The Cuticle, Epidermis and Stomatal Ontogeny of Casuarina equisetifolia Forst

The cuticle, epidermis and stomatal ontogeny of Casuarina equisetifoliaForst. is described. The cuticle shows well marked impressionsof the epidermal cells and stomata. The epidermis of leaf andstem shows transversely oriented, tetracytic, mesoperigenousstomata with two lateral mesogene subsidiaries and two polarperigene neighbouring cells. Although the epidermal structureof Casuarina shows a good deal of resemblance with that of theBennettitales, it may not indicate any phylogenetic relationshipssince there are important differences in the structure and reproductionof the plants of these two groups.     

Epidermal Structure and Ontogeny of Stomata in Vegetative and Reproductive Organs of Ephedra and Gnetum

The epidermal structure and development of stomata in vegetativeand reproductive organs of Ephedra foliata and Gnetum ula isdescribed. The epidermal cells are polygonal, isodiametric,or elongated with thick or thin straight, arched, or slightlysinuous anticlinal walls. The cuticle is thin or thick. Papilla-likeunicellular outgrowths are present in Ephedra foliata. The maturestomata are orientated parallel to the longitudinal axes orirregularly. The mature stomata are anomocytic, paracytic, witha single subsidiary cell, cyclocytic, and actinocytic. Arresteddevelopment, contiguous stomata, and stomata with aborted guardcells have been observed. The ontogeny of stomata on differentorgans of these two plants is typically haplocheilic or perigenousbut the stomatal apparatus varies from organ to organ.     

Epidermal Structure and Stomatal Ontogeny in Some Eusporangiate Ferns

Cuticles, mature epidermis, and stomatal ontogeny in some speciesof the three genera of Ophioglossaceae and in Angiopteris evectawere studied. Development of stomata is perigenous in all Ophioglossaceaebut it is mesoperigenous (Piper type) in A. evecta.     

Stomatal Pattern in Four Species of Monocotyledons

The distribution of stomata has been investigated in the leafepidermis of Chlorophytum comosum, Galanthus nivalis, Schizostyliscoccinea and Scilla lancifolia. The epidermis was consideredto consist of units of construction of two kinds: type A, along epidermal cell with a stoma at its distal end, and typeB, a long epidermal cell without an associated stoma. Exceptin Scilla, the probability of an epidermal unit being type Aincreases approximately with its length. Considering the epidermisas rows of units, alternating sequences of type A and type Bdo not occur randomly along the rows. In Chlorophytum, Galanthusand Schizostylis, both type A and B units tend to be aggregatedinto longer sequences than would be expected on a random basis.It is suggested that homoeogenetic induction (i.e. of like bylike) may be occurring during development. No case can be madefor homoeogenetic induction of units in Scilla. There is a slighttendency to periodicity of distribution of type A units in Galanthus,Schizostylis and Scilla, but this does not seem to representa primary element of pattern. There is interaction between rowsin the sense that unit ends (transverse walls) tend to avoidthose in neighbour rows; this affects the relative distributionof stomata, but there is no evidence of any direct interactionbetween stomata in different rows. Chlorophytum comosum, Galanthus nivalis, Schizostylis coccinea, Scilla lancifolia, leaf, epidermis, stomata, pattern     

Cellular Interactions in the Development of Stomatal Patterns in Vinca major L

The development of the leaf epidermis of Vinca major L. wasfollowed in situ by epi-illumination microscopy and evidencewas sought for cellular interactions. Stomata were often foundto be initiated in adjoining cells. The epidermal cells whichseparated such stomata when they had matured were formed fromthe same cells as the stomatal complexes themselves. The presenceof developing and mature stomata may influence only the orientationof divisions in neighbouring cells, and not the initiation andmaturation of stomata. There is great variability in the relativeorientation, timing and number of divisions which intervenebetween the first unequal division and the maturation of a stomaas well as the location of stomata relative to the spongy mesophylland minor veins. The results indicate that continuous short-rangeinteractions between the future guard cells and the adjoiningcells, rather than interactions between future stomata or afixed programme of development, are essential for the formationof the pattern of functional stomata in the mature leaf. Vinca major L., cell lineage, cellular interactions, development of stomata, epi-illumination microscopy, meristemoids, patterned differentiation, stomata     

