The aim of the present study was to evaluate the influence of the seed structures on the dormancy of the palms Attalea vitrivir Zona, Butia capitata (Mart.) Becc. and Acrocomia aculeata (Jacq.) Lodd. ex Mart., which are found in the cerrado biome (Brazilian savanna). The effects of seed structures on the imbibition and effects of the operculum on germination were evaluated. The effects of the collection area on the seed biometric characteristics and influence of the embryo mass and length on their germination capacity and vigour were also evaluated. The operculum was anatomically characterised, and the effects of the operculum thickness on seed germination were evaluated. The seed structures partially restricted water absorption by the embryos, but this did not affect germination; however, removing the operculum promoted germination. The mass of A. vitrivir and A. aculeata embryos positively influenced their germination capacity and vigour, and the thicknesses of the opercular seed coat and operculum negatively controlled the germination capacity of B. capitata. The greater thickness and rigidity of the operculum of A. aculeata increased the intensity of seed dormancy and possibly contributed to the wider distribution pattern of this species. The interaction between the embryo and operculum structures modulate the dormancy and possibly influence the distribution patterns of the palms in the cerrado biome.

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Heterobaric leaves have bundle sheath extensions (BSEs) that compartmentalize the sub-stomatal cavity, whereas homobaric leaves do not. In tomato (Solanum lycopersicum), BSE development is controlled by the OBSCURAVENOSA (OBV) locus. The obv mutant lacks BSEs, whereas leaves carrying the wild-type allele have BSEs. Here, we identify the obv gene and the causative mutation, a non-synonymous amino acid change. This mutation exists as a rare polymorphism in the natural range of wild tomatoes but has increased in frequency in domesticated tomatoes, suggesting that the latter diversified into heterobaric and homobaric leaf types. The mutation disrupts a C2H2 zinc finger motif in the OBV protein, resulting in the absence of BSEs in leaves and alterations to leaf function: Photosynthetic assimilation rate and leaf hydraulic conductance are both reduced in obv. Here, we show that both of these and other pleiotropic effects, including changes in leaf insertion angle, leaf margin serration, minor vein density, and fruit shape, are controlled by OBV via changes in auxin signalling. Loss of function of the transcriptional regulator AUXIN RESPONSE FACTOR 4 (ARF4) also results in defective BSE development, revealing an additional component of a genetic module controlling aspects of leaf development important for ecological adaptation and for breeding selection.