Callus Formation and Differentiation at an Exposed Cambial Surface

The origin of callus from the exposed surface of the cambialzone in Trema orientalis Bl. and Julbernardia globiflora (Benth.)Troupin is described and discussed in relation to what has beenobserved in other species. It is suggested that in differentspecies callus may develop from any of the undifferentiatedcentripetal products of the vascular cambium, but that the kindof tissue contributing to callus initiation depends upon thespecies and on the histology of the cambial zone. The establishment of a new vascular cambium and phellogen isalso described. It is found that cambium formation is not dependenton the presence of a preexisting cambium in the surroundingtissues and that the first-formed xylem is abnormal in structure.     

Basal Plate Tissue in Narcissus Bulbs and in Shoot Clump Cultures: Its Structure and Role in Organogenic Potential of Single Leaf Cultures

Light microscopy demonstrated that the apparently amorphous,achlorophyllous tissue at the base of in vitro shoot clump cultureof Narcissus was comparable in structure to the basal plateof Narcissus bulbs. Both had very complex vascularisation andsmall, densely packed parenchymatous cells. In shoot clump cultures, primordia were produced by meristematiczones at the surface of this achlorophyllous tissue, very closeto the base of leaves. Single leaf units excised from the invitro shoot clump cultures with a wedge of basal achlorophylloustissue were highly organogenic when used as secondary explantsfor in vitro culture of Narcissus. No organogenesis occurredin the absence of the leaf base and achlorophyllous (basal plate)tissue and little organogenesis occurred unless the leaf baseand basal plate tissue were immersed in the culture medium (i.e.explants inoculated into liquid medium or upright in agar-solidifiedmedium). After two 5-week culture passages in liquid medium, more thanfive leaves were produced per leaf base inoculated. Thus rapidmicropropagation of Narcissus can be achieved using only thebase of single leaf units excised from shoot clump cultures.Copyright1993, 1999 Academic Press Anatomy, basal plate, bulb, in vitro, leaf culture, Narcissus, organogenesis     

突尼斯非洲跳鼠(Jaculus jaculus)和埃及跳鼠(J.orientalis)群体的等位酶多态及遗传分化(英文)

运用16种酶蛋白编码的23个遗传座位对突尼斯非洲跳鼠(Jaculus jaculus)和埃及跳鼠(J. orientalis)自然群体的遗传变异和分化进行了电泳分析。结果表明,与其他啮齿动物等哺乳动物的相关数据比较,发现这两个种群体的遗传变异水平较低。非洲跳鼠群体的观测杂合度 (H_obs) 为0.08—0.19,多态座位百分比(P)为26.2%—45.2%,每个座位的平均等位基因数(A)为1.1—1.4;埃及跳鼠的H_obs为0.10—0.15,P为29.3%—44.1%,A为1.1—1.7。两个种群体各自的遗传分化程度较低(非洲跳鼠和埃及跳鼠的F_st分别为0.0017和0.0019)。而两个种群体间的F_st为0.607（P<0.05）,表明两个种之间高度的遗传分化。本研究支持这两个种分类地位的合法性,并强调了地理因素（环境类型和生物气候阶段）对两个种遗传结构的影响。     

Microfibrillar Structure, Cortical Microtubule Arrangement and the Effect of Amiprophos-methyl on Microfibril Orientation in the Thallus Cells of the Filamentous Green Alga, Chamaedoris orientalis

Microfibrillar structure, cortical microtubule orientation andthe effect of amiprophos-methyl (APM) on the arrangement ofthe most recently deposited cellulose microfibrils were investigatedin the marine filamentous green alga, Chamaedoris orientalis.The thallus cells of Chamaedoris showed typical tip growth.The orientation of microfibrils in the thick cell wall showedorderly change in longitudinal, transverse and oblique directionsin a polar dependent manner. Microtubules run parallel to thelongitudinally arranged microfibrils in the innermost layerof the wall but they are never parallel to either transverseor obliquely arranged microfibrils. The ordered change in microfibrilorientation is altered by the disruption of the microtubuleswith APM. The walls, deposited in the absence of the microtubules,showed typical helicoidal pattern. However, the original crossedpolylamellate pattern was restored by the removal of APM. Thissuggests that cortical microtubules in this alga do not controlthe direction of microfibril orientation but control the orderedchange of microfibril orientation. Amiprophos-methyl, Chamaedoris orientalis, coenocytic green alga, cortical microtubule, microfibrillar structure, tip growth     

