Root allocation in metal-rich patch by Thlaspi caerulescens from normal and metalliferous soil: new insights into the rhizobox approach

We compared root responses to spatial heterogeneity of Zn and Ni in Thlaspi caerulescens J. and C. Presl from normal (NM plants) and metalliferous soil (M plants). We investigated whether the strong metal accumulation capacity of NM plants (compared to M plants) was related to a greater capacity of roots to grow towards metal-enriched soil compartments. Two similar experiments were conducted in summer (slow growth) and spring (high growth), respectively. Our study is the first to show that NM plants of T. caerulescens have the ability to allocate more roots in the Zn-enriched compartment of soil. However, the positive response to Zn by roots of NM plants does not explain their higher Zn accumulation capacity as M plants express a similar level of root allocation in Zn-enriched compartment of soil. In M plants, root response to the Zn-rich compartment appears to be more susceptible to variations in growth conditions. Preferential root allocation in Ni-enriched compartment was consistently found in M plants only, suggesting that Ni supply is critical in their native metalliferous soil. Our study also illustrates bias in the interpretation of root allocation studies using two dimensional boxes, as interferences between root response to metal and root chirality have been highlighted. © 2008 Springer Science+Business Media B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Charcoal anatomy of Brazilian species. I. Anacardiaceae

ABSTRACT Anthracological studies are firmly advancing in the tropics during the last decades. The theoretical and methodological bases of the discipline are well established. Yet, there is a strong demand for comparative reference material, seeking for an improvement in the precision of taxonomic determination, both in palaeoecological and palaeoethnobotanical studies and to help preventing illegal charcoal production. This work presents descriptions of charcoal anatomy of eleven Anacardiaceae species from six genera native to Brazil (Anacardium occidentale, Anacardium parvifolium, Astronium graveolens, Astronium lecointei, Lithrea molleoides, Schinus terebenthifolius, Spondias mombin, Spondias purpurea, Spondias tuberosa, Tapirira guianensis, and Tapirira obtusa). They are characterized by diffuse-porous wood, vessels solitary and in multiples, tyloses and spiral thickenings sometimes present; simple perforation plates, alternate intervessel pits, rounded vessel-ray pits with much reduced borders to apparently simple; parenchyma paratracheal scanty to vasicentric; heterocellular rays, some with radial canals and crystals; septate fibres with simple pits. These results are quite similar to previous wood anatomical descriptions of the same species or genera. Yet, charcoal identification is more effective when unknown samples are compared to charred extant equivalents, instead of to wood slides