Endogenous Gibberellins of Pine Pollen: III. Conversion of 1,2-[H]GA(4) to Gibberellins A(1) and A(34) in Germinating Pollen of Pinus attenuata Lemm

Gibberellins A₁ and A₃₄ (possibly A₂) were found as products of metabolism of 1,2-[³H]GA₄ during germination of Pinus attenuata pollen. The conversion from GA₄ to GA₁ and GA₃₄ occurred as hydroxylations at atoms C-13 and C-2 of the ent-gibberellane skeleton, respectively. Percentage interconversion of the GA₄ absorbed was in the range of 0.15 to 0.43% for GA₁ and 1.54 to 3.22% for GA₃₄. Identifications were made on a gas-liquid chromatograph with radioactive monitoring by comparison with standards.     

Endogenous Inhibitors for Pollen Germination and Pollen Tube Elongation in Pinus densiflora SIEB,et Zucc.

Sulfur metabolism in Cephalosporium acremonium was investigated using a mutant, 8650⁺/ OAH^?/SeMe^R, which could not convert cysteine or inorganic sulfur to methionine. The production of cephalosporin by the mutant depended on the amount of S-sulfocysteine in a chemically defined medium supplemented with a low level of methionine sufficient to support optimal growth. S-Sulfocysteine was detected in an extract of cells grown in the presence of sodium thiosulfate and l-serine. Furthermore, an NADPH-linked reduction of S-sulfocysteine to cysteine was demonstrated in a cell-free extract. These facts suggest that S-sulfocysteine is a direct precursor in cysteine biosynthesis in C. acremonium and an alternative pathway involving the compound is one of the most important ones in cephalosporin C production by this fungus.     

Studies on the Germination of Pine Pollen (Pinus mugo) in vitro. II. Effects of Different Ions

Studies on the initial germination of pollen of Pinus mugo showed no significant influence of ions on O₂ uptake and uptake of ³²P-labelled phosphate. At the onset of tube growth O₂ uptake decreased in the absence of calcium. In inorganic media tube growth and ³²P uptake were reduced in the absence of calcium or boric acid. In the absence of calcium a requirement for magnesium was observed. When the medium was deprived of polyvalent ions with EDTA, growth and ³²P uptake ceased. The presence of calcium in the medium was found to be essential for the maintenance of the structural and functional integrity of the cell membranne. — The ion requirement was more pronounced when tube growth was stimulated with sucrose. Calcium, magnesium, boric acid, and nitrate (as nitrogen source) were essential constitutents of the medium. The stimulation due to calcium required either magnesium or boric acid. — A density effect was observed which can be related to diffusible substances from the pollen into the medium. This was not observed when calcium and magnesium were present in the medium. The phenomenon is explained as an enrichment of the medium with diffusible substances from non-germinated dead pollen. — Germination and the tube growth were found to be greatly dependent on a short period of equilibration of pollen at room temperature before sowing.     

美国黄松、班克松和油松的抗寒性比较

通过人工冰冻和电导率的测定,对黄土丘陵沟壑区引种载培的美国黄松、班克松和乡土树种油松的抗寒性进行了鉴定,并探讨其抗寒机理.结果表明,班克松的抗寒性比油松强,而美国黄松的抗寒性比油松稍弱.班克松的束缚水/自由水比值高达7.0,组织中ABA含量高达164.3 μg·g^-1 FW;但可溶性糖和K⁺含量较低,分别为12.0%和2 450 μg·g^-1 DW.油松则是可溶性糖、K⁺和ABA含量都较高,分别为18.68%、4 538 μg·g^-1 DW和95.8 μg·g^-1 FW;束缚水/自由水比值较低,为2.58.美国黄松的可溶性糖含量较高,18.05％;但束缚水/自由水比值、K⁺和ABA含量都较低,分别为2.18、2 275 μg·g^-1 DW和63.3 μg·g^-1 FW,可能是其抗寒性较弱的内在原因.班克松较低的叶绿素含量和较高的类胡萝卜素/叶绿素比值对其抗寒性也有贡献.说明3种树种虽然都是抗寒树种,但其内在机理仍有差异.     

