Seasonal uptake of 15N-nitrate and distribution of absorbed nitrogen in peach trees

The absorption and distribution of N was measured monthly throught a calendar year in 3-year old peach trees (Prunus persica (L) c.v. Maycrest) grafted on Nemaguard rootstock. Plants were grown on siliceous sand in 500-L pots and fertilized with a solution containing ¹⁵N enriched KNO₃. During flowering and fruit set (March) approximately 7% of N found in new growth came from the fertilizer and the remainder came from the N stored in the old organs. Maximum N absorption took place during the periods of fruit ripening and maximal vegetative growth (May to August). This nitrogen was relocated from leaves to woody tissues and stored as reserve-N before leaf fall. In the following growth season reserve-N was used for flower development and new shoot growth. The N absorbed during plant dormancy was quite low and remained in the stem bark and roots mainly as soluble-N.     

A FERTILE AXIS OF TRILOBOXYLON ASHLANDICUM,A PROGYMNOSPERM FROM THE UPPER DEVONIAN OF NEW YORK

A partially petrified impression of Triloboxylon ashlandicum (Aneurophytales) is the first recognized fertile axis of the genus. Identification of the fertile axis rests on the similarity of its anatomy with that of previously described vegetative specimens. Fertile organs replace some vegetative branches along part of the main axis. Fertile organs are twice dichotomized in one plane and bear elongate sporangia arranged pinnately. Vegetative branches differ in that they bear the ultimate appendages of the plant helically. The latter organs dichotomize many times in one plane. Although similar in size and morphology to the ultimate appendages, the fertile organs are homologous by position and vascular supply to the vegetative branches which they replace. Sporangia of T. ashlandicum dehisce longitudinally and terminate in an apiculate tip. Spores are unknown. Fertile organs of T. ashlandicum resemble those of other Aneurophytales and support the earlier placement of Triloboxylon in the order on anatomical grounds. T. ashlandicum differs from other Aneurophytales, however, by bearing vegetative organs at the distal end of its fertile axis.     

Carbohydrate Composition during Germination and Outgrowth of Ascospores of Saccharomyces cerevisiae

Single spores of Saccharomyces cerevisiae were examined to distinguish changes in the synthesis and degradation of intracellular and wall carbohydrates during germination and outgrowth. Intracellular carbohydrate was fractionated into trehalose and glycogen. Trehalose degradation occurred during germination and outgrowth. The intracellular glycogen was degraded during germination and then synthesized during outgrowth. Wall carbohydrate was fractionated into glycogen, glucan and mannan. The wall glycogen and the KOH-soluble glucan were degraded during germination and then synthesized prior to and during outgrowth, respectively. The major component of the KOH-insoluble glucan in the wall is β-1,3-glucan. The glucan and mannan were synthesized during outgrowth.

The study revealed that the development of a vegetative cell from a spore follows rapid decreases in the amounts of trehalose, glycogen and KOH-soluble glucan during germination, and great increases in the amounts of glycogen, β-1,3-glucan and mannan during outgrowth.     

Vegetative regeneration on sexual organs inPhycomyces blakesleeanus

Phycomyces blakesleeanus produced an abundance of sexual organs when two mating types met on solid medium, but only about 14.7% of the sexual organs developed to the final stages. On the sexual organs showing arrested development, vegetative hyphae or dwarf sporangiophores (microphores) often regenerated. This vegetative regeneration was accelerated when the paired and looped progametangia were isolated from mycelia, when the counterparts of the progametangial cells constructing the loop were surgically incised, and whenPhycomyces was mated at high temperature (25–27°C). A leaky-carotenogenic mutant, whose sexual reaction was imperfect and arrested at an intermediate stage even when mated with the wild type, also regenerated hyphae with a high frequency on these arrested intermediate organs. The vegetative regeneration seems to result from interruption of a cell-to-cell recognition system between cells of different mating type, which is believed to be essential for the mating process of this fungus in addition to the pheromonal actions.     

