Hairy pinnae in Kerala

The study of hairs on the different parts of the pinna of adult males among the endogamous groups of Kerala province, India, revealed age trends, differences among the groups, and high correlations between the frequency of hairs in certain regions of the ear. The greatest incidence of hypertrichosis was found in the lower helix, followed by the tragus, middle helix, lobe, and top of helix. A gradual increase in the frequency of the trait with age occurred in the antitragus and tragus, and a decrease with age in the lower and middle helix. As hair at the top of the helix remains constant in frequency with age and is present in all populations studied, it is a useful anthropological marker.     

Cataphylls of the Middle Triassic cycad Antarcticycas schopfii and new insights into cycad evolution

Cataphylls associated with the Middle Triassic stem genus Antarcticycas are described, and their impact on understanding cycad evolution is discussed. The cataphylls of Antarcticycas are triangular in outline and flattened adaxially with lateral flanges. The outer surfaces are covered with a ramentum of filamentous hairs, the epidermis is a single cell layer thick, and the ground tissue is parenchymatous with mucilage canals and sclereids. Vascular bundles form a distinct inverted omega-shaped pattern characteristic of the Cycadales observed in petioles of extant species. The structures in Antarcticycas are interpreted as cataphylls based on overall morphology, presence of straight vascular strands in the cortex of the associated stem, and lack of fascicular cambia in the vascular bundles. Because much of the overall diversity of Cycadales is represented by fossils, integrating fossil taxa into explicit phylogenetic hypotheses is important for understanding cycad evolution. Therefore, character and minimum age mapping were performed on a phylogeny of extant and fossil taxa including Antarcticycas. The results suggest that major extant lineages of Cycadales had diverged by the Permian to Triassic and that certain synapomorphies for Cycadales had evolved by the Permian. Evidence of insect feeding on Antarcticycas suggests that associations between cycads and insects are ancient.     

A comparative study of cycad mucilages

The patterns of monosaccharide distribution of the mucilages of Cycadales are characteristic at the generic level. Arabinose, fucose, galactose, mannose, rhamnose and methylrhamnose were identified in the hydrolysed mucilage of Bowenia, Ceratozamia, Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas and Zamia. Stangeria contains no rhamnose and methylrhamnose, and Ceratozamia contains galactose only in traces. American genera may easily be distinguished from the others by means of their different monosaccharide composition. Lepidozamia appears to be well separated from Macrozamia.     

Molecular electronics in pinnae of Mimosa pudica

Bioelectrochemical circuits operate in all plants including the sensitive plant Mimosa pudica Linn. The activation of biologically closed circuits with voltage gated ion channels can lead to various mechanical, hydrodynamical, physiological, biochemical and biophysical responses. Here the biologically closed electrochemical circuit in pinnae of Mimosa pudica is analyzed using the charged capacitor method for electrostimulation at different voltages. Also the equivalent electrical scheme of electrical signal transduction inside the plant''s pinna is evaluated. These circuits remain linear at small potentials not exceeding 0.5 V. At higher potentials the circuits become strongly non-linear pointing to the opening of ion channels in plant tissues. Changing the polarity of electrodes leads to a strong rectification effect and to different kinetics of a capacitor. These effects can be caused by a redistribution of K⁺, Cl⁻, Ca²⁺ and H⁺ ions through voltage gated ion channels. The electrical properties of Mimosa pudica were investigated and equivalent electrical circuits within the pinnae were proposed to explain the experimental data.Key words: electrophysiology, plant cell electrostimulation, charged capacitor method, electrical circuits, electrical signaling, Mimosa pudica     

Analysis of cyclitols in cycad plant tissues

Cyclitols (and sugar alcohols) in extracts of plant tissues may be analyzed by gas chromatography as trimethylsilyl ethers after removal of reducing sugars by treatment with barium hydroxide followed by deionization. A known amount of one of the components already present may be used as an internal standard. The method was applied to various samples of cycad plant tissue and some common forage crops. Neither the content of pinitol nor its ratio to myoinositol appears likely to be implicated in cycad toxicity.     

A new cycad subspecies from Nigeria

A new subspecies of the West African Encephalartos barteri is described from plains on the Jos Plateau of northern Nigeria.     

