Brassica juncea (Indian mustard) has been widely used in phytoremediation because of its capacity to accumulate high levels of chromium (Cr) and other metals. The present study was conducted to investigate mechanism(s) involved in Cr binding and sequestration by B. juncea. The plants were grown under greenhouse conditions in field-moist or air-dried soils, amended with 100 mg kg(-1) of Cr (III) or VI). The plant concentrated Cr mainly in the roots. B. juncea removed an average of 48 and 58 microg Cr per plant from Cr (III) and Cr (VI)-treated soils, respectively. The uptake of Cr was not affected by the moisture status of the soils. X-ray absorption near-edge spectroscopy measurements showed only Cr (III) bound predominantly to formate and acetate ligands, in the bulk and rhizosphere soils, respectively. In the plant tissues, Cr (III) was detected, primarily as acetate in the roots and oxalate in the leaves. X-ray microprobe showed the sites of Cr localization, and probably sequestration, in epidermal and cortical cells in the roots and epidermal and spongy mesophyll cells in the leaves. These findings demonstrate the ability of B. juncea to detoxify more toxic Cr (VI), thereby making this plant a potential candidate for phytostabilization.
1986. Morphogenesis of the compound leaf in three genotypes of the pea, Pisum sativum. Can. J. Bot. 64: 1268-1276. Leaf anatomy, ontogeny, and morphology were described and compared in a pea line (Pisurn sativum L.) with conventional leaves and in isogenic lines canying the mutations af (afila) or tl (tendril-less or acacia). The anatomy of stem, petiole, and rachis is not modified by these mutations. The tendrils, which in af replace leaflets, have normal tendril anatomy, and the terminal leaflets of the tl form have normal leaflet anatomy. The shoot apical dome has the same size and shape in the three genotypes, as does the leaf primordium up to the stage of initiation of the first laterals. ' The mature morphology of leaves varies with node of insertion. Some leaves, especially at nodes 3 and 4, have structures that are not typical of their genotype. An in vitro culture system is described for axillary shoots. Such shoots recapitulate most of the foliar features of seedling plants, but leaf morphology is on average more complex, and aberrant structures are more frequent. All these observations are discussed in relation to Young's algebraic model for compound leaf development. GOULD, K. S., E. G. CUTTER, et P. W. YOUNG. 1986. Morphogenesis of the compound leaf in three genotypes of the pea, Pisum sativum. Can. J. Bot. 64: 1268 -1276. L'anatomie, I'ontogCnie et la morphologie foliares sont dCcrites et comparkes dans une ligntk de pois (Pisum sativum L.) ifeuilles conventionnelles et dans des IignCes isogkniques portant les mutations af ou tl. L'anatomie de la tige, du pCtiole et du rachis n'est pas affectCe par ces mutations. Les vrilles qui, dans les individus af, se trouvent i la place des folioles, ont une structure normale de vrille, et les folioles terminales des individus tl ont une structure normale de foliole. Le dbme apical caulinaire est de la m&me taille et de la m&me forme chez les trois genotypes; il en est de m&me pour le primordium foliaire jusqu'au stade d'initiation des premikres IatCrales. La morphologie ultime des feuilles, spCcialement celles des noeuds 3 et 4, ont une structure qui n'est pas typique de leur gCnotype. Un systkme de culture in vitro pour les pousses axillaires est dCcrit. On retrouve chez de telles pousses la plupart des traits foliaires des semis, mais la morphologie foliaire est, en gCnCral, plus complexe et des structures anormales sont plus frkquentes. Toutes ces observations sont discutCes en relation avec le modkle algkbra'ique de Young pour le dCveloppement des feuilles composkes.[Traduit par la revue]
Environmentally induced developmental plasticity is characteristic of many heterophyllous semiaquatic species, including Ranunculus flabellaris. Underwater shoots of this species form leaves with elongate narrow lobes, while aerial shoots form leaves with shorter, broader lobes. In this study, a series of transfer experiments was undertaken to determine the competence of developing leaves to respond to a change in environmental conditions. Plants were transferred from terrestrial to submerged conditions at 8, 16, and 24 days after the approximate time of initiation of leaf 4; these times correspond to the developmental stages before differences in size and shape of aerial and underwater leaves can be detected, the time of divergence, and postdivergence when leaves are about half expanded. Morphological and anatomical traits of mature leaves grown terrestrially, submerged, or after transfer at 8, 16, or 24 days were measured and assessed using analysis of variance and principal components analysis. We found that some traits of leaves (such as lobe number) transferred at 8 days were similar, but not identical, to those of the water control, indicating that some features are determined prior to structural divergence. Leaves transferred at 16 and 24 days were intermediate between the land and water controls in most respects, indicating that traits such as epidermal and mesophyll cell shape are determined gradually during expansion. Other anatomical features, such as development of a palisade layer and extent of intercellular space, did not differ between transfer treatments and the water control, indicating that these features can respond to ambient conditions late in development. Keywords: heterophylly, leaf development, plasticity, Ranunculus, principal components analysis.
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