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Starch degradation enzymes and their products were determined from chloroplasts and leaves of cotton (Gossypium hirsutum L. cv Coker 100) exposed t

Methods are described for the isolation and characterization of the nucleic acids of Oenothera organensis pollen. Alkaline hydrolysis, followed by paper chromatography served to characterize the ribonucleic acid. However, the low concentration of deoxyribonucleic acid and the large amounts of interfering polysaccharide material required application of special techniques and column chromatographic methods. In addition, a method is described for the isolation of “native” deoxyribonucleic acid from root tips of Zea mays and Oenothera .

A study was made of the relationship between the level of r RNA and the rate of growth in pinto bean plants treated with 0·35 ppm ozone for 20–40 min. Cytoplasmic ribosomes and a fraction containing both cytoplasmic and chloroplast ribosomes were initially isolated from primary leaves. The r RNA components of 25S, 23S, and 16S were extracted from these fractions and analysed by sucrose density gradient. The levels of cytoplasmic r RNA components, 25S and 16S, are not significantly affected by ozone. In contrast, ozone specifically decreases the relative level of 23S of chloroplast r RNA, as the rate of growth is inhibited.

A study was made of cytoplasmic and chloroplast ribosomes in the primary leaves of pinto bean plants exposed to ozone. The isolated ribosomes were analysed by sucrose density gradient. Ozone at the levels of 0·35 ppm for 20–35 min does not change the concentrations of various sedimenting particles of the cytoplasmic ribosomes. Ozone at similar levels, however, specifically decreases the population of chloroplast ribosomes per unit fresh weight of leaves. The distribution pattern of these chloroplast ribosomes is characterized by the low concentration of the fast-sedimenting polysome particles concomitant with the low magnitude of other slow-sedimenting components. The kinetics of ribosome populations during leaf growth demonstrates that ozone does not influence the daily levels of different ribosomal components of cytoplasmic ribosomes. However, ozone prematurely decreases the concentrations of polysomes and other components of chloroplast ribosomes below control level at the early stage of leaf development. These findings are discussed to explain initiation of the premature senescence caused by ozone.

Nonaqueous fractionation of leaves of the cotton plant suggested that carbonic anhydrase was associated with the chloroplasts. Activity of this enzyme in aqueous extracts prepared in media containing no reductants was stable at 4°. Response to sulfhydryl reagents varied. The results indicated that thiol groups, necessary for the activity of the enzyme, were partially protected from oxidation.

Spinach plants were treated with 0.35 ppm ozone and the photochemical activity of photosystem II determined after separation from the isolated chloroplasts using digitonin. Ozone impaired the activity of the system and also reduced the amount of β-carotene in the chloroplasts.