changes in light availability, we transferred three-year-old seedlings cultivated for six months under natural shade understory [≈ 1.3 mol(photon) m−2 d−1] to a forest gap [≈ 25.0 mol(photon) m−2 d−1]. After the transfer, changes in chlorophyll fluorescence and leaf gas-exchange parameters, as well as in the light-response curves of photosynthesis and photosynthetic induction parameters, were analyzed during the following 110 days. Simultaneously measured photosynthetic characteristics in the shaded seedlings grown in understory served as the control. Despite the fact that the understory seedlings were under suboptimal conditions to achieve their light-saturated net photosynthetic rate (PNmax), light-response curves and photosynthetic induction parameters indicated that the species had the low respiration rate and a fast opening of stomata in response to the intermittent occurrence of sunflecks, which exerted a feed-forward stimulation on PNmax. Sudden exposure to high light induced photoinhibition during the first week after the transfer of seedlings to gap, as it was shown by the abrupt decline of the maximal quantum yield of PSII photochemistry (Fv/Fm). The photoinhibition showed the time-dependent dynamics, as the Fv/Fm of the seedlings transferred to the forest gap recovered completely after 110 days. Furthermore, the net photosynthetic rate increased 3.5-fold in relation to priorexposure values. In summary, these data indicated that more than 21 days was required for the shade-acclimated seedlings to recover from photoinhibition and to relax induction photosynthetic limitations following the sudden exposure to high light. Moreover, the species responded very quickly to light availability; it highlights the importance of sunflecks to understory seedlings.

Diurnal regulation of photosynthesis in Jatropha curcas under drought during summer in a semi-arid region

The diurnal photosynthetic responses to drought in Jatropha curcas have not been well assessed under field conditions in harsh semi-arid habitats. To illustrate this, diurnal changes in chlorophyll fluorescence and gas exchange rates were measured in field-grown Jatropha with or without a short (13 days) water recovery treatment under drought conditions during hot summer in a semi-arid. Sensitive stomatal closure coordinated with a drying atmosphere strictly limited a net CO2 assimilation rate with a predominant morning peak, eventually turning negative during the day. Even though the risk of excess excitation energy which potentially causes photodamage increased with the extremely low capacity for CO2 fixation, Jatropha preserved the integrity of PSII. Quantitative analysis of quenching partitioning revealed that regulated thermal energy dissipation accounted a large fraction of both instantaneous and daily absorbed energy by up to 80 and 72%, respectively, under the drought condition. Water recovery treatment more than doubled daily CO2 uptake via mitigating diurnal stomatal closure. The regulated thermal dissipation flexibly adjusted PSII quantum efficiency to capacity of CO2 fixation. In addition, downregulation of PSII quantum efficiency via sustained regulated thermal dissipation was observed and thought to be an additional photoprotective function. It is clear that Jatropha strongly rely upon the regulated thermal dissipation under drought condition, which must be critically important for this strict water conserving species, especially under a climate with high solar radiation loads as is seen in semi-arid regions.

Drought-induced changes in chlorophyll fluorescence, photosynthetic pigments, and thylakoid membrane proteins of Vigna radiata

The effects of drought on chlorophyll fluorescence characteristics of PSII, photosynthetic pigments, thylakoid membrane protein (D1), and proline content in different varieties of mung bean plants were studied. Drought stress inhibits PSII activity and induces alterations in D1 protein. We observed a greater decline in the effective quantum yield of PSII, electron transport rate, and saturating photosynthetically active photon flux density (PPFDsat) under drought stress in var. Anand than var. K-851 and var. RMG 268. This may possibly be due to either downregulation of photosynthesis or photoinhibition process. Withholding irrigation resulted in gradual diminution in total Chl content at Day 4 of stress. HPLC analysis revealed that the quantity of β-carotene in stressed plants was always higher reaching maxima at Day 4. Photoinactivation of PSII in var. Anand includes the loss of the D1 protein, probably from greater photosynthetic damage caused by drought stress than the other two varieties.