夹竹桃科2种引种植物分泌结构的解剖学研究

为了解夹竹桃科(Apocynaceae)植物乳汁管的发生发育,对爱之蔓(Ceropegia woodii)和百万心(Dischidia ruscifolia)营养器官中的分泌结构进行了显微观察。结果表明,爱之蔓和百万心营养器官中均有无节分枝乳汁管的分布,茎皮层中的乳汁管大部分具有明显的分枝,叶中乳汁管具明显分枝,分布与走向多与叶脉维管组织平行。另外,爱之蔓营养器官中的分泌结构除乳汁管外,还有分泌腔。这为夹竹桃科植物的系统分类研究提供了解剖学依据。     

(1–3)-β-Glucan synthesis ofNeurospora crassa

(1–3)--d-Glucan synthase activity ofNeurospora crassa was localized to the plasma membrane by autoradiography of colloidal gold-labeled plasma membranes. The active site of glucan synthase for substrate hydrolysis was determined to be cytoplasmic facing. However, glucan synthase activity present in intact protoplasts was partially sensitive to Novozym 234 and to glutaraldehyde treatments, suggestive that enzyme activity is transmembrane. Enzyme activity also directed the formation of microfibrils in vitro. Taken together, these and previous results support the following scheme for glucan synthesis: 1. The sequential addition of glucose residues from UDP-glucose to glucan chains occurs on the cytoplasmically facing portion of glucan synthase. 2. As each glucan chain is synthesized, it is extruded to the extracytoplasmic side of the plasma membrane. 3. As each chain is extruded, it forms interchain hydrogen bonds with adjacent chains, resulting in glucan microfibril assembly.     

OCCURRENCE AND CHARACTERIZATION OF ARABINOGALACTAN‐LIKE PROTEINS AND HEMICELLULOSES IN MICRASTERIAS (STREPTOPHYTA)1

The cell wall of the green alga Micrasterias denticulata Bréb. ex Ralfs (Desmidiaceae, Zygnematophyceae, Streptophyta) was investigated to obtain information on the composition of component polysaccharides and proteoglycans to allow comparison with higher plants and to understand cell wall functions during development. Various epitopes currently assigned to arabinogalactan‐proteins (AGPs) of higher plants could be detected in Micrasterias by immuno TEM and immunofluorescence methods, but the walls did not bind the β‐d ‐glycosyl‐Yariv (β‐GlcY) reagent. Secretory vesicles and the primary wall were labeled by antibodies against AGPs (JIM8, JIM13, JIM14). Dot and Western blot experiments indicated a proteoglycan nature of the epitopes recognized, which consisted of galactose and xylose as major sugars by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC‐PAD). Epitopes of alkali‐soluble polysaccharides assigned to noncellulosic polysaccharides in higher plants could be detected and located in the wall during its formation. The polyclonal anti‐xyloglucan (anti‐XG) antibody labeled primary and secondary wall of Micrasterias, whereas the monoclonal antibody CCRC‐M1, directed against the fucose/galactose side chain of xyloglucan (XyG), did not recognize any structures. Labeling by anti‐XG antibody at the trans‐sites of the dictyosomes and at wall material containing vesicles indicated that secretion of the epitopes occurred similar to higher plants. The presence of (1→3, 1→4)‐β‐glucan (mixed linked glucan) in the secondary cell wall but not in the primary cell wall of Micrasterias could be demonstrated by an antibody recognizing this glucan type, whereas (1→3)‐β‐glucan (callose) could not be detected. The analytical results revealed that alkali‐soluble polysaccharides in the secondary wall of Micrasterias consist mostly of (1→3, 1→4)‐β‐d ‐glucan.     

白花前胡营养器官结构及其分泌道分布规律的研究

运用石蜡切片方法,观察白花前胡营养器官的显微结构及其分泌道的分布特征,以明确营养器官内分泌结构的分布规律,为揭示白花前胡次生代谢产物的积累提供解剖学依据。结果表明,(1)白花前胡成长根从外到内由周皮、中柱鞘薄壁组织和次生维管组织组成,而且中柱鞘薄壁组织不同于一般双子叶植物根的结构;茎从外到内由表皮、皮层和维管柱组成;叶为异面叶结构。(2)白花前胡根、茎及叶中均有分泌道存在,分泌道在根中分布于中柱鞘薄壁组织和次生韧皮部中,茎中分布于皮层和髓中,叶中分布于维管束上下两侧的薄壁组织中。     

Characterization of Aspergillus nidulans α‐glucan synthesis: roles for two synthases and two amylases

