Chlorophyll levels in l-cm sections of the youngest fully expanded leaves of normal (Y) Festuca pratensis L. declined almost to zero over a period of 6 days after excision. Chlorophyll in a mutant genotype (NY) remained near the initial level for the whole of this period. Abscisic acid promoted pigment loss in Y but had no significant effect on chlorophyll in NY. Kinetin retarded pigment loss i...

Leaf chlorophyll content provides valuable information about physiological status of plants. Reflectance measurement makes it possible to quickly and non-destructively assess, in situ, the chlorophyll content in leaves. Our objective was to investigate the spectral behavior of the relationship between reflectance and chlorophyll content and to develop a technique for non-destructive chlorophyll...

The pigment content of isolated reaction centers of photosystem II was modified using an exchange protocol similar to that used for purple bacterial reaction centers. With this method, which is based on incubation of reaction centers at elevated temperature with an excess of chemically modified pigments, it was possible to incorporate [3-acetyl]-chlorophyll a and [Zn]-chlorophyll a into photosy...

Barley leaves grown under a natural light/dark regime have a chlorophyll content of 1300 [ig/g fresh weight and a chlorophyll a /b ratio of 2 .5 -3 . When the plants are grown under cycles of 2 min light/118 min dark, the respective values are 50 and 5 — 9. With chloroplasts with low chlo­ rophyll b content variable fluorescence is depressed by about 30% by MgCl2; with those of high chlorophyll...

The low-temperature (77 K) emission and excitation chlorophyll fluorescence spectra in thylakoid membranes isolated from pea mutants were investigated. The mutants have modified pigment content, structural organization, different surface electric properties and functions [Dobrikova et al., Photosynth. Res. 65 (2000) 165]. The emission spectra of thylakoid membranes were decomposed into bands be...

The seasonal distributions of phytoplankton biovolume and chlorophyll a content were monitored for 14 months in a deep oligotrophic, high mountain lake (Redó, Pyrenees). An allometric relationship of chlorophyll with biovolume was found throughout the period studied, with a correlation coefficient of 0.66. However, the relationship changed with season and the taxonomic composition of the phytop...

Impact of the wheat stem sawßy, Cephus cinctus Norton (Hymenoptera: Cephidae), feeding injury on chlorophyll content and photosystem II (PSII) photochemistry in heads of wheat, TriticumaestivumL., at the grain-Þlling developmental stagewas evaluated by biochemically assessing the total chlorophyll, chlorophyll a (Chla), chlorophyll b (Chlb), chlorophyll a/b ratio (Chla/b), and carotenoid concen...

There is now evidence that aerobic anoxygenic phototrophic (AAP) bacteria are widespread across aquatic systems, yet the factors that determine their abundance and activity are still not well understood, particularly in freshwaters. Here we describe the patterns in AAP abundance, cell size and pigment content across wide environmental gradients in 43 temperate and boreal lakes of Québec. AAP ba...

The effect of salinity on growth, photosynthetic pigment content, and alkaloid secondary metabolite accumulation were studied in an economically important medicinal plant, Catharanthus roseus (L.) G. Don., under pot culture conditions. Plants were treated with different concentrations of NaCl, (e.g. 50 and 100 mM) 30, 45, 60, and 75 days after sowing (DAS). The plants were uprooted randomly 90 ...

The effect of temperature and light intensity have been studied in relation to the greening of etiolated corn (Zea mays cv. Pioneer 309-B) seedlings. Chlorophyll accumulation is rapid at high temperature (28 degrees ) under all conditions of light intensity. At low temperature (16 degrees ), and particularly in combination with high light intensity (3000-4500 ft-c), the accumulation of both chl...