Leaf Growth in Cotton (Gossypium hirsutum L.) 1. Growth in Area of Main-stem and Sympodial Leaves

A model is presented for growth of individual and successivemain-stem leaves of cotton, based on a series of indoor experimentsand data sets from the literature. Three variable parametersare used to describe individual leaf growth: relative growthrate of meristematic tissue (R¹), relative rate of approachof final area (R₂) and a ‘position parameter’ (t_0.5)which governs the transition from meristematic to extensiongrowth. Final area of a leaf does not occur in the model asa deterministic quantity but it is a result of the processesduring growth. The model generates successive mainstem leavesand sympodial leaves as an integrated system. Assimilate shortagesoccurring in the plant operate on R₁ leading to the characteristicchange of final leaf area along the mainstem. Gossypium hirsutumL., cotton, leaf growth, relative growth rate, meristematic tissue, extension growth, mathematical model     

Comparative Studies of Leaf Tissue 4: III. EFFECTS OF WALL-DEGRADING ENZYMES AND OSMOTIC STRESS

Commercially available cell wall-degrading enzymes frequentlyused for protoplast isolation inhibited CO₂ fixation and photosyntheticO₂ evolution, and stimulated dark respiration by leaf tissueand isolated mesophyll protoplasts of Nicotiana tabacum L. andAntirrhinum majus L. They also depolarized the membrane potentialof cells of leaf tissue, inhibited uptake of ⁸⁶Rb by tobaccoleaf tissue and isolated mesophyll protoplasts, and stimulated³⁶CI uptake by tobacco leaf tissue. Where studied, these effectswere found to be reversible. The depolarization effect on Antirrhinumleaf cells occurred even when the enzyme preparations had beendenatured, dialysed, or desalted, and the effect was greatestin those fractions of the enzyme preparation which showed thehighest cellulase activity. Plasmolysis of tobacco leaf tissue inhibited photosyntheticO₂ evolution, CO₂ fixation, and ⁸⁶Rb uptake to levels belowthose exhibited by isolated protoplasts in media of the samecomposition and osmolarity. The implications of these resultsfor work with leaf tissue and isolated protoplasts are discussed.     

THE DIET, PREY SIZE AND CONSUMPTION OF PHILINE ORIENTALIS (OPISTHOBRANCHIA: PHILINIDAE) IN HONG KONG

Philine orientalis occurs on Hong Kong's beaches for {smalltilde}2 months each year, in May and June when it breeds, laysegg capsules and dies. It is believed to have a life span ofone year. Hoi Sing Wan, a sandy beach in the New Territoriesof Hong Kong is dominated at lower levels by the venerid bivalveTapes philippinarum, the population of which in May and June,following spring recruitment, mostly comprises juveniles. P.orientalis, occurring at a density of {small tilde} 1.m^–2,feeds voraciously upon these juveniles consuming, in laboratoryexperiments, a mean of 25.day^–1. At Hoi Sing Wan, P. orientalisappears to be highly prey specific. It is, however, known tofeed on other prey items and probably has a catholic diet, duringits annual migration from deeper to shallower sediments, accordingto the prevailing fauna. In terms of wet weight, P. orientalis consumes a mean of {smalltilde}4.4% (2.2–6.7%) of its body weight day^–1.In terms of dry weight, however, this figure increases to amean of 35.5% and one figure of 208% has been recorded. Althoughthis is because of the large body fluid content of this, essentiallyshell-less, gastropod, using a hydrostatic skeleton to achieveburrowing, such figures further attest to the voracity of thebreeding adults. This study joins others in questioning ourpresent understanding of the scale of energy budgets on suchshores, i.e., are our estimates of loss to predation grosslyunderestimated? ^*Present address: Department of Biology, Baptist College, WaterlooRoad, Kowloon, Hong Kong. (Received 20 May 1989; accepted 3 July 1989)     

