Stimulation of Nitrate Reductase by Light and Ammonium in Spirodela oligorrhiza

Light-enhanced nitrate reductase (NR) activity was 8 times greaterthan the dark control. Exogenous application of sucrose, glucoseand fructose increased the induction of NR in the light as wellas in the dark, whereas glycolate had no effect. DCMU [3-(3,4-dichlorophenyl)-1, 1-dimethyl urea] completely inhibited thedevelopment of NR in light. Sucrose, when added with DCMU, reversedthis inhibitory effect NR in vivo was more stable in light thanin darkness, the half-lives being 9.6 h and 6.4 h, respectively.The addition of sucrose did not change the half-life of NR ineither light or darkness. Ammonium, the end product of the inorganicnitrogen assimilatory pathway, stimulated the NR activity whereasamino acids decreased it. Key words: Spirodela oligorrhiza, nitrate reductase, ammonium, light     

Dual Origin and Dimorphism of the Anther Tapetum in Alectra thomsoni Hook

The ontogeny of the dimorphic tapetal cells of Alectra thomsonihas been investigated. A layer of hypodermal cells first developsin each lobe of the anther and, from this, the primary parietallayer is cut off towards the outside of the lobe. Towards theinside, the primary sporogenous cells are formed. The primaryparietal layer undergoes a second periclinal division givingrise to two layers of cells; the outer of these develops intothe endothecium and the upper middle layer, while the inward-facinglayer forms the lower middle layer and part of the tapetum.The remainder of the tapetum is formed from the cells of theconnective tissue closest to the inner side of the sporogenousmass. No sterilization of the sporocytes has been observed.     

The Nature of Covering Around the Aggregate of Microspores in Pergularia daemia (Forsk.) McC. & Blat.

The covering around the pollinium of Pergularia daemia is sporopolleninin nature. It is homologous to the tapetal membrane investingthe inner tangential surface of the tapetum which is of theSecretory type.     

Absence of Callose Around the Microspore Tetrad and Poorly Developed Exine in Pergularia daemia

Callose is not localized in the walls of the microspore tetradof Pergularia daemia. At anthesis, the exine is thin and sparselydeposited.     

Ontogeny, Structure and Breakdown of Protein Bodies in Linum usitatissimum Linn.

In Linum usitatissimum protein bodies are observed in the cellsof endosperm and embryo. They originate in vacuoles. Proteinbodies have both crystalloid and globoid inclusions. The breakdownoccurs by vacuolization and fragmentation. Linum usitatissimum, seed, embryo, endosperm, protein bodies