Ultrastructural Observations on Proliferating Storage Cells of Mature Cotyledons of Phaseolus vulgaris L. Cultured in vitro

Explants of mature cotyledons of Phaseolus vulgaris form callusrapidly when cultured in vitro with their adaxial surfaces embeddedin a solidified nutrient medium containing coconut milk, kinetinand 2,4-D. Proliferation is confined to the highly polyploidstorage cells and commences near the adaxial epidermis, whichis soon ruptured by the callus developing internally. Callusformation progresses to the abaxial tissue and within 3–4weeks sub-culturing is possible. The in vitro grown storage cells undergo thinning of their walls,loss of food reserves, hypertrophy, development of various new-wallsand nuclear activation leading to division. The induction ofnuclear and cell divisions within this mature storage tissuecontrasts with normal germination in which these cells undergorapid senescence after depletion of their food reserves. Nuclear division in early callus growth is apparently mainlyamitotic. It is preceded by the development of multiple nucleoli.The nuclear envelope also becomes more complex and deeply lobed;leading to formation of a nuclear isthmus and final separationinto two nuclei. No chromosomes are visible during nuclear fragmentation.Amitosis is accompanied by freely-forming walls, which may developadjacent to a nuclear isthmus and perhaps participate in nuclearfragmentation. Large labyrinthine wall bodies frequently occuron these walls. Mitoses are only observed in already dividedstorage cells. A cell plate forms between the two daughter nuclei,and microtubules are present at its margins in contrast to freely-formingwalls where none are evident. Phaseolus vulgaris L., bean, in-vitro culture, cotyledon, ultrastructure     

Plant growth regulator-induced xylogenesis in cotyledons of Solanum aviculare

Treatment of explanted cotyledons of Solanum aviculare with2,4-dichlorophenoxyacetic acid and 6-benzylaminopurine resultsin the transformation of the mesophyll cells into tracheary,sclereid-like and vessel xylem elements. The initial programmingfor xylogenesis can be achieved with as little as 10 h exposureto the plant growth regulators when endogenous auxin levelsremain relatively high. The externally applied growth regulatorswould appear to enter the cotyledons both from the cut end andvia the adaxial epidermis. Key words: 4-D, BAP, Solanum aviculare, cotyledons, xylogenesis, vessels, carboxylesterase     

Nucleostemin-like 1 is required for embryogenesis and leaf development in Arabidopsis

Arabidopsis NSN1 encodes a nucleolar GTP-binding protein and is required for flower development. Defective flowers were formed in heterozygous nsn1/+?plants. Homozygous nsn1 plants were dwarf and exhibited severe defects in reproduction. Arrests in embryo development in nsn1 could occur at any stage of embryogenesis. Cotyledon initiation and development during embryogenesis were distorted in nsn1 plants. At the seedling stage, cotyledons and leaves of nsn1 formed upward curls. The curled leaves developed meristem-like outgrowths or hyperplasia tissues in the adaxial epidermis. Long and enlarged pavement cells, characteristic of the abaxial epidermis of wild type plants, were found in the adaxial epidermis in nsn1 leaves, suggesting a disoriented leaf polarity in the mutant. The important role of NSN1 in embryo development and leaf differentiation was consistent with the high level expression of the NSN1 gene in the developing embryos and the primordia of cotyledons and leaves. The CLAVATA 3 (CLV3) gene, a stem cell marker in the Arabidopsis shoot apical meristem (SAM), was expressed in expanded regions surrounding the SAM of nsn1 plants, and induced ectopically in the meristem-like outgrowths in cotyledons and leaves. The nsn1 mutation up-regulated the expression levels of several genes implicated in the meristem identity and the abaxial cell fate, and repressed the expression of other genes related to the specification of cotyledon boundary and abaxial identity. These results demonstrate that NSN1 represents a novel GTPase required for embryogenesis, leaf development and leaf polarity establishment in Arabidopsis.     