Studies on the Germination of Pine Pollen (Pinus mugo) in vitro. III. Inhibition by D-Mannose and Deoxyhexoses

D-Mannose, 2-deoxy-D-glucose, 6-deoxy-D-galactose, and 2-deoxy-D-galactose inhibit germination of pine pollen (Pinus mugo Turra) probably competitively with a metabolizable sugar. Inhibition by D-mannose, 2-deoxy-D-glucose, or 6-deoxy-D-galactose is reversed by transfer of pollen to sucrose medium, if the inhibitors was added before tube growth has started. In contrast, inhibition by 2-deoxy-D-galactose is irreversible except after very short exposures to the inhibitor, in which case the transfer results in reduced growth and germination. Incubation with 2-deoxy-D-glucose, 6-deoxy-n-galactose, or 2-deoxy-D-galactose after tube growth has started, results in irreversible inhibition of growth. If D-mannose is used, growth is resumed if the pollen are transferred to sucrose medium. Addition of D-mannose or lowering of the temperature prior to incubation with the deoxyhexoses protected against the irreversible growth inhibition. Uptake of oxygen and ³²P-labelled phosphate is reduced upon addition of either of the inhibitors.     

Changes in Endogenous Cytokinins of Lettuce Seed during Germination

Using the soybean callus bioassay it has been shown that dormant lettuce seeds (Lactuca sativa L. cv. Grand Rapids) contain large amounts of water soluble cytokinins and small amounts of butanol soluble ones. When the seeds are irradiated with red light, or imbibed with 5 mg/1 gibberellic acid in the dark, the total cytokinin content of the seeds decreases, the level of water soluble cytokinins decreases, and the level of the butanol soluble cytokinins increases. Far-red light does not reverse this effect completely although cytokinin activity in the butanol extracts decreases following such irradiation. It is proposed that the interconversion of cytokinins initiated by red light, or gibberellic acid in the dark, is one of the primary events leading to radicle elongation in light-sensitive lettuce seed.     

Changes in Nucleic Acid Fractions of Seed Components of Red Pine (Pinus resinosa Ait.) during Germination

Changes in nucleic acid fractions of Pinus resinosa during seed germination were studied. At various stages of seed germination, embryos and megagametophytes were surgically separated and nucleic acids were extracted separately by a phenol-method. Total nucleic acids were fractionated on single-layer methylated albumin kieselguhr (MAK) columns. Total nucleic acids in embryos increased significantly 2 days after seeds were moistened, whereas, in megagametophytes, total nucleic acids stayed almost at a constant level until they degenerated at the time of shedding. In embryos, ribosomal RNAs (rRNA) increased 2 days after seeds were sown, whereas soluble RNA (sRNA) increased at 3 days. By comparison, nucleic acid fractions of megagametophytes did not show any quantitative changes during germination, except that rRNA fractions decreased shortly before shedding of seed coats. In dormant embryos the proportion of DNA was high and the proportions of sRNA and rRNA were low, whereas in megagametophytes at dormancy the proportions were completely reversed. As seed germination progressed, proportions of nucleic acid fractions in embryos changed significantly. In megagametophytes, although proportions of individual fractions remained almost constant throughout the experimental period, incorporation of ³²P into sRNA and rRNA of megagametophytes indicated turnover of these fractions.     

Studies on the Germination of Pine Pollen (Pinus mugo) in vitro. I. Growth Conditions and Effects of pH and Temperature on Germination, Tube Growth and Respiration

The ability of pine pollen to grow in vitro is discussed in relation to its in situ. Optimal conditions of growth in vitro were investigated. All the experiments were made with pollen of Pinus mugo Turra. A satisfactory medium is described as that which at pH 5.2 and at 29 °C can lead to a tube growth bigger than in vivo. The initial growth (0–30) hours) in terms of tube growth and respiration is described in detail. It is shown that a correlation exists between tube growth and respiration. A method for estimating the metabolism and growth of the pollen tube, based on the uptake of ³²p-labelled phosphate, is described. Addition of known stimulators of plant growth and extension does not stimulate tube growth. Temperature studies show that under 20°C germination does not take place.     

Primers designed to amplify a mitochondrial nad1 intron in ponderosa pine, Pinus ponderosa, limber pine, P. flexilis, and Scots pine, P. sylvestris

The b/c intron of the mitochondrial nad1 gene, was sequenced to characterize the indel region of ponderosa pine, Pinus ponderosa. The sequence in ponderosa pine was aligned with the sequence in Scots pine, Pinus sylvestris, to design seven primers that are useful for sequencing and for revealing size variation in amplified fragments in ponderosa pine, Scots pine, and limber pine, Pinus flexilis. These primers reveal variability in all three species, and the pattern of variability within ponderosa pine is described by a preliminary survey. The indel region of ponderosa pine contains three distinct elements with lengths of 31, 32, and 34 bp. Received: 1 March 2000 / Accepted: 14 April 2000<@head-com-p1a.lf>Communicated by P.M.A. Tigerstedt     

Changes in Endogenous Growth Kegulators in Loblolly Pine Seeds During the Process of Stratification and Germination