Adventitious bud formation on leaf and stem segments of Heloniopsis orientalis grown at various temperatures

The effect of different temperatures on bud formation in excisedleaf fragments and in stem segments of Heloniopsis orientalis,a monocotyledonous plant, was investigated in light and in darkness.The optimal temperature for bud formation was 21?C to 25?C.16?C pretreatment for 7 to 21 days promoted bud formation inleaf segments. 30?C pretreatment for 7 days or more reducedthe number of buds in both young etiolated and mature greenleaf segments but not in young green leaf segments. In younggreen leaf segments grown in darkness, however, 30?C pretreatmentreduced the number of buds. Inhibition of bud formation dueto high temperature could not be reversed by BA. (Received November 15, 1978; )     

锡林郭勒草原布氏田鼠体蚤和巢蚤数量动态及蚤类群落演替

1989～1998年对内蒙古阿巴嘎旗那仁宝力格苏木布氏田鼠Microtus brandti体蚤和巢蚤的数量进行了调查和分析,所得体蚤包括3科7属9种, 其中优势种有: 原双蚤田野亚种Amphipsylla primaris mitis占41.84%, 近代新蚤东方亚种Neopsylla pleskei orientalis占41.18%, 光亮额蚤Frontopsylla luculenta占13.18%。所得巢蚤包括2科6属9种, 其中优势种近代新蚤占74.94%; 光亮额蚤占10.04%, 原双蚤占8.20%, 宽圆纤蚤Rhadinopsylla rothschildi占6.44%, 是常见种。田鼠体的原双蚤、近代新蚤、光亮额蚤和体蚤指数间呈正相关(P<0.05)。田鼠巢的近代新蚤、光亮额蚤、宽圆纤蚤和巢蚤指数间正相关显著(P<0.01)。春季巢蚤指数∶春季体蚤指数≈5∶1, 秋季巢蚤指数∶秋季体蚤指数≈75∶1。近代新蚤既是体型蚤又是巢型蚤, 为田鼠的优势蚤种; 原双蚤数量占体蚤的 41.84%, 是体型蚤; 光亮额蚤为体蚤和巢蚤中的常见种。     

Ochna pulchra Hook: Leaf Growth and Development Related to Photosynthetic Activity

Ochna pulchra Hook. is a deciduous broad-leaved tree in theMixed Bushveld vegetation of the Northern Transvaal. The growthand development of leaves taken from trees in the field werestudied from a stage shortly before bud break, in late spring,until they were fully expanded and at the peak of photosyntheticactivity. Leaf area was measured by photographing the leaf against a transparentmm² grid. Finally a constant relationship between leaf area(A) and the linear dimension of length (L) and breadth (B) wasestablished: A = b x LB, where coefficient b = 0.72. Transverse sections of the lamina of the youngest leaves showeda five-layered plate meristem with a few functional conductingelements in the midrib. During further leaf development, celldivision was followed by means of autoradiography using [³H]thymidine.It was most active during the week after bud break. Leaf cell increment following on cell division made the majorcontribution to leaf growth resulting in a lamina that was atleast 90% expanded 4 weeks after bud break. The histologicalchanges accompanying cell division were observed using lightand electron microscopy. Even in late stages of leaf development mature and differentiatingstomata occurred together, limited to the abaxial epidermisand the midrib. Scanning electron microscopy showed stomataldistribution, their increasing density and gradual opening.The structure of these sunken stomata could reduce the outwarddiffusion of water vapour and increase the diffusion resistanceto carbon dioxide. Carbon assimilation rates of the developing leaves were measuredusing an IRGA (infra-red gas analyser) and their chlorophyllvalues were calculated. Photosynthesis was first measured amonth after bud break when the leaves were fully expanded, over50 % of the stomata exposed and leaf mesophyll tissue differentiatedwith mature chloroplasts. Net photosynthetic rates and chlorophyllvalues peaked 1 month later. Ochna pulchra Hook., photosynthesis, leaf development, leaf area, stomata, chlorophyll, savanna     