Cell walls are essential for fungal survival and growth. Fungal walls are ～ 90% carbohydrate, mostly types not found in humans, making them promising targets for anti‐fungal drug development. Echinocandins, which inhibit the essential β‐glucan synthase, are already clinically available. In contrast, α‐glucan, another abundant fungal cell wall component has attracted relatively little research attention because it is not essential for most fungi. Aspergillus nidulans has two α‐glucan synthases (AgsA and AgsB) and two α‐amylases (AmyD and AmyG), all of which affect α‐glucan synthesis. Gene deletion showed that AgsB was the major synthase. In addition, AmyG promoted α‐glucan synthesis whereas AmyD had a repressive effect. The lack of α‐glucan had no phenotypic impact on solid medium, but reduced conidial adhesion during germination in shaken liquid. Moreover, α‐glucan level correlated with resistance to Calcofluor White. Intriguingly, overexpression of agsA could compensate for the loss of agsB at the α‐glucan level, but not for phenotypic defects. Thus, products of AgsA and AgsB have different roles in the cell wall, consistent with agsA being mainly expressed at conidiation. These results suggest that α‐glucan contributes to drug sensitivity and conidia adhesion in A. nidulans, and is differentially regulated by two synthases and two amylases.     

<Emphasis Type="Italic">compact shoot and leafy head 1</Emphasis>, a mutation affects leaf initiation and developmental transition in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

The shoot apical meristem (SAM) produces lateral organs in a regular spacing (phyllotaxy) and at a regular interval (phyllochron) during the vegetative phase. In a Dissociation (Ds) insertion rice population, we identified a mutant, compact shoot and leafy head 1 (csl1), which produced massive number of leaves (∼70) during the vegetative phase. In csl1, the transition from the vegetative to the reproductive phase was delayed by about 2 months under long-day conditions. With a reduced leaf size and severe dwarfism, csl1 failed to produce a normal panicle after the transition to reproductive growth. Instead, it produced a leafy panicle, in which all primary rachis-branches were converted to vegetative shoots. Phenotypically csl1 resembled pla mutants in short plastochron but was more severe in the conversion of the reproductive organs to vegetative organs. In addition, neither the expression nor the coding region of PLA1 or PLA2 was affected in csl1. csl1 is most likely a dominant mutation because no mutant segregant was observed in progeny of 67 siblings of the csl1 mutant. CSL1 may represent a novel gene, which functions downstream of PLA1 and/or PLA2, or alternatively functions in a separate pathway, involved in the regulation of leaf initiation and developmental transition via plant hormones or other mobile signals.     

UDPGLUCOSE PYROPHOSPHORYLASE ACTIVITY IN THE DIATOM CYCLOTELLA CRYPTICA. PATHWAY OF CHRYSOLAMINARIN BIOSYNTHESIS 1

UDPglucose pyrophosphorylase activity was detected in cell-free extracts of the diatom Cyclotella cryptica TI3L Reimann, Lewin and Guillard. When assayed in the direction of UDPglucose formation, the enzyme had maximal activity at pH 7.8 and was stimulated by Mg²⁺and Mn²⁺ions. 3-Phosphoglycerate and inorganic phosphate had little effect on enzymatic activity, and the enzyme was relatively insensitive to feedback inhibition from UDPglucose (K, > I millimolar). A glucan was formed from UDP-[¹⁴C]glucose in cell-free extracts of C. cryptica. This glucan had a median molecular weight of 4600 (as determined by gel filtration chromatograbhy) and could be hydrolyzed by laminarinase. Partial acid hydrolysis of the glucan resulted in the formation of glucose and laminaribiose. but not cellobiose. These results suggest that the synthesis of chrysolaminarin (the major storage carbohydrate of diatoms) occurs via the activity of UDPglucose pyrophosphorylase. followed by glucosyl transfer from UDPglucose to the growing β-(1–3)-linked glucan.     

