Electron-probe Microanalysis Studies of Silicon in the Elongating Basal Internodes of Avena sativa (L.), Hordeum sativum (Jess.) and Triticum aestivum (L.)

Silicon deposits in the elongating basal internodes of almostmature, field grown specimens of Avena sativa, Hordeum sativumand Triticum aestivum were investigated using electron-probemicroanalysis. In A. sativa and H. sativum silicon was foundto be confined to the cells in the endodermal layer, being presentwithin the inner tangential and radial walls, and occasionallyin the outer tangential wall. In T. aestivum some silicon wasalso located in walls of cells surrounding the vascular bundles. The anatomy of the internodal tissues is discussed for the threespecies from light micrographs. The endodermal layer is discontinuousin A. sativa and H. sativum, in the former species it partlyextends around individual vascular bundles. In T. aestivum itforms a complete cylinder around the stelar region and alsoshows considerably more thickening of the inner tangential wallthan in the other species. The results are discussed in relation to the anatomy of theinternodal tissues and the possible function of silicon in theendodermis. Avena sativa L., Hordeum sativum Jess, Triticum aestivum L., oat, barley, wheat, silicon deposition, electron-probe microanalysis     

Desiccation and Freezing Sensitivity in Recalcitrant Seeds of Tea, Cocoa and Jackfruit

Investigations were undertaken on the desiccation and freezingsensitivity of recalcitrant seeds of three species: tea [Camelliasinensis (L.) O. Kuntze], cocoa (Theobroma cacao L.) and jackfruit(Artocarpus heterophyllus Lamk.). All species showed changesin the physiological characteristics, desiccation and freezingsensitivity of both the seed and the embryonic axes with increasingseed maturity. Fully mature seeds of tea, cocoa and jackfruitsurvived desiccation to 24, 35 and 31% moisture content, respectively,but at these moisture levels seeds were not able to toleratefreezing in liquid nitrogen (-196 °C). Some survival ofcryopreservation was, however, achieved for excised embryonicaxes of partially and fully-mature tea and jackfruit seeds afterdrying to 14% moisture content; cocoa axes were totally freezingsensitive at all three stages of physiological maturity studied.Biochemical investigations on fully mature axes after desiccationand freezing showed that the decline in viability with moisturelevel was associated with increased leachate conductivity, lipidperoxidation products and/or soluble carbohydrates. Evidencefor disruption of cell membranes during desiccation and freezingwas supported by ultrastructural studies.Copyright 1995, 1999Academic Press Camellia sinensis (L.) O. Kuntze, Theobroma cacao L., Artocarpus heterophyllus Lamk., Phaseolus vulgaris L., tea, cocoa, jackfruit, french bean, seeds, embryonic axes, desiccation, freezing, cryopreservation     

Recent bivalve molluscs of the genus Calyptogena (Vesicomyidae)