Somatic Embryogenesis in Cassava: The Anatomy and Morphology of the Regeneration Process

Anatomical and morphological studies demonstrated that somaticembryos developed similarly on mature seed and clonal leaf explantsof cassava (Manihot esculenta Crantz) cultured for 20–24d on Murashige and Skoog (MS2) basal medium supplemented with4.0 mg l^–1 2,4-D (Stage 1) before transfer to MS2 basalmedium supplemented with 0–01 mg l^–1 2,4-D and 0–1mg l^–1 6-benzylaminopurine (Stage II medium). Within 7d of inoculation onto Stage I medium, cell divisions occurredin the adaxial tissues of cotyledon-piece and leaf-lobe explants,and associated with this was the development of embryogeneticprotusions and ridges on the adaxial surface. Foliose structuresand somatic embryo initials developed from these tissues oncotyledon, embryonic axis and leaf-lobe explants and, when cultureswere transferred to Stage II medium, further somatic embryodevelopment occurred. Somatic embryos apparently originatedfrom groups of cells and were identified by the presence ofa closed root axis, a shoot axis and cotyledons of similar shapeand venation to those of zygotic embryos. Somatic embryos hadno vascular connection with parental cultures. Manihot esculenta, cassava, somatic embryogenesis, tissue culture, anatomy, morphology, morphogenesis     

Early Cellular Events During Direct Somatic Embryogenesis in Cotyledon Explants of Solanum aviculare Forst.

A detailed light and electron microscope study of early cellularevents at the onset of somatic embryogenesis in cotyledon explantsof Solanum aviculare Forst., cultured on MS medium supplementedwith 1 mg l^–1 2,4-dichloro-phenoxyacetic acid (2,4-D)for periods of 0–12 d in darkness, is described. Examinationsof longitudinal sections in a plane offset from the centralveins indicated that the earliest embryogenic events in explantstook place within the first 3–4 d of culture in the parenchymacells associated with the vascular traces closest to the cutbasal ends of cotyledons. Thereafter, parenchyma associatedwith more distal vascular traces became active in an apparentlysequential manner such that, by the second week of culture,progressive stages of embryogenesis could be observed alongthe lengths of cotyledon sections. Despite the fact that epidermalcells and palisade tissues were exposed directly to the 2,4-Dmedium, initiation of embryogenic development was never observedin cells other than those directly associated with vasculartraces. None of the embryogenic events characterized at theultrastructural level were observed in cotyledons cultured onMS medium in the absence of 2,4-D with the exception that starchaccumulated in decreasing amounts from the wounded basal endto the distal end of each cotyledon. This system provides a valuable model with which to study earlybiochemical and molecular events occurring in explants duringthe onset of somatic embryogenesis because they occur in a predictablefashion at sequentially situated sites along the explant tissues. Somatic embryogenesis, Solanum aviculare, cotyledon explants, cellular changes     

Micromorpho-Anatomical Examination of 2,4-D Phytotoxicity in Grapevine (Vitis vinifera L.) Leaves

The anatomical and micro-morphological alterations as induced by the auxinic herbicide, 2,4-D (2,4-dichlorophenoxy acetic acid) have not yet been elucidated for a commercially important fruit crop such as grapevine despite its super sensitivity to 2,4-D. Light and scanning electron microscopy techniques were employed to examine 2,4-D induced internal and external structural abnormalities in Merlot grapevines (Vitis vinifera L.). Healthy leaves were dorsiventrally flattened with well developed patterns of cellular structure and composition involving adaxial palisade parenchyma and abaxial spongy mesophyll. Dorsiventral variations in epidermal features involved large epidermal cells on the adaxial surface, and trichomes and stomata with turgid elliptical guard cells on the abaxial surface. The 2,4-D injured leaves were small and enated; the veins were fasciated with rugose bands of lamina existing between fasciated veins. The epidermal cells aggregated instead of being positioned coplanar to the epidermal plane. The adaxial elongated palisade parenchyma cells were transformed into an ovoid shape with intercellular spaces. An extensive development of replacement tissues took place on the abaxial surface wherein the stomata became roundish and were either raised or sunken with collapsed and cracked guard cells that developed abnormal outer stomatal ledges. These abnormalities are expected to severely perturb the vital functions of photosynthesis and transpiration ultimately leading to vine death attributable, at least in part, to the injured leaves.     