SPIRAL DEVELOPMENTAL PATTERNS IN THE STEM AND INFLORESCENCE OF LILIUM TIGRINUM

Extensive correlations in spirality were observed among vegetative and floral organs in Lilium tigrinum Ker. Organs involved were vegetative leaves, bracts, and bracteoles. These correlations varied in their degree of constancy depending upon the organs involved. The mature inflorescences of L. tigrinum appeared to fit the common definition of a raceme. In 67.3% of the flowers at node 3 on the raceme, the bract-bracteole spirals reversed the spiral of vegetative leaves on the stem. These reversals resembled those observed on essentially cymose inflorescences of certain members of the Caryophyllaceae. Cymose branching was found to be an invariable feature of the inflorescence of L. tigrinum when secondary flowers appear. The apparently indeterminate tips of inflorescence main axes were interpreted as exhibiting stages in progression from a basically determinate (cymose) inflorescence. It was concluded that the ancestors of L. tigrinum had well-developed cymose branching patterns in the inflorescence. Reversal of stem spirals by the bract-bracteole spirals at the apices of many inflorescences was considered to be the result of complete utilization of the inflorescence meristem. Explanations for those reversals were provided by the field theory and by the theory of the first available space.     

Characterization of sexual reproductive processes in Chara braunii (Charales,Charophyceae)

Chara braunii is distributed worldwide and is the most common charalean species in Japan. This species is monoecious and produces numerous sets of sex organs, each of which consists of one antheridium and one oogonium, under laboratory culture conditions. In this study, we report that light intensity strongly affected the vegetative phase and sexual reproductive phase of this species. Under high‐light conditions (70.0 μmol photons m^?2 s^?1), thalli grew but did not form reproductive organs. Under a low‐light intensity (10.0 μmol photons m^?2 s^?1), algal bodies formed many reproductive organs. In addition, antheridia without the corresponding oogonia (lone antheridia) were observed under low‐light conditions. The absence of oogonium primordia adjacent to the lone antheridium was confirmed by several microscopic approaches. The addition of liquid fertilizer increased the total number of sex organs and growth; however, the number of lone antheridia decreased with increasing fertilizer concentrations. Exogenously applied gibberellin did not affect the number of lone antheridia. These results suggest that regulatory mechanisms for the appropriate allocation of resources exist in this alga, similar to those reported in some land plants.     

DISTRIBUTION AND INHERITANCE OF INCONSTANT SEX FORMS IN NATURAL POPULATIONS OF DIOECIOUS BUFFALOGRASS (BUCHLOE DACTYLOIDES)

Variations of sex inconstancy were examined for vegetative and seed samples from eight natural populations of buffalograss located along two east-west transects crossing the shortgrass prairies of Oklahoma, New Mexico, and Texas. Each of the eight populations was found to contain inconstant (monoecious) sex forms. Sex form distributions ranged from the Guymon vegetative sample, having no inconstant sex forms, to the Chillicothe seed sample in which the frequency of inconstant sex forms was nearly 70%. Frequencies of inconstant sex forms were generally higher for seed samples than for vegetative samples. Male to female sex ratio of constant (dioecious) sex forms generally did not differ from 1:1 expectations. Inconstant sex forms were more common among peripheral populations where buffalograss vegetation coverage was sparse than for more central populations having a higher concentration of buffalograss vegetation. Quantitative measures of sex inconstancy from artificial crosses were significantly (P < 0.001) correlated with the additive linear model of general combining ability, suggesting that sex determination in buffalograss has high heritability. The possible selection forces affecting the frequency of monoecious sex forms among natural populations are discussed.     

ANATOMICAL STUDIES OF CATHAYA (PINACEAE)

Cathaya Chun et Kuang is a monotypic genus and one of the gymnosperms endemic to China. We investigated Cathaya argyrophylla with both light and scanning electron microscopy to study the external and internal surfaces of leaf cuticle, leaf blade, petiole, shoot apex, young stem, bark, wood, young and old roots, and mycorrhizae. It is shown that Cathaya has unique characteristics as well as common features of the Pinaceae, there being a difference between Cathaya and Pinus and the rest of the family. So far as the vegetative organs are concerned, the genus is most closely related to Pseudotsuga and Larix. Data derived from the study of structures of vegetative organs of Cathaya are very different from those of reproductive organs, indicating the complexity of the problem of systematics and evolution in these plants. However, the present study supports the view that Cathaya should not be included in the genus Pseudotsuga as a new species.     

