Changes in Phosphorus Fractions and Phytase Activity of Rice Seeds during Germination

The present experiment provides information on the phosphorus compounds in rice seeds and elucidates the changes they undergo during germination. In ungerminated seeds, the bulk of total-P appears in phytin (about 76 per cent). It is then dephosphorylated in course of germination with a simultaneous accumulation of large amounts of inorganic-P. Lipid-P increases very rapidly from 0 to 24 hours. The increase up to 72 hours is gradual, after which it drops at 96 hours and again rises to a maximum after 120 hours. The ester-P and RNA-P, fractions increase in concentration with time of germination (except 120 hours). Protein-P begins to fall after 48 hours, while DNA-P remains more or less constant throughout the experiment. The two pH optima recorded for phytase activity at 4.0 and 9.0, suggests that there exist two phytases, one acidic and the other alkaline. Both behave similarly during germination with a continuous increase throughout the course of the experiment. The enzyme with an optimal pH at 4 hydrolyses phytin more actively than the other with the pH optimum at 9.0. Phytase shows maximum activity at a stage when most of the phytin has disappeared; the metabolic significance is uncertain.     

Metabolic Changes in Developing Rice Seeds

Metabolic changes in developing rice seeds were studied with respect to respiration, carbohydrate and nitrogen fractions, nucleic acids and hydrolytic enzymes, viz. α-amylase, adenosine triphosphatase (ATPase) and phytase. — Respiration rate was maximum after 12 days from the date of pollination and became feeble afterwards with the fall in the moisture content of the maturing seeds. In the early stage, there was a preponderance of reducing sugars which were replaced later by nonreducing forms. Dry matter accumulation was mainly due to the steady rise in starch content. There was a gradual accumulation of protein nitrogen throughout the experiment, the rate being highest between 12–16 days. RNA content increased steadily till the seeds became mature, while DNA formed rapidly during the first 20 days and was maintained at the same level thereafter. —α-Amylase activity increased up to 20 days and declined sharply afterwards. The peak activities of ATPase and phytase were recorded at 32 and 24 days after pollination, respectively.     

Penicillin Induction of Gibberellin and {alpha}-Amylase Biosynthesis in Rice Endosperm

Penicillin induces the synthesis of -amylase in embryoless riceendosperm and enhances the gibberellin-induced response. Penicillininduction of -amylase can be prevented by inhibitors of nucleicacid and protein synthesis, CCC and 2,4-DNP. A characteristic gibberellin-like activity in the extracts frompenicillin-treated endosperms becomes detectable after 12 hfrom the addition of penicillin. This gibberellin-like activityis located on paper chromatograms at the R_F typical for GA₃and its formation is blocked by CCC, an inhibitor of GA biogenesis.Glucose has no effect on the biosynthesis of either gibberellinor -amylase induced by penicillin. The time-course study of the levels of different constituentsshows that penicillin probably induces RNA and DNA synthesisin the first place, which results in gibberellin biosynthesis,which in turn stimulates the synthesis of -amylase. The possiblemode of action of penicillin in higher plants is discussed.     

Characterization of Copper Texicity in Lettuce Seedlings

This paper provides information on the effects of toxic concentrations of cupric sulphate on the growth of lettuce (Lectuca sativa) seedlings. Root growth is completely inhibited at 5 x 10^-2M and germination stops altogether at 10^-1M. The relative inhibition of root growth is stronger than that of hypocotyl growth. Various metabolites and hormones are partially capable of relieving copper inhibition. Catalase, peroxidase and IAA-oxidase activity shows increments directly proportional to the concentration of copper. It is obvious that growth is inversely proportional to enzyme activity. The increased level of these enzymes is probably due to an accelerated protein synthesis.     

Modulation of Chlorophyll, Carotene and Xanthophyll Formation by Penicillin, Benzyladenine and Embryonic Axis in Mung Bean (Phaseolus aureus L.) Cotyledons

Penicillin stimulated the synthesis of pigments in the cotyledonsof intact embryos and excised cotyledons of mung bean (Phaseolusaureus L.) and enhanced benzyladenine-induced accumulation ofchloroplast pigments. The presence of the embryonic axis duringlight exposure proved to be beneficial for chlorophyll synthesisby the cotyledons whereas its presence in dark germination producedan adverse effect. The possible involvement of nucleic acidand protein synthesis in light-regulated chlorophyll formationis suggested. The stimulating effect on pigment synthesis providedby penicillin in this system seems to involve a maintenanceof nucleic acid and protein synthesis. Phaseolus aureus L., mung bean, pigment synthesis, cotyledons