Variable Development and Cellular Patterning in the Epidermis of Ruscus hypoglossum

The general problem was the meaning of the variability of cellulardevelopment of the stomata-bearing epidermis of Ruscus hypoglossumin which 'immature stomata' occur, i.e. cells that have gonethrough part but not the final stages of stomatal development.The development of the epidermis was followed in vivo, by makingrepeated replicas of the same developing tissues using dentalimpression material. The development of stomata occurred overthe entire surface of large phyllodes and was not synchronous.The early development of future and 'immature stomata' couldnot be distinguished, neither by the form of the cells nor bythe timing of the initial, unequal divisions. The process ofstomatal development did not stop at any one, characteristicsstage. Statistical analyses indicated that the pattern of functionalstomata would have been less orderly if all stomatal initialshad developed into mature structures. The results suggest thatin Ruscus epidermal patterning occurs during, rather than preceding,stomatal development: many stomata are initiated, but they followa labile developmental program and cellular interactions selectthose that reach the mature functional state.Copyright 1993,1999 Academic Press Cellular patterns, epigenetic selection, immature stomata, Ruscus hypoglossum, spacing patterns, stomata, subsidiary cells, unequal divisions     

Structure and Function in the Grass Ligule: Optical and Electron Microscopy of the Membranous Ligule of Lolium temulentum L.

Aspects of the structure and ultrastructure of the membranousligule of mature leaves of Lolium temulentum L. are described.In transverse section the ligule was lens-shaped and wedge-shapedin longitudinal section, 6 or 7 cells wide near the base and1 or 2 cells wide at the edges. Two uniseriate epidermes encloseda chlorenchymatous mesophyll tissue of varying thicknesses;both epidermes were continuous with the leaf adaxial epidermis.The cells comprising these three issues all appeared like typicalgrass epidermal long cells; elongate papillate cells were presentat the edges. No stomata, trichomes, intercellular spaces orvascular tissue were found in the ligule. A marked polarizationof ultrastructural complexity existed from the large-vacuolateabaxial epidermis to the ‘densely cytoplasmic’ small-vacuolateadaxial epidermis. Cells of the latter tissue contained numerousmitochondria, hypersecretory dictyosomes and abundant strandsof rough endoplasmic reticulum. Fluorescence microscopy providedevidence for the accumulation of a polysaccharide-containingmaterial within the periplasmic space next to the outer tangentialwall of adaxial epidermal cells. The ligule is considered tobe a highly organized and differentiated leaf organ with a pholosyntheticmesophyll and an adaxial epidermis active in the synthesis ofprotein and polysaccharide. Darnel, fluorescence microscopy, ligule, Lolium temulentum L., Poaceae, ultrastructure     

Variable Cell Lineages form the Functional Pea Epidermis

Evidence was sought for cellular programs and cellular interactionsacting during the formation of stomatal spacing patterns. Dailyreplicas of the surfaces of Pisum sativum leaves were used toreconstruct the cellular development of specific regions ofthe epidermis. During the period studied small primordia becamemature leaves; this involved a 250-fold increase in area anda 20-fold increase in cell number. The earliest event correlatedwith the development of a stoma was an unequal division, andsuch divisions were common in neighbouring and even within thesame cells. A distinct cell lineage started with these unequaldivisions, forming both a stoma and most of the cells that separatedit from its neighbours. Both products of an unequal divisionbecame regular epidermal cells only where such development preventedthe formation of two stomata that would have been in directcontact with one another. Neighbouring stomata often developedand matured together, indicating that there was no mutual inhibitionbetween developing stomata that were more than one cell apart.It is concluded that stomata are products of an intracellularprogram which generates stomatal patterns during rather thanpreceding development. This program can be modified and evenstopped during its entire course, allowing for the correctionof local ‘mistakes’ of stomatal patterning. Cell lineages, cell determination, cellular interactions, epidermal development, garden peas, immature stomata, pattern formation, Pisum sativum, spacing patterns, stomata, unequal divisions     

