Water added to dry seeds of jack pine evoked changes at the shoot apex which reflected the mobilization and consumption of food reserves for the synthesis of new protoplasm and for the formation of the prospective shoot. In shoot apices the distal zone contained large cells having nuclei with low affinity for stains. Flank and subapical zones had smaller cells with densely stained nuclei. These features did not alter during imbibition nor after the first wave of mitosis at 96 h when radicles emerged from seeds. Cells in the distal zone divided rarely. Mitosis, most abundant in subapices, decreased acropetally to the distal zone.In dry seeds, protein bodies and amyloplasts increased in size and frequency per cell from the distal zone in the basipetal direction towards the flanks and subapical zone. During imbibition most proteinaceous reserves, rich in arginine N, disappeared from all cells of the shoot apex. Lipid bodies in distal cells were small, numerous, and disappeared slowly as germination proceeded. Proplastids, mitochondria, and unidentified pleomorphic bodies were distributed in close proximity to the nucleus particularly in apical cells.Products of imbibed tritiated water (nonexchangeable tritium), and tritiated D-glucose, thymine, thymidine, and uracil were localized at the shoot apex and revealed assimilatory patterns consistent with cytochemical zonation. The covalent incorporation of tritium from water, while spread through most cells, was greatest in nuclei of flank and subapical cells. The radioactivity from glucose was found mainly in cell walls. Labelling by uracil, thymine, and thymidine by salvage mechanisms was especially abundant in nuclei of the flanks. These events coincided with dense RNA and DNA staining during germination. Collectively, observations indicated that at the flanks, water and seed reserves were concentrated at specific binding sites for the synthesis and dispersion of macromolecules before the visual production of leaf primordia.

In germinating jack pine, changes in nitrogenous compounds were separated into two phases, the first, where through imbibition, seeds expanded but the prospective seedling remained enclosed by the haploid and nutritive female gametophyte (0 to 3 days), and second, when radicles emerged and only cotyledons remained in contact with the gametophyte (4 to 11 days).During imbibition, total soluble N in seeds dropped and the amino acid pool was dominated by high levels of free arginine. As levels of arginine N declined the greatest changes in percentage composition involved glutamic acid (gametophyte) and glutamine (embryo). Thereafter, arginine N accumulated. By 7 days, arginine N was recovered in seedlings primarily from cotyledons. High asparagine levels were observed in stems and roots as glutamine N in the emerging seedling declined.Protein reserves in the seedling were nearly depleted by 4 days. Total protein and, at later stages, the ratio of hexone bases to dicarboxylic acids was generally higher in the gametophyte than in the seedling. Soluble proteins of the embryo were separated into at least 18 bands by disc electrophoresis and contained peroxidase activity which increased strongly after the first week of germination. The increase of nine isoenzymes of peroxidase with mobilities towards the anode correlated with the histochemical localization of peroxidase at the emerging shoot and root tips and throughout the vascular tissues.

1971. The metabolism and subcellular organization of the jack pine embryo (Pinus banksiana) during germination. Can. J. Bot. 49: 927-938. Les graines de Pin grts (Pinus but~ksiat~a) imbibCes d'eau absorberent rapidement de I'oxygene et 95% d'entre elles germerent. A mesure que les cellules des cotyledons grossissaient et se divisaient, la redistribution des hydrates de carbone, protdines et acide~ nucleiques, sous observation cytochimique, correspondait a certains chanqements dans I'organisation subcellulaire.Chez !es cotyledons dormants, il n'y avait aucun chloroplaste dans les cellules; cependant les rberves en lipides, les protides et les arnyloplastes abondaient. Mais apres 97 h dans I'eau, les rCserves en nourriture furent entiirernent consurrees, le nouveau cytoplasme apparut et de nombreuses particules similipolyscrnes quitterent le noyau et se repandirent dans le cytoplasme. Correspondant au premier cycle mitotique, les proportions de nucleotides solubles dans I'acide, d'ARN et d'ADN augnlentirent pendant les 4 premiers jours de la germination. L'ARN etait concentre dans les phrag~nosomes et dans les plaques cell~~laires nouvellement formees. Les proteines acidiques, d'abord trouvees surtout dans les protides des cellules seches, se trouvaient maintenant dans les nucleoles. Les histones Ctaient surtout associes aux chromosomes, bien que les proteines de reserve, riches en arginine, fussent observees dans les protides des cellules dormantes. Les proplastides, qui tventuellement se developperent dans les chloroplastes demeuraient t o~~t pres du noyau jusqu'a I'utilisation quasiment totale des reserves cytoplasrniques.Au moment oh le cotyledon etait "sevre," le cytoplasme des cellules en pleine croissance contenait plus de mitochondries, aussi de I'endoplasme brut reticulaire, des ribosomes, des appareils de Golgi et des chloroplastes a au pluq quatre grains d'amidon. Dix A d0ui.e jours apres le debut de la germination, le cytoplasme apparut sur le pourtour des membranes cellulaires par suite, de I'accumulation d'eau dans une grande vacuole.Water imbibed by jack pine seeds induced rapid oxygen uptake and over 95% germination. As cells of cotyledons expanded and divided the redistribution of carbohydrates, proteins, and nucleic acids, followed cytochemically, corresponded to changes in subcellular organization.In dormant cotyledons, cells lacked chloroplasts and were packed with lipid reserves, protein bodies, and a~nyloplasts. After 96 h of imbibing water, storage materials were consumed as new cytoplasm appeared and numerous polysome-like particles extended from the n~tcleus into the cytoplasnl. Levels of acid-soluble n~~cleotides, RNA. and DNA increased up to the f o~~r t h day of germination coinciding with the completion of the first mitotic cycle. RNA was concentrated in phragmoso~nes and at the newly formed cell plates. Acidic proteins, found mainly in the protein bodies of dry cells, were now localized in nucleoli. Histones were associated mainly with chromosomes, although in dormant cells, reserve pr...

