Transport and Metabolism of Dihydrozeatin Riboside in Germinating Lupin Seeds

[³H]-dihydrozeatin riboside was applied selectively to the embryonicaxes or to the cotyledons of germinating lupin (Lupinus luteusL. cv. Weiko III) seeds 6 h following the start of imbibition.There was little transport of dihydrozeatin riboside from embryoto cotyledons up to 6 h after the application, but a substantialamount of radioactivity had moved into the cotyledons at theend of the 10 h incubation period. However, there was no detectablemovement of [³H]-dihydrozeatin riboside from the cotyledonsto the embryonic axis. This indicated a highly polarized movementof cytokinins during the early stages of seed germination. Exogenouslyapplied [³H]-dihydrozeatin riboside was found to be very stable,both when applied to the embryonic axes and cotyledons of intactseed, or following excision, and there was little metabolismwith only small amounts of radioactivity found associated withdegradative metabolites. The embryonic axis of this specieshas recently been found to synthesize cytokinins within 12 hfrom the start of imbibition, and the results of this studyindicate that the embryo-derived cytokinin is probably transportedto the cotyledons where it accumulates and subsequently participatesin the control of cotyledon function. Key words: Lupinus luteus, cytokinin transport and metabolism, dihydrozeatin riboside, seed germination     

The Biosynthesis of Cytokinins in Germinating Lupin Seeds

Imbibed intact seeds, and excised embryos and cotyledons ofyellow lupin (Lupinus luteus L. cv. Weiko III) have been incubatedwith [¹⁴C]-adenine to investigate cytokinin biosynthesis duringthe early stages of germination. Following incubation the tissueswere extracted and purified by solvent partition and chromatographyon cellulose phosphate, diethylaminoethyl cellulose and SephadexLH-20 columns. Using a variety of thin layer chromatographic,high performance liquid chromato-graphic and chemical procedures,incorporation of ¹⁴C into dihydrozeatin riboside and its nucleotidewas demonstrated in extracts of intact embryos, intact cotyledonsand excised embryos. However, radioactivity was not found associatedwith cytokinins in fractions derived from the isolated cotyledons.This is the first direct demonstration of cytokinin biosynthesisin germinating seeds and the results indicate that the capacityfor cytokinin biosynthesis is probably confined to the embryonicaxes. If this is so, the levels of [¹⁴CJ-dihydrozeatin ribosideassociated with intact embryo and intact cotyledon fractionsindicate that the synthesized cytokinin is transported to andaccumulates in the cotyledons. Key words: Lupinus luteus, cytokinin biosynthesis, seed germination     

印度东北部白垩纪-第三纪Xylariaceae化石孢子

在印度东北部白垩纪-第三纪沉积中发现了各种类型单沟无隔壁的Xylariaceae化石孢子,例如:Hypoxylonites,Spirotremesporites.Hypaxylonites等共计15种,其中6新种,它们是Hypoxylonites bhubanensis,H.elsikii,H.minimus,H.neogenicus,H.subrotundus和H.thindii,Hypoxylonites在本地区一般出现于晚白垩世地层中,占化石微体植物群总数的3%-4%,而在始新世它们的含量上升到植物群总数的20%-25%,从中新世直到早上新世这类孢子类型最多,含量最高,达植物群总数的40%-45%,到晚上新世含量突然下降,而Spirotremesporites在白垩纪未发现,到晚始新世时才出现,仅占孢粉总数的5%-6%,中新世时达25%-30%,到上新世末衰落,该属含5新种,Spirotremespores ellipticus,S.longilentus,S.miocenicus,S.reniformis,S.tertiarus.考虑到和这些种共生的Xylaria,Hypoxylon,Rosellinia及Daldina的孢子以及它们的地层分布,这类孢子的演化历史可能是受沉积盆地附近的古气候控制的.     

Possibility of a DNA-containing Mammary Tumour Virus in Red Blood Cells of Mouse

THE classical mammary tumour virus (MTV), also referred to as the Bittner virus, is transmitted in milk from mother to offspring. Studies^1–4 of the fate and biological behaviour of MTV in BALB/cfC3H (C⁺) mice suggested to us that MTV goes through a cycle in the infected host. Milk-borne MTV (M-MTV), assumed to be B particles, is abundantly present in milk and mammary tissues of infected mice. It seems likely that, on entering the host, M-MTV first infects the erythropoietic cells; subsequently the virus is carried into the general circulation chiefly inside the reticulocyte fraction² of red blood cells (RBC) in a form which we have called R-MTV⁴. We have also suggested⁴ that, in the MTV cycle, R-MTV functions in the infection of mammary tissues, which are the primary sites of production of M-MTV (or B particles). The latter form of the virus, in turn, is involved in the transport of the viral genome to the young through milk.     

Multiphasic uptake of phosphate by corn roots

Abstract The concentration dependence of phosphate uptake was studied using root sections of corn (Zea mays L. cv. Ganga 5). Detailed and wide-range (57 concentrations in the range 1 μmol m^?3-75 mol m^?3), precise (average SEM < 2.5%, n= 6) and reproducible (similar patterns in three independent experiments and for 5, 10, 15, 20, 25 and 30°C) data revealed six (or seven) concentration-dependent phases separated by ‘jumps’ or sharp breaks. These transitions were independent of temperature and occurred over relatively narrow concentration ranges (0.0001–0.0004, 0.08–0.31, 1.0–3.5, (7.5–10), 18–20 and 57–59 mol m^?3). The intermediate phases obeyed Michaelis-Menten kinetics, whereas sigmoidal kinetics were observed at lower concentrations. Uptake within each of the two highest phases increased more rapidly with increasing external phosphate concentration than predicted from Michaelis-Menten kinetics but also saturated more rapidly. The latter finding is not consistent with free diffusion across the plasmalemma at high external phosphate concentrations. Kinetic models yielding continuous isotherms, e.g. the sum of one or two Michaelis-Menten terms and a diffusion term, cannot account for the data.     

ANTIBIOTIC SUBSTANCES FROM A STRAIN OF BACILLUS SUBTILIS

SUMMARY: Strain B₇ of B. subtilis , isolated from soil collected from the gardens of the Bose Institute, Calcutta, was found to elaborate at least four different antibiotic substances. Fraction I was a brick red amorphous powder with certain resemblances to the bacillomycin group of antibiotics, soluble in alcohols, pyridine, etc., but insoluble in ether, water and acids. It had an ultraviolet absorption maximum at 276 mμ, melted with decomposition at 311°, and was a polypeptide positive to ninhydrin. On hydrolysis 12 amino acids were found. Fraction II was a white amorphous powder soluble in alcohols and ether but insoluble in water and petroleum ether. It melted at 158–162° and was a ninhydrin positive polypeptide composed of 7 amino acids. Fraction III was a yellow amorphous powder soluble in water and acetone, less soluble in ether and practically insoluble in chloroform. It was not a polypeptide. Fraction IV was a yellowish white amorphous powder with solubility characteristics similar to those of fractions I and II. It was a polypeptide composed of 10 amino acids.