Guard Cells Extrude Protons Prior to Stomatal Opening--A Study using Fluorescence Microscopy and pH Micro-electrodes

A method for the demonstration of pH changes in the apoplastis described. The fluorescent pH indicator pnmulin was usedto follow pH changes in the epidermis of leaves of Commelinacommunis during stomatal movements. Previously darkened leavesexposed to light showed quenching of fluorescence in the apoplastsurrounding theuard cells up to 20 min before the stomata opened.This indicated that proton efflux by the guard cells precededstomatal opening. This result was substantiated by apoplasticpH measurements using pH micro-electrodes. Acidification ofthe apoplast spread outwards from the guard cells to the surroundingsubsidiary and epidermal cells. This phenomenon persisted forsome time after subsequent stomatal closure, supporting thehypothesis that closure is brought about by a process otherthan the cessation of proton pumping. Key words: Commelina communis, stomata, proton pumping     

Epidermal structure and development of stomata in vegetative and floral organs ofHybanthus enneaspermus (Linn.)F. Muell

The present paper deals with the epidermal structure and ontogeny of stomata in vegetative and floral organs ofHybanthus enneaspermus. The epidermal cells are either polygonal or elongated with straight, sinuous or arched thick anticlinal walls. The surface of the cuticle shows parallel striations radiating from the guard cells or hair bases. Unicellular and uniseriate bicellular trichomes with verrucose margins have been observed on all organs. The mature stomata are anisocytic, paracytic, anomocytic and transitional between anisocytic and paracytic. The ontogeny of anisocytic and paracytic stomata is syndetocheilic or mesogenous, anomocytic is haplocheilic or perigenous, while that of the transitional type is mesoperigenous. Four types of stomata have been observed on all the vegetative and floral organs and their ontogeny from organ to organ of this plant is constant. Stoma with a single guard cell is the result of disintegration of one of the guard cells before or after pore formation. Contiguous stomata are also occasionally noticed.     

Major Element Composition of Epidermal and Mesophyll Tissues2Commelina Communis L. and Vicia Faba L.: Some Further Considerations of the Role of Ions in Stomatal Functioning

Epidermal and mesophyll tissues of Commelina communis L. andVicia faba L. were analysed by atomic absorption spectrometryfor the major plant inorganic cations and anions (K, Na, Ca,Mg, P, NO₃-N, Cl) when stomata of the leaf were open and closed.Water-soluble and residual levels of the elements were estimatedand a charge balance of the soluble fraction made. The major portion of K, Na, Cl, and P was extracted in the water-solublefraction of the epidermal and mesophyll tissues of both species.In both species the bulk of Ca remained in the insoluble residueof the epidermis whereas in mesophyll tissue it was equallydistributed be-between the two fractions in C. communis butmainly in the insoluble residue in V. faba. Magnesium was predominantlyfound in the water-soluble fraction of V. faba mesophyll tissueand distributed approximately equally between the two fractionsin the epidermal tissue. In C. communis Mg was slightly moreabundant in the water-soluble fraction of both mesophyll andepidermis. In both species no statistically significant differences inthe levels of the elements could be detected between epidermaland mesophyll tissues from leaves with open stomata and thesame tissues from leaves with closed stomata, suggesting thatthere was no major flux of ions between mesophyll and epidermisduring stomatal movements. Regardless of whether the stomata were open or closed, therewere considerably more water-soluble inorganic cations thananions present in all tissues of both species with K being themajor cation and Cl being the major anion. In V.faba and C-communis epidermis there was 49–53 per cent and 56%68per cent excess cation respectively. In the mesophyll tissuethe excess cation was 63–75 per cent and 75%78 per centin V.faba and C. communis respectively. When the partitioning of the levels of the elements betweenepidermis and mesophyll of a leaf is considered, except forNO₃-N in both species and Na in V. faba, 20 per cent or lessof each element was present in the epidermis.     