Changes in chlorophyll content and fluorescence and fruit yield contributing traits in different genotypes of strawberry (Fragaria x ananassa DUCH.)

Analysis of changes in chlorophyll fluorescence parameters in strawberry leaves was based on a field experiment performed in the years 2009–2010. Ten genotypes including 5 cultivars: ‘Kent’, ‘Teresa’, ‘Senga Sengana’, ‘Chandler’ and the breeding clone 1387 as well as their inbred progeny, were the object of the study. During the experiment the following indicators were evaluated: chlorophyll a and b content in fresh leaf mass as well as fluorescence parameters: minimum (F0) and maximum fluorescence yield (Fm), photochemical efficiency of PS II (Fv/Fm), actual quantum yield of PSII photochemistry (Y), minimum (F0’) and maximum efficiency of fluorescence (Fm’) in the light, coefficient of photochemical (qP) and non-photo- chemical (qN) fluorescence quenching. In this work, we also examined the effect of repeated inbreeding on strawberry fruit yield and yield components. The analysis of changes of these parameters showed that inbreeding caused a reaction in all tested cultivars. In all inbred progeny, chlorophyll a and b content decreased compared to the cultivars. Generally, the photoche- mical efficiency of photosystem II (Fv/Fm) and the parameter ΔF/ Fm’ were not affected by strong inbreeding. In analyzing the values of the coefficients qP and qN, it has been observed that changes in their values depend on the sensitivity of the examined genotypes to self-pollination. The functioning of PS II is the most sensitive indicator of the effect of various factors on plants and is useful, among others, in breeding to select plants with a required genotype. The yield – determining features such as: fruit yield per plant, weight of single fruit, number of fruit per plant and weight of leaves per plant in S3 generation, were lower as compared with parental forms.

David Alan Walker. 18 August 1928 — 13 February 2012

David Alan Walker was born in Kingston upon Hull, England. He entered King’s College, Newcastle, then part of the University of Durham, where he received his BSc, and subsequently his PhD under Meirion Thomas FRS in 1958. Later, in 1968 he was awarded a DSc at the University of Newcastle in recognition of his exceptional contributions of published work in his field. In 1991 he received a Humboldt Research Prize, and in 2004 the inaugural Communications Award from the International Society of Photosynthesis Research. He was the author of more than 230 publications, including several books. He made important contributions to the understanding of photosynthesis, in particular the fixation of carbon dioxide by the biochemical transformations of the Benson–Calvin cycle in the stroma of chloroplasts of higher plants. Based on the meticulous attention to detail and technical prowess derived from his earlier training as an enzymologist, his work prompted totally new thinking about how this cycle was regulated and how it interfaced with the synthesis of ATP and NADPH in the light reactions of photosynthesis. Later, he was one of a very small group of people to recognize that this regulation was observable in whole leaves through the changes in chlorophyll fluorescence, helping to open the door to one of the most widely used tools in plant physiology. After periods at Newcastle, Purdue, Cambridge, Queen Mary College and Imperial College, London, he spent the largest part of his academic career as a professor at the University of Sheffield. There he established a world-renowned photosynthesis research group that grew into one of the university’s first semi-autonomous research institutes, the Research Institute for Photosynthesis, later renamed the Robert Hill Institute. This legacy persists more than 30 years later. He also distinguished himself in the wider aspects of being a scientist: long before it became fashionable, he wrote about the issues of food, energy and global change in his 1992 book Energy, plants and man . His enthusiasm for communicating both the joy of science and these serious issues led to many other imaginative schemes and endeavours, again long before the need for greater ‘public understanding of science’ became recognized.

Bark and leaf chlorophyll fluorescence are linked to wood structural changes in Eucalyptus saligna.

