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Start Over Coverage 127-134

1. Decomposition of complete bipartite even graphs into closed trails

Creator:
Horňák, Mirko and Woźniak, Mariusz
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
complete bipartite graph, closed trail, and arbitrarily decomposable graph
Language:
English
Description:
We prove that any complete bipartite graph $K_{a,b}$, where $a,b$ are even integers, can be decomposed into closed trails with prescribed even lengths.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

3. Partitioning of photosynthetic electron flow between CO2 assimilation and O2 reduction in sunflower plants under water deficit

Creator:
Tezara, W., Driscoll, S., and Lawlor, D. W.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence, electron transport, fluorescence quenching, Helianthus annuus, intercellular CO2 concentration, net photosynthetic rate, and stomatal conductance
Language:
Multiple languages
Description:
In sunflower (Helianthus annuus L.) grown under controlled conditions and subjected to drought by withholding watering, net photosynthetic rate (PN) and stomatal conductance (gs) of attached leaves decreased as leaf water potential (Ψw) declined from -0.3 to -2.9 MPa. Although gs decreased over the whole range of Ψw, nearly constant values in the intercellular CO2 concentrations (Ci) were observed as Ψw decreased to -1.8 MPa, but Ci increased as Ψw decreased further. Relative quantum yield, photochemical quenching, and the apparent quantum yield of photosynthesis decreased with water deficit, whereas non-photochemical quenching (qNP) increased progressively. A highly significant negative relationship between qNP and ATP content was observed. Water deficit did not alter the pyridine nucleotide concentration but decreased ATP content suggesting metabolic impairment. At a photon flux density of 550 µmol m-2 s-1, the allocation of electrons from photosystem (PS) 2 to O2 reduction was increased by 51 %, while the allocation to CO2 assimilation was diminished by 32 %, as Ψw declined from -0.3 to -2.9 MPa. A significant linear relationship between mean PN and the rate of total linear electron transport was observed in well watered plants, the correlation becoming curvilinear when water deficit increased. The maximum quantum yield of PS2 was not affected by water deficit, whereas qP declined only at very severe stress and the excess photon energy was dissipated by increasing qNP indicating that a greater proportion of the energy was thermally dissipated. This accounted for the apparent down-regulation of PS2 and supported the protective role of qNP against photoinhibition in sunflower. and W. Tezara, S. Driscoll, D. W. Lawlor.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Photosynthesis, chlorophyll fluorescence, inorganic ion and organic acid accumulations of sunflower in responses to salt and salt-alkaline mixed stress

Creator:
Liu, J. and Shi, D.-C.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
botanika, botany, salt stress, salt-alkaline mixed stress, chlorophyll fluorescence, photosynthesis, inorganic ions, and organic acids
Language:
Multiple languages
Description:
Sunflowers were treated with mixing proportions of NaCl, Na2SO4, NaHCO3, and Na2CO3. Effects of salt and saltalkaline mixed stress on growth, photosynthesis, chlorophyll fluorescence, and contents of inorganic ions and organic acids of sunflower were compared. The growth of sunflower decreased with increasing salinity. The contents of photosynthetic pigments did not decrease under salt stress, but their contents decreased sharply under salt-alkaline mixed stress. Net photosynthetic rates, stomatal conductance and intercellular CO2 concentration decreased obviously, with greater reductions under salt-alkaline mixed stress than under salt one. Fluorescence parameters showed no significant differences under salt stress. However, maximal efficiency of PSII photochemistry, photochemical quenching coefficient, electron transport rate, and actual PSII efficiency significantly decreased but non-photochemical quenching increased substantially under salt-alkaline mixed stress. Under salt-alkaline mixed stress, sunflower leaves maintained a low Na+- and high K+ status; this may be an important feature of sunflower tolerance to salinity. Analysis of the mechanism of ion balance showed that K+ but not Na+ was the main inorganic cation in sunflower leaves. Our results indicated that the change in organic acid content was opposite to the change of Cl-, and the contribution of organic acid to total charge in sunflower leaves under both stresses decreased with increasing salinity. This may be a special adaptive response to stresses for sunflower. Sunflower under stress conditions mainly accumulated inorganic ions instead of synthesizing organic compounds to decrease cell water potential in order to save energy consumption. and J. Liu, D.-C. Shi.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6. Photosynthetic thermotolerance is quantitatively and positively correlated with production of specific heat-shock proteins among nine genotypes of Lycopersicon (tomato)

Creator:
Preczewski, P. J., Heckathorn, S. A., Downs, C. A., and Coleman, J. S.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chloroplast, heat stress, heat tolerance, photosynthesis, and stress proteins
Language:
Multiple languages
Description:
We recently showed that the chloroplast small heat-shock protein (herein referred to as chlp Hsp24) protects photosystem 2 (PS2) during heat stress, and phenotypic variation in production of chlp Hsp24 is positively related to PS2 thermotolerance. However, the importance of chlp Hsp24 or other Hsps to other aspects of photosynthesis and overall photosynthetic thermotolerance is unknown. To begin investigating this and the importance of genetic variation in Hsp production to photosynthetic thermotolerance, the production of several prominent Hsps and photosynthetic thermotolerance were quantified in nine genotypes of Lycopersicon, and then the relationships between thermotolerance of net photosynthetic rate (PN) and production of each Hsp were examined. The nine genotypes exhibited wide variation in PN thermotolerance and production of each of the Hsps examined (chlp Hsp70, Hsp60, and Hsp24, and cytosol Hsp70). No statistically significant relationship was observed between production of chlp Hsp70 and PN thermotolerance, and only a weak positive relationship between cytosolic Hsp70 and P N was detected. However, significant positive relationships were observed between production of chlp Hsp24 and Hsp60 and PN thermotolerance. Hence natural variation in production of chlp Hsp24 and Hsp60 is important in determining variation in photosynthetic thermotolerance. This is perhaps the first evidence that chlp Hsp60 is involved in photosynthetic thermotolerance, and these in vivo results are consistent with previous in vitro results showing that chlp Hsp24 protects PS2 during heat stress. and P. J. Preczewski ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8. Shifts in photosynthetic responses to írradiance and temperature in Viola species

Creator:
Mishio, M.
Format:
print
Type:
model:internalpart and TEXT
Subject:
chlorophyll, Viola keiskei, Viola hondoensis-, specific leaf mass, seasonal course of gas exchange, and dark respiration rate
Language:
Multiple languages
Description:
The steady-state photosynthetic irradiance and temperature responses of Viola hondoensis and V. keiskei (Violaceae) growing in proximity in their nati ve environment and under three levels of artificial shade of relative irradiance (RI) of 7, 20 and 50 % were investigated. The maximum photosynthetic rates and temperature optima under natural conditions were much higher in V. keiskei than in V. hondoensis, except when in leaves of V. keiskei chlorophyll was degraded due to autumn frosts. When grown under artificial shade, both species had higher temperature optima as RI decreased. Since leaves under the three RI conditions experienced a similar leaf temperature, it was concluded that the shifts in the temperature responses with RI resulted from acclimation to the varying irradiance. The higher temperature optima observed in V. keiskei under natural conditions were probably due to the fact that V. keiskei grew in more shady microhabitats than V. hondoensis.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public