The genus Calyptogena (Bivalvia: Vesicomyidae) comprises highlyspecialized bivalves living in symbiosis with sulphur-oxidizingbacteria in reducing habitats. In this study, the genus is revisedusing shell and anatomical features. The work is based on typematerial, as well as on the extensive collection of vesicomyidsobtained during twelve expeditions to the Pacific and IndianOceans. Nine Recent species are ascribed to the genus Calyptogena,four of which are new: C. pacifica Dall, 1891, C. fausta Okutani,Fujikura & Hashimoto, 1993, C. rectimargo Scarlato, 1981,C. valdiviae (Thiele & Jaeckel, 1931), C. gallardoi Sellanes& Krylova, 2005, C. goffrediae n. sp., C. starobogatovin. sp., C. makranensis n. sp. and C. costaricana n. sp. Thecharacteristic features of Calyptogena are: shell up to 90 mmin length, elongate-elliptical or elongate; presence of escutcheon;presence of broad posterior ramus (3b) of right subumbonal cardinaltooth as well as right posterior nymphal ridge; absence of pallialsinus as a result of attachment of intersiphonal septal retractorimmediately adjacent to ventral surface of posterior adductor;absence of processes on inner vulva of inhalant siphon; presenceof inner demibranch only, with descending and ascending lamellaewith interlamellar septa not divided into separate tubes. Themost closely related taxa to Calyptogena are probably the genusIsorropodon Sturany, 1896, and the group of species representedby ‘Calyptogena’ phaseoliformis Métivier,Okutani & Ohta, 1986. These groups have several charactersin common, namely absence of pallial sinus, presence of singleinner pair of demibranchs and absence of processes on innervulva of inhalant siphon. The worldwide distribution of thegenus Calyptogena suggests that methane seeps at continentalmargins are the major dispersal routes and that speciation waspromoted by geographical isolation. Recent species diversityand fossil records indicate that the genus originated in thePacific Ocean. Sufficient data to discuss the distribution atspecies level exist only for C. pacifica, which has a remarkablynarrow bathymetric range. Published studies on the physiologyof C. pacifica suggest that adaptation to a specific geochemicalenvironment has led to coexisting vesicomyid genera. The bacteria-containinggill of C. pacifica and other Calyptogena species is one ofthe most specialized in the family Vesicomyidae and may reflectthese ecological adaptations. (Received 23 December 2005; accepted 3 April 2006)     

The Interactive Effects of Atmospheric Carbon Dioxide and Light on Stem Elongation in Seedlings of Four Species

Four species,Sinapis albaL.,Medicago sativaL.,Gypsophila paniculataL.andPicea abies(L.) Karsten, were grown in three light regimes:darkness, low light (25 µmol m^-2s^-1for 10 min d^-1) andhigh light (120 µmol m^-2s^-1for 12 h  d^-1) and fourlevels of carbon dioxide: 0, 350, 700 and 1400±50 µll^-1. Germination was not affected by any of the treatments.The effects of carbon dioxide on stem elongation were identicalin low and high light: stem length increased at a decreasingrate with level of carbon dioxide in all species. Level of carbondioxide also affected stem elongation in complete darkness,but the pattern was more complex and varied among species. Totalweight did not vary with level of carbon dioxide to any significantextent in either darkness or low light, but increased with levelof carbon dioxide at high light in all four species. Due tothe absence of any effect of carbon dioxide on growth in darknessand low light, we suggest the effects of carbon dioxide on stemelongation are independent of effects on growth and may be dueto a direct interaction with developmental processes. In contrast,level of carbon dioxide had little effect on allocation patternsin the dark and low light experiments, but had marked effectsin high light. Therefore, the effect of carbon dioxide on allocationwas probably due to the effects of carbon dioxide on growthrather than to any direct interaction between carbon dioxideand development. An understanding of the mechanisms by whichcarbon dioxide affects development may help us understand theoften variable effects of carbon dioxide upon plants.Copyright1998 Annals of Botany Company Sinapis albaL.;Medicago sativaL.;Gypsophila paniculataL. andPicea abies(L.) Karsten; elevated carbon dioxide; stem elongation; germination; allocation; phytochrome.     

The Distribution of Silicon Deposits in the Roots of Molinia caerulea (L.) Moench. and Sorghum bicolor (L.) Moench.

The occurrence of silica in relation to meristematic zones andthe thickening of the endodermis in the roots of Molinia caerulea(L.) Moench. and Sorghum bicolor (L.) Moench. has been investigatedby means of the electron-probe microanalyser and the scanningelectron microscope. In proximal regions of mature roots ofM. caerulea, the central strengthening tissue of the stele,the vessel walls, the endodermis and the sub-epidermal sclerenchymaare areas of heavy accumulation. The distal regions of suchroots are relatively free of silicon and show little thickeningof the inner tangential walls of the endodermis or of the cellsof the strengthening tissues. The thickening of these elementsis shown to be associated with their location and the age ofthe root. In the proximal regions of S. bicolor, silicon is detected andlargely confined to the inner tangential walls of the endodermiswhich display some thickening. In addition, discrete and evenly-distributeddeposits varying in size partly fill the lumen of this layer.Some cells exhibit a number of smaller protrusions. High magnificationsof these lumen deposits show a distinct granular structure incontrast to the very uniform pattern of the wall deposits. The results are compared with deposits in grass leaves and inflorescencebracts and in woody perennials. The presence of silicon in additionto suberin, lignin and polyphenols in the thickened endodermalwall is also discussed in relation to the recognized functionof the endodermis.     