The seeds of loblolly pine (Pirns taeda L.) were cold-stratified for 0, 14, 28, 42, and 56 days. Endogenous growth regulators were extracted from these seeds, and also from the germinating and the 28-day warm stratified seeds. Partially purified extracts were separated on chromatographic paper. The chromatograms were cut into 10 equal segments, and these were tested for biological activity using three different btoassays. The results indicated that the unstratified seeds and those stratified up to a period of 28 days contained very little or no growth promoter (GA-like substances), and a relatively high concentration of an inhibitor (presumably abscisic acid), Following 42-day stratification, the promoter concentration gradually increased while the inhibitor level fell almost to zero. A high level of promoter but no inhibitor was detected in germinating seeds. No auxin-like activity was noted in the unstratified seeds. This activity slowly increased up to a period of 28 days and remained at this level for the subsequent stratification periods. However, the activity greatly increased in the germinating seeds. Very little changes in the levels of growth regulators were noted in warm-stratified seeds as compared to the unstrati-fied controls.     

朱顶红花粉萌发过程中营养细胞质的超微结构变化

本文应用透射电镜对朱顶红成熟花粉水合、活化和萌发的动态过程中营养细胞质的结构和组成变化进行了观察。成熟花粉具质体、线粒体、内质网、高尔基体。微丝束以聚集体的形式存在。花粉活化后,细胞器的数目和结构发生显著变化：质体和线粒体的片层明显增加,内质网片层狭窄,高尔基体活跃产生小泡,脂体降解及微丝聚集体散开。花粉萌发后,细胞质中出现周质微管和被刺小泡,此期细胞器的变化不明显。微丝以纤丝状遍布整个花粉管中。     

Isolation and culture of protoplasts from cotyledons of Pinus coulteri D. Don.

A protocol was developed for the isolation and culture of protoplasts from the cotyledons of seedlings of Pinus coulteri D. Don. Incubation of cotyledon pieces in a mixture consisting of cellulase Onozuka R10 2%, Pectolyase Y-23 0.1%, mannitol 10%, CaCl₂ 500 mg/l and other macro and micro-nutrients yielded viable protoplasts. After 24 hours of culture in a complex nutrient medium, the protoplasts regenerated new cell walls and the first divisions were observed within 7–10 days. Small cell colonies were formed within 15–20 days, but these started to accumulate phenolics and no further growth of the colonies was observed.     

Role of Endogenous Plant Growth Regulators in Seed Dormancy of Avena fatua: II. Gibberellins

Gibberellin A₁ (GA₁) was identified by combined gas chromatographymass spectrometry as the major biologically active gibberellin (GA) in seeds of wild oat (Avena fatua L.) regardless of the depth of dormany or stage of imbibition. Both unimbibed dormant and nondromant seeds contained similar amounts of GA₁ as estimated by the d5-maize bioassay. During imbibition, the level of GA₁ declined in both dormant and non-dormant seeds, although the decline was more rapid in dormant seeds. Only in imbibing nondormant seeds did the GA biosynthesis inhibitor, 2-chloroethyltrimethyl ammonium chloride (CCC), cause a reduction in the level of GA₁ from that observed in control seeds. These results are interpreted as an indication that while afterripening does not cause a direct change in the levels of GAs during dry storage, it does induce a greater capacity for GA biosynthesis during imbibition.

Nondormant seeds imbibed in the presence of 50 millimolar CCC germinated equally as well as untreated seeds. When wild oat plants were fed CCC throughout the entire life cycle, viable seeds were produced that lacked detectable GA-like substances. These seeds afterripened at a slightly slower rate than the controls. Moreover, completely afterripened (nondormant) seeds from plants fed CCC continuously contained no detectable GA-like substances, and when these seeds germinated, dwarf seedlings were produced, indicating GA biosynthesis was inhibited during and after germination. In total, these results suggest that the increased capacity for GA biosynthesis observed in imbibing nondormant seeds is not a necessary prerequisite for germination. It is therefore possible that GA biosynthesis in imbibing nondormant seeds is one of many coordinated biochemical events that occur during germination rather than an initiator of the processes leading to germination.

     

Changes in Endogenous Cytokinin Levels in Kernels of Zea mays L. during Imbibition and Germination

In order to assess the potential role of endogenous cytokininsin the germination of Zea mays L. caryopses, cytokinin activitywas determined in mature kernels and in kernels 1, 2, and 3d after imbibition. Cytokinin activity was also recorded inthe endosperm and embryo tissue of mature kernels and of kernels3 d after imbibition to establish the localization and changesin the levels of endogenous cytokinins during imbibition andearly germination. Using chromatographic, chemical, and enzymic techniques, compoundswith chromatographic properties resembling those of zeatin,zeatin riboside, zeatin glucoside, zeatin riboside glucoside,and their respective dihydro derivatives were detected in extractsfrom mature maize kernels. From analyses of the endosperm andembryo tissue at the two stages, it appears that the cytokininglucosides present in the endosperm are transported to the embryonicaxis for utilization in growth and development of the seedling.This concept is supported by the fact that the levels of ß-glucosidaseactivity detected were highest in the embryos, particularlyin the radicles, 3 d after imbibition.     

