John D. Curtis

Oil bodies in leaf mesophyll cells of angiosperms : Overview and a selected survey

Neutral (storage) oil bodies occur in leaf mesophyll cells of many angiosperms, but their literature has been largely forgotten. We review this literature and provide a survey of 302 species and hybrids from mostly north-central US species representing 113 families. Freehand cross sections of fresh leaves stained with Sudan IV verified the presence of oil. In 71 species from 24 families we observed 1-15 oil bodies per mesophyll cell. The eudicot families Asteraceae, Caprifoliaceae, Lamiaceae, and Rosaceae had the highest number of species with oil bodies, whereas few or no species in the Apiaceae, Betulaceae, Fabaceae, and Scrophulariaceae had them. Only three of 19 monocot species sampled had oil bodies. Repeat sampling of a Malus (crabapple) cultivar and a Euonymus species showed conspicuous oil bodies in mid-summer and also in mid-autumn in both attached and recently shed leaves. Oil bodies in leaf mesophyll cells are conspicuous (visible in hand cross sections using moderate magnification in unstained water mounts) in numerous species, and they occur throughout the growing season in at least some species. Neutral oil bodies in leaf mesophyll cells are not mentioned in contemporary textbooks and advanced works, but they deserve recognition as significant cellular components of many taxa, in which they may be significant sources of commercial oils.

Leaf anatomy inCaesalpinia andHoffmannseggia (Leguminosae, Caesalpinioideae) with emphasis on secretory structures

Leaflets of 65 species ofCaesalpinia s.l. and seven species ofHoffmannseggia were studied in clearings supplemented by resin sections and scanning electron microscopy. Three types of secretory structure occurred among 46 species; in 43 species they were distributed mutually exclusively (external glands: 8 species; internal cavities: 5 species; idioblastic cells: 30 species); three other species each had two types. Species with secretory structures conform mostly to proposed subgenera and informal “groups.” Other unusual features were external glands with internal spaces, thickened walls or conspicuous localized wall thickenings in epidermal cells or mesophyll cells of certain species, and differentially stained epidermal cells surrounding stomata. Prismatic crystals predominate but druse crystals also occur.

Survey of leaf anatomy, especially secretory structures, of tribeCaesalpinieae (Leguminosae, Caesalpinioideae)

We studied leaflet anatomy, emphasizing secretory structures, from herbarium specimens of 128 species of 44 genera of tribeCaesalpinieae, using clearings, resin sections, and scanning electron microscopy. These observations, combined with those from our three earlier papers, provide a survey of 210 species representing all genera. Seventy-three species had secretory structures: 21 had glands or gland-like trichomes, 40 had living mesophyll idioblasts, and nine had cavities (three species each had two different types). Five additional species, all inCercidium (Caesalpinia group), had paired or clustered large spheroidal, thick-walled, empty cells (veinlet idioblasts) interconnected by perforation plate-like gaps. Secretory structures have systematic significance at various taxonomic levels.

Foliar anatomy ofPolygonum (Polygonaceae): Survey of epidermal and selected internal structures

Several anatomical characters in leaves were described, and their distribution determined, for 153 species ofPolygonum, mostly from herbarium specimens. Structures surveyed were epidermal (glandular and nonglandular trichomes, nodules, specialized parenchyma, stomatal apparatus) and internal (cavities, crystals, laticifer-like cells, nodules, subepidermal fibers). Cleared leaves were supplemented by resin-embedded sections and SEM preparations of selected species. No feature defines any taxonomic section, but some features occur only within one section. Laticifer-like cells, epidermal and internal nodules, resin cups, and unique epidermal and subepidermal cavities seem to be unknown elsewhere; other features (invaginated epidermal cells; enlarged crystal cells confined to paraveinal layer) are rare among angiosperms.

Idioblasts and other unusual internal foliar secretory structures in Scrophulariaceae

Abstract. Leaf samples of mostly herbarium specimens (237 species of 172 genera) were cleared. Internal secretory structures of large size or unusual shape were detected and observed. Selected samples were processed into resin and sectioned for light microscopy or prepared for scanning electron microscopy. Adding results from two earlier publications, our survey includes 365 species from 174 genera. Five types of internal secretory structure, mostly unknown previously in the traditional Scrophulariaceae, occur in only nine genera: 1) single-celled subepidermal idioblasts, empty at maturity, in Scrophularia and Verbascum (Lersten and Curtis 1997), 2) 2–16 (or more)-celled nodules, with fibrous contents, in mid-mesophyll strata of Graderia and Radamaea, 3) epithelium-lined oil cavities in Leucophyllum (Lersten and Beaman 1998) and Capraria, 4) Kranz-type enlarged bundle sheath in Anticharis, and 5) paraveinal mesophyll (PVM) in Picria and Bonnaya.

DISTRIBUTION AND ANATOMY OF HYDATHODES IN ASTERACEAE

Hydathodes have been reported as rare for the Asteraceae, but we collated published reports of guttation, water pores, and hydrathodes from ca. 80 genera of 10 tribes. Only a few incomplete anatomical descriptions were found. Leaf teeth with guttation droplets were removed for anatomical study from Ambrosia trifida, Arctium minus, Erigeron annuus, Eupatorium rugosum, Lactuca scariola, Rudbeckia laciniata, and Silphium perfoliatum. Conspicuous xylem, but very little phloem, enters each tooth. Phloem ends well before xylem termination. Xylem diverges distally into individual files of tracheary elements separated by parenchyma. Progressively toward the tooth apex, xylem parenchyma proliferates, and successive cells are at first more elongate with increasingly sinuous walls, then shorter, broader, and lobed. The epithem beyond xylem termination resembles ordinary mesophyll chlorenchyma. The bundle sheath is variably developed but always incomplete. Water pores resemble ordinary stomata but are mostly sunken, permanently open, and occur only in contact with eipthem.