Histodifferentiation of somatic embryos in cotyledons of pineapple guava (Feijoa sellowiana Berg)

Summary Somatic embryos of pineapple guava (Feijoa sellowiana Berg, Myrtaceae) were induced particularly well from the adaxial face of the cotyledons of zygotic embryos cultured on MS medium containing 1.0 mg/l 2,4-D and 0.3 M sucrose. Somatic embryos were never obtained from globular and heart-shaped zygotic embryos and embryos at the torpedo stage produced somatic embryos at lower frequencies than mature zygotic embryos. At the time of explantation, cotyledonary cells were rich in storage proteins and lipids but no starch was found. After the first 5 days of culture most of the reserves had been mobilized in cotyledons of germinating embryos, but were still present in large amounts in cotyledons undergoing embryogenie induction. In contrast to cotyledons following the normal pattern of development, cells of embryogenically-induced cotyledons accumulated starch, especially those cells not involved in the embryogenie process. Two patterns of somatic embryo differentiation were observed: (1) from single epidermal cells or (2) from groups of meristematic cells near the adaxial surface. Comparative observations on cotyledons from germinating embryos and those undergoing embryogenesis suggest that the meristematic layer arises as the result of successive divisions of cells that, under normal conditions, would form the palisade parenchyma. These were the only mesophyll cells that showed mitotic divisions during the normal development.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - FAA formalin/acetic acid/ethyl alcohol - PAS periodic acid-Schiff     

Arrangement of Cortical Microtubules in Avena Coleoptiles and Mesocotyls and Pisum Epicotyls

Cortical microtubules (MTs) in coleoptiles and mesocotyls ofAvena sativa and epicotyls of Pisum sativum were examined byimmunofluorescence. In elongating Avena coleoptiles whose elongationis less localized, the orientations of cortical MTs of parenchymaand adaxial epidermal cells, and abaxial epidermal cells aretransverse, and oblique or longitudinal, respectively, and doesnot differ between the upper, middle and lower parts. The transverseMTs in parenchyma and adaxial epidermal cells turns to obliqueor longitudinal ones after elongation stops. The obliquity ofMTs in abaxial epidermal cells also tends to become steeperas elongation comes to a stop. In Avena mesocotyls and Pisumepicotyls whose elongation is localized, the orientation ofcortical MTs of cortical cells in the elongating region is relativelytransverse. The epidermis has intermingling cells of transverseor oblique MTs. In the non-elongating region, MT orientationbecomes steeper both in the cortex and epidermis. The present results indicate that whatever the degree of localizationof the elongation, the obliquity of MTs in these organs is steeperin epidermal than in inner tissue cells and becomes steeperas elongation stops in both tissues. (Received October 26, 1987; Accepted April 19, 1988)     

大豆体细胞胚胎发生影响因素的研究

研究了影响大豆幼胚培养体细胞胚胎发生频率的9个因素。诱导体细胞胚胎发生的适宜幼胚长度为4mm;随着供体植株发育阶段的提高诱导频率下降;最适基本培养基为MS培养基; 蔗糖浓度从1.5％提高到9％,诱导频率逐渐下降;过高的维生素B1浓度对胚胎发生不利;2,4 — D的诱导效果优于NAA,适宜的2,4—D浓度为20ppm; 光、暗处理与生长素种类和浓度之间存在交互作用,接种方式对诱导频率影响很大,体细胞胚只在下表皮与培养基接触的幼子叶的上表皮上产生,当上表皮与培养基接触时,两个表皮都不能产生体细胞胚;被试的所有基因型都能被诱导胚胎发生,不同基因型的诱导频率存在差异。     

Developmental Ultrastructure of Cells and Plastids in the Petals of Wallflower (Erysimum cheiri)

An ultrastructural study of petal cells of wallflower (Erysimumcheirii) of the family Brassicaceae shows that the adaxial epidermalcells are of the conical papillate type whereas the cells ofthe abaxial epidermis are lenticular in shape. The abaxial epidermiscontains stomata, which are solitary and lack any obvious subsidiarycells. Pigmentation is apparent in both epidermal and internalmesophyll cells and results from the presence of both chromoplastsand large cytoplasmic vesicles containing pigment. These pigmentedvesicles are very obvious in preparations of fixed isolatedpetal cells. Chromoplasts are of the globular type and are presentin significant numbers in both epidermal and mesophyll cells.Division of chloroplasts in young petals prior to bud breakappears to give rise to the populations of chromoplasts observedin mature petals since there was no evidence of chromoplastdivision itself. The development of wallflower petals and theirchromoplasts is discussed in relation to development of petalsin the related species Arabidopsis thaliana. Copyright 1999Annals of Botany Company Wallflower, Erysimum cheiri, Chieranthus, petal development, chromoplasts, chloroplast differentiation.     