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.     

Histological Changes of the Peanut (Arachis hypogaea) Gynophore and Fruit Surface During Development, and their Potential Significance for Nutrient Uptake

Histological changes in gynophores and fruits of Arachis hypogaeaL.cv. White Spanish were examined, utilizing scanning electronmicroscopy as well as light microscopy. The epidermis of theabove ground parts of gynophores is characterized by the presenceof stomata, lenticels and multicellular trichomes. Below groundportions of the same plant organ exhibit unicellular root-hair-likestructures. These protuberances of the epidermal cells can reacha very high density and length (up to 0.75mm) . Identical structurescan be found on the developing pod and are most prominent atthe reproductive stages R5-R6. In later developmental stagesthe hairs degenerate and the presence of large lenticels becomesthe obvious external feature of the pod. It is suggested thatthe substantial increase in surface area due to the hairs maywell be an anatomical adaptation for nutrient and water uptake. Arachis hypogaea, peanut fruit development, nutrient uptake     

The Floral Nectary of Tropaeolum majus L.--The Nature of the Secretory Cells and the Manner of Nectar Secretion

The floral nectary of Tropaeolun majus L. was studied with theaid of a microscope with transmitting and incident light, atransmission electron microscope and a scanning electron microscope.The Gomori method was used for the localization of acid phosphatase.As a result of this investigation the previously accepted viewthat nectar in this plant is secreted only from the hair tipsof the inner epidermis of the calyx spur was found to be inaccurate.The present studies showed that the parenchyma cells locatedbetween the inner epidermis and the region of the vascular bundlesof the lowest third of the spur, are the main nectar-secretingelements of the nectary. These secretory cells release the nectarsolution into intercellular spaces leading to modified stomata,through which it is exuded into the spur cavity. The modifiedstomata occur in the lowest portion of the spur only. At thestage of secretion small droplets of liquid of high viscositywere observed on the epidermal hairs. These droplets presumablycontain polysaccharides and a certain amount of sugar.     

The Generic Position of Protorhus namaquensis Sprague (Anacardiaceae): Evidence from Fruit Structure

In Protorhus namaquensis the outer epidermis of the ovary formsthe exocarp. At maturity it is uniseriate and consists of palisade-likeparenchyma cells and modified stomata (MS). A cuticle, extensivecutinization of the outer cell walls and starch also characterizethe exocarp. The mesocarp develops from the ground tissue ofthe ovary wall and includes an outer zone of large-celled tanniniferousparenchyma, secretory ducts associated with some of the vascularbundles, prismatic crystals of calcium oxalate and brachysclereids.The inner epidermis of the ovary undergoes successive periclinaldivisions whose derivatives form the mature endocarp. It isstratified and tetraseriate, comprising successive layers (frommesocarp inwards) of crystalliferous cells, brachysclereids,osteosclereids and macrosclereids. The morphology of the femaleflower, and the fruit structure of P. namaquensis are comparedwith that of P. longifolia (lectotype of the genus and onlyother African species) and species of Ozoroa. We present abundantevidence that P. namaquensis should be associated with somemembers of the genus Ozoroa , rather than with P. longifolia.The new combination, Ozoroa namaquensis (Sprague) Von Teichman& Van Wyk, is proposed. Characters of the perianth and pericarp,inter alia the occlusion of the pores of most MS, are consideredadaptations of the species to its harsh semi-desert habitat.Copyright1994, 1999 Academic Press Anacardiaceae, Protorhus namaquensis, Ozoroa namaquensis, pericarp, fruit, flower, modified stomata, ontogeny, histochemistry, cutin     