Mycorrhizae are present in cycad roots

We describe the occurrence of arbuscular mycorrhizae in the roots ofZamia pumila andDioon edule. Seedlings were grown on native, unsterilized soil taken from local pinelands of south Florida, whereZ. pumila occurs naturally. Arbuscules, hyphae, hyphal coils, and vesicles occur in the parenchyma cells of the root cortex, especially the half of the cortex next to the stele. Hyphae of the arbuscular mycorrhizal fungi (AMF) occur mainly in longitudinal intercellular spaces and conform to theAcorus type. The finest, ultimate roots have AMF, but these roots are extremely brittle, detach with the slightest disturbance, and are usually lost when plants are uprooted from the ground. No AMF were found in the cortex of coralloid roots. Vovides (1991) previously reported that AMF occur onDioon edule and Ceratozamia mexicana, and we reconfirm this inD. edule. In this species, AMF appear to be mostly associated with the outer and to a lesser extent the inner cortex. However, roots of a potted plant of C.hildae growing in native soil lacked AMF. When grown on low phosphorus soils, legumes are known to require AMF in order for theirRhizobium nodules to fix nitrogen. Without AMF, the legumes are deficient in phosphorus, which inhibits nodule production and nitrogen fixation. It is probable that cycads, with their nitrogen-fixing coralloid roots containingNostoc, may also require AMF for successful nitrogen fixation when phosphorus is limiting.     

Gas-liquid chromatographic analysis of cyasin in cycad flour

A method for the quantitative determination of cycasin from cycad flour by gas-liquid chromatography is described. The flour is extracted with 70% ethanol and the residue from the dried extract is directly trimethylsilylated. Androsterone was found to be an excellent internal standard. The average content of cycasin from ten separate analyses of one lot of flour was $\text{0.429 gm}\text{100 gm}$. The method is rapid, sensitive, and not hindered by contaminating compounds.     

Preservation of cycad and Ginkgo pollen

Pollen grains of Ginkgo, Cycas, and Encephalartos were chemically treated together with pollen of Quercus, Alnus, and Pinus, the latter three genera being used as standards. The experiments showed that: (1) boiling the pollen for 8–10 hours in 10% KOH had little if any effect on any of the grains; (2) lengthy acetolysis treatment produced some degradation or corrosion, particularly in Ginkgo and Cycas, but the grains of even these genera remained easily recognizable; (3) oxidation with KMnO₄ followed by H₂O₂ showed that pollen of Ginkgo, Cycas, and Encephalartos remains better preserved than that of Quercus and Alnus, and although Ginkgo and Encephalartos probably are slightly less resistant to oxidation than Pinus, no great differences exists between these monosulcate types and Pinus. Thus the experiments show that, at least for sediments low in bacteria, cycad and Ginkgo pollen should be well represented in the fossil record as far as their preservational capabilities are concerned.     

Seed dispersal in a cycad,Macrozamia riedlei

The influence of animals on patterns of seed dispersal has not been well explored, despite the importance of seed dispersal in plant population biology. Furthermore, the exploitation of animals as dispersal agents has been considered one reason for the replacement of gymnosperms by angiosperms in the Cretaceous. We studied seed dispersal in a cycad, Macrozamia riedlei, and showed that in the absence of animals, ripe seeds drop directly beneath the parent not more than 40 cm from the base. Several animals eat the fleshy outer integument of the seeds, and possums (Trichosurus vulpecula), transport seeds up to 24 m from the parent. The postdispersal positioning of seeds gave a log density-log distance relationship of y = 7.20 – 2.85x (r²= 0.96, N = 17). Effective local dispersal may have contributed to the persistence of cycads in the world flora for the last 200 million years.     

Biochemical characterization of developmental stages of cycad somatic embryos

The effect of two light intensities (25 μmol m⁻²s⁻¹ and 50 μmol m⁻²s⁻¹) on four developmental stages ofCeratozamia mexicana somatic embryos growing on semisolid plant growth medium at 25°C was measured. Growth parameters included fresh weight, morphology, and invertase and peroxidase activity. Under low light conditions, fresh weight was greater in stages 1 and 2 than in stages 3 and 4. In addition, there was a high frequency of hyperhydricity and polyembryogenesis in stages 1 and 2, whereas stages 3 and 4 were nonhyperhydric and unbranched. Stages 2–4 were green. Under high light conditions, embryos had lower fresh weights and less hyperhydricity, and stages 2–4 were green. Under low light conditions, peroxidase activity was less, although stage 1 embryos under both light conditions showed the highest activity. Stage 1 embryos required three to four months to develop to stage 2 under high light conditions and two to three months under low light conditions. Invertase activity under low light conditions was minimal in stage 2. All embryos had low invertase activity under high light intensity, and stages 2–4 had high levels of glucose. Embryo development from stage 2 to the next and for each subsequent stage under high light conditions required three to four months, and under low light conditions required four to five months. Higher light intensity therefore promotes the speedy recovery of plants.

