Organ-coordinated response of early post-germination mahogany seedlings to drought.

Water deficit tolerance during post-germination stages is critical for seedling recruitment. In this work, we studied the effect of water deficit on morphological and biochemical responses in different organs of newly germinated mahogany (Swietenia macrophylla King) seedlings, a woody species that occurs in the Amazon rainforest. The root : shoot ratio increased under water deficit. The leaf number and water potential were not altered, although reductions in leaf area and stomatal conductance were observed. Osmotic potential became more negative in leaves of seedlings under severe stress. Water deficit increased fructose, glucose, sucrose and myo-inositol levels in leaves. Stems accumulated fructose, glucose and l-proline. Nitric oxide (NO) levels increased in the vascular cylinder of roots under severe stress while superoxide anion levels decreased due to augmented superoxide dismutase activity in this organ. Water deficit induced glutathione reductase activity in both roots and stems. Upon moderate or severe stress, catalase activity decreased in leaves and remained unaffected in the other seedling organs, allowing for an increase of hydrogen peroxide (H2O2) levels in leaves. Overall, the increase of signaling molecules in distinct organs-NO in roots, l-proline in stems and H2O2 and myo-inositol in leaves-contributed to the response of mahogany seedlings to water deficit by triggering biochemical processes that resulted in the attenuation of oxidative stress and the establishment of osmotic adjustment. Therefore, this body of evidence reveals that the development of newly germinated mahogany seedlings may occur in both natural habitats and crop fields even when water availability is greatly limited.

[The morphological and histological identification of Chukrasia tabularis].

In this paper the descriptions and microscopic characters of Chukrasia tabularis were reported. The results provided scientific evidences for recognition and resources utilization.

The mahogany family "out-of-Africa": divergence time estimation, global biogeographic patterns inferred from plastid rbcL DNA sequences, extant, and fossil distribution of diversity.

With information on fossils and extant distribution of diversity/endemism in the mahogany family, we perform a global biogeographic study of Meliaceae using plastid rbcL data for all subfamilies, tribes and nearly all genera. Our study indicates that: (1) Meliaceae are of western Gondwanan origin; (2) dispersal played an important role for the current distribution of mahogany biota; and (3) the direction of dispersal was most likely an "out-of-Africa" scenario with important dispersal routes across Eurasia and between Eurasia and North America provided by Beringia and the North Atlantic land bridge and North America and South America via island chains and/or direct land connections. Populations in North America, Europe, and East Asia were presumably eliminated as tropical climates disappeared from these areas during the Miocene. Extensive Meliaceae fossil findings confirm that the entry of megathermal (frost-intolerant) angiosperms into southern continents from Oligocene to Pliocene must be considered as an important means of establishing pantropical distribution patterns.

[Morphology and anatomy of the fruit and seed in development of Guarea macrophylla Vahl. (Meltaceae)]. / Morfo-anatomia do fruto e da semente em desenvolvimento de Guarea macrophylla Vahl. (Meliaceae).

Morphology and anatomy of the fruit and seed in development of Guarea macrophylla Vahl. were studied in flowers and fruits collected in secondary forests of Maringá, Paraná, Brazil. Pericarp originates from the wall of the ovary and is constituted of epidermic exocarp, parenchymatous mesocarp with brachysclereids and fibrous and lignified endocarp. The seed develops from the hemianatropous, bitegmic and crassinucellate ovule and it is classified as an exotegmic and exalbuminous one. Exotesta and mesotesta constitute the red sarcotesta, with oily content.