Wood structure and wood anatomy are usually considered to be largely independent of the physiological processes that govern tree growth. This paper reports a statistical relationship between leaf and bark chlorophyll fluorescence and wood density. A relationship between leaf and bark chlorophyll fluorescence and the quantity of wood decay in a tree is also described. There was a statistically significant relationship between the leaf chlorophyll fluorescence parameter Fv/Fm and wood density and the quantity of wood decay in summer, but not in spring or autumn. Leaf chlorophyll fluorescence at 0.05 ms (the O step) could predict the quantity of wood decay in trees in spring. Bark chlorophyll fluorescence could predict wood density in spring using the Fv/Fm parameter, but not in summer or autumn. There was a consistent statistical relationship in spring, summer and autumn between the bark chlorophyll fluorescence parameter Fv/Fm and wood decay. This study indicates a relationship between chlorophyll fluorescence and wood structural changes, particularly with bark chlorenchyma.

Behavior of Native Species Arrhenatherum Elatius (Poaceae) and Sonchus Transcaspicus (Asteraceae) Exposed to a Heavy Metal-Polluted Field: Plant Metal Concentration, Phytotoxicity, and Detoxification Responses

The application of vegetation cover for the phytomanagement of heavy metal-polluted soils needs prior investigation on the suitability of plant species. In this study, behaviors of Arrhenatherum elatius and Sonchus transcaspicus, two native perennial grasses that currently grow in a mine tailing, were investigated through plant metal concentration, phytotoxicity and their detoxification responses. Both of the species accumulated Ni, Cu, Cd, Co, Mn, Pb, Cr, and Zn in shoots far below criterion concentration as a hyperaccumulators; thus, neither of them were found to be hyperaccumulators. A. elatius accumulated metals in roots and then in shoots, on the contrary, in S. transcaspicus metals were preferentially accumulated in shoots. Plants exposure to such metals resulted in oxidative stress in the considered organs as indicated by the changes in chlorophyll fluorescence, chlorophyll contents, malondialdehyde (MDA) levels and antioxidative enzyme activities. A. elatius seemed to be more affected by metal-induced oxidative stress than S. transcaspicus. Correspondingly, S. transcaspicus showed a greater capacity to adapt to metal-induced oxidative stress, depending on more effective antioxidative defense mechanisms to protect itself from oxidative damage. These findings allowed us to conclude that both of these plant species could be suitable for the phytostabilization of metal-polluted soils.

Tolerance of Miscanthus × giganteus to salinity depends on initial weight of rhizomes as well as high accumulation of potassium and proline in leaves

Miscanthus×giganteus, a species useful for sustainable agriculture, can be cultivated on soils with lower bonitation and also with higher salinity. The study aimed to estimate NaCl concentrations which limit growth of Miscanthus×giganteus plants and to determine physiological parameters best reflecting the response of Miscanthus to salt stress. The experiment was conducted on plants grown at 0–200mM of NaCl. All analyses were done after 12 weeks of salt treatment. In rhizomes and leaves, fresh (FW) and dry weight (DW), relative water content (RWC), electrolyte leakage (EL), and ion content were determined; in leaves only, chlorophyll fluorescence, net photosynthesis rate (PN), transpiration (E), stomatal conductance (gs) and proline content. Shoots developed at all NaCl concentrations, but at 200mM many rhizomes produced none; thus analyses on leaves were done only on plants grown at 0–150mM of NaCl. Salinity decreased FW and DW of roots and shoots significantly, and retarded increases in rhizome weight. In leaves, salinity of 100 and 150mM NaCl did not damage membrane structures, while in rhizomes only 200mM increased EL considerably. Most parameters of chlorophyll fluorescence and gas exchange declined under salinity. High amounts of proline, K and Na were accumulated in leaves at 100 and 150mM NaCl. RWC remained unchanged in roots and leaves and decreased in rhizomes under rising salinity. The initial FW of the rhizomes studied correlated with the salt tolerance of Miscanthus plants. Changes in chlorophyll fluorescence, PN, FW and DW of roots and leaves as well as potassium and proline concentrations in leaves are the most reliable indicators of the response of Miscanthus to salinity. A high accumulation of K+ and proline in leaves reduces the sodium effect and determines the tolerance of Miscanthus to salinity.