Gibberellins and heterosis in maize : I. Endogenous gibberellin-like substances

Under controlled environment and/or field conditions, vegetative growth (height, internode length, leaf area, shoot dry weight, grain yield) was greater in an F₁ maize hybrid than in either parental inbred. Endogenous gibberellin (GA)-like substances in apical meristem cylinders were also higher in the hybrid than in either inbred, both on a per plant and per gram dry weight basis. There were no apparent qualitative differences in GA-like substances, however. Levels of GA-like substances in all genotypes were highest prior to tassel initiation. Chromatographic comparisons of the GA-like substances and authentic standards of GA native to maize on gradient-eluted SiO₂ partition and reverse-phase C₁₈ high-pressure liquid chromatography columns are described. No consistent differences in abscisic acid levels of the three genotypes were observed. This correlation of heterosis for endogenous GA-like substances with heterosis for growth suggests that amounts of endogenous GA may be related to hybrid vigor in maize.     

Preformed mRNA and Light-induced Germination of Pine (Pinus thunbergii) Seed

The mRNAs were isolated from dry, dark-imbibed and light-imbibedpine (Pinus thunbergii) seeds, in which germination is inducedupon exposure to light, and their translational activities ina wheat embryo cell-free system were examined. A portion ofthe mRNA extracted from each type of seed appeared to be poly(A)⁺RNA.A significant translational activity was already present inthe RNA fraction isolated from the dry pine seeds. The preformedmRNA seems not to be translated in vivo during the dark-imbibition,since most of the in vivo protein synthesis did not occur untilthe seeds were exposed to light. The SDS polyacrylamide gelelectrophoregrams of the polypeptides synthesized in vitro inresponse to either the preformed mRNA or the mRNAs from thedark-imbibed or light-imbibed seeds were qualitatively identical;thus it seems that the preformed mRNA is conserved during darkimbibition, and that its translation is initiated after theexposure of the imbibed seeds to light. (Received August 10, 1981; Accepted May 15, 1982)     

Variations in Endogenous Gibberellins in Developing Bean Seeds II. Changes Induced in Acidic and Neutral Fractions by GA(1)

Immature (8-mm), medium mature (11-mm), and mature green (16- and 17-mm) bean seeds (Phaseolus vulgaris L. cv. Kentucky Wonder and Bountiful) were incubated in gibberellin A₁ solutions for 24 hours at 20°. Extracts from the seeds were separated into nonacidic, acidic ethyl acetate, and acidic butanol fractions. These were chromatographed. The eluates of the chromatograms were tested on Progress No. 9 dwarf peas grown under red light. The level of neutral gibberellin-like substances remained unchanged in immature seed, but they increased markedly in mature green seeds. Coincident with increased levels of the neutral substances, there were significant decreases in acidic ethyl acetate-soluble gibberellin-like substances, including applied GA₁, and in 1 acidic butanol-soluble gibberellin-like substance. Seed incubation in GA₁ brought about increased activity of substance B-II in immature and medium mature seeds. The level of butanol-soluble gibberellin-like substance B-I in seeds of any size was not affected by incubation in GA₁. Considering the marked increases in activity induced in the neutral fraction and the decreases in activity of certain eluates from the chromatograms of the acidic fractions, it was concluded that the neutral fraction may serve as a reserve form of gibberellins in the dry seed. The acidic ethyl acetate substances and substance B-II may be required for normal development of the bean seed.     

Effect of Growth Regulators and Light on Pollen Germination and Pollen Tube Growth in Pinus roxburghii Sarg

Pine (Pinus roxburghii) pollen grown in suspension cultureswas used to study the effects of growth regulators and lightconditions on germination and pollen tube growth. Indol-3-ylacetic acid, gibberellic acid, ethylene, abscisic acid and cyclicAMP (cAMP) at low concentrations (1–10 mg 1^–1) promotedgermination and tube growth. Addition of 1 and 10 mg 1^–1cAMP to any of the growth regulators had a promotory effect.Pollen tube growth decreased in white light as compared to thedark, and was increased in red light. Far-red light counteractedthe effect of red light. The effect of growth regulators incausing the enhanced tube growth appears to be manifested throughsubstances such as cAMP, and phytochrome seems to be involved. Pinus roxburghii, pine, pollen germination, pollen tube growth, growth regulators, cyclic AMP, phytochrome