The yield of energy transfer from photosystem II to photosystem I in Porphyridium cruentum varies from a minimum value of about 0.50 when the photosystem II reaction centers are all open to a maximum value between 0.90 and 0.95 when the centers are all closed.

The relationship between photochemical quantum yield (phi(s)) and fluorescence yield have been investigated in leaf tissue from Nicotiana tabacum using CO(2) exchange and a modulated fluorescence measuring system. The quantum yield of CO(2) fixation at 1.6% (v/v) O(2) and limiting irradiance was reduced 20% by increasing the mean H(2)O vapor pressure deficit (VPD) from 9.2 to 18.6 mbars. As [CO...

In response to excessive light, the thylakoid membranes of higher plant chloroplasts show dynamic changes including the degradation and reassembly of proteins, a change in the distribution of proteins, and large-scale structural changes such as unstacking of the grana. Here, we examined the aggregation of light-harvesting chlorophyll-protein complexes and Photosystem II core subunits of spinach...

The marine picocyanobacteria Synechococcus and Prochlorococcus numerically dominate open ocean phytoplankton. Although evolutionarily related they are ecologically distinct, with different strategies to harvest, manage and exploit light. We grew representative strains of Synechococcus and Prochlorococcus and tracked their susceptibility to photoinactivation of Photosystem II under a range of li...

The rate of CO(2) reduction in the S-triazine-resistant biotype of smooth pigweed (Amaranthus hybridus L.) was lower at all levels of irradiance than the rate of CO(2) reduction in the susceptible biotype. The intent of this study was to determine whether or not the lower rates of CO(2) reduction are a direct consequence of the same factors which confer triazine resistance. The quantum yield of...

Herbicide Resistance, Photosystem II, psbA G ene, Photosynthesis, Chloroplast, Phalaris para­ doxa Triazine resistance in a mutant biotype of Phalaris paradoxa is accompanied by changes in the chlorophyll fluorescence induction curve, and by reduced quantum yield for electron transport, indicating altered photosystem II activity. H owever, light-saturated rates of electron transport in isolated...

Two naturally occurring colonies of Millepora alcicornis were monitored during 1997 and 1998, both years in which this species bleached in the Mexican Caribbean. One colony (HL) was naturally exposed to a high light environment and another nearby colony (LL) was exposed to 5.9 times lower light levels due to shadowing by a pier. For 10 days in August 1997, seawater temperatures in the surroundi...

extended abstract background and objectives sugarcane (saccharum officinarum l.) is from poaceae trible and perennial native plant of asia continent warm areas. ratio fv/fm estimates the maximum quantum yield of photosystem ii. under conditions of stress fv/fm decreased, this decreasing is due to low activity of reaction of photosynthesis centers and reducing of proteins that are responsible fo...

This work identifies LOW QUANTUM YIELD OF PHOTOSYSTEM II1 (LQY1), a Zn finger protein that shows disulfide isomerase activity, interacts with the photosystem II (PSII) core complex, and may act in repair of photodamaged PSII complexes. Two mutants of an unannotated small Zn finger containing a thylakoid membrane protein of Arabidopsis thaliana (At1g75690; LQY1) were found to have a lower quantu...

Our knowledge of the processes involved in speciation of microalgae remains highly limited. In the present study, we investigated a potential role of ecological speciation processes in diversification of the filamentous green alga Klebsormidium. We examined 12 strains representing four different genotypes. The strains were collected from sandstone and limestone rocks and were cultivated at five...