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Resumen  El efecto de dos intensidades de luz (25 μmol m⁻²s⁻¹ y 50 μmol m⁻²s⁻¹) fue registrado en cuatro estados de desarrollo de embriones somáticos deCeratozamia mexicana cultivados en medio semisólido, 25°C. Los parámétras de crecimiento incluyeron peso fresco, peso seco, morfología, y actividad peroxidasa e invertasa. Bajo condiciones de baja iluminación, el peso fresco de los estados 1 y 2 fue mayor que en los estados 3 y 4. Además, hubo una alta frecuencia de hiperhidratación y poliembriogénesis en estados 1 y 2, mientras que los estados 3 y 4 no resultaron hiperhidratados ni ramificados. Los estados 2–4 fueron verdes. Bajo alta iluminación, los embriones tuvieron un menor peso fresco y menos hiperhidratación. En baja iluminación la actividad peroxidasa fue menor, aunque en los embriones en estado 1 en ambas condiciones de iluminación mostraron la más alta actividad. Los embriones en estado 1 requirieron tres o cuatro meses para desarrollarse hasta el estado 2 bajo condiciones de alta iluminación; y dos o tres meses en baja iluminación. La actividad invertasa en condiciones de baja iluminación fue minima en el estado 2. Todos los embriones tuvieron altos nivelés de glucosa. El desarrollo de los embriones de estado 2 al siguiente y a los subsecuentes, bajo alta iluminación, requirió tres o cuatro meses, y bajo condiciones de baja iluminación requirió cuatro o cinco meses. Una alta intensidad luminosa parece promover la velocidad de recuperación de plantas.

     

The primary structure of histone H3 from cycad pollen

The complete primary structure of cycad pollen histone H3 has been established. Microheterogeneity in several positions revealed the presence of H3 variants. Various lysine residues in the N-terminus were found to be completely or partially methylated. The cycad H3 sequence is compared to that of pea and calf.     

Heterocysts with reduced cell walls in populations of cycad cyanobionts

The ultrastructure of the cyanobionts of the greenhouse-grown cycads Cycads circinalis, Ceratozamia mexicana, and Encephalartos villosus was studied. In addition to heterocysts with the typical ultrastructure, the cyanobiont microcolonies also contained altered heterocysts with reduced cell walls, which might dominate in all regions of the coralloid roots. The altered heterocysts represented a protoplast enclosed in a heterocyst-specific envelope with additional layers. Some heterocysts contained an additional reticular protoplast-enclosing sheath below the heterocyst-specific envelope, whereas the other heterocysts contained an additional electron-opaque outer layer. The substance of the inner sheath of the former heterocysts resembled the polysaccharides of mucilage, which fills the intercellular space of plant tissues, whereas the electron-opaque outer layer of the latter heterocysts probably had a protein nature. The substances that constitute the sheath and the outer layer are likely to be synthesized intracellularly and then released with the aid of membrane-bounded vesicles or by channels in the cytoplasmic membrane.     

Demographic variation in cycad populations inhabiting contrasting forest fragments

Reduced habitat quality after fragmentation can significantly affect population viability, but the effects of differing quality of the remaining habitat on population fitness are rarely evaluated. Here, I compared fragmented populations of the cycad Zamia melanorrhachis from habitats with different history and subject to contrasting levels of disturbance to explore potential demographic differences in populations across habitat patches that could differ in habitat quality. Secondary-forest fragments had a lower canopy cover and soil moisture than remnant-forest fragments, which may represent a harsh environment for this cycad. A smaller average plant size and lower population density in the secondary-forest fragments support the hypothesis that these fragments may be of lower quality, e.g., if plants have reduced survival and/or fecundity in these habitats. However, variation in the stage-structure of populations (i.e., the relative proportions of non-reproductive and reproductive plants) was associated with the area of the forest fragments rather than the type of habitat (remnant versus secondary forest). These results suggest that different demographic parameters may respond differently to habitat fragmentation, which may be explained if processes like adult survival and recruitment depend on different characteristics of the habitat, e.g., average light/water availability versus suitable area for plant establishment. This study shows that forest fragments may differ drastically in environmental conditions and can sustain populations that can vary in their demography. Understanding how forest fragments may represent different habitat types is relevant for evaluating population viability in a heterogeneous landscape and for designing conservation programs that account for this heterogeneity.