RESUMO -(Algumas respostas fotossintéticas e do crescimento de plântulas de Annona glabra L. ao alagamento do solo). Um experimento foi conduzido com o objetivo de analisar os efeitos do alagamento e da posição das folhas na produtividade primária líquida e no balanço de carbono em plântulas de Annona glabra L. (Annonaceae), uma espécie altamente tolerante ao alagamento e nativa na América tropical. Todas as plântulas sobreviveram ao período de alagamento de 56 dias sem apresentarem sintomas de estresse. O alagamento induziu incrementos significativos (P <0,01) na biomassa de raízes, caules e planta inteira, e na razão raízes/parte aérea. Medições das trocas gasosas foliares foram conduzidas aos quatro, 11, 18 e 56 dias após o alagamento, na primeira (L1), quarta (L4) e sétima (L7) folha completamente expandida a partir do ápice em cada plântula. Os valores médios da condutância estomática ao vapor de água (g s ) e da taxa fotossintética líquida (A) nas plântulas controle foram 0,26 mol m s -1 , respectivamente. Reduções significativas (P <0,05) em A foram observadas entre L1 e L7 nas plântulas controle em todos os três