Studies on Foliar Penetration: 2. THE ROLE OF LIGHT IN DETERMINING THE PENETRATION OF 2,4 DICHLOROPHENOXYACETIC, ACID

A further study has been made of the factors determining thelevel of penetration of 2,4-dichlorophenoxyacetic acid (2,4-D)into leaves. The technique involves the use of leaf disks and2,4-D containing carbon-14 in the carboxyl group. For Phaseolus vulgaris the influence of the pH of the appliedsolution is greater in the light than in the dark. Between 0and 1,000 f.c. at 27° C there is a small increase in therate of penetration into the abaxial surface. Under these conditionsthe rates remain constant up to 56 hours. This linear relationshipholds for concentrations ranging from 100 to 1,000 mg/l, andthe rate of penetration is directly proportional to the concentration.For intensities in excess of 1,000 f.c. the light response ismarkedly different: over the first few hours there is a steadyand relatively slow rate of penetration which is followed bya second phase when the rate is greatly accelerated. This acceleratedrate can be reversed by transferring the disks to darkness,and does not take place at 1° C. Likewise, if excised disksare left for more than one hour in either the light or the darkbefore applying 2,4-D then there is subsequently no phase ofaccelerated penetration. The course of penetration into theadaxial surface exhibits no accelerated rate, and compared tothe abaxial surface the rates are lower. For leaves of Ligustrum ovalifolium, which lack stomata on theadaxial surface, the rates of penetration at 27° C intoboth surfaces remain constant in either light or darkness. Forboth the adaxial and abaxial surfaces, the rate progressivelyincreases from 0 to; 2000 f.c. and there is no phase of acceleratedpenetration. Penetration into the adaxial surface is less. At1° C the rates for both surfaces in either light or darknessare depressed. If disks of Phaseolus are irradiated with ultraviolet light,subsequent penetration is markedly depressed in the light at27° C, but in the dark or at 1° C it is enhanced. On the basis of these findings it is concluded that both physicaland metabolic factors control the rate of penetration of 2,4-DTransport through the cuticle will be dependent on adsorptionand the length of the diffusion paths. Once diffusion gradientshave been established between the surface of the cuticle andthe outer surface of the cytoplasm in the epidermal cells, thesteepness will be dependent on the rates at which 2,4-D is eitherconverted into some metabolite or moved away from the surfaceor into other cells. The relative importance of physical andmetabolic process will be dependent on the permeability andthickness of the cuticle and the level of metabolic activity.The possible role of ectodesmata in determining both the lengthand steepness of the diffusion paths is discussed.     

Ultrastructural Development of Plastids in the Epidermis and Starch Layer of Glossy Ranunculus Petals

The differentiation of chromoplasts and amyloplasts has beenfollowed in developing petals of Ranunculus acris, R. ficariaand R. repens from small bud stages through anthesis. Theseare typical of Ranunculus species with glossy yellow petals.The plastids in the adaxial epidermis of the glossy part developmany globules which enlarge and coalesce with the eventual completebreakdown of plastid structure. At anthesis only a few cytoplasmicremnants remain in the dispersed pigment in these cells whichpartially collapse with folding of the anticlinal walls. Inthe non-glossy proximal part of the petal the adaxial epidermalcells have more convex outer walls and the chromoplast developmentdoes not progress beyond a stage found in the glossy regionjust before the petal tips emerge from the bud: they have largeperipheral globules with irregular tubular lamellae betweenthem and in the central stroma. In the abaxial epidermis theplastids produce small globules and retain some grana; somehave small starch grains and differ little from the plastidsin the mesophyll. The starch layer beneath the adaxial epidermisin the glossy region is formed from a single embryonic celllayer. Amyloplasts differentiate rapidly in these cells andall plastid structure has disappeared before the flower budopens leaving the sloping palisade cells packed with starchgrains. Chromoplast, amyloplast, petal, ultrastructure, development, Ranunculus, buttercup, lesser celandine     

Regulation of organogenesis and somatic embryogenesis by auxin in melon,Cucumis melo L.

