During ontogeny of Gossypium hirsutum L. floral buds (squares), increases in area and dry mass (DM) of floral bracts and the subtending sympodial leaf followed a sigmoid growth curve with increasing square age. The maximum growth rates of the bract area and bract DM occurred between 15 and 20 d after square first appearance (3 mm in diameter). Net photosynthetic rate (PN) of the sympodial leaf at first fruiting branch position of main-stem node 10 reached a maximum when the subtended square developed into a white flower. Floral bracts had much lower PN and higher dark respiration than the subtending leaf. The amount of 14CO2 fixation by the bracts of a 20-d-old square was only 22 % of the subtending leaf, but 56 % of 14C-assimilate in the floral bud was accumulated from the bracts, 27 % from the subtending leaf, and only 17 % from the main-stem leaf at 6 h after 14C feeding these source s. Hence floral bracts play an important role in the carbon supply of developing cotton squares. and Duli Zhao, D. M. Oosterhuis.
The southernmost presence of Rhizophora mangle in the western Atlantic coast occurs in coastal wetlands between 27 and 28°S in the State of Santa Catarina, Brazil. We selected mangrove communities at the estuary of the River Tavares, Florianopolis, and the Sonho Beach, Palhosa, for measurement of photosynthetic performance and intrinsic water-use efficiency of R. mangle and coexisting individuals of Avicennia schaueriana and Laguncularia racemosa, during the spring season. We used gas-exchange techniques and isotopic signatures of C and N to estimate instantaneous water-use and carboxylation efficiency (CE), long-term water-use efficiency, and potential N limitation. Results showed that R. mangle had significantly lower photosynthetic rates but similar conductance values as the other two species resulting in lower intrinsic water use (WUEi) and CE. WUEi and CE were positively correlated in L. racemosa and A. schaueriana, but not in R. mangle. At each site, δ13C values of A. schaueriana were consistently higher than those for the other species, indicating that these species are subjected to contrasting water stress conditions. Leaf concentrations of C were lower, whilst those of N were always higher in A. schaueriana, indicating accumulation of salts and nonprotein N-compounds in leaves. Nitrogen concentrations and moderate positive δ15N values indicated that plant growth at the study sites was not inhibited by nutrient deficiency, and was not influenced by urban residual waters. Lower photosynthetic rates and values of CE of R. mangle compared to the other two species may constitute constraining factors preventing this species from establishing at higher latitudes., M. L. Gomes Soares, M. M. Pereira Tognella, E. Cuevas, E. Medina., and Obsahuje seznam literatury
2-years-old cypress needles (A2) were physiologically most active with regard to net photosynthetic (PN) and electron transport rates. Variable to maximum fluorescence (Fv/Fm) ratios of dark-adapted needles were higher in A2 needles than in current year (A1) or senescent (A4) needles. Lower Fv/Fm values in these stages seemed to be caused not by photoinhibition but by a low photochemical capacity as suggested from the chlorophyll (Chl) a/b ratios. In isolated thylakoids, lower rates of whole chain and photosystem 2 (PS2) activities were observed in A4 needles, while higher rates were observed in A2 needles. A similar trend was noticed for contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC) and total soluble proteins. The artificial exogenous electron donor Mn2+ failed to restore the loss of PS2 activity in 3-year-old (A3) and A4 needles, while diphenylcarbazide and NH2OH significantly restored the loss of PS2 activity. The marked loss of PS2 activity in A4 needles was primarily the result of the loss of 33, 28-25, 23, and 17 kDa polypeptides. A marked loss of RuBPC activity in A4 needles is mainly due to the loss of 15 (SSU) and 55 (LSU) kDa polypeptides. and N. La Porta ... [et al.].
Sodium chloride (NaCl) concentratíons 200 to 900 mM enhanced the photosynthetic rate (Pn) both in whole leaves and in mechanically isolated, intact mesophyll cells of a salt marsh halophyte Sesuvium portulacastrum wilh a maximum at 600 mM NaCl. These changes were in agreement with changes in chlorophyll concentration in leaves. Though the increasing salt concentratíons resulted in leaf succulence, no change in the photosynthetic carbon pathway was observed.
In the untransformed rice (WT) and transgenic rice with the PEPC and PPDK genes (CK) we determined activities of C4 photosynthetic enzymes, photosynthetic response to irradiance and temperature, the metabolic index of active oxygen, and the yield component factors. The activities of C4 photosynthetic enzymes in WT were very low, while those of corresponding enzymes in CK were highly observable. Moreover, after adenosine triphosphate (ATP) treatment, and under high irradiance and high temperature, the net photosynthetic rate of CK increased by 17 and 12 %, respectively, as compared to that achieved without ATP treatment. The resistance of CK against photo-oxidation was enhanced under these conditions, and CK yield increased by 15 %. ATP treatment enhanced the photosynthetic productivity of CK, thereby proving that ATP is the key factor in enhancing the photosynthetic capacity of transgenic rice with C4 gene. Our new technical approach can be used in breeding rice with high photosynthetic efficiency and high grain yield. and B. J. Zhang ... [et al.].
We investigated the photosynthetic characteristics of Chorispora bungeana under conditions of drought stress caused by different concentrations of polyethylene glycol-6000 (PEG; 0, 5, 20, and 40%) and various concentrations of exogenous glycine (0, 5, 10, and 20 mM) with 20% PEG. We showed that moderate and severe drought stress of PEG reduced the chlorophyll (Chl) content (both Chl a and b), maximal quantum yield of PSII photochemistry (Fv/Fm), actual photochemical efficiency of PSII in light (YII), and quantum yield of regulated energy dissipation (YNPQ), while Chl a/b and quantum yield of nonregulated energy dissipation (YNO) increased. The low and moderate drought stress increased Mg2+ and Fe3+ contents, while a decrease in Mg2+ and Fe3+ was found under severe drought stress. Compared to sole PEG stress, the addition of exogenous 10 mM glycine increased Chl, Mg2+ and Fe3+ contents, Fv/Fm, YII, and YNPQ, and reduced YNO. On the contrary, 20 mM glycine showed an opposite effect, except for YNO. Our results proved that Chl contents and fluorescence parameters are reliable indicators for drought tolerance of C. bungeana. We suggest that a proper glycine content can relieve the effect of drought stress on C. bungeana., N. Yang, C.-L. Wang, W.-P. He, Y.-Z. Qu, Y.-S. Li., and Seznam literatury
Three-month-old plants of mulberry (Morus alba L. cv. Kanva-2) were subjected to a drought stress by withholding water supply. As the leaf water potential (ΨW) was dropping progressively with the severity of treatment and increasing stress duration, the values of leaf area, dry mass accumulation, total chlorophyll (Chl) content, net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were declined. The photosystem 2 (PS2) photochemical efficiency significantly decreased only at a severe stress treatment. The intercellular CO2 concentration (Ci) remained unaltered during a mild stress, yet it increased under moderate and severe stresses. The Ci/gs ratio reflected the mesophyll efficiency during water stress. Rewatering of the plants led to an almost complete recovery of PN, E, and gs, indicating that a short-term stress brings about reversible effects only. and S. Ramanjulu ... [et al.].
Photosynthetic rate (PN), SPAD value, specific leaf area (SLA), flag leaf area (FLA), and nitrogen content (LN) of genus Oryza were investigated and their correlation was analyzed to assess some of the main photosynthetic traits among different species in the genus Oryza. The results revealed wide variation in these traits. The species O. rufipogon and O. australiensis exhibited maximum photosynthetic rate. Comparison of different types of genomes (diploid: 2n=2x=24; tetraploid: 2n=4x=48) and growth habit (shade- or sun-grown) showed the species of diploid (with genome symbol EE; 2n=2x=24) genomes, with perennial and sun-grown species, had high apparent photosynthesis compared to others. The species with BB/BBCC, shade-grown and the tetraploids showed high SPAD value, and the flag leaf in sun-grown species and diploids were thicker (low SLA) compared with others. However, no significant difference could be noticed among the different types of genomes. Higher leaf area was noticed among the species of CC/CCDD genome, perennial shade-grown species and tetraploids than in others. The variety IR 36 exhibited highest leaf nitrogen concentration. Correlation analysis showed a strong relationship between PN and leaf nitrogen concentration while no marked relationships were observed among other characteristics. It implies that the species with thick and small leaves with high nitrogen concentration and high photosynthesis evolved better than others. O. rufipogon, with the same genome as O. sativa, could be one of the wild rice resources for elite crop improvement. and M. Zhao ... [et al.].
Unlike mulberry (Morus alba, M.a.), paper mulberry (Broussonetia papyrifera, B.p.) can acclimate to Karst soil and incline to alien invasion. The photosynthetic parameters, diurnal changes of carbonic anhydrase, and chlorophyll fluorescence induction, and water potential were measured on sunny days (SD) and cloudy days (CD). Photosynthetic midday depression occurred in B.p. but not in M.a. The irradiance-and CO2-saturated photosynthetic rates of B.p. were significantly higher than those of M.a. There was no significant difference in water use efficiency between the two species on a SD. The maximum fluorescence, maximum quantum yield, photochemical quenching, and relative electron transport rate in the leaves of B.p. were much higher than those in M.a. The activity of carbonic anhydrase (CA) of B.p., on either an SD or a CD, was much greater than that of M.a. Higher transpiration rate (E) and net photosynthetic rate (PN) of B.p. resulted in the lack of water in mesophyll cells. Although a higher CA activity of B.p. supplied both water and CO2 for the photosynthesis of mesophyll cells, water in mesophyll cells was the factor limiting photosynthesis, and the intercellular CO2 concentration of B.p. was high and stable. and Y.-Y. Wu ... [et al.].
Contents of chlorophylls and carotenoids in yellow-green mutant Biao 810S were approximately half those in control type 810S. Biao 810S had fewer grana lamellae and looser structure than 810S, lower volume of starch granules in chloroplasts, but under high temperature and high irradiance the net photosynthetic rate (PN) of Biao 810S was higher than that of 810S. The chlorophyll fluorescence parameter Fv/Fm of Biao 810S was little higher and photochemical quenching qP was obviously higher than those of 810S. No significant differences in PN and biomass were observed in their hybrid combination. The yellow-green mutant phenotype may be a useful genetic marker of P(T)GMS rice used for hybrid seed production. and L.-J. Ou ... [et al.].