Plant-derived smoke solutions stimulate the growth of Lycopersicon esculentum roots in vitro

Aqueous extracts of smoke, derived from Themeda triandra, a fire-climax grass, and Passerina vulgaris, a fynbos plant, stimulated the growth of primary root sections of tomato roots in suspension culture. The optimal dilution for both extracts was 1:2000. Several of the fractions obtained from TLC separation of the Themeda and the Passerina extracts significantly promoted primary root growth. The auxins naphthaleneacetic acid (NAA), indolebutyric acid (IBA) and indoleacetic acid (IAA) were found to stimulate the growth of the primary root axis, with IAA and NAA significantly promoting lateral root number. Similarly, the naturally occurring cytokinins, zeatin and its derivatives (zeatin-O-glucoside; dihydrozeatin and zeatin riboside) stimulated primary root length. Zeatin and dihydrozeatin promoted secondary root growth, but only at very low concentrations.     

A method for the harvest,culture, and characterization of human adult atrial myocardial cells: Correlation with age of donor

Summary Myocardial cell culture methods are now well established for animal and fetal human tissue. We present here a method for harvesting and culturing adult human atrial myocardiocytes. Cells are obtained from fresh atrial tissue normally discarded after being removed to cannulate the right atrium during open heart surgery. The atrial tissue is minced and then digested using collagenase. The single cell suspension is initially cultured in serum-containing growth medium, then transferred to defined medium, selective for myocardial cell growth. The cells are characterized by immunoperoxidase stains and transmission electron microscopy. The cultured cells stain positive for myoglobin, whereas control cultured fibroblasts and endothelial cells do not. Electron microscopy shows the presence of numerous myofibrils, Z-bodies, pleomorphic mitochondria, and secretory granules. The chronological age of the donor was an important factor in culturing the adult tissue, the younger tissue correlated with a higher success rate. This method provides a means for in vitro study of human adult myocardial cells and provides guidelines for appropriate atrial tissue to use.     

Adaptation to salinity at the plant cell level

Summary Various mechanisms of adaptation of plant cells to salinity are reviewed: (1) protection of enzymes and maintenance of turgor by organic solutes; (2) prevention of ion toxicity by compartmentation; and (3) energization of solute transport by the proton pump. All these mechanisms seem to play a role in adaptation. The particular advantages of using salt-adapted cells in suspension culture to identify mechanisms of adaptation are pointed out.     

SPATIAL POPULATION STRUCTURE IN THE WHIRLIGIG BEETLE DINEUTUS ASSIMILIS: EVOLUTIONARY INFERENCES BASED ON MITOCHONDRIAL DNA AND FIELD DATA

The spatial population structure of the pond-living water beetle Dineutus assimilis (Coleoptera: Gyrinidae) was investigated through a field study of population dynamics and dispersal, with a concurrent assessment of the spatial distribution of mitochondrial DNA (mtDNA) restriction-fragment-length polymorphism (RFLP). A comprehensive 2-yr survey within a 60-km² study area revealed pronounced fluctuations in local abundances, including extinctions and colonizations. The recapture of marked individuals showed that dispersal among ponds is frequent in both males and females and connects populations on a large geographic scale (maximum observed flight distance: 20 km). The population structure of D. assimilis is thus characterized by both pronounced genetic drift and frequent gene flow. Together, these two forces generate a pattern of very local and transient genetic differentiation. Mitochondrial DNA samples collected within a few kilometers indicate highly significant spatial structure, if newly founded demes or those that experienced recent bottlenecks are included. These results based on four demes within the study area were placed into a regional context by further samples collected at distances of 100 km and 200 km. F_st estimates computed on increasing spatial scales were variable but showed no increasing trend. Thus, gene flow exerts a strong homogenizing force over a wide geographic range but is counteracted locally by genetic drift. These findings highlight the need to supplement estimates of F_st with additional data to arrive at valid interpretations of the genetic information. More generally, this study raises questions about how to capture the relevant features of dynamic, subdivided populations to understand their evolutionary dynamics.     

SEX-RATIO BIAS WITH ASYMMETRIC EXCHANGE OF POLLEN BETWEEN DEMES

In a patch of hermaphroditic plants, with a low level of pollen migration between patches, a prevailing wind creates a gradient, within the patch, in the strength of local competition among pollen for reproductive success. This leads to a sex ratio gradient, with a male (pollen) bias in downwind individuals, which can be quite strong even for large patches. The effect can be understood as follows: downwind individuals have relatively low reproductive value and respond by putting more resources into the gamete (pollen) with the best long-range (extra-patch) reproductive success.     