NaCl 처리에 따른 멀꿀과 다정큼나무의 내염성 평가

상록활엽 조경소재 연구개발의 일환으로써, 기후변화에 대응하여 내한성이 우수한 남부지역 상록활엽수 중에서 멀꿀과 다정큼나무에 대하여 가시적 피해, 엽록소 형광이미지, MDA(malondialdehyde) 농도 분석으로 내염성을 평가하였다. NaCl 농도가 증가함에 따라서 토양 pH는 감소하고 EC는 증가하였으며 멀꿀이 생육 중은 토양은 다정큼나무가 생육 중인 토양보다 더 강하게 영향을 받았다. 시각적 피해에서 멀꿀은 처리 후 20일에 200mM NaCl 농도 이상에서 고사하였다. 다정큼나무는 비록 400mM NaCl 농도에서 잎의 피해를 나타냈지만 실험기간 동안 모두 생존하였다. 엽록소 형광이미지에서 색상변화는 시각적 피해 결과와 강한 일관성을 보였다. NaCl 농도가 증가함에 따라서 멀꿀 잎의 적색은 유의성 있게 낮은 형광 값인 청색으로 변화하였고 변화는 가장자리에서 중앙으로 옮겨갔다. 다정큼나무의 형광이미지 반응은 NaCl 처리일이 증가할수록 잎의 가장자리에 변화가 나타났으나 여전히 실험기간 동안 적색을 나타냈다. 가장 높은 시각적 피해와 EC를 보였던 처리 후 5일에 멀꿀의 MDA 농도는 <TEX>$4.56nmol{\cdot}g^{-1}$</TEX>였다. 다정큼나무의 MDA 농도는 400mM NaCl 농도 처리구를 제외한 모든 처리구들에서 <TEX>$1.5nmol{\cdot}g^{-1}$</TEX> 이하를 나타냈다. Stauntonia hexaphylla and Raphiolepis indica, cold-tolerant broadleaved evergreens ranging through the southern region of South Korea, were assessed on salt tolerance with NaCl treatment using visual damage, chlorophyll florescence image, and malondialdehyde (MDA) analysis. As NaCl concentrations increased, the soil pH decreased and EC increased, and the soil of S. hexaphylla was affected more strongly by the treatment than that of R. indica. In visual damage, S. hexaphylla withered above 200 mM NaCl at 20 days after the treatment. All individuals of R. indica survived during the experiment though the leaves of R. indica showed visual damages up to 400 mM NaCl. The color changes in chlorophyll fluorescence showed a strong correlation with the degree of visual damage. As NaCl increased, the red color of the leaves of S. hexaphylla was distinctly changed to blue and chlorophyll fluorescence decreased starting from the margin to the middle of a leaf. R. indica showed subtle color changes and remained in red color during the experiment. At five days after the NaCl treatment, the MDA of S. hexaphylla was above <TEX>$4.56nmol{\cdot}g^{-1}$</TEX> when plants showed the highest visual damage and EC. The MDA of R. indica in all treatments showed below <TEX>$1.5nmol{\cdot}g^{-1}$</TEX> except 400 mM NaCl treatment during the experiment.

Pleiotropic effect of sigE over‐expression on cell morphology, photosynthesis and hydrogen production in Synechocystis sp. PCC 6803

Over-expression of sigE, a gene encoding an RNA polymerase sigma factor in the unicellular cyanobacterium Synechocystis sp. PCC 6803, is known to activate sugar catabolism and bioplastic production. In this study, we investigated the effects of sigE over-expression on cell morphology, photosynthesis and hydrogen production in this cyanobacterium. Transmission electron and scanning probe microscopic analyses revealed that sigE over-expression increased the cell size, possibly as a result of aberrant cell division. Over-expression of sigE reduced respiration and photosynthesis activities via changes in gene expression and chlorophyll fluorescence. Hydrogen production under micro-oxic conditions is enhanced in sigE over-expressing cells. Despite these pleiotropic phenotypes, the sigE over-expressing strain showed normal cell viability under both nitrogen-replete and nitrogen-depleted conditions. These results provide insights into the inter-relationship among metabolism, cell morphology, photosynthesis and hydrogen production in this unicellular cyanobacterium.