Aluminate-Induced Changes in Morphology and Ultrastructure of Thinopyrum Roots

The effects of aluminate [Al(OH)_4$$$] on the morphology andultrastructure of root cells were studied in the salt-tolerantgrasses Thinopyrum bessarabicum (Savul. and Rayss) A. Lve (2) and Thinopyrum junceum (L.) A. Lve (6) by light and transmissionelectron microscopy. Seedlings were grown in nutrient solutioncontaining 1 mol m^–3 [Al] and 5 mol m^–3 Na₂CO₃ atpH 100. Light microscopy revealed that root tips of [Al]-treated plantsdisplayed bending. Many cells of the cortex in the elongatingregion contained a fibrillar/granular material which renderedthem densely staining. Radial (anticlinal) walls of the epidermalcells were either cleft apart of unusually thickened. Amyloplastsof the central root cap cells contained fewer starch grains,while their distribution was disturbed. Electron microscopy showed that the most serious effects of[Al] toxicity occurred at the cell walls of the epidermal androot cap cells, as they lost their fibrillar fine structureand contained an amorphous electron-dense material distributedall over the wall section. Electron-opaque droplets were encounteredat the plasma membrane region of epidermal cells, while theelectron-dense material observed in the vacuoles of cortex cellscould be aluminate which had accumulated there. Thus, despitethe presence of a barrier to aluminate uptake, some [Al] doesenter the symplast. However, the cytoplasm of many epidermalcells displayed a normal fine structure and contained the usualsubcellular components. Dictyosomes, in particular, were abundantand surrounded by many vesicles denoting an active state. Theseobservations stress the role of cell walls as the major [Al]pool and of the plasma membrane as the ultimate barrier thatprotects the cytoplasm. Results are further discussed in relation to the findings inother plant species and it is concluded that, although aluminateis less toxic than Al³⁺, it causes morphological, structuraland, presumably, functional damage-to the roots of the speciesinvestigated. Key words: Thinopyrum, aluminate toxicity, cell walls, root bending     

Genome relationships between octoploid and decaploid Thinopyrutn ponticum

MOUSTAKAS, M., 1993. Genome relationships between octoploid and decaploid Thinopyrum ponticum . The genomic relationships between octoploid and decaploid Thinopyrum ponticum were determined by computer-aided karyotype analysis. All the chromosome pairs of the octoploid race can be matched with those of the decaploid chromosome race. Four chromosome pairs that were recognized as marker chromosomes in octoploid and decaploid T. ponticum were almost identical. It is suggested that the two chromosome races of T. ponticum are segmental allopolyploids with genome designations J^jJ^jJ^eJ^e and J^jJ^jJ^jJ^eJ^e. Genome designations Jand J^e represent the same genome but with structural differentiation. Phylogenetic relationships between Thinopyrum species may be indicated by the presence or absence and type of marker chromosomes in the different species.     

Seed Protein Electrophoresis in Agropyron junceum (L.) P.B. Complex

Agropyron striatulum (Elymus striatulus Run.) 2n = 14, A. rechingeriRun. 2n = 28, A. junceum (L.) P.B. subsp. boreoatlanticum simonetet Guinochet (A. junceiforme Löve and Löve) 2n = 28,A. junceum (L.) P.B. subsp. mediterraneum Simonet (A. junceum(L.) P.B.) 2n = 42 and A. diae (Elymus diae Run.) 2n = 56 werestudied by isoelectric focusing of seed soluble proteins. The electrophoretic phenotypes obtained from the five materialsshowed a striking degree of similarity. The typical proteinprofile was recognized to consist of 40 bands. No qualitativeprotein phenotypic differences were found and all observed variationconcerned the intensities of some particular bands. The data of the present study combined with cytological informationprovided by other workers indicate that in the composition ofthe polyploid taxa another genome besides that of the diploidA. striatulum is not likely to participate. Consequently thepolyploid taxa of A. junceum (L.) P.B. complex can be characterizedas segmental allopolyploids with the same basic genome moreor less modified at different ploidy levels. Agropyron junceum (L.) P.B. complex, seed storage proteins, protein profile, isoelectric focusing, genomic constitution, segmental allopolyploids