Effects of Copper Toxicity on Leaves of Oregano (Origanum vulgare subsp. hirtum)

The effects of increasing concentrations of soil copper on anumber of leaf structural parameters in oregano plants werestudied to determine the effect of copper toxicity. Copper-stressedleaves were small and chlorotic and underwent a thickening oftheir lamina, due principally to an increase in the number andvolume of mesophyll cells. The number of stomata and glandularand non-glandular hairs increased significantly. Chloroplastsof mesophyll cells declined dramatically in number and volume.Grana and stroma thylakoids of chloroplasts did not undergoany noticeable alterations, but starch grains disappeared, plastoglobulibecame larger and the double membrane limiting the chloroplastbecame dilated. Leaf chlorosis was determined by total chlorophyllanalysis and measurement of the leaf Cu, Fe and Mg content.The effects of copper toxicity on oregano leaves comprised significantstructural alterations which reflect reduced metabolic activity.Copyright 2001 Annals of Botany Company Origanum vulgare subsp, hirtum, oregano, copper toxicity, leaf, structure and ultrastructure, morphometry, inorganic elements, tissue relative volumes     

Fatty Acids in Chloroplasts and Leaves

The fatty acid composition of green and white leaf tissue inAcer negundo, Zea mais, and Ilex aquifolium, of green and yellowtissue in Ligustrum ovatifolium and of etiolated and green tissuein Vicia faba has been determined. The mesophytic green leavesexamined show a general similarity in fatty acid composition,characterized by a high concentration of non-conjugated octadecatrienoicacid. Chloroplasts were isolated from Vicia and Acer and containan even higher concentration of this acid and only traces ofnon-conjugated octadecadienoic acid. Conjugated diene and trieneacids occur in traces in chioroplasts, but are also found innon-green leaf tissue. The fats of non-green leaves are in generalmore saturated than those from green tissue but vary considerablyin composition. The relationship between fat composition andplastid development is discussed.     

Effects of Developing Leaves on Stelar Pattern Development in the Shoot Apex of Matteuccia struthiopteris

A developmental study of the normal shoot apex of Matteucciastruthiopteris suggested that patterned stelar differentiationis initiated immediately beneath the single layer of promeristemand occurs prior to the initiation of the youngest leaf primordium.A developmental study in which all leaf primordia were suppressed,with or without lateral isolation of the terminal meristem byvertical incisions, has confirmed this interpretation of stelardifferentiation. Experimentally-induced changes in the tissueimmediately below the promeristem were reflected in the resultingmature structure of the stele. Failure of leaf gap initialsto differentiate, if all leaf primordia were suppressed at theincipient stage, resulted in a mature stele without leaf gaps.Similarly the disappearance of pith mother cells after severalweeks of leaf removal was associated with the formation of astele without pith. Leaf influence was further assessed by allowingone primordium to develop while all others were suppressed.The developing leaf had a small promoting effect on caulinevascular tissue differentiation but its major impact on theexpansion of the parenchymatous tissues of the stele. Characteristicprotoxylem and protophloem failed to differentiate when allleaves were suppressed and, when leaf was allowed to develop,formed only in relation to the leaf.Copyright 1995, 1999 AcademicPress Leaf influence, vascular pattern formation, experimental surgery, shoot apex development, protoxylem, protophloem, Matteuccia struthiopteris     

The involvement of photosynthesis in inducing bud formation on excised leaf segments of Heloniopsis orientalis (Liliaceae)

The role of photosynthesis in inducing adventitious bud formationon leaf segments of Heloniopsis orientalis was investigated.The effect of white light reached a maximum at about l25 J?m^–2?sec^–1.White, red, blue and far-red light were effective in inducingbud formation, but green light was not. In darkness, bud formationwas induced if sugar was added to the nutrient medium. The photosyntheticinhibitors DCMU and AT blocked the effect of light. Bud formationwas inhibited in CO₂-free air. The requirement of sucrose forbud formation in darkness could be replaced by citrate. It wasconcluded from these results that light appears to induce budson leaf segments through some processes dependent upon photosynthesis. (Received January 11, 1978; )     

Function and structure of leaves contributing to increasing water storage with height in the tallest <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> trees of Japan

Key message

In Cryptomeria japonica , transfusion tissue in leaves may have functions of water storage and supply, which could compensate for hydraulic constraints with increasing height.

