The kinetics of chlorophyll fluorescence were measured in Portulacaria afra (L.) Jacq. when the plants were functioning in either Crassulacean acid metabolism (CAM) or C(3)/CAM cycling (called cycling) modes, as determined by fluctuation in titratable acidity and gas exchange properties. Cycling plants showed primarily daytime CO(2) uptake typical of C(3) plants, but with a slight diurnal acid ...

Cells of the cyanobacterium Synechococcus 6301 were grown under illumination whose spectral composition favoured absorption either by the phycobilisome (PBS) light-harvesting antenna of photosystem II (PS II) or by the chlorophyll (Chi) a light-harvesting antenna of photosystem I (PS I). Cells grown under PS I-light developed relatively high PS II/PS I and PBS/Chl ratios. Cells grown under PS I...

The npq1 Arabidopsis mutant is deficient in the violaxanthin de-epoxidase enzyme that converts violaxanthin to zeaxanthin in excess light (xanthophyll cycle). We have compared the behavior of mature leaves (ML) and developing leaves of the mutant and the wild type in various light environments. Thermoluminescence measurements indicated that high photon flux densities (>500 micromol m(-2) s(-1))...

Photosynthesis uses light as a source of energy but its excess can result in production of harmful oxygen radicals. To avoid any resulting damage, phototrophic organisms can employ a process known as non-photochemical quenching (NPQ), where excess light energy is safely dissipated as heat. The mechanism(s) of NPQ vary among different phototrophs. Here, we describe a new type of NPQ in the organ...

high temperature, high radiance, low vapor pressure, and lack of precipitation in most months characterize arid ecosystems. under these conditions, tree crops such as pistachio suffer from drought combined with salinity stress. in order to investigation effects of combined salinity and drought stress on function of photosynthetic apparatus, mutica pistachio (pistacia mutica) seedlings were subj...

The pomegranate is one of the most essential crop fruits in world. 5-Aminolevulinic acid (ALA) regulates growth and development 5-year-old pomegranate. However, for plenty pome crops, conventional information on physio-chemical characteristics underlying 5-ALA limited. Therefore, this study, we applied four different concentrations treatments (0 mg L−1, 10 20 50 100 L−1), where 0 L−1 was consid...