Unique calcium oxalate "duplex" and "concretion" idioblasts in leaves of tribe Naucleeae (Rubiaceae).

PREMISE OF THE STUDY: This basic study may help plant biologists better understand the variety and occurrence of crystal forms and their function in plants. Literature records hold four examples of two different crystal types in one cell. One, unillustrated report mentions druses and crystal sand from one species of tribe Naucleeae (Rubiaceae) and "occasional occurrences" in additional unnamed taxa. Here, we surveyed Naucleeae (103 of 179 species, 23 of 24 genera, all seven subtribes) for "duplex idioblast" distribution for systematic significance and describe examples of this rare feature. METHODS: Cleared, dehydrated, herbarium leaves were mounted unstained in resin. Slides were examined with polarization optics for crystal types and locations, and representative areas were electronically digitized. Scanning electron microscopy and x-ray analysis verified calcium oxalate composition. KEY RESULTS: Idioblast configurations occur as crystal sand (CS) only (most common, 92 spp.) to CS plus one embedded druse (55 spp.), to CS plus 2-3 druses (6 spp.), to one druse with scanty surrounding CS (a few spp.), to a "naked" druse (16 spp.). Trends occur in some subtribes. A previously undescribed conspicuous, spheroidal calcium oxalate aggregate "concretion" idioblast occurs in only four species of Mitragyna (Mitragynineae). Idioblasts are most common along vascular bundles and in mesophyll, less so only along vascular bundles, and least common only in mesophyll. Tiny "secondary" crystals are common in ordinary mesophyll cells. CONCLUSIONS: Crystal types appear to be systematic features in Naucleeae. Duplex idioblasts (CS and druses) and aggregate concretions are a demonstration that much is yet to be discovered about crystals.

Crystal macropattern development in Prunus serotina (Rosaceae, Prunoideae) leaves.

BACKGROUND AND AIMS: Prunus, subgenus Padus, exhibits two completely different calcium oxalate crystal macropatterns in mature leaves. Foliar macropattern development has been described previously in P. virginiana, representing one version. Prunus serotina, in the group exhibiting the second macropattern, is described here. The goal was to describe developmental details for comparison with P. virginiana, and to extend the sparse current knowledge of crystal macropatterns. METHODS: Leaves at various developmental stages were removed from local trees and from herbarium specimens. Early leaf stages and freehand leaf and stem sections were mounted directly in aqueous glycerine; larger leaves were processed whole or in representative pieces in household bleach, dehydrated in alcohol/xylol, and mounted in Permount. Crystals were detected microscopically between crossed polarizers. KEY RESULTS: Bud scales have a dense druse population. Druses appear first at the stipule tip and proliferate basipetally but soon stop forming; growing stipules therefore have a declining density of druses. Druses appear at the tip of leaves <1 mm long, then proliferate basipetally in the midrib. Lamina druses appear in the distal marginal teeth of leaves 3 cm long; from here they proliferate basipetally and towards midrib along major veins. In about two-thirds-grown leaves (6-9 cm length) druses are all adaxial to veins of most orders; a shift occurs then to formation of prisms, which appear first abaxial to, then all around, veins. Mature leaves have virtually all prisms encrusting all major veins, more sparsely along smaller minor veins. Late season leaves form epitactic crystals on existing prismatics. CONCLUSIONS: The developing and mature macropattern of P. serotina is almost the reverse of the pattern described previously in P. virginiana, and shows that two closely related species can develop radically different modes of crystallization. The few detailed macropattern studies to date reveal striking variations that indicate a new level of organization that must be integrated with the anatomical, physiological and molecular approaches that have been dominant so far.

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.

Development of the calcium oxalate crystal macropattern in pomegranate (Punica granatum, Punicaceae).

Oxalate crystals are very common in angiosperms, but few descriptions of their macropattern (crystal types, their tissue distribution, and development) exist. Because unusually large prismatic crystals and druses, are known from pomegranate, we traced the development of crystal macropattern in various-aged leaf samples from a living plant and from herbarium specimens using unstained whole mounts (some bleached and cleared), stained leaf samples, and leaf and stem cross sections. Preparations were viewed with bright-field light microscopy and with crossed polarizers. Prismatics appear first in the subapical mid-mesophyll layer of a leaf 650 µm long. Additional prismatics form basipetally in the enlarging lamina. A preemptive wave of small prismatics appears basipetally in the midrib. Druses form secondarily acropetally in petiole and midrib, while existing lamina prismatics enlarge and new ones develop among them in mid-mesophyll. Prismatics produced early expand vertically, and many eventually extend from epidermis to epidermis. Later-formed prismatics attain intermediate sizes. No crystals form along lamina veins, but in older leaves, druses occur in spongy mesophyll, mostly near major vein junctions. In the stem, druses are restricted to phloem fibers. No phloem fibers occur in the leaf trace or midvein; therefore, petiolar and midrib druses are only in parenchyma, not in phloem.

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.

DEVELOPMENT OF BICELLULAR FOLIAR SECRETORY CAVITIES IN WHITE SNAKEROOT, EUPATORIUM RUGOSUM (ASTERACEAE).

Bicellular secretory cavities in Eupatorium rugosum occur only in foliar mesophyll, distributed uniformly from leaf tip to base, with a mean density of 450 per mm2 . They are absent from petiole and all other vegetative and floral organs. Each cavity contains an oily droplet, which is surrounded by two cup-shaped cells. An initial cell divides into two equal cavity cells with their shared wall always perpendicular to the epidermis. After vacuoles form, each protoplast retracts from the other and deposits a new, callosic wall around the cavity, and a thicker callose deposit on the remaining shared walls outside of the cavity. The original shared wall remains intact across the cavity until maturity. It is pulled taut by cavity cell growth and restricts further expansion except in one paradermal direction. Later, this shared wall disappears from the cavity. An oily fluid of unknown composition is secreted into the enlarging cavity. Because bicellular cavities develop neither lysigenously nor in true schizogenous fashion, we propose the term "pseudoschizogeny" for this type of development. Unusual, or perhaps unique, features of this cavity: bicellular condition, protoplast retraction from the common shared wall, and deposition of a callose wall. Preliminary results of a survey of Eupatorium show that bicellular cavities are uncommon but widely distributed geographically.

RE-INVESTIGATION OF SECRETORY CAVITY DEVELOPMENT IN LYSIMACHIA (PRIMULACEAE).

Nineteenth century studies described Lysimachia cavities as schizogenous, but Guttenberg (1928) reported them as only being schizogenous initially. Inner epithelial cell walls then swelled and dissolved in mucilage secreted into the cavity. Later, as a gradually solidifying resin accumulated, epithelial cells reportedly formed a new and cellulosic cell wall. My re-examination of cavity development in Lysimachia nummularia L., using a resin embedding method, revealed only typical schizogenous development, thus refuting Guttenberg's interpretation and supporting earlier workers.