Biosynthesis of Purine Alkaloids in Camellia Plants

The metabolism of [8-¹⁴C]adenine and [8-¹⁴C]hypoxanthine infour species of Camellia plants was investigated in relationto the synthesis of purine alkaloids, caffeine and theobromine.Young leaves of C. sinensis had the ability to synthesize caffeine,but in C. irrawadiensis, these labelled precursors were incorporatedinto theobromine, not caffeine. No synthesis of purine alkaloidscould be detected in C. japonica and C. sasanqua leaves. Conventional"salvage" and degradation pathways of purines were present inall species of Camellia plants examined. ¹ Present address: Research Center, Mitsubishi Chemical IndustriesLtd., 1000 Kamisida-cho, Midori-ku, Yokohama, 227 Japan. (Received September 29, 1986; Accepted January 22, 1987)     

A Cytochemical Study of Differentiation and Breakdown of Vessel End Walls

A cytochemical approach was used to study the architecture ofthe end wall and its modifications during vessel differentiationin Populus italica and Dianthus caryophyllus. The combinationof cytochemical techniques with selective extractions to removeend wall subunits provides information on the different componentsof the end wall and on the method of perforation. The end wallappears to be formed mainly from pectins and hemicelluloses.No cellulosic components nor lignin were found though the 3,3'-diaminobenzidine assay revealed the presence of peroxidases.That the method of perforation may depend on the species isdiscussed. Dianthus caryophyllus L., carnation, Populus italica, poplar, xylem vessel, cell wall, cytochemistry, vessel differentiation     

Genotype Affects the Morphogenic Response in vitro of Epicotyl Segments of Citrus Rootstocks

The influence of light, hormones and explant orientation onin vitro regeneration in epicotyl cuttings was compared in fourCitrus species (C. aurantium, C. macrophylla, C. reshni andC.sinensis ) and the hybrid Troyer citrange (C. sinensis x Poncirustrifoliata). In all cases, explants planted vertically regeneratedshoots at the apical end by a process of direct organogenesiswithout callus formation. When the Troyer citrange explantswere incubated horizontally, regeneration at the apical endoccurred by an indirect organogenic pathway after callus formation.This change in the pathway of regeneration did not occur inany of the Citrus species, and incubation horizontally resultedin a reduction in the number of buds and shoots formed throughthe direct organogenic pathway. Shoot formation through thedirect organogenic pathway was inhibited by darkness, and thisinhibitory effect was counteracted by the cytokinin benzyladeninein Troyer citrange and, partly, in C. sinensis, but not in C.macrophylla. A non-organogenic callus formed at the basal endof most of the cuttings of C. reshni. InC. sinensis and C. aurantium,a non-organogenic callus formed only in a low proportion ofexplants. Troyer citrange formed an organogenic callus in whichbuds or roots differentiated depending on the auxin/cytokininbalance. C. macrophylla formed callus in the dark but not inthe light. Root formation occurred both in the presence of theauxin naphthaleneacetic acid or low concentrations (2.2 to 4.4µM) of the cytokinin benzyladenine, but no buds were formed.These qualitative and quantitative differences in the organogenicresponse indicate that the conditions for regeneration mustbe optimized for each genotype. Copyright 2000 Annals of BotanyCompany Benzyladenine, citrus, Citrus aurantium, Citrus macrophylla, Citrus sinensis, Citrus sinensis x Poncirus trifoliata, naphthaleneacetic acid, organogenesis, rooting, shoot regeneration, Troyer citrange     