Abstract

The tallest trees of Cryptomeria japonica occur in climatic regions similar to the world’s tallest trees. We hypothesized that tall C. japonica trees would have evolved adaptive mechanisms to overcome height growth limitation. Here, we focused on foliar water storage, a mechanism recently discovered in Sequoia sempervirens. In C. japonica, leaf water potential at turgor loss did not change with height or light availability, while leaf hydraulic capacitance and succulence (water content per leaf surface area) increased, suggesting hydraulic compensation. Plasticity of leaf morphology could contribute to avoiding negative effects of height on photosynthesis. We also focused on the structure and function of transfusion tissue in leaves and its role in water storage and supply. Cross-sectional area of transfusion tissue increased with height, whereas that of xylem was constant. We confirmed that water flowed from vascular bundle to mesophyll via the transfusion tissue. Cryo-scanning electron microscopy images of leaf cross sections showed that transfusion cells were flattened, but not fully dehydrated when leaf water potential decreased in situ and by experimental dehydration, and cell deformation was more marked for treetop leaves than for lower-crown leaves. The shape of transfusion cells recovered at predawn as well as after experimental rehydration. As in S. sempervirens, transfusion tissue of C. japonica may function as a hydraulic buffer, absorbing and releasing water according to leaf water status. Anatomical and hydraulic properties contributing to foliar water storage may be an adaptive mechanism acquired by tall Cupressaceae trees to overcome the hydraulic constraints on physiological function with increasing height.

     

Stomatal Characteristics, Leaf Waxes, and Transpiration Rates of Theobroma cacao and Hevea brasiliensis Seedlings

Stomatal size and frequency as well as structure and distributionof leaf waxes were compared in seedlings of two varieties ofTheobroma cacao and three families of Hevea brasiliensis. Stomataof both species were located on the abaxial leaf surface only.The stomata of Theobroma averaged 45% shorter and 29% narrowerthan those of Hevea, but stomatal frequency was 44% higher inTheobroma. Stomatal size and frequency differed more among Heveafamilies than between Theobroma varieties. The structure ofthe leaf waxes of Theobroma and Hevea differed appreciably.It also varied greatly between the abaxial and adaxial leafsurfaces of Hevea, but only slightly in Theobroma. The structureof leaf waxes varied little between Theobroma varieties or amongHevea families. Leaf conductances and transpiration rates weremuch higher in Hevea than in Theobroma seedlings. The implicationsof water relations in interplanting of Theobroma and Hevea arediscussed. Cacao, Theobroma cacao, rubber, Hevea brasiliensis, stomatal size, stomatal frequency, leaf waxes, transpiration     

Vascular Differentiation in the Shoot Apex of Matteuccia struthiopteris

Initial vascular differentiation is generally considered tooccur in procambium. In ferns, however, a provascular tissueimmediately subjacent to the promeristem has been suggestedas an initial stage within which the procambium is subsequentlyformed. In contrast to this interpretation, a zonation conceptapplied in ferns recognizes a promeristem consisting of severallayers of cells in which no differentiation takes place. Thisstudy demonstrates that the shoot apex of Matteuccia struthiopterishas one cell layer of promeristem. Immediately subjacent tothe promeristem is the provascular tissue surrounding a centralgroup of pith mother cells. The developmental continuity betweenthe provascular tissue and the mature vascular tissue, and betweenthe pith mother cells and the pith, through transitional stages,indicates that the initial differentiation of vascular tissueand pith takes place in this prestelar tissue. The continuityof vascular differentiation in the area confronting young leavesor incipient leaf positions is interrupted by the formationof leaf gap initials. Developing leaves thus begin to exertinfluence on the vascular system at the prestelar stage. Smallprotoxylem elements with helical cell wall thickening, and distinctiveprotophloem elements are present in the leaf traces, but endabruptly near the junction regions of leaf traces to the meristele.Copyright1994, 1999 Academic Press Initial vascular differentiation, provascular tissue, pith mother cells, shoot apex, Matteuccia struthiopteris     