Responses of the stomata of Aster tripolium to calcium and sodium ions in relation to salinity tolerance

In previous work, the stomata of the maritime halophyte Astertripolium L. were shown to close when NaCl concentrations risein the vicinity of the guard cells. Further studies have nowrevealed important effects of calcium on the ionic responsesof the stomata. When the guard cells were presented with KCl,Ca²⁺ suppressed opening in a manner similar to that which hasbecome familiar in other species such as Commelina communisL. However, in the presence of NaCl, Ca²⁺ had the opposite effect,reducing the closing response to NaCl. This pattern of behaviouris discussed in relation to known salt effects on membranes,but the underlying physiological basis remains obscure. A previous study led to the hypothesis that the closing responseof the stomata to Na⁺ ions may make an important contributionto the salinity tolerance of this species. Here we report thatincreasing supplies of Ca²⁺ ions reduce the effect of salinityon stomatal conductance in the whole plant as well as in theisolated epidermis. This finding is consistent with the wellestablished role of calcium in increasing resistance to salinity:in the presence of high calcium the plant can tolerate a greatersalt intake, and hence there is a reduced need for transpirationto be restricted by partial stomatal closure. Key words: Sodium, calcium, Aster tripolium, stomata, salinity tolerance     

Epidermal Structure and Stomatal Ontogeny in Some Polygonales and Centrospermae

The epidermal structure and ontogeny of stomata in 19 speciesof Centrospermae and two of Polygonales are described. The cellsof the epidermis are polygonal, isodiametric, or elongated invarious directions and arranged irregularly. The anticlinalepidermal walls are thick, sinuous, straight, or arched. Eleventypes of glandular and eglandular trichomes have been observed.Six types of stomata: anomocytic, paracytic, stomata with asingle subsidiary cell, diacytic, anisocytic, and transitionalbetween diacytic and paracytic, have been noticed in the speciesinvestigated. The ontogeny of anomocytic stomata is haplocheilicor perigenous, while that of the other five types is syndetocheilicor mesogenous. Abnormal stomata with a single guard cell, unequalguard cells, aborted guard cells, and arrested development arecommon. Groups of stomata are also frequent but contiguous stomataare rather rare.     

Circadian Rhythm of Stomatal Movements in Epidermal Strips

Measurements were made of changes in stomatal pore widths inepidermal strips of leaves ofVicia faba and Commelina communis.Strips were incubated in dilute KCI solutions (1 and 10 molm^–3) flowing through a perfusion chamber on the stageof a microscope and kept for 4 d in continuous light. Circadianrhythms of stomatal apertures were detected in both species.Although the amplitude was small it was statistically significant.It is concluded that at least partof the mechanism for the stomatalrhythm resides in the epidermis, probably in the guard cells. Key words: Cireadian rhythm, epidermal strips, stomata     

An Investigation into the Stomatal Behaviour of a Wilty Mutant of Pisum sativum

The water relations and stomatal behaviour of a wilty line ofpea (JI 1069) were investigated and compared with those of severalnon-wilty lines (JI 1180, JI 1194, and JI 74). The leaves ofthe wilty line were found to have a lower percent water content,water potential and diffusive resistance and the dimensionsof the stomatal cells were larger than those of the non-wiltytypes. The aperture of stomata on epidermal samples taken from plantsin the light or dark period of a diurnal rhythm was consistentlylarger for the wilty pea than for the non-wilty lines, however,their stomatal responses on detached epidermis to light, CO₂and KC1 concentration were similar. There was no differencein response to ABA of stomata on detached epidermis of wiltyor non-wilty types of pea. Key words: Pisum sativum, Wilty mutant, Water relations, Stomatal behaviour