Subepidermal Idioblasts in Leaflets of Caesalpinia pulcherrima and Parkinsonia aculeata (Leguminosae: Caesalpinioideae)

LERSTEN, NELs R. (Department of Botany, Iowa State University, Ames, IA 50011-1020) AND JoHN D. CURTIS (Department of Biology, University of Wisconsin, Stevens Point, WI 54481-3897). Subepidermal idioblasts in leaflets of Caesalpinia pulcherrima and Parkinsonia aculeata (Leguminosae: Caesalpinioideae). Bull. Torrey Bot. Club 120: 319-326. 1993.-Leaflets of Caesalpinia pulcherrima Sw. and Parkinsonia aculeata L. (Caesalpinia group, Tribe Caesalpinieae, Subfamily Caesalpinioideae, Leguminosae) were examined fresh or processed for clearing, resin-embedded sectioning, and scanning electron microscopy. Both species have dimorphic idioblasts restricted to adaxial and abaxial subepidermis: broadly ovoid to pyriform (adaxial) and obloid (abaxial) in C. pulcherrima, and cylindrical (adaxial) and obloid to lobedobloid (abaxial) in P. aculeata. Cell contents were not identified but all idioblasts tested negative for oil. In both species, several thousand idioblasts occur per leaflet, with the preponderance, at least twice as many, being adaxial. Caesalpinia pulcherrima has two possibly unique features: idioblasts are connected to the epidermis by peglike invaginations from overlying epidermal cells; and numerous scattered epidermal patches, each consisting of 2-8 tiny cuboidal cells, occur among, but not in contact with, idioblasts. These subepidermal foliar idioblasts were described briefly only once before, in a German dissertation of 1892. Although idioblast function is unknown, these unusual cells are perhaps potential taxonomic characters in this still tentatively classified tribe.

Anatomy and distribution of foliar idioblasts in Scrophularia and Verbascum (Scrophulariaceae).

Internal secretory structures have rarely been reported from Scrophulariaceae, and foliar idioblasts only once before, in 1887. Presented here are the first unambiguous descriptions of subepidermal foliar idioblasts in the family, from Scrophularia and Verbascum, genera regarded as closely allied on other grounds. Leaf samples from 183 mostly herbarium specimens (128 species, with 55 replicates) were cleared and stained, which revealed idioblasts in 62 (69.7%) of 89 Scrophularia species and 13 (33.3%) of 39 Verbascum species. We then chose 14 representative species to examine by resin sectioning and scanning electron microscopy. Idioblasts occurred both adaxially and abaxially. Most were conspicuous, in some species penetrating to vasculature level. Idioblasts had a thin primary wall and were empty at maturity. Verbascum and Scrophularia species with and without idioblasts were scattered among the subgeneric taxa without taxonomic clustering; likewise, both types occurred in approximately proportionate numbers throughout the geographic range, except that 14 of 15 North American Scrophularia species had idioblasts. Petals of two species had abundant idioblasts. The 1887 report illustrated a huge idioblast in S. deserti and we also found the largest in either genus in this species. We also noted trichome and stomata types and report that paraveinal mesophyll and foliar endodermis with casparian strip were both absent.

Laminar hydathodes inUrticaceae: Survey of tribes and anatomical observations onPilea pumila andUrtica dioica

Laminar hydathodes are known from only three dicot families. InUrticaceae they are associated with minor vein junctions in all five tribes, as surveyed from cleared leaves of 43 species in 30 genera. Only one species lacked hydathodes. Exclusively adaxial hydathodes were found in 28 genera. In tribeElatostemeae, laminar hydathodes inPilea andPellionia species are abaxial, adaxial, or on both surfaces. Guttation was observed in four species.Urtica dioica (adaxial) andPilea pumila (abaxial) were studied anatomically in detail. Hydathodes in the former have normal bundle structure but xylem gaps sometimes occur. In the latter, phloem is displaced in three previously undescribed ways: 1) ends abruptly near hydathode, 2) curves into connecting vein at adjacent junction, or 3) departs xylem, skirts hydathode independently, and rejoins adjacent xylem strand. Laminar hydathodes are a unifying character of theUrticaceae, and they also strengthen its close relationship to theMoraceae.

Paraveinal mesophyll in Calliandra tweedii and C. emarginata (Leguminosae; Mimosoideae)

Paraveinal mesophyll (PVM) in Leguminosae, subfamily Mimosoideae, was first reported in 1894 but never described in detail before now. We cleared, and sectioned in resin, leaflets of Calliandra tweedii and C. emarginata (Tribe Ingeae). Lamina anatomy in both species is very similar: one palisade layer, two to three spongy layers, and the horizontal veinal network with its interconnected PVM in between. PVM is a unistratose cellular lacework extending between veins and attached medianly along each flank of all veins. PVM cells have a normal complement of typical chloroplasts similar to other mesophyll cells. Most veins are ensheathed by fibers except for an extended lateral slit along each flank where the PVM is attached; a parenchymatous bundle sheath is therefore lacking. All vein endings lack phloem, although the tracheary elements of some vein endings are flanked by one or two long, slender, seemingly undifferentiated cells. Occasional small gaps occur between the PVM cell wall and adjacent tracheary elements, which expose xylem directly to mesophyll intercellular space. PVM anatomy of Calliandra, including its physical relationship to the various vein orders, differs in some important respects from PVM of the few other leguminous and nonleguminous species studied anatomically in any detail.