Ontogeny of Stomata on the Foliar and Floral Or{dot}gans of some Species of Crotalaria L.

The structure and development of stomata in eight species ofCrotalaria belonging to the family Papilionaceae are described.The study is mostly confined to the leaves but it has also beenmade on the floral organs of C. mysorensis, C. retusa, C. sericea,and C. triquetra. The stomata may be paracytic, anisocytic,anomocytic, diacytic, or with one subsidiary cell. The differenttypes occur individually or they are placed side by side evenon the same surface of an organ. In general the paracytic typeis by far the commonest, followed by anisocytic and anomocyticones. Diacytic stomata and those with one subsidiary cell arerelatively rare. Different types of stomata in various organsof the same plant develop mesogenously. The present investigationalso indicates that the inconstancy of stomata in the familyis due to (a) their diversity and (b) an increase in the numberof subsidiary cells either by their division or by the neighbouringperigenes becoming subsidiary cell-like.     

Structure and Development of Stomata on the Vegetative and Floral Organs in Some Members of Caesalpiniaceae

The structure and development of stomata in 19 species of thefamily Caesalpiniaceae are described. The study is mostly confinedto the leaves, but observations have also been made on othervegetative and floral organs of some species Stomata may beparacytic, anisocytic, anomocytic, and with one subsidiary cell.Occasionally a stoma is diacytic, cyclocytic, or actinocytic.Different types occur individually or may be found side by sideeven on the same surface of an organ. The most prevalent typein all the genera is paracytic except in Caesalpima where itis anomocytic. The development of an anomocytic stoma is perigenous,but those with subsidiary cells are largely mesogenous; rarelyparacytic stomata are mesoperigenous. In spite of diversityof stomata, different types of stomata have similar patternsof development in different organs of the same plant. The presentinvestigation also indicates that the inconstancy of stomatain the family is due to (a) their diversity and (b) an increasein the number of subsidiary cells either by their division orby the neighbouring perigenes becoming subsidiary cell-like.     

Stigma-surface Esterase Activity and Stigma Receptivity in Some Taxa Characterized by Wet Stigmas

Stigma-surface esterase activity and stigma receptivity througha sequence of developmental stages of the pistil have been studiedin four taxa characterized by having wet stigmas — Petuniahybrida, Nicotiana tabacum, Crinum defixum and Amaryllis vittata.The style is solid in the first two and hollow in the lattertwo taxa. In all the taxa, stigma—surface esterase couldbe detected in a thin surface layer (pellicle) from a very earlystage of pistil development, irrespective of the presence orabsence of the exudate. However, the taxa showed variation instigma receptivity. In Petunia and Nicotiana, stigmas from pistilsof all the stages supported pollen germination and tube growth.In Amaryllis and Crinum, stigmas of only the mature pistils,when the exudate is present on the stigma, supported normalpollen germination and tube growth. It is inferred that in taxacharacterized by a wet stigma and solid style, the factors requiredfor pollen germination are present from an early stage of pistildevelopment and the exudate per se is not involved in pollengermination. In taxa characterized by a wet stigma and hollowstyle, however, the pellicle does not carry the factors requiredfor pollen germination and tube growth; they appear to be presentin the exudate. Petunia hybrida Vilm, Nicotiana tabacum L., Crinum defixum, Ker-Gawl, Amaryllis vittata Ait., tobacco, pollination, pollen germination, stigmatic exudate, stigma receptivity, stigma-surface esterase, esterase activity     

Some Observations on the Diversity of Stomata and Trichomes in Six Species of Dioscorea

Stomata and trichomes are described on the leaves of six speciesof Dioscorea. As many as six types were found in D. bulbiferaand D. oppositifolia, four types in D.hispida and D. wallichii,three types in D. belophylla, but only two types in D. alata.Although there is a diversity of stomata even on the same surface,the predominant type is anomocytic in all the species exceptD. bulbifera in which it is tricytic. Rarely a stoma is alsocyclocytic in D. bulbifera. An increase in the number of subsidiarycells in paracytic, tricytic, or diacytic stomata takes placeby the wall formation in them. Similarly a reduction in thenumber of subsidiary cells of a tetracytic stoma is the resultof lateral subsidiary cells assuming the form of epidermal cells.Abnormalities such as a stoma with one guard cell, degenerationof guard cells, and contiguous stomata are also met with. Theorganization of different types of stomata is studied in D.bulbifera and D. wallichii and shown to be perigenous. Capitateglandular hairs were seen on the leaves of D. belophylla, D.bulbifera, D. hispida, and D. wallichii but non-glandular, uniseriate,3-celled trichomes were observed only in D. hispida.     