Stomatal Responses of Variegated Leaves to CO2 Enrichment

The responses of stomatal density and stomatal index of fivespecies of ornamental plants with variegated leaves grown attwo mole fractions of atmospheric CO₂ (350 and 700 µmolmol^-1) were measured. The use of variegated leaves allowed anypotential effects of mesophyll photosynthetic capacity to beuncoupled from the responses of stomatal density to changesin atmospheric CO₂ concentration. There was a decrease in stomataldensity and stomatal index with CO₂ enrichment on both white(unpigmented) and green (pigmented) leaf areas. A similar responseof stomatal density and index was also observed on areas ofleaves with pigmentation other than green indicating that anydifferences in metabolic processes associated with colouredleaves are not influencing the responses of stomatal densityto CO₂ concentrations. Therefore the carboxylation capacityof mesophyll tissue has no direct influence on stomatal densityand index responses as suggested previously (Friend and Woodward1990 Advances in Ecological Research 20: 59-124), instead theresponses were related to leaf structure. The stomatal characteristics(density and index) of homobaric variegated leaves showed agreater sensitivity to CO₂ on green portions, whereas heterobaricleaves showed a greater sensitivity on white areas. These resultsprovide evidence that leaf structure may play an important rolein determining the magnitude of stomatal density and index responsesto CO₂ concentrations.Copyright 1995, 1999 Academic Press Leaf structure, photosynthesis, stomatal conductance, CO₂, stomatal density, stomatal index     

悬铃木叶片对悬铃木方翅网蝽为害的生理响应

为了认识近年来入侵中国的外来害虫悬铃木方翅网蝽Corythucha ciliata刺吸为害对寄主的影响,将室内饲养虫源接入野外悬铃木Platanus×acerifolia叶片上,利用光合作用仪和比色法,测定了不同受害级别下悬铃木叶片几种生理性状的变化。结果表明：随着受害级别的增高,叶片光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)总体呈下降趋势。叶片不同受害级别与胞间CO₂浓度(Ci)呈正相关(P< 0.01)。悬铃木方翅网蝽刺吸悬铃木叶片组织后, 叶片叶绿素a、b和类胡萝卜素都较对照降低,且随着被害级别的增高,降低程度逐渐增大。叶面积受害级别与叶绿体色素之间呈显著的负相关关系(P< 0.01)。随着叶片受害级别的增大,可溶性糖含量呈下降趋势,而游离脯氨酸含量的变化则无规律性。这些结果说明, 悬铃木方翅网蝽的刺吸为害能造成寄主植物光合作用的减弱及叶片其他生理生化指标变化。     

Leaf Survival and Evolution in Betulaceae

Studies on the changes in leaf number of 12 species of Betulaceaewere carried out by repeated observations during several years.The inner structure of the winter buds of these species wasalso examined. The periods of leaf emergence were long in Alnusand Betula, intermediate in Corylus and short in Ostrya andCarpinus. A heavy summer leaf fall is characteristic only ofthe Gymnothyrsus subgenus of Alnus. One lamina and two stipulesis the basic unit constituting the winter buds. Only the budsof Gymnothyrsus are composed of several of these units. In theAlnaster subgenus of Alnus, Betula and Corylus, there are oneor two scales that seem to have originated from the two stipulesremaining after reduction of the lamina. Eight and 24 scalesof similar origin were found in Ostrya and Carpinus respectively.A common ancestral species having the following primitive charactersis proposed: shoot constituted only of the equal-sized units,period of leaf emergence long, and leaf fall usually occurs.Alnus (Gymnothyrsus) is assumed to be the most primitive typeas it has many characters similar to those of the proposed ancestralspecies. Carpinus is assumed to be the most advanced group.The leaf survivorship curve is assumed to have changed fromthe primitive bell-shaped to an advanced trapezoid concurrentwith an increase in the number of bud scales. Betulaceae, Alnus, Betula, Carpinus, Corylus, Ostrya, leaf survival, leaf emergence, stipules, winter buds, evolution