Effects of Fluctuating Temperatures on Germination

Germination responses to alternating daily cycles involvingtransfers between different temperatures over the range 0 toc. 40?C were investigated in four species: Lycopus europaeusL., Clarkia unguiculata Lindl., Apium graveolens L. cv. GiantRed, and Silene dioica (L.) Clairv. Comparisons of the germination of these species revealed distinctivedifferences which could be related to particular features ofthe geographical regions or ecological habitats in which theyoccur naturally. The effects of fluctuating as opposed to constant temperaturesvaried from one species to another. L. europaeus depended almostabsolutely on fluctuating temperatures for germination. Germinationof S. dioica was greatly increased by fluctuating temperatures.Moderate increases occurred over a restricted temperature rangein A. graveolens cv. Giant Red and C. unguiculata was affectedin only minor ways. These results are discussed in relationto previous attempts to explain the mechanisms responsible forthe frequently beneficial effects of fluctuating temperatureson germination.     

Relative Embryo Growth Rates in the Annual Cicer L. Species

Early embryo growth rates were studied in the nine annual speciesof Cicer L., namely, C. arietinum L., C. bijugum Rech., C. chorassanicum(Bge.) M. Pop., C. cuneatum Rich., C. echinospermum Dav., C.judaicum Boiss, C. pinnatifidum J. and S., C. reticulatum Lad.and C. yamashitae Kit. The number of embryo cells increasedexponentially with time and was log linear in all the species.Species differed in their mean cell doubling time (MCDT). Cicerechinospermum and C. yamashitae had, respectively, the longestand the shortest MCDT which ranged from 9.67 to 16.15 h forthe nine species. Failure of successful interspecific hybridizationbetween C. arietinum and the wild annual species was only partlyexplained by differences in MCDT of the parental species. Relativegenetic closeness still plays the major role in determiningsuccess of interspecific hybridization in Cicer. Chickpea, Cicer, embryo, interspecific hybridization, suspensor     

Changes in the Distribution of Plasmodesmata in Developing Fibre-tracheid Pit Membranes of Sorbus aucuparia L.

The distribution of plasmodesmata in cambial pit fields anddeveloping fibre-tracheid pit membranes in Sorbus aucupariaL. has been studied using conventional and high voltage transmissionelectron microscopy. In cambial pit fields, plasmodesmata arewidely separated while, during cell enlargement and the stageof secondary wall formation, they occur exclusively in a denselypacked cluster, eccentrically located on the pit membrane ina thickening of primary wall material. It is not clear at themoment whether the cluster arises by aggregation of the cambialpit field plasmodesmata, or by de novo formation in a localizedregion coupled with loss of plasmodesmata outside this region.The significance of these changes is discussed. Sorbus aucuparia L., plasmodesmata, pit membranes, xylem differentiation     

Structure of Hair Roots in Lysinema ciliatum R. Br. and its Implications for their Water Relations

The fine lateral roots ofLysinema ciliatum R. Br., an epacridfrom habitats subject to periodic drought in Western Australia,are hair roots resembling those of Ericaceae. The finest (ultimate)hair roots have a cortex consisting only of an endodermis andan exodermis. Both layers have Casparian strips on the radialwalls. The exodermis develops to state III very close to theroot tip, showing wall thickening and a suberized lamella encirclingeach cell. In many roots collected after tip-growth had ceasedand the tip had fully differentiated this suberized exodermiscompletely encircled the apex. In older hair roots the epidermiscollapses or is sloughed off leaving the suberized exodermisas the outermost layer. The very fine hair roots have a verysmall stele containing only one xylem tracheid, and phloem consistingof a single sieve element with companion cell. The very smalldiameter of the single tracheid indicates a high resistanceto water flow along the hair roots. This may tend to conservesoil moisture in the region of the hair roots, leading to improvedsurvival and prolonged function of mycorrhizas in the field. Lysinema ciliatum R. Br.; hair root; endodermis; exodermis; water; xylem     