Epigenetic repressor-like genes are differentially regulated during grapevine (Vitis vinifera L.) development

Grapevine sexual reproduction involves a seasonal separation between inflorescence primordia (flowering induction) and flower development. We hypothesized that a repression mechanism implicating epigenetic changes could play a role in the seasonal separation of these two developmental processes in grapevine. Therefore, the expression of five grapevine genes with homology to the Arabidopsis epigenetic repressor genes FERTILIZATION INDEPENDENT ENDOSPERM (FIE), EMBRYONIC FLOWER 2 (EMF2), CURLY LEAF (CLF), MULTICOPY SUPPRESSOR OF IRA 1 (MSI1) and SWINGER (SWN) was analyzed during the development of buds and vegetative and reproductive organs. During bud development, the putative grapevine epigenetic repressor genes VvCLF, VvEMF2, VvMSI1, VvSWN and VvFIE are mainly expressed in latent buds at the flowering induction period, but also detected during bud burst and inflorescence/flower development. The overlapping expression patterns of grapevine PcG-like genes in buds suggest that chromatin remodeling mechanisms could be operating during grapevine bud development for controlling processes such as seasonal flowering, dormancy and bud burst. Furthermore, the expression of grapevine PcG-like genes was also detected in fruits and vegetative organs, suggesting that epigenetic changes could be at the basis of the regulation of various proliferation–differentiation cell transitions that occur during grapevine development.     

ULTRASTRUCTURE DURING DEVELOPMENT OF THE NUCLEUS OF BATOPHORA OERSTEDII (CHLOROPHYTA; DASYCLADACEAE)1

The primary nucleus of Batophora oerstedii J. Agardh like that of the related Acetabularia, undergoes a great increase in size throughout vegetative development. Formation of small secondary nuclei represents an irreversible stage in the development of reproductive structures in the gametangia. Changes observed in the course of the life cycle include: i) an increase from 3 to 200 μm diam, of the nucleus; ii) increase in number of nucleoli; iii) development of the perinuclear region; iv) increased pore density in the nuclear membrane; v) development of chromosomes in the nucleoplasm; vi) formation of secondary nuclei; and, vii) division of secondary nuclei.     

Stress induction and developmental regulation of a rice chitinase promoter in transgenic tobacco

A 1.5 kb promoter fragment from the rice (Oryza sativa L.) RCH10 gene, which encodes a basic endochitinase inducible by wounding and fungal elicitor, was translationally fused to the β-glucuronidase (GUS) reporter gene and transferred to tobacco by Agrobacterium tumefaciens-mediated leaf disc transformation. Wounding of leaves induced GUS activity from low basal levels, and addition of fungal elicitor to the wounded tissue caused a further marked activation of the gene fusion. During vegetative development high levels of GUS activity were observed in roots and moderate levels in stems. Histochemical analysis indicated that the promoter was active in vascular and epidermal tissue, and the root apical tip. In flowers, high levels of GUS activity were observed in stigmas, ovaries and pollen-containing anthers, but only low levels in sepals and petals. The promoter 5′-deleted to ?160 exhibited the same patterns of expression in floral organs, and was also strongly induced by wounding and elicitor, but GUS activity was markedly reduced in vegetative organs. More detailed 5′ deletions showed that a cis-element required for floral expression was located between ?160 and ?74, and a cis element sufficient for stress induction was located 3′ of ?74. This proximal region 3′ of ?74 was also sufficient for expression in transfected rice protoplasts derived from suspension cultured cells. These data indicate that the complex developmental and environmental regulation of RCH10 promoter activity involves several distinct cis-elements for vegetative expression, floral expression and stress induction, and that signal pathways for wound and elicitor induction are conserved between monocotyledonous and dicotyledonous plants.     

Purification and characterization of a recombinantCaulobacter crescentus epoxide hydrolase

ACaulobacter crescentus epoxide hydrolase (CCEH) from a recombinantEscherichia coli was purified to homogeneity using a three-step procedure. The CCEH protein was purified 7.3-fold with a 22.9% yield in overall activity. The optimal reaction temperature and pH were determined to be 37°C and pH 8.0, respectively. The addition of 10% (v/v) dimethylsulfoxide as a cosolvent improved the enantioselectivity of CCEH for a batch kinetic resolution of racemic indene oxide.