EVIDENCE FOR A MOSAIC HYBRID ZONE IN THE GRASS SHRIMP PALAEMONETES KADIAKENSIS (PALAEMONIDAE) AS REVEALED BY MULTIPLE GENETIC MARKERS

Molecular techniques provide powerful tools for studying the geographic structure of hybrid zones and the dynamics of gene exchange between incipient species. We examined allozyme variation at five loci (PGM, GPI, MDH-1, MDH-2, and LDH) for 27 populations of Palaemonetes kadiakensis from the central, coastal, and eastern regions of Texas. Central Texas populations of P. kadiakensis exhibited highly significant linkage disequilibrium and departures from Hardy-Weinberg genotype proportions. In populations with linkage disequilibrium, allelic differences at GPI defined two types of P. kadiakensis, designated A and B. Both types existed in central Texas with little or no evidence of interbreeding, whereas the populations from all other localities showed complete introgression of type B alleles into the type A gene pool. We also examined ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA) variation in a subset of populations, chosen to cover a range of geographic locations and levels of linkage disequilibrium. Two groups of mtDNA haplotypes and two restriction fragment patterns for the rDNA corresponded to allozyme type A and B individuals in populations exhibiting linkage disequilibrium. In populations with ongoing hybridization, all hybrid animals (N= 15) exhibited type A mtDNA. Exhibition of type A mtDNA indicated that type A females had mated successfully with type B males, but type B females had not mated successfully with type A males. Genotype distributions suggest reduced reproduction by hybrid offspring in central Texas populations. These patterns are consistent with a mosaic model of hybrid zone dynamics.     

The effects of culture medium rigidity on adventitious bud production and tissue vitrification in needle cultures of Sitka spruce [Picea sitchensis (Bong.) Carr.]

Adventitious bud formation on Sitka spruce [ Picca sitchensis (Bong.) Carr.] needle explants was strongly dependent upon the rigidity of the culture medium. In general, of organogenesis was greatest on weak gels and poorest on more rigid gels resulting from increased medium pH or agar strength. There was a significant interaction between agar strength and pH, with the optimum pH for organogenesis declining with increasing agar strength. Poor organogenesis at high agar concentrations was not due to toxic impurities since increased adventitious bud production could be stimulated by decreasing the medium pH whilst maintaining a high agar strength and an agar washing treatment had no significant effect. Although high levels of organogenesis could be sustained on weak gels the resultant adventitious shoots often showed severe vitrification. The frequency of shoots showing vitrification could be reduced by growing the tissues on harder media but this resulted in reduced shoot elongation. Vitrification of needle tissues did not stimulate the formation of adventitious buds in the absence of cytokinins.     

Plant regeneration from protoplasts of the monocotyledonous Haworthia magnifica v. Poelln.

Calli were initiated from flower buds, gynoecia and inflorescence segments of Haworthia magnifica v. Poelln. and subcultured on solid medium. Two liquid culture steps were necessary to prepare the calli for the isolation of protoplasts capable of sustained cell divisions. Plants were regenerated from protoplast-derived calli. The influence of both the osmolality of the culture media and exudates on the viability of protoplasts and protoplast-derived cell colonies is briefly discussed.     

Activation of fatty acids by non-glyoxysomal peroxisomes

Ethylene treatment (approx. 20 l ·1^-1 in air for 2 d) of tobacco (Nicotiana tabacum L. cv. Havana 425) plants markedly increases the endo--1,3-glucanase (EC 3.2.1.39) content of leaves. The antigenic form of the enzyme induced is the same one whose production is blocked by treating cultured cells with combinations of auxin (1.1 · 10^-5 M -naphthaleneacetic acid) and cytokinin (1.4 · 10^-6 M kinetin). Evidence is presented that cultured tobacco cells require ethylene for -1,3-glucanase accumulation: i) ethylene treatment increased the accumulation of \-1,3-glucanase in callus tissues >10 d after subculturing and in cell-suspension cultures; ii) callus tissues can produce ethylene; iii) conditions known to inhibit ethylene production (1 mM CoCl₂; 33° C treatment) or ethylene action (approx. 1.6 mmol · 1^-1 norbornadiene in air) inhibited -1,3-glucanase accumulation by callus tissues treated for 4 d following subculturing; and, these inhibitory effects were prevented by exogenous ethylene. Combinations of auxin and cytokinin blocked ethylene-induced accumulation of -1,3-glucanase by cell-suspension cultures. The results favor a model in which ethylene induces results favor a model in which ethylene induces 1,3-glucanase accumulation, and auxin and cytokinin inhibit this induction process.Abbreviations NAA -naphthaleneacetic acid - NDE norbornadiene     

Intersubgeneric hybridization of soybeans with a wild perennial species,Glycine clandestina Wendl

Summary The exploitation of wild perennial species of subgenus Glycine has been formidable in soybean breeding programs because of extremely poor crossability and an early pod abortion. The combination of gibberellic acid application to hybridized gynoecia and improved seed culture media formulations resulted in a new intersubgeneric hybrid between Glycine max (L.) Merr. (2n=40) and G. clandestina Wendt. (2n=40). Of the 31 immature seeds cultured, 1 regenerated 21 plants through organogenesis while the remaining 30 failed to germinate. All the regenerated plants were similar morphologically, carried expected 2n=40, possessed hybrid isozyme patterns and were completely sterile. Complete absence of chromosome pairing was observed in 40.9% sporocytes. The occurrence of 1 to 6 loosely paired rod bivalents suggests some possibilities of allosyndetic pairing. Hybrid plants set aborted pods after backcrossing to G. max.