Purine Alkaloids of the Fruits of Camellia sinensis L. and Coffea arabica L. during Fruit Development

The amounts of two purine alkaloids, caffeine and theobromine,in the fruit of tea (Camellia sinensis L.) increased markedlyduring the growing season until the fruit was full-ripened anddried. In the dry fruit, the pericarp contained the most alkaloids,but there were also considerable amounts in the seed coat and,to a lesser extent, the fruit stalk and the seed. The shed seedsalso contained significant amounts of the alkaloids, especiallyin the seed coats. In contrast with the dry fruit of tea, seedsand pericarp of coffee (Coffea arabica L.) fruit contained aconsiderable amount of caffeine and a small amount of theobromide.A small amount of theophylline was also present in the pericarpof the ripened fruit. Relationships between growth and purinealkaloid content in tea and coffee fruits and their roles duringseed formation are discussed. Camellia sinensis L., tea, Coffea arabica L., coffee, purine alkaloids, fruit development, seed, seed coat, caffeine, theobromine, theophylline     

Fruit Development and Structure in Some Indian Bamboos

Fruit structure and development of seven species belonging tofive genera of Indian bamboos are described. The fruit in fourspecies is a caryopsis typical of the family Poaceae. The ovuleis bitegmic; the outer surface of the cells of nucellar epidermisbecomes cutinized and forms the seed coat. Three species beara fleshy fruit with a unitegmic ovule. In a mature fruit theendosperm is either completely absorbed by the embryo or ispresent only in small quantity. The developing embryo comesin direct contact with the fruit wall due to the disintegrationof the nucellus and integument. The embryo is covered by a thickbrown mat from the disorganized cells of the inner layers ofthe fruit wall. Poaceae, Bambusoideae, Bambusa, Dendrocalamus, Melocalamus, Ochlandra, Pseudostachyum (fleshy fruits), fruit wall     

黑龙江苹果亚科5属14种植物导管分子形态结构研究

利用扫描电子显微镜对黑龙江苹果亚科5属14种植物导管分子的管腔微形态结构特征进行了比较研究。结果显示:(1)该亚科植物导管分子的管腔长度、宽度及端壁斜度角有较大的差别。(2)孔纹导管在该亚科植物种中均存在,网纹导管和螺纹导管仅见于苹果属和花楸属中。(3)导管分子管壁除苹果属及山楂属中的毛山楂、辽宁山楂外均有螺纹加厚。(4)纹孔的排列方式为互列式、对列式及互列、对列同时存在。(5)在所观察的植物中花楸、山荆子、无毛山楂导管端壁具单穿孔板和梯状穿孔板,其余种的导管端壁仅具单穿孔板。(6)导管纹孔膜残留现象普遍存在。研究表明,导管分子管腔的微形态结构特征,可为该亚科植物的系统演化提供形态学依据;导管分子微形态结构特征与其所处的环境存在一定的适应性。     

用树脂铸型法研究4种植物木质部导管结构

导管的大小、形态和彼此连接方式的不同对水分运输和应力支撑有重要作用。本研究采用树脂铸型法对毛白杨(Populus tomentosa Carr)、旱柳(Salix matsudana)、榆树(Ulmus pumila L.)和紫藤(Wisteria sinensis)4个树种的导管分子三维结构进行比较研究,分析导管结构特征和其水分输运的关系。导管内壁结构被印在铸型的表面上,将铸型放在扫描电子显微镜下观察。结果表明：旱柳和毛白杨的导管分子特征较接近,与榆树和紫藤存在明显差异,相对于榆树和紫藤较原始。毛白杨和旱柳的导管分子长、侧壁纹孔少,有利于水分的输运。榆树和紫藤的导管分子相对宽,穿孔板几乎平直,更加利于水分的输运。榆树和紫藤的细导管分子有螺纹加厚,可增加导管的机械强度,减少管内产生空穴化的风险,从而保证水分更有效的运输。     