Structure and Development of Stomata in Some Leptosporangiate Ferns

The structure and development of stomata are described for 17species of leptosporangiate ferns. In these species the maturestomata are anomocytic, diacytic, Pyrrosia(applied), tetracytic,suspended, or floating type. Stomata are present on both surfacesof floating as well as sub merged leaves of Azolla and Marsilea.In a few species twin stomata, arrested development, and persistentstomatal initials are present Floating stomata result from disintegrationof the anticlinal suspending wall in Pleopeltis, and by detachmentand displacement in Azolla pinnata. The development of stomatais haplocheilic, syndetocheilic, or syndetohaplocheilic. InCyathea spinulosa the guard cell nuclei divide amitoticallyand the resulting two daughter nuclei occupy the opposite polesof the guard cells     

Epidermal Structures and Stomatal Ontogeny in Some Mimosaceae

The structure of trichomes and stomata on leaflets of 21 speciesof the Mimosaceae are described. Non-glandular trichomes inMimosa pudica are of three types: unicellular, with a roundedthick-walled base and a terminal unicellular body, and multicellular.Capitate, clavate, or cylindric, 3–6-celled glandularhairs are observed on leaflets of Mimosa pudica only. Leafletsare amphistomatic in all species except Adenanthera pavonina,Calliandra sp., Parkia biglandulosa, Pithecellobium dulce, andSamanea saman in which they are hypostomatic. Only paracyticstomata are found in Leucaena leucocephala and Mimosa pudica.In the rest stomata are of more than one type. In spite of thediversity, the most frequent type in these species is paracytic.Anisocytic stomata, in all cases, are secondarily derived fromparacytic ones by transverse or oblique wall formation in asubsidiary cell. Similarly some stomata with one subsidiarycell are also secondary derivatives of the paracytic ones becauseof one of the subsidiary cells assuming the form of an epidermalcell. The development has been traced in 14 species and thatof paracytic stomata may be mesogenous or mesoperigenous, thatof stomata with one subsidiary cell mesogenous but anomocyticstomata are ontogenetically perigenous. Occasionally a meristernoidis cut off from one of the subsidiary cells of a paracytic stoma.The organization of a stoma from such a meristemoid has beentraced.     

Stomata and Structure of Tetraploid Apple Leaves cultured in Vitro

Leaves of anther-derived tetraploid apple (Malus pumila Mill.)shoots were examined by low-temperature scanning electron microscopy(LT-SEM). Leaves were serrate and wide with an undulating adaxialsurface due to convex epidermal cells, apparently without crystallineepicuticular wax. Stomata were absent from the adaxial surface,except for the marginal teeth which exhibited 40-60 stomataper leaf; they probably originated from residual mitotic activity.One third of abaxial stomata was occluded by the residual cuticleof the mother guard cell across the stomatal pore which rupturedwhen the stomata became functional. The stomatal index was 7·2(± 1·6) with 60-75 stomata mm^-2, i.e. abaxialstomata of tetraploid leaves expanded in vitro were less frequentthan those in triploid leaves either cultured in vitro (475-575stomata mm^-2) or grown on the tree (320-390 stomata mm^-2) wherethe stomatal index was 21 (± 4). Freeze-fracture transsectionsshowed that the tetraploid in vitro leaves were composed ofa layer of adaxial epidermal cells, followed by a single layerof palisade cells and four to five layers of spongy mesophyllcells and the abaxial layer of epidermal cells, in contrastto juvenile seedling-grown apple leaves in which the two layersof palisade cells comprised the majority (52-60%) of the leafvolume. The same morphological features, such as wide and lesspointed leaves, reduced stomatal density and stomatal index,and increased stomatal size that were previously reported fortree-grown tetraploid leaves were also expressed in vitro. Thus,causes of the stomatal deformation in tissue-cultured Rosaceaeare interpreted to be in part genetic and not purely environmental.Copyright1994, 1999 Academic Press Malus pumila Mill., apple, biotechnology, breeding, cryo-preservation, CO₂, juvenile, low temperature-scanning electron microscopy (LT-SEM), micropropagation, ploidy, stomata, tissue-culture, transpiration     

