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Seeds of many Amazonian floodplain forest trees are dispersed during high-water periods and spend weeks or months underwater until the flooding retreats. To assess whether prolonged seed submersion affects germination and early seedling development, an experiment was carried out in a greenhouse with seeds of Campsiandra laurifolia , Cassia leiandra , Crataeva tapia , Ilex inundata , Macrolobium acaciifolium , Nectandra amazonum , Pouteria glomerata , Psidium acutangulum , Sorocea duckei , and Vitex cymosa. They are common in this type of forest, differ in fruit type, number of seeds per fruit, fruit dimensions, and fresh mass and have fruits or seeds that can float. Seeds were collected in a Central Amazonian floodplain forest (flooded approximately 6 months year−1; water column of 5 m) and germinated in (1) irrigated soil or (2) underwater (water column of 5–7 cm) for 6 months. Seeds that germinated underwater were transferred to drained soil. Seeds of all species germinated underwater and developed seedlings when transferred to soil. However, submersion reduced the germination percentage of Psidium acutangulum , N. amazonum , P. glomerata and V. cymosa. Six species delayed germination in water. Ca. leiandra , I. inundata and P. glomerata did not differ in mean germination time in drained soil and underwater, whereas S. duckei seeds germinated faster underwater. Seed submersion negatively affected seedling growth (shoot length) of three species but did not affect seedling biomass. Timing of fruit dispersal, fruit buoyancy and high number of seeds per fruit can be critical for species with seeds that are not as able to cope with long-term submersion. [ABSTRACT FROM AUTHOR]

Scleromorphic leaf structures are associated with plants growing under drought-prone conditions, high irradiances, and nutrient-poor soils. Sclerophylly can also be a valuable deterrent against herbivores. However, comprehensive studies of leaf anatomical traits encompassing different growth forms are lacking. The savannas of central Brazil (Cerrado) are characterized by high species diversity and a variety of growth forms. We performed a field study to characterize leaf anatomical traits and leaf mass per area (LMA) in 57 co-occurring Cerrado species of distinct plant families (located at different positions in the angiosperm phylogeny) and categorized according to the following growth forms: trees, palms, shrubs, subshrubs, vines, grasses and herbs. Plant growth form and leaf structure were interrelated. Four groups with distinct leaf anatomical syndromes were identified by NMDS analysis: grasses, palms, herbaceous (herbs, vines, and most subshrubs), and woody (trees and shrubs) plants. Trees and shrubs had scleromorphic dorsiventral leaves, with high tissue thickness and LMA. Herbaceous plants had thin, mesomorphic leaves. While most herbaceous plants had dorsiventral type of mesophyll, grasses and palms had homogenous mesophyll with sclerenchymatous bundle sheath extensions. Palms differed from grasses by having thicker leaves and sclerenchymatous hypodermis. In conclusion, Neotropical savannas cannot be exclusively described as scleromorphic vegetation. Keywords: Cerrado, growth forms, leaf anatomy, LMA, NMDS analysis. Les structures foliaires scleromorphiques sont associees aux plantes qui poussent sous des conditions sujettes a la secheresse, a un eclairement energetique par rayonnement solaire eleve et a des sols pauvres en nutriments. La sclerophyllie peut aussi constituer un precieux moyen de dissuasion envers les herbivores. Cependant, des etudes exhaustives des traits anatomiques foliaires englobant differentes formes de croissance sont absentes. Les savanes du centre du Bresil (Cerrado) se caracterisent par une haute diversite en especes et une variete de formes de croissance. Les auteurs ont realise une etude sur le terrain afin de caracteriser les traits anatomiques foliaires et la masse foliaire par unite de surface chez 57 especes co-occurrentes de familles distinctes du Cerrado (situees a differentes positions de la phylogenie des angiospermes) et categorisees en fonction des formes de croissance suivantes : arbres, palmiers, arbustes, sous-arbrisseau, lianes ou plantes grimpantes, graminees et herbes. Les formes de croissance des plantes et la structure foliaire etaient inter-reliees. Quatre groupes possedant des traits anatomiques foliaires observables distincts ont ete identifies par analyse multidimensionnelle non metrique : herbes, palmiers, herbacees (graminees, lianes ou plantes grimpantes et la plupart des sousarbrisseaux) et vegetaux ligneux (arbres et arbustes). Les arbres et les arbustes possedaient des feuilles scleromorphiques dorsiventrales, a epaisseur tissulaire et masse foliaire par unite de surface elevees. Les plantes herbacees possedaient des feuilles mesomorphiques minces. Alors que la plupart des plantes herbacees presentaient un mesophylle de type dorsiventral, les herbes et les palmiers avaient un mesophylle homogene possedant des extensions sclerenchymateuses de gaine perivasculaire. Les palmiers differaient des herbes par des feuilles plus epaisses et un hypoderme sclerenchymateux. En conclusion, les savanes neotropicales ne peuvent pas etre exclusivement decrites en tant que vegetation scleromophique. [Traduit par la Redaction] Mots-cles : Cerrado, forme de croissance, anatomie foliaire, masse foliaire par unite de surface, analyse multidimensionnelle non metrique., Introduction Savannas are widespread in tropical and subtropical regions, and consist of a variable mixture of trees and grasses (Bourliere 1983). Seasonal water stress, fire, and herbivory are the most [...]

Fatty acids (FAs) stored as triacylglycerols (TAGs) are an important source of carbon and energy for germination and seedling development, particularly for plants with small wind-dispersed seeds, allowing greater efficiency in storing both energy and carbon. These plants should be under strong selection to produce seeds rich in FAs and with large amounts of saturated FAs. Their closely packed single-chain configuration allows greater packing, more carbon and energy per unit mass, and are less costly to produce. Efficient carbon storage would be less crucial for zoochorous species, which can reach much larger seed sizes (mass). We analysed the transesterified FA profile from seeds of 22 anemochorous and zoochorous tree species from the Cerrado savannas of Central Brazil. We tested if seed FA content covaried with seed mass and if anemochorous and zoochorous seeds differed in FA contents and distribution. Fatty acids were an important seed source of carbon and energy for most species. Fifteen different FAs were identified. Oleic, linoleic and linolenic tended to be the predominant unsaturated FAs. Oleic acid corresponded to more than 60 % of the total transesterified FAs in seeds of Kielmeyera coriacea, Qualea dichotoma and Triplaris americana. Linoleic acid corresponded to more than 50 % of total FA in Dalbergia miscolobium, Parkia platycephala and Ferdinandusa elliptica while linolenic acid was the dominant component in Inga cylindrica. Across species, palmitic and stearic were the dominant saturated FAs. The only exception was lauric acid (68 % of total FA) in seeds of Qualea grandiflora. On a log10 scale, as the seed increased in mass, accumulation of FAs tends to proceed at a faster rate in anemochorous species than in zoochorous species. They also became increasingly richer in saturated FAs. Zoochorous species had seed TAGs with higher proportion of polyunsaturated FAs. [ABSTRACT FROM AUTHOR]