Various tissues of seeds and seedlings of melon were cultured in vitro to study the effects of auxin concentration on organogenesis and embryogenesis. Adventitious shoots and somatic embryos were formed from explants of cotyledons of mature seeds, hypocotyls of seedlings, and leaves and petioles of young plantlets. Expanded cotyledons of seedlings formed only adventitious shoots. All tissues responded similarly to the 2,4-D concentration in the media, that is, adventitious shoots were formed at low concentration, callus proliferated without differentiation at intermediate concentration and somatic embryos were induced at high concentration. Cotyledons of mature seeds formed both adventitious shoots and somatic embryos more efficiently than any other tissues cultured.Effects of three auxins, 2,4-D, NAA and IAA, on organogenesis and embryogenesis were compared using cotyledons of mature seeds. Adventitious shoots were formed at low level of auxins (0 to 0.01 mg/l 2,4-D; 0 to 0.1 mg/l NAA; 0 to 1.0 mg/l IAA), and embryos were formed at high level of auxins (1.0 to 2.0 mg/l 2,4-D; 3.0 to 10.0 mg/l NAA; 20.0 to 100.0 mg/l IAA). IAA gave more efficient shoot formation and embryogenesis than the other auxins.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - NAA -naphthaleneacetic acid - IAA 3indoleacetic acid - BA 6-benzylaminopurine - MS Murashige and Skoog     

Auxin and heat shock activation of a novel member of the calmodulin like domain protein kinase gene family in cultured alfalfa cells

A calmodulin like domain protein kinase (CPK) homologue wasidentified in alfalfa and termed MsCPK3. The full-length sequenceof cDNA encoded a 535 amino acid polypeptide with a molecularweight of 60.2 kDa. The deduced amino acid sequence showed allthe conserved motifs that define other members of this kinasefamily, such as serine-threonine kinase domain, a junction regionand four potential Ca²⁺-binding EF sites. The recombinant MsCPK3protein purified from E. coli was activated by Ca²⁺and inhibitedby calmodulin antagonist (W-7) in in vitro phosphorylation assays.The expression of MsCPK3 gene increased in the early phase ofthe 2,4-D induced alfalfa somatic embryogenesis. Heat shockalso activated this gene while kinetin, ABA and NaCl treatmentdid not result in MsCPK3 mRNA accumulation. The data presentedsuggest that the new alfalfa CPK differs in stress responsesfrom the previously described homologues and in its potentialinvolvement in hormone and stress-activated reprogramming ofdevelopmental pathways during somatic embryogenesis. Key words: Medicago sativa, CPK, stress, 2,4-D, phosphorylation, somatic embryogenesis.     

Guard cells on adaxial and abaxial epidermes of <Emphasis Type="Italic">Erythrina corallodendron</Emphasis> sepals

This study investigated guard cells on the adaxial and the abaxial epidermes during Erythrina corallodendron sepal development. On the adaxial epidermis, the morphology of guard cells was highly variable and changes in aperture induced by abscisic acid (ABA) were observed in 9.1 % stomata, while on the abaxial epidermis 86.7 % stomata responded to ABA. On the adaxial epidermis, stomata did not close even when guard cell pressure potential was reduced to zero by plasmolysis, even if fluorescein diacetate revealed that guard cells were alive. It was concluded that guard cells on the adaxial and the abaxial epidermes of sepals sensed environmental conditions differently, maybe due to different guard cell wall elasticity.     

Studies on Foliar Penetration: IX. PATTERNS OF PENETRATION OF 2,4-DICHLOROPHENOXYACETIC ACID INTO THE LEAVES OF DIFFERENT SPECIES