Functional Stomata in a Variegated Leaf Chimera of Pelargonium zonale L. without Guard Cell Chloroplasts

Fluorescence microscopy indicated that chlorophyll was absentfrom epidermal and guard cells overlying all white areas andgreen areas (of certain leaves) in variegated leaves of Pelargoniumzonale, cv. Chelsea Gem. Stomata with chlorophyll-free guardcells, in general, responded normally to light and CO₂ as gaugedby direct measurements of stomatal aperture and by transpirationalwater loss studies, although stomata from white regions of variegatedleaves were more reluctant to open than stomata from green regionsof the leaves. Thus, functional stomata without guard cell chloroplastshave been discovered in another genus, namely Pelargonium, besidesthat originally discovered in Paphiopedilum. When stomata withchlorophyll-free guard cells opened, K⁺ accumulated in the guardcells. This indicates that chloroplasts are not essential forthe normal functioning of stomata and that the energy sourcefor driving stomatal movements can come from sources other thanphotophosphorylation. Key words: Guard cell chloroplasts, Leaf chimera, Pelargonium, Stomata     

Stomata of Micropropagated DelphiniumPlants Respond to ABA, CO2, Light and Water Potential, but Fail to Close Fully

Morphological and physiological characteristics of micropropagatedplants of Delphinium cv. Princess Caroline were studied. Leavesproduced in vitro showed poor control of water loss which appearsto result from restricted responses by stomata and not frompoor cuticular development. Stomata of leaves produced in vitrowere larger and more frequent than those produced during acclimatization.Despite the fact that stomata from isolated epidermis of leavesproduced in vitro reduced their apertures when exposed to turgor-reducingtreatments, they did not close fully. This, together with highstomatal frequencies might explain the poor control of waterloss shown by intact leaves produced in culture when exposedto dry air. While leaves from acclimatized plants showed almostcomplete closure with ABA, low water potentials, darkness andCO₂, stomata from leaves produced in vitro reduced their apertureswhen exposed to those factors, but only to a limit. Therefore,stomata from leaves cultured in vitro seem to be partially functional,but some physiological or anatomical alteration prevents themfrom closing fully. Stomata from leaves produced in vitro wereparticularly insensitive to ABA which appears to be partly associatedwith the high cytokinin concentration in the culture medium.In the long-term, this stomatal insensitivity to ABA might contributeto plant losses when micropropagated plantlets are transferredto soil. Key words: Micropropagation, stomatal physiology, dehydration, PEG, ABA, BAP, darkness, CO₂, Delphinium     

The significance of the Presence of Stomata on Seedling Roots

Slightly squashed and transversely sectioned sprouts (seedlingroot + hypocotyl to cotyledons) of Pisum arvense, Ornithopussativus and Helianthus annuus were examined. The presence ofstomata is described on seedling roots, including the root hairzone, in Pisum and Ornithopus and in the root hair zone of thehypocotyl of Helianthus. The stomata found in the root hairzones are almost always open, usually without chloroplasts andare not sensitive to the action of abscisic acid (ABA). TheABA sensitivity of the stomata appears first above the roothair zone and increases gradually towards the cotyledons. Thepossible role of stomata in the root hair zone is discussed. Seedling root, hypocotyl, root hair zone, stomata     

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.     

Nitrogen Fixation in the Canopy of Temperate Forest Trees: A Re-examination

¹⁵N₂ studies and acetylene reduction assays of leaves and shootsof Douglas fir and other forest trees do not confirm previousreports that extensive nitrogen fixation occurs on leaf surfacesand it is concluded that the importance of nitrogen fixationin the canopy of forest trees has been exaggerated. The presenceof nitrogen-fixing bacteria on the leaves of trees is confirmed,however, and they have been identified as Enterobacter agglomerans,Clostridium butyricum and Bacillus sp. Their distribution onleaves is fortuitous since dead oak leaves and artificial leavesbecome colonized to the same extent as living oak leaves. nitrogen fixation, acetylene reduction, Enterobacter agglomerans, Clostridium butyricum, Bacillus sp, Douglas fir, Pseudotsuga menziensii, larch, Larix x oak, Quercus petraea.     

