Constant reduction of stratospheric ozone layer and the increase of ultraviolet radiation intensity were observed in last twenty years of the 20th century. Four tree species; Acacia amplicepsis, Acacia gerradii, Casuarina glauca and Eucalyptus intertexta grown in Experimental station of Food and Agriculture Sciences Collage, King Saud University were used to study the impact of UV-C on potentia...

Chlorophyll b is found in photosynthetic prokaryotes and primary and secondary endosymbionts, although their light-harvesting systems are quite different. Chlorophyll b is synthesized from chlorophyll a by chlorophyllide a oxygenase (CAO), which is a Rieske-mononuclear iron oxygenase. Comparison of the amino acid sequences of CAO among photosynthetic organisms elucidated changes in the domain s...

Biogenesis of thylakoid membranes in the conditional chlorophyll b-deficient CD3 mutant of wheat is dramatically altered by relatively small differences in the light intensity under which seedlings are grown. When the CD3 mutant is grown at 400 microE/m2 S (high light, about one-fifth full sunlight) plants are deficient in chlorophyll b (chlorophyll a/b ratio greater than 6.0) and lack or conta...

objective: in order to study the effect of drought stress, salicylic acid (sa) and  jasmonic acid (ja) foliar application on hill reaction and photosynthetic pigments. methods:experiment was done as factorial on the basis of completely randomized design in 4 replications. irrigation in 3 levels (fc,   fc and  fc), salicylic acid in 2 levels (0 and 0.5 mm) and jasmonic acid in 2 levels (0 and 50...

Anabaena variabilis, a blue-green alga lacking chlorophyll b, shows an absence of the major 22 and 24 kilodalton polypeptides which are present in the photosynthetic membranes of Chlamydomonas reinhardi and higher plants. These data are consistent with other investigations which have shown that these polypeptides are associated with chlorophyll b in the chloroplasts of higher plants, and indica...

In an earlier paper (7) the chlorophyll composition of a number of chlorina mutants of barley obtained from D. W. Robertson (10) were described and it was then pointed out that one of the mutants appeared to be entirely lacking in chlorophyll b. Thus, it was of considerable interest to learn whether the chlorophyll b deficiency was affecting the photosynthetic activity of this mutant. Comparati...

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...