Rate of Change in Dormancy Level and Light Requirement in Weed Seeds During Stratification

The rate of change in dormancy level and light requirement,induced during stratification at 3.2 °C, was investigatedin seeds ofStellaria media, Cerastium fontanum, Veronica agrestisandTaraxacumofficinale.Two stratification environments, soil and wet filterpaper in petri-dishes, were used. On nine occasions during a6 week stratification period, germination was tested under threelight conditions at 3.5/18.5 °C: (1) darkness; (2) light;and (3) short-term light exposure followed by darkness. Priorto stratification, germination in all species was 89% in lightand 53% in darkness. Within 2 weeks of stratification, germinabilityinV. agrestisandS. mediaseeds decreased in all treatments. InC.fontanumandT. officinaleseeds, germinability also decreasedafter 2 weeks but only in the dark treatment, indicating inductionof a light requirement. After two more weeks of stratification,the induced dormancy inS. mediaseeds stratified in soil becameweaker and the light requirement inT. officinaleseeds was lost.Differences between the two stratification environments and/orinteractions between light conditions, stratification environmentsand time were found for all species. These results suggest that:(1) the dormancy level and the light requirement of seeds maychange dramatically over relatively short-time periods duringstratification; and (2) germinability depends on the stratificationenvironment experienced by the seeds. Predicting the dormancylevel or light requirement in a seed batch is difficult andrequires a thorough knowledge of the effect of the stratificationconditions used.Copyright 1997 Annals of Botany Company Burial; Cerastium fontanumBaumg.; chickweed; cold stratification; common mouse-ear; dandelion; dormancy; light requirement; seed; Stellaria media(L.) Vill.; speedwell; Taraxacum officinalegroup; Veronica agrestisL.; weed     

Male Sterility and Anther Wall Structure in Copper-deficient Plants

Anther development and pollen sterility were followed in plantsof wheat, oat, barley, sweetcorn, sunflower, petunia and subterraneumclover grown at a range of copper supplies. Copper-deficientplants had increased pollen sterility. Lignified wall thickenings were reduced or absent in the endotheciaof anthers from Cu-deficient plants. Reduced seed set may resultboth from reduced pollen fertility or failure of the stomiato rupture due to decreased lignification of anther walls. Triticum aestivum L., wheat, Hordeum vulgare L., barley, Avena sativa L., oat, Zea mays L., corn, sweetcorn, maize, Helianthus annuus L., sunflower, Petunia hybrida L., Trifolium subterraneum L., subterranean clover, male sterility, anther development, copper deficiency     

Electron Microscopic Observations of the Structure of Sieve-connexions in the Phloem of Angiosperms and Gymnosperms

The sieve elements of Pinus silvestris L., Sorbus aucupariaL., Vitis vinifera L., and Cucurbita pepo L. have been examinedelectron microscopically in ultra-thin section, and the structuresof the corresponding sieve areas or sieve plates have been describedand compared. In Pinus the sieve areas contain groups of connectingstrands which enter the wall from the lumen side as individualsbut coalesce within it in the median cavity. This cavity hasdeveloped by wall breakdown in the middle lamella and primarywall region and corresponds to the median nodule visible undera light microscope. Neither in this nor in the other speciesobserved is there any visible closing membrane. Structural differences between the four species are shown tosuggest that the major evolutionary trend in the evolution ofspecialized conducting strands has been the enlargement of theconnecting strands from groups of small separate strands toa smaller number of larger strands as the median cavity becomesenlarged to form a canal through the wall. The connecting strands appear invariably to be dense, highlyosmiophilic and continuous with the cytoplasmic surface of thecell. No signs of micropores or of other tubular structure inthe strands have been found. The structures thus revealed aremore nearly compatible with active transport of materials acrossthe sieve plate than they are with any purely physical mechanism.It is suggested that they are incompatible with any mass flowhypothesis.