Microbody fractions not contaminated by mitochondria, plastids, or protein bodies were isolated from sunflower cotyledons during the transition of the cotyledonary microbody population from glyoxysomal to leaf peroxisomal function. In these microbody fractions, specific enzyme activities could be determined based on microbody protein content. The amount of microbody protein per cotyledon was estimated from the specific and total activities of isocitrate lyase and glycolate oxidase. This can be considered to be a relative measure of the size of the cotyledonary microbody population (number of microbodies per cotyledon). The amount of microbody protein per cotyledon remained constant over most of the transition period, declining only during the final stage. This result suggests that there is no pronounced and selective degradation of glyoxysomes during the transition in cotyledonary microbody function.
In order to elucidate the origin of the transtonoplast potential difference (PD) measured on isolated vacuoles, the possible contribution of the surface potential to the transmembrane PD was studied. The PD and the electrophoretic mobility were measured on vacuolar preparations, isolated from Beta vulgaris roots and Acer pseudoplatanus cells. Zeta potential was calculated from the electrophoretic mobility. The changes in zeta potential, in response to pH or to a cationic surfactant, were shown to induce parallel variations in the PD. These results suggest that the surface potential could contribute to the transmembrane PD of isolated vacuoles. Various hypotheses on the origin of this transtonoplast PD are discussed.
An enzymatic NAD(P)H oxidase activity that generates species of toxic oxygen was located at the level of the lutoidic tonoplast. The partial characterization of this enzyme shows that it is insensible towards classical inhibitors of respiratory chains, and still functions at very low oxygen concentrations. It is greatly activated by physiological concentrations of metallic cations (Fe3+ and Cu++), and by quinone-like compounds, among which naphtoquinones and ubiquinones may act as physiological activators or electron carriers.
Callus of Euphorbia tirucalli L. was initiated with stem segments cultured on MS medium containing 2,4-D (1 ppm) and NAA (2 ppm) (1-MS-N medium), and was maintained on the same medium plus kinetin (0.5 ppm) (1-MS-NK medium). A fine suspension culture was obtained by subculturing the fast growing callus in liquid medium made up of three volumes of 1-MS-NK medium and one volume of modified B5 medium (medium 8p) as described by Kao and Michayluk (1975). Cells then were subcultured in 1-B5 liquid medium. Protoplasts were isolated by digesting the walls of cells cultured as suspension by Driselase (1%) and Pectolyase (0.1%). When transferred to medium 8p the protoplasts divided and formed large cell clusters.
The resistance of the photosynthetic apparatus of primary leaves from Phaseolus vulgaris to short-term heat-shock (5 min) and to long-term heat-stress (1 to 5h) is studied. A model system is used, in which the aging of primary leaves is retarded by decapitation (removal of the apex). This offers the opportunity to compare leaves from the same calendary age (25 to 32 d) but being in different physiological states (mature or senescing). Photosynthetic CO2-uptake, chlorophyll fluorescence and the field-indicating absorbance change at 518 nm are measured with intact leaves after different heat-stress to characterize the pattern of heat-damage. It is shown, that there is no significant difference between the sensitivity of mature or aged leaves to short heat-treatments. However, the ability of leaves to increase their thermal stability during incubation at high, but not yet damaging temperatures (heat-hardening), clearly demonstrated in mature leaves, declines during aging and is almost absent in senescent leaves. This loss in adaptive changes may account for the decline in the overall resistance of the photosynthetic apparatus to longterm heat-stress observed during leaf-senescence.
We investigated the influence of monospecific antisera to monogalactosyl diglyceride and to digalactosyl diglyceride on the photosynthetic electron transport in chloroplasts of higher plants. Both antisera inhibit the photoreduction of dichlorophenolindophenol (DCPiP) with water as the native electron donor as well as the reduction of anthraquinone-2-sulfonate with the electron donor couple DCPiP/ascorbate. The degree of inhibition of the galactolipid antisera in the region of photosystem I depends on the pH and the temperature of the reaction assay. Treatment of the chloroplasts with sodium periodate or with lipase results in a complete loss of any inhibition by the galactolipid antisera. Treatment with β-galactosidase, however, had no influence on the reactions with galactolipid antisera. The sites of inhibition of the galactolipid antisera could be localized on the donor side of photosystem I as well as on the donor side of photosystem II. From this we conclude that the mono- and digalactosyl diglyceride molecules that are localized on the stroma side of the membrane are components of the photosystem I- and also of the photosystem II-protein-lipid-complex. We may conclude that there are obviously interactions between the galactolipid molecules and the photosynthetically active proteins, since the binding of antibodies leads to a partial blocking of electron transport.
The chloroplast-specific glycolipids monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulfoquinovosyldiacylglycerol and the prenylquinones α-tocopherol, plastoquinone-9 and phylloquinone were formed in the 70S ribosome-deficient leaf tissue of rye seedlings grown at a non-permissive temperature of 32°C. In light 32°-grown 70S ribosome-deficient leaves were chlorotic. Etiolated 32°-grown leaves contained about 50% of the protochlorophyll(ide) content of control leaves from permissive growth conditions (22°C). As in chloroplasts, monogalactosyldiacylglycerol and digalactosyldiacylglycerol were the predominating polar lipids in isolated bleached ribosome-deficient plastids. Sulfoquinovosyldiacylglycerol and the phospholipids phosphatidylcholine, phosphatidylglycerol and phosphatidylinositol were also present. The 32°-grown 70S ribosome-deficient leaves contained the same molecular species of monogalactosyldiacylglycerol and digalactosyldiacylglycerol as 22°-grown control leaves. As under permissive conditions linoleic and linolenic acid were the prevailing fatty acids of the galactolipids from 70S ribosome-deficient leaves. All enzymes of the biosynthesis of protochlorophyll(ide) and of the chloroplast glycolipids and prenylquinones must be synthesized on cytoplasmic 80S ribosomes. In accord with the reduction of the thylakoid system the ratio of monogalactosyldiacylglycerol to digalactosyldiacylglycerol was lower in 70S ribosome-deficient than in normal green leaves. In etiolated leaves grown at either 32°C or 22°C the amounts of the glycolipids and prenylquinones did not differ markedly. However, in light the glycolipid and prenylquinone contents remained almost as low in the bleached 70S ribosome-deficient leaves as in darkness, while several-fold increases accompanied greening of normal leaves in light. The data suggest that the light-mediated increase of glycolipids and prenylquinones depends on the availability of chlorophyll. The contents of steroidal saponins in oat leaves were slightly higher in light than in darkness and showed no specific relationship to the presence of etioplasts. They did not notably differ in 22°- or 32°-grown leaves.
Stock callus cultures of Carica papaya L. maintained in modified White's medium were grown in twenty media types. Growth, protease activity and total protein in extratives is reported. The basic Wood and Braun medium produced good growth and high protease activity. Reduction of macro- and/or microelements in Murashige and Skoog basic medium increased protein content and enzyme activity of the callus. In most cases, peptone was found to significantly increase growth, protease activity and protein content of callus cultures.
Spring and summer treatments like pruning, defoliation, disbudding and shoot bending greatly affect the depth and the development of bud dormancy in the following winter period. Correlations between plant parts are thus among the factors that control onset and course of dormancy and through which the behaviour of the plant in given winter climates could be modified.
A system for the regeneration of callus and albino plantlets from protoplasts of proso millet is described. Rapidly growing albino suspensions derived from mature seeds were used as the source of protoplasts. Protoplasts were cultured in drops of 0.07–0.25 ml in KM medium containing 1.0 mg · l−1 2,4-D and BAP. After 5 days, 7% of protoplasts had reformed cell walls and divided to form microcalli, but only 0.4% of plated protoplasts formed macrocalli. Over 20 albino shoots, 5 plantlets, and many roots were initiated by apparent somatic embryogenesis from protoplast-derived calli cultured for one or more passages on LS medium minus hormones.
Lutoids, the vacuo-lysosomes of the Hevea latex cells, compartmentalize, in vivo, numerous ions such as H+, Mg++, Ca++, Pi, citrate, some of them strongly toxic for the cytosolic metabolism. Evidence is given for the correlation of the in vivo compartimentation of some of these ions inside the lutoids with the latex production by Hevea.
While cytokinin-like activity was detected in aseptically cultured excised roots of Zea mays no evidence could be found that (8-14C)adenine or (U-14C)adenosine was incorporated into the biologically active compounds over a 42 day culturing period. This information raises serious doubts as to whether adenine and/or adenosine serve as primary precursors for cytokinin biosynthesis. The possibility does however, exist that the excised roots lacked a shoot produced precursor necessary for cytokinin production.
The resistance of cotton to water stress can be modified by the photoperiod: plants grown under short day conditions are resistant to water stress, and FR enhances their resistance. It has been shown that FR improves water economy.
The accumulation of abscisic acid (ABA) in wheat seedlings in response to drought stress was studied following treatment with cycloheximide, an inhibitor of protein synthesis on cytosol ribosomes, and with chloramphenicol, lincomycin and spectinomycin, inhibitors of protein synthesis on plastid ribosomes. Cycloheximide treatment for 2 h completely inhibited subsequent ABA accumulation, but treatment for 5 h with the three inhibitors of protein synthesis on plastid ribosomes had no effect. It seems likely, therefore, that stress-induced ABA synthesis requires rapid enzyme production in the cytosol but not in the plastid.
We have examined the effects of various inhibitors of glycollate metabolism on glycollate excretion, photosynthetic CO2 assimilation and N2 fixation by cyanobacteria. α-HPMS (α-hydroxy-α(2-pyridyl)-methane sulphonate) increased the rate of glycollate excretion by Anabaena cylindrica considerably, but also inhibited net CO2 photoassimilation and N2 fixation. α-HPMS inhibted glycollate dehydrogenase in A. cylindrica extracts but did not affect ribulose bisphosphate carboxylase or phosphoglycollate phosphatase activities. Diamox (5 acetamido-1,3,5-thiadizaole-S-sulphonamide) also stimulated glycollate excretion, inhibited CO2 fixation and caused a low inhibition of N2 fixation. INH (isonicotinic acid hydrazide) enhanced glycollate excretion by A. cylindrica, suggesting the metabolism of glycollate via the glycineserine pathway, but again inhibited CO2 fixation and N2 fixation. Glyoxylate also stimulated glycollate excretion by A. cylindrica, Anabaena variabilis and Nostoc muscorum. The data are discussed in terms of the specificity of glycollate metabolism inhibitors in cyanobacteria and the regulation of glycollate metabolism in these organisms.
The influence of ammonium on the development patterns of proteolytic enzymes and glutamine synthetase was examined during the germination and early seedling growth of mung bean. Protease and carboxypeptidase activities in the cotyledons of seedlings grown on water increased 15-fold and 7-fold, respectively over a 5-day germination period. The provision of 10 mM NH4+ to the seedlings decreased the enzyme activities by 30% in the cotyledons. A similar decrease in both protease and carboxypeptidase was observed with the hypocotyl of NH4 grown seedlings as compared to water control. Germination was accompanied by a marked decline in leucine aminopeptidase activity, and NH4+ did not appear to have a significant effect on the development pattern of this enzyme. A comparison of glutamine synthetase activity on day 5 between control and NH4+ showed that the enzyme level was repressed by 50%, 30%, and 25% in root, hypocotyl, and cotyledon, respectively, due to NH4+ treatment.
Gibberellic acid at 0.05 to 10 mg·l−1 stimulated asexual embryogenesis from embryogeniccompetent callus of clone BC 5 but not BC 36 of Theobroma cacao. AMO 1618 stimulated embryogenesis at 0.05 to 0.1 mg·l−1 but depressed embryogenesis above 0.1 mg·l−1 for clone BC 5. A similar but smaller effect was observed for BC 36. Daminozide and CCC depressed embryogenesis with both clones.