In hypocotyls of dry jack pine seeds, RNA was localized mainly in nucleoli and throughout nuclei. After 4 days of imbibition, RNA increased in the cytoplasm and was concentrated particularly in phragmosomes during the first wave of cell divisions. At 5-6 days, when radicles had emerged, uracil-5 or 6-3H was readily degraded to β-alanine via dihydrouracil and β-urcidopropionic acid. The remaining 10% of the radioactivity was recovered mainly as uracil from ribosomal RNA. Polyacrylamide gel electrophoresis was used to separate RNA into ribosomal and transfer RNA fractions. Within 90 min up to 70% of the tritium incorporated into RNA was recovered from 18 and 25 S ribosomal RNA (0.7 and 1.3 × 106 daltons). At the shoot apex, radioactivity per unit area was localized nearly 2-fold more in nuclei than in the cytoplasm and particularly in nuclei from the anneau initial (peripheral zone). At later exposure times to uracil, more radioactivity was detected in the cytoplasm and throughout the shod apex.

Biochetnistry Sectior~, Forest Ecology Resetrrch Itrstitrrte, E t~~~i r o t~t n e t~r C(rt~crtln, Orr(rnvr, Can(r(I(r KIA OW5 Received May 6, 1974 DURZAN, D. J., V. CHALUPA, and A. J . MIA. 1976. Growth and metabolism ofcells and tissues of jack pine (Pit~rrs brrt~ksicrtlo). 1. The establishment and some characteristics of a proliferated callus from jack pine seedlings. Can. J. Bot. 54: 437445.No more than 2% of the embryos from dry seeds of jack pine (Pirrrts bntrksicrt~n Lamb.) produced callus on agar with a defined nutrient medium. When contact of the embryo with the nutritive female gametophyte was maintained during imbibition, callus production by excised seedlings on the medium increased to over 80%. Callus production was optimal with 5-day-old seedlings. Percentage callus formation was greater when the initial contents of the explant in dry weight. glutamate N. amide N, total nucleotides, RNA, adenylate energy charge, and oxygen uptake were alsogreater. Small initial increases in levels of these components over those found in dry embryos and resultingfrom imbibition substantially improved callus production. Subsequent increases, concomitant with germination and seedling development, gave only slightly more callus. By contrast, inverse or poor relations were observed with DNA. total soluble protein. and aminoacyl tRNA synthetase activity. In the initial explants the most conspicuous cytological events, leading to optimal callus production, were the onset of the first wave of mitosis and prominence of nucleoli. Seed reserves were nearly consumed and ribosome-like particles, which were associated with chromatin, appeared as new cytoplasm was being synthesized during the onset of proliferation of cells on the agar medium. DURZAN, D. J., V. CHALUPA et A. J . MIA. 1976. Growth and metabolism of cells and tissues of jack pine (Pitrrrs b(rt~k.sirrt~c~). 1. The establishment and some characteristics of a proliferated callus fromjack pine seedlings. Can. J . Bot. 54: 437445. Pas plus que 2% des embryons de graines seches d e pin gris (Pir1r1.s h(rt~k.sitrtrtr Lamb.) produisirent des callus sur un agar-agar milieu de nourriture definie. Lorsque le contact de I'embryon avec legamktophype femelle nutritiffut maintenu durant I'imbibition. la productionde callus par semis excises sur le milieu augmenta de plus de 80%. La production de callus etait optimale chez les semis de 5jours. Le pourcentage de formation de callus fut plus eleve lorsque le contenu initial de I'explante en poids anhydre. N glutamate. N amide, nucleotides totaux, ARN, charge d'energie d'adenylate et d'absorption d'oxygene s'avkraient aussi plus elevts. De petites augmentations initiales d e niveaux de ces composantes par rapport a ceux trouves dans les embryons secs et resultant de I'imbibition augmenttrent substantiellement la production de callus. Les augmentations subsequentes, concomitantes avec la germination et le developpement des semis produisirent seulement un peu plus de callus. Par contraste. des rapports inverses ou pauvres furent observes...