Understanding how plants survive drought and cold is increasingly important as plants worldwide experience dieback with drought in moist places and grow taller with warming in cold ones. Crucial in plant climate adaptation are the diameters of water-transporting conduits. Sampling 537 species across climate zones dominated by angiosperms, we find that plant size is unambiguously the main driver of conduit diameter variation. And because taller plants have wider conduits, and wider conduits within species are more vulnerable to conduction-blocking embolisms, taller conspecifics should be more vulnerable than shorter ones, a prediction we confirm with a plantation experiment. As a result, maximum plant size should be short under drought and cold, which cause embolism, or increase if these pressures relax. That conduit diameter and embolism vulnerability are inseparably related to plant size helps explain why factors that interact with conduit diameter, such as drought or warming, are altering plant heights worldwide.

No abstract

The cambial activity and periodicity of secondary xylem and phloem formation have been less studied in tropical tree species than in temperate ones. This paper describes the relationship between seasonal cambial activity, xylem and phloem development, and phenology in Schizolobium parahyba, a fast growing semideciduous seasonal forest tree from southeastern Brazil. From 2002 to 2003, wood samples were collected periodically and phenology and climate were recorded monthly in the same period. S. parahyba forms annual growth increments in wood, delimited by narrow initial parenchyma bands. The reduction of the cambial activity to a minimum correlates to the dry season and leaf fall. The higher cambial activity correlates to the wet season and the presence of mature leaves. In phloem, a larger conductive region was observed in the wet season, when the trees were in full foliage. The secondary phloem did not exhibit any incremental zone marker; however, we found that the axial parenchyma tends to form irregular bands.

Cambial activity and periodicity of secondary xylem formation in Cedrela fissilis, a semi-ring-porous species, were studied. Wood samples were collected periodically from 1996 to 2000. The phenology was related to climate data of the region. The cambium has one active and one dormant period per year. The active period coincides with the wet season when trees leaf-out. The dormant period coincides with the dry season when trees lose their leaves. Growth rings are marked by parenchyma bands that begin to be formed, together with the small latewood vessels, just before the cambium becomes dormant at the beginning of the dry season. These bands are added to when the cambium reactivates in the wet season. At this time, the large earlywood vessels of the growth rings are also formed. As these bands consist of both terminal and initial parenchyma, we suggest the general term marginal bands be used to describe them. The growth layers vary in width among and within the trees.

-(Comparative wood anatomy of Copaifera langsdorffii Desf. (Leguminosae-Caesalpinoideae) in forest and "cerradão"). The present study compares qualitative and quantitative characters of the wood of a tree species (Copaifera langsdorffii Desf.-Leguminosae-Caesalpinoideae) from semideciduous mesophytic forest and "cerradão". Analysis revealed vessels with significantly larger diameter in trees from "cerradão" and intervascular pits being significantly larger in trees from forest. In contrast to the trees from the forest, gelatinous fibers, which have a special layer innermost of the wall, were found in great quantity in trees from "cerradão". Furthermore, the presence of subdivided marginal parenchyma and the absence of axial canals in some of the parenchyma bands are for the first time mentioned for this species.RESUMO -(Anatomia comparada do lenho de Copaifera langsdorffii Desf. (Leguminosae-Caesalpinoideae) de floresta e cerradão). O presente estudo compara a estrutura do lenho de uma espécie arbórea (Copaifera langsdorffii Desf.) que ocorre em floresta mesófila semidecídua e em cerradão. Objetivou-se verificar diferenças estruturais qualitativas e quantitativas nos espécimes em relação aos dois ecossistemas. A análise estatística revelou um maior diâmetro tangencial dos vasos nos espécimes do cerradão e um maior diâmetro tangencial das pontoações intervasculares nos espécimes da floresta, ambos ao nível de 0,05. Fibras gelatinosas foram encontradas em maior quantidade nos espécimes do cerradão quando comparadas com os espécimes da floresta. A presença de um parênquima marginal que se subdivide e algumas faixas parenquimáticas que não apresentam canais axiais são pela primeira vez mencionadas em Copaifera langsdorfii.

The genus Styrax L. (Styracaceae) has a wide distribution in Brazil, occurring in diverse ecosystems. To get a better insight into the ecologieal adaptations ofwood strueture, we studied two speeies, S. camporum and S.jerrugineus from the cerrado, and three species, S. latifolium, S. martii and S. leprosus from the Atlantie forest. For each species, the wood of root and stern was analyzed separately and observations inc1uded qualitative as well as quantitative wood characteristics. The results show that there were significant anatomical differences between the forest and cerrado species as well as between the root and stern wood within single species. Quantitatively, the most informative features in the root wood that separated the forest from the cerrado species were diameter, length and number of vessels, length of fibres, and width and frequeney of rays. In the stern wood, length and frequency of vessels, length of fibres, and width and frequency of rays were the most informative features. In contrast to the forest species, which had larger vessel diameters in their stem wood, the cerrado species had larger vessel diameters in their root wood. The ca1culated vulnerability index indicates that all Styrax species have adaptations to mesic conditions. The cerrado species had the smallest index values, which could be related to the seasonally dry condition of this environment.

Brazil is the world’s largest producer of charcoal and a great part of this material still comes from native forests – especially from the cerrado biome, which is highly impacted by anthropogenic degradation. The need to control charcoal production increases the demand of charcoal identification, but there is little information about the anatomical modifications due to carbonization. In this paper, fresh and charred wood samples from five Brazilian species were analyzed (Dalbergia violacea, Stryphnodendron polyphyllum, Tapirira guianensis, Vochysia tucanorum, and Pouteria torta). Anatomical characters were described and measurements of the main anatomical features of wood and charcoal were statistically compared. Minor modifications were observed: reduction of tangential vessel diameter was the most evident change after carbonization; shrinkage of rays (in width) occurred only in some individuals. The present study supports the identification of charred woods, hopefully contributing to the control of charcoal production, and to palaeoenvironmental and archaeobotanical studies.

Non-structural carbohydrates (NSC) are crucial for forest resilience, but little is known regarding the role of bark in NSC storage. However, bark's abundance in woody stems and its large living fraction make it potentially key for NSC storage. We quantified total NSC, soluble sugar (SS) and starch concentrations in the most living region of bark (inner bark, IB), and sapwood of twigs, trunks and roots of 45 woody species from three contrasting tropical climates spanning global extremes of bark diversity and wide phylogenetic diversity. NSC concentrations were similar (total NSC, starch) or higher (SS) in IB than wood, with concentrations co-varying strongly. NSC concentrations varied widely across organs and species within communities and were not significantly affected by climate, leaf habit or the presence of photosynthetic bark. Starch concentration tended to increase with density, but only in wood. IB contributed substantially to NSC storage, accounting for 17-36% of total NSC, 23-47% of SS and 15-33% of starch pools. Further examination of the drivers of variation in IB NSC concentration, and taking into account the substantial contribution of IB to NSC pools, will be crucial to understand the role of storage in plant environmental adaptation.