Effect of Elevated CO2 on Stomatal Size and Distribution in Perennial Ryegrass

Plants of ryegrass (Lolium perenne L. cv. Melle) were grownfrom the early seedling stage in growth cabinets at a day/nighttemperature of 20/15 °C, with a 12-h photoperiod, and aCO₂ concentration of either 340 or 680 ± 15 µl1^–1 CO₂. Young, fully-expanded, acclimated leaves fromprimary branches were sampled for length of stomata, and ofepidermal cells between stomata, numbers of stomata and epidermalcells per unit length of stomatal row, numbers of stomatal rowsacross the leaf and numbers of stomatal rows between adjacentvein ridges. Elevated CO₂ had no significant effect on any ofthe measured parameters. Elevated CO₂, Lolium perenne, ryegrass, stomatal distribution, stomatal size     

Giant Stomata

The presence of abnormally large stomata on leaves of Mangiferaindica L. and Limoma acidissima L. is reported. Apart from theirsize, these stomata are indistinguishable from normal stomatapresent on these leaves, and it is likely that they functionin a similar way.     

In situ Observations of Stomatal Movements

Kappen, L., Andresen, G. and L?sch, R. 1987. In situ observationsof stomatal movements.—J. exp. Bot. 38: 126–141. A device is described by which stomatal movements in situ canbe observed and recorded continuously in light and in darkness.It is mounted in a conditioned CO₂ exchange measuring chamberso that stomatal movements can be observed whilst CO₂ exchange(photosynthesis and respiration) of the same leaf is measured.Advantages and limitations are discussed. By this method itwas shown that stomata of Vicia faba although responding inthe same direction to environmental stimuli exhibited a widerange of pore widths. Responses to changes of air humidity andof CO₂ content were clearly evident when the leaves were exposedto light. Before stomata closed due to decreasing water vapourpressure differences between leaf and air they showed a markedwidening of the pore. An inverse response occurred when watervapour pressure deficit decreased. In darkness stomata did notrespond to such changes. Key words: Stomata, leaf gas exchange, microscopic observation     

Expression of Plasma Membrane Water Channel Genes under Water Stress in Nicotiana excelsior

Deduced amino acid sequences encoded by the cDNAs related tothe MIP gene family from Nicotiana excelsior were characterized.Phylogenetic characterization of the products of correspondinggenes named NeMip1, NeMip2, and NeMip3 strongly suggested thatthey are water channel proteins localized in the plasma membrane.Organ specificity of the gene expression was examined in leaves,roots, and reproductive organs. NeMip1 was expressed in rootsand reproductive organs; however, it was hardly detectable inleaves. Two other genes, NeMip2 and NeMip3, were expressed inall of organs examined. mRNA accumulation from the genes wasinvestigated in leaves under salt- and drought-stresses. Theresults demonstrated that mRNA accumulation from all three genesincreased under salt- and drought-stresses within one day. However,they showed different accumulation patterns. In addition totheir up-reg-ulation under salt- and drought-stresses, dailychanges in NeMip2 and NeMip3 mRNA accumulation was observedunder unstressed conditions in leaves. (Received May 2, 1997; Accepted September 3, 1997)     

Structure and Development of Stomata in Vegetative and Floral Organs of Three Species of Kalanchoe

The structure and ontogeny of stomata in vegetative and floralorgans of three species of Kalanchoe is described. The matureanisocytic stomata are mono-cyclic or completely or incompletelyamphicyclic, rarely paracytic, transitional between paracyticand anisocytic and with a single subsidiary cell. The developmentof all the types is syndetocheilic or mesogenous from organto organ but the mature stomatal apparatus varies from organto organ as regards the number and arrangement of subsidiarycells. Abnormal stoma with a single guard cell and arresteddevelopment were observed on all organs. An abnormal stoma witha single guard cell develops directly from the meristemoid.     

Development of Stomata in Lactuca sativa L.

The structure of the epidermis on various parts of the plantof Lactuca sativa Linn. is described. Development of stomatais studied in young leaves and stems. Tognini (1897) has previouslymentioned that the stomata on stems of L. virosa develop froma meristemoid with four cutting faces but the present studypoints out that the meristemoid cuts off only two mesogene neighbouringcells and the two others are perigene.     

Development of Stomata in some Ophioglossum Species

This paper deals with the development of stomata in vegetativeand reproductive organs of five species of Ophioglossum. Thestomata are typically hap-locheilic or perigenous from organto organ. Superimposed twin stomata, stoma with aborted guardcells and persistent stomatal initial are seen. The presentstudies support the view of foliar nature of the spike of Ophioglossum.