The comparative patterns of penetration of 2,4-dichlorophenoxyaceticacid (2,4-D) into the leaves of Phaseolus vulgaris, Zea mays,Pisum sativum, Beta wlgaris, Helianthus annuus and Gossypiumhirsuium have been examined. Save for Zea and Gossypium where there is little change withthe stage of leaf development the rates of penetration intoboth surfaces decrease as the leaf matures. The relative ratesare dependent on the species and the age of the leaf but thereare differences between the surfaces. In Phaseolus the characteristicsof primary leaves differ from those of trifoliate leaves sinceonly in immature trifoliate leaves is penetration into the adaxialsurface greater. In darkness the rates of penetration over 24 h remain constantor fall but slightly for all species. Light consistently promotespenetration but with Beta there is a lag before entry is acceleratedinto the abaxial surface as has previously been reported foryoung primary leaves of Phaseolus. For the remaining speciesthe courses of penetration in both light and darkness into bothsurfaces follow similar patterns. As the light intensity isincreased entry is enhanced but the limit of response variesbetween species, between surfaces within species, and in trifoliateleaves of Phaseolus with age. For the six species the order of the relative rates of entryis closely similar whether comparisons are made in light ordarkness or between abaxial and adaxial surfaces: viz. Zea >Helianthus > Phaseolus (primary) > Phaseolus (trifoliate)> Pisum = Beta = Gossypium. The observed specific differencesare discussed in relation to variations in leaf structure, theproperties and thickness of the cuticle and the physiologicaland metabolic processes which influence transport within theepidermal tissues after it has passed through the cuticle bydiffusion.     

Hormonal Control of Morphogenesis in Leaf Explants of Perilla frutescens Britton var. crispa Decaisne f. viridi-crispa Makino

Leaf discs of Perilla frutescens var. crispa f. viridi-crispawere cultured on a defined medium to investigate factors influencingbud and root formation, callus induction, somatic embryogenesis,and floral bud formation. Addition of naphthalene-acetic acid(NAA) to the culture medium caused compact callus whereas 2,4-dichlorophenoxyacetic acid (2,4-D) promoted soft and friable callus formationon the surface of the explants. Benzyladenine, when appliedwith auxin, suppressed callus and root formation. Somatic embryogenesisoccurred, when the explants were first grown on nutrient mediumcontaining 2,4-D and organic elements, and then transferredto the 2,4-D free medium. Treatments with cytokinins, N-phenyl-N'-(4-pyridyl)urea and its derivatives induced bud formation. A low concentrationof NAA and naphthoxy-acetic acid promoted bud development. Occasionalfloral bud formation was observed depending on the originalleaf positions on mother plants from which the leaf discs wereexcised. A gradient of floral bud forming capacity along thestem was noted. Perilla frutescens, tissue culture, embryogenesis, morphogenesis, benzyl adenine, kinetin, naphthalene-acetic acid, naphthoxy-acetic acid, 2,4-dichlorophenoxy acetic acid, indol-3yl-acetic acid, cytokinins, auxins     

Somatic embryogenesis and plant regeneration from leaflets of peanut,Arachis hypogaea

Somatic embryos were induced on peanut (Arachis hypogaea) leaflets from aseptically germinated embryo axes. Leaflet size influenced percent somatic embryogenesis; 5–8 mm long cut leaflets were superior to 2–3 mm long uncut leaflets. Maximum embryogenesis of 14.6% was obtained after a 15 d incubation on induction medium (modified MS with B5 vitamins, 30 g/l sucrose, 4 g/l Gel-Gro, 40 mg/l 2,4-D +0.2 mg/l kinetin) followed by transfer to a secondary medium with 5 mg/l 2,4-D+0.2 mg/l kinetin. Primary somatic embryos were fused along the axes with no distinct cotyledons, but secondary embryos had single axes with two cotyledons. Other treatments had lower percent embryogenesis, no secondary embryogenesis, and embryos with single axes with two cotyledons. Some somatic embryos converted into normal plants capable of greenhouse survival.Abbreviations MS Murashige and Skoog (1962) medium - B5 Gamborg et al. (1968) B5 medium - 2,4-D 2,4-dichlorophenoxyacetic acid - BAP 6benzylaminopurine - NAA 1-naphthaleneacetic acid     

葛(豆科)叶的解剖学研究

利用光学显微镜和扫描电镜观察了葛(Pueraria lobata)叶的解剖学特征。结果表明,葛叶片的上、下表皮都只有一层表皮细胞,上表皮比下表皮厚。上、下表皮都有腺毛和非腺毛。气孔主要分布在下表皮,下表皮的气孔密度为(261±17)mm-2,上表皮只有(6±3)mm-2。叶肉由两层栅栏组织细胞和一层海绵组织细胞构成。叶肉细胞中有丰富的叶绿体。在栅栏组织和海绵组织之间有一层平行于叶脉的薄壁细胞。叶脉中含有大量的草酸钙晶体。葛叶的这些形态特征与其喜阳、耐旱的特点相适应。