At the vegetative growth stage (40 d), the mean photosynthetic rate (PN) and canopy photosynthesis (PN × LAI) in F1 hybrids and their parents were similar, whereas the maintenance respiration rate (RM) was considerably higher and PN/RM lower in the F1 hybrids than in the parents. Yet at the flowering stage, the hybrids showed higher PN and PN × LAI values, while RM and PN/RM were similar in both. A specific F1 hybrid like IR 62829A×Vajram showed high readings in PN, PN/RM, and PN × LAI at the flowering stage, while IR 62829A×Swarna followed by IR 62829A×Vajram had high values 40 d after planting. The parents Swarna and Vajram, although moderate in PN, had the highest PN × LAI at the flowering stage due to a greater LAI. and M. J. Baig, P. Swain, K. S. Murty.
The photosynthetic pathway of the roots (both the white velamentous main portions and the green, nonvelamentous tips) was investigated in twelve taxa (natural species and intergeneric hybrid cultivars) of epiphytic orchids having CAM leaves. All organs contained chlorophyll, and the a/b ratios indicate that the organs, especially the roots, are likely shade-adapted. Stable carbon isotope ratios of the tissues were near -15‰ for all organs, a value typical of obligate (constitutive) CAM plants. Values for root tissues were slightly lower (more negative) than those of the leaves. The presence of CAM in the leaves of these orchids did not ensure that their roots performed CAM photosynthesis. Further work is needed to address the questions raised in this study and to determine if the photosynthetic roots of these taxa are capable of assimilating atmospheric CO2. and C. E. Martin ... [et al.].
Field measurements of gas exchange were made using a portable infra-red gas analyser on six species of early-successional woody plants in Singapore. Macaranga heynei, Mallotus paniculatus and Trema tomentosa grow on relatively fertile soils. Adinandra dumosa, Uillenia suffruticosa and Melostoma malabalhricum are species typical of extremely acidic and infertile soils. The six species were similar in their photosynthetic responses to irradiance when net photosynthetic rate (P^) was expressed on a leaf area basis. However, when PN was converted to a rate per unit leaf dry mass, the fertile soil species showed higher rates of dark respiration and photosynthesis. No difference in water use efficiency between the two sets of species was found.
We studied the photosynthetic performance of sterile and fertile sporophytes in a natural population of the fern Dryopteris affinis growing within a riparian forest (Central Italy) using chlorophyll (Chl) a fluorescence transients, the OJIP phase, where O is for the minimum fluorescence, P is for the peak (the maximum), and J and I are inflections. The “vitality” of the samples was assessed by the maximum quantum yield of primary photochemistry obtained indirectly from the fluorescence data (Fv/Fm); in the same way, the so-called performance index (PIABS) was obtained from fluorescence data. The photosynthetic performance (inferred from PIABS) of D. affinis changed significantly with the seasonal development of the fronds. The highest photosynthetic performance was recorded in the summer, corresponding to the period of spore release. The photosynthetic performance decreased in the winter, down to the minimal values of senescent fronds reached at the end of the seasonal cycle (May-June). On the whole, during the seasonal development, sterile and fertile fronds had a similar photosynthetic behaviour, as inferred from fluorescence data. At the end of spore maturation and dispersal (September-October), the fertile fronds showed somewhat lower photosynthetic performance than the sterile fronds, as revealed by PIABS. Being a long-lived fern, confined to humid and undisturbed sites in the Mediterranean, D. affinis deserves to be further investigated as a potential indicator of ecological continuity in Mediterranean riparian forests., L. Paoli, M. Landi., and Obsahuje bibliografii
The effects of a high temperature on leaf photosynthetic response of Lupinus albus, a species native from the Mediterranean zone, were studied under varying tissue water status and irradiance (/). At leaf temperatures optimal (25 °C) or near-optimal (15 ®C) for carbon assimilation in lupins, photosynthetic capacity (P^) was decreased at leď relative water content (RWC) around 60 %. The temperature above the optimum (e g. 35 oC) decreased at high RWC (80 %). Irrespective of the leaf water status the optimum leaf temperature for in lupins was around 25 "C. The inhibition of P^ by lupin leaf discs at 35 °C was greatly enhanced at high I. Leaf disc treatment at 35 in the dark did not change quantum yield or Pn. When in addition to 35 the leaves were subjected to high I (TS + IS) or to high I and dehydration (TS + IS + WS), then a substantial decrease was observed in the quantum yield (66 and 77 % of the values in Controls, respectively) and in (31 and 56 %, respectively).
Plants of Solanum curtilobum (from high altitude) and Solanum tuberosum (from low altitude) were grown in open-top chambers in a greenhouse at either ambient (AC, 360 µmol mol-1) or ca. twice ambient (EC, 720 µmol mol-1) CO2 concentrations for 30 d. CO2 treatments started at the reproductive stage of the plants. There were similar patterns in the physiological response to CO2 enrichment in the two species. Stomatal conductance was reduced by 59 % in S. tuberosum and by 55 % in S. curtilobum, but such a reduction did not limit the net photosynthetic rate (PN), which was increased by approximately 56 % in S. curtilobum and 53 % in S. tuberosum. The transpiration rate was reduced by 16 % in both potato species while instantaneous transpiration efficiency increased by 80 % in S. tuberosum and 90 % in S. curtilobum. Plants grown under EC showed 36 and 66 % increment in total dry biomass, whereas yields (dry mass of tubers) were increased by 40 and 85 % in S. tuberosum and S. curtilobum, respectively. EC promoted productivity by increasing PN. Thus S. tuberosum, cultivated around the world at low altitudes, and S. curtilobum, endemic of the highland Andes, respond positively to EC during the tuberisation stage. and N. Olivo, C. A. Martinez, M. A. Oliva.
The aim of the study was to investigate the genetic distances and their relationships among pepper species using photosynthetic features under different stresses and genetic variability. The photosynthetic features under drought, waterlogging and
low-temperature stresses, rDNA internal transcribed spacer (ITS) sequences of nuclear genome and trnH-psbA sequence of chloroplast genome of 25 varieties from 5 pepper species Capsicum annuum L. (CA), Capsicum baccatum L. (CB), Capsicum chinense Jacquin. (CC), Capsicum frutescens L. (CF) and Capsicum pubescens Ruiz & Pavon (CP) were analyzed and used to construct the dendrograms. The results showed the photosynthetic rate of different pepper species could be greatly but differentially decreased by stresses. For example, CB and CF had the smallest and the highest decrease to drought, CC had the highest decrease to waterlogging, and CP had the smallest decrease to low temperature. The ITS sequences of 25 pepper varieties are 591-619 bp in length and have GC% between 51.1% and 64.5%. Their trnH-psbA sequences are 537-558 bp in length and have GC% between 27.2% and 28.5%. The cluster analysis of the five pepper species based on the changes in PN under stresses is similar to that based on genetic variability, that is, CP clusters with CB, and CC clusters with CA after first clusters with CF. In addition, the clustering methods based on the photosynthetic stress responses and genetic variability are unable to completely distinguish pepper varieties within the same species. The results indicate that similarly to genetic variability, changes in PN under stresses (specifically the stress corresponding to the climate of plant’s original habitat) could be used to identify genetic distance of pepper species., L. J. Ou and X. X. Zou., and Obsahuje bibliografii
Ultrafast time resolved emission spectra were measured in whole cells of a PSI-deficient mutant of Synechocystis sp. PCC 6803 at room temperature and at 77K to study excitation energy transfer and trapping. By means of a target analysis it was estimated that the terminal emitter of the phycobilisome, termed allophycocyanin 680, transfers its energy with a rate of (20 ps)-1 to PSII. This is faster than the intraphycobilisome energy transfer rates between a rod and a core cylinder, or between the core cylinders., A. M. Acuña, P. Van Alphen, R. Van Grondelle, I. H. M. Van Stokkum., and Obsahuje bibliografické odkazy
Tropical savanna ecosystems are extremely diverse and important for global carbon storage. In the state of Mato Grosso, tropical savanna (locally known as the Cerrado), turns from well-drained, upland areas into seasonally flooded areas within the Pantanal; however, the Cerrado and the Pantanal share many common tree species, such as Vochysia divergens, a flood-adapted tree native to the Amazon Basin, and Curatella americana, a tree, adapted native to the welldrained the Cerrado. We measured the photosynthetic light response of these species in the the Cerrado and the Pantanal over a 1-year period to determine how these species physiologically adjust to these hydrologically distinct habitats. We hypothesized that neither species would experience a significant decline in maximum, light-saturated photosynthetic rate (Pmax) in their naturalized habitat. Physiological performance of each species was generally higher in the habitat that they were adapted to; however, our data indicated that both species have broad tolerance for seasonal variations in hydrology, allowing them to tolerate seasonal drought during the dry season in the Cerrado, and seasonal flooding during the wet season in the Pantanal. In V. divergens, flexible water-use efficiency, higher specific leaf area (SLA), and a greater ability to adjust mass-based Pmax (Pmax,m) to variations in leaf N and P concentration appeared to be key traits for withstanding prolonged drought in the Cerrado. In C. americana, increases in SLA and higher nutrient-use efficiency appeared to be important in maintaining high rates of Pmax,m in the seasonally flooded Pantanal. Flexibility in physiology and resource-use efficiency may allow these species to survive and persist in habitats with broadly differing hydrology., H. J. Dalmagro, F. de A. Lobo, G. L. Vourlitis, Â. C. Dalmolin, M. Z. Antunes Jr., C. E. R. Ortíz, J. de S. Nogueira., and Obsahuje bibliografii
The cells of purple photosynthetic bacterium Rhodobacter sphaeroides embedded in stretched polymer films were irradiated by strong polarized "white light" with an electric vector parallel to the direction of film stretching. The polarized absorption and photoacoustic spectra before and after strong irradiation were measured. Measurements of absorbance showed no confident anisotropy before and after strong irradiation. In contradiction, the photoacoustic method showed after strong irradiation some changes in anisotropy of thermal deactivation due to the perturbation of the fate of excitations. The increase in yield of thermal deactivation, higher in a region of light-harvesting complex 2, can be explained by the irreversible changes in the conformation of the complexes due to strong irradiance reported up to now predominantly for thylakoid antenna complexes. and J. Goc, K. Klecha.