Cell Morphogenesis and Macromolecule Synthesis during Phytochrome-controlled Germination of Spores of the Fern, Pteris vittata

The object of this study was to characterize the pattern ofcell morphogenesis and synthesis of nucleic acids and proteinsduring phytochrome-controlled germination of spores of the fern,Pteris vittata. Phytochrome activation and germination wereinitiated in fully imbibed spores by exposure to a saturatingdose of red light. At timed intervals thereafter, spores werefixed in acrolein and embedded in glycol methacrylate for examinationin the light microscope. The first sign of germination, visiblein sections of the spore 12 h after irradiation, was the hydrolysisof storage protein granules. This was followed by a migrationof the nucleus from its central location to one side of thespore. Subsequently, the protoplast enlarged at the site ofthe nucleus and appeared outside the exine as a papillate structure.An asymmetrical division of the protoplast gave rise to a smallcolourless rhizoid cell and a large, chloroplast-containingprotonemal cell. During the early phase of germination, DNAwas synthesized both in the nucleus and cytoplasm as judgedby autoradiography of [³H]thymidine incorporation. [³H]Uridine,a precursor of RNA synthesis, was incorporated into the nucleolusand the rest of the nuclear material of germinating spores.Protein synthesis monitored by [³H]leucine incorporation occurredboth in the nucleus and cytoplasm during the early stage ofgermination, although a strictly cytoplasmic protein synthesiswas observed later. Addition of cycloheximide completely inhibitedgermination of photoinduced spores and incorporation of labelledprecursors of macromolecule synthesis into cellular components.Actinomycin D was much less effective as an inhibitor of germinationand, even in high concentrations of the drug which effectivelyinhibited DNA and RNA synthesis in spores, proteolysis and proteinsynthesis appeared normal. These findings are discussed withrespect to the regulation of nucleic acid and protein synthesisduring spore germination and the role of phytochrome in theprocess.     

A Role for Purines and Pyrimidines of Ribonucleic Acid in the Induction of Two-dimensional Growth in the Gametophytes of the Fern, Asplenium nidus

The inhibition of two-dimensional growth in the gametophytesof Asplenium nidus induced by purine and pyrimidine analoguesand the reversal of inhibition by natural purine and pyrimidinebases and their derivatives have been studied. Adenine and guanineand their ribosides and ribotides were more effective than cytosine,uracil, thymine, and their derivatives in preventing the inhibitiondue to 8-azaadenine and 8-azaguanine. Likewise, the inhibitoryeffects of 2-thiocytosine, 2-thiouracil,6-azauracil, and 5-fluorouracilwere overcome by the pyrimidines and their derivatives, butnot usually by the purines.Combinations of two purine analoguesor two pyrimidine analogues or one purine analogue and one pyrimidineanalogue inhibited growth more effectively than single compounds.The combined inhibitions were maximally reversed when both naturalbases or their derivatives were added to the medium. It is concludedthat there is a requirement for both purines and pyrimidinesof ribonucleic acid in the induction of two-dimensional growthin the gametophytes of Asplenium nidus.     

ELECTROPHORETIC AND IMMUNOLOGICAL STUDIES OF THE MALE ACCESSORY REPRODUCTIVE GLAND PROTEINS OF POECILOCERA PICTA FABR. (ACRIDIDAE: ORTHOPTERA)

Electrophoretic separation of the protein extracts of the whole accessory reproductive gland (ARG) reveals a progressive increase in number of fractions from day 0 to day 12 of adult life. The number of fractions secreted by the different types of tubules, viz., white tubules, hyaline tubules and seminal vesicles, varies. The protein concentration of the ARG of 12-day-old insects is four times higher than that of newly emerged adult insects. Three protein fractions of the ARG extract are immunologically precipitatale by antiserum to whole accessory gland complex. Immunoelectrophoresis of the oocyte extract from mated females and total protein extract of empty spermatophores revealed that one fraction of the oocyte protein and two of the spermatophores have their immunological counterparts in the whole ARG extract.     

Somatic Embryogenesis in Carrot Cell Suspension: I. PATTERN OF PROTEIN AND NUCLEIC ACID SYNTHESIS

The role of macromolecule synthesis during the early hours ofundifferentiated growth of carrot cell suspension in a mediumcontaining the synthetic auxin, 2,4-dichlorophenoxyacetic acidand during embryogenic growth in an auxin-free medium was investigated.For each set of cultures, total protein and RNA, rate of proteinsynthesis, changes in ATP pool, and rate of RNA synthesis weredetermined. Although no changes in protein and RNA contentsof cells were noted during the first 48 h of their growth infresh media, the rate of protein synthesis in the embryogeniccells markedly increased over that of the non-embryogenic cellsas early as 2 h. ATP pool size in both types of cells stabilizedwithin 1 h and it registered only a slight decrease over a 24h period. Rate of RNA synthesis increased in the embryogeniccells from 4 to 12 h following their transfer to fresh medium,after which it decreased. Transfer of carrot cells of zero embryogenicpotential to an auxin-free medium did not however elicit themacromolecule synthetic pattern characteristic of the highlyembryogenic cells.     

Effects of fluorinated pyrimidines on the growth of excised pea embryos

The effects of some fluorinated pyrimidines on the growth ofexcised pea embryos {Pisum sativum var. Alaska) in sterile culturewere studied. Even the lowest concentrations of the compoundstested inhibited growth in length of the embryos. In order ofdecreasing activity, the compounds tested were : 5-fluorodeoxyuridine,5-fluorodeoxycytidine, 5-fluorouridine, 5-fluoroorotic acidand 5-fluorouracil. Inhibition of growth in length of the rootprimordia was found to be mainly due to inhibition of cell divisionwith no effect on cell elongation. Reversal of fluoropyrimidineinduced inhibition of growth by pyrimidine bases and their relatedmetabolites indicated that the analogues primarily inhibitedDNA synthesis. ¹Part of a thesis submitted by the senior author for the degreeof M.Sc. of the University of Malaya ²Present address: Department of Botany, University College ofWales, Aberystwyth, U.K. (Received October 27, 1969; )     

Effects of Light and Growth Substances on the Diurnal Movements of the Leaflets of Mimosa pudica

The leaflets of Mimosa pudica show diurnal opening and closingmovements for some days when they are removed in pairs fromthe parent plant along with the pulvini and a small sectionof the rachis, and floated in water. The movements can be measuredfrom changes in the angle of the blades. When the leaflets arekept in darkness they show a diurnal movement of opening inthe morning at the same time as opening occurs in light. Light,however, is necessary to prevent the leaflets from closing duringthe day after an initial opening. Blue light was most effectivein maintaining the open condition throughout the day. Low concentrationsof indole-3-acetic acid (IAA) and gibberellic acid (GA) promotedopening of the leaflets while higher concentrations preventedtheir closure at night. IAA and GA acted synergistically inreducing dark-closure. Growth substances also prevented daylightclosure of the leaflets in the dark. The results arre discussedin relation to the changes in the osmotic relations of pulvinarcells regulating leaf movements.     

Effects of Growth Retardants on the Growth of Excised Roots of Dolichos lablab L. in Culture

The effects of various growth-retarding chemicals on the growthof excised roots of Dolichos lablab in sterile culture are investigated.Application of a range of concentrations of CCC, phosfon, andB-995 inhibited growth in length of the roots by reducing thefrequency of cell division, with little or no effect on cellelongation. Treated roots had generally lower DNA, RNA, andprotein contents than controls, although CCC-treatment significantlyenhanced the soluble nitrogen content of the roots. The inhibitoryeffects of growth retardants were not reversed by IAA or GA,but substances like choline chloride and pyridoxine hydrochloridewere partially effective in reinstating normal growth in rootsgrowing in concentrations of CCC producing about 50 percentinhibition of growth in length.     

DNA Synthesis and Cell Division During Spore Germination in Lygodium japonicum

This paper describes the ontogenetic sequence of cell divisionsand associated DNA synthetic patterns observed in sectionedspores of Lygodium japonicum (Thunb.) Sw., collected at differentstages of germination. Following exposure to a saturating doseof red light, the spore undergoes an asymmetric division toform a basal cell, which retains nearly all of the storage inclusions,and an apical cell which expands and protrudes from the rupturedsporoderm. Division of the apical cell results in formationof a protonemal cell and an intermediate cell. Subsequently,the latter cell divides to form the primary rhizoid and a wedgecell adjacent to the protonemal cell. Secondary rhizoids mayarise from later divisions of either the basal cell or the wedgecell. In addition, the wedge cell appears to have the capacityto form a secondary prothal-lial filament. Histochemical localizationof cell constituents indicates an increasing concentration ofcytoplasmic RNA and protein in the presumptive protonemal regionof the spore cell prior to division. Autoradiography of ³H–thymidineincorporation has shown that synthesis of nuclear DNA precedeseach cell division. Although strictly nuclear DNA synthesisoccurs during early stages of germination, extra-nuclear DNAsynthesis increases greatly following division of the sporecell. The results are discussed in relation to earlier studieson cell division patterns seen in whole mount preparations ofgerminating spores of different species of Lygodium. Lygodium japonicum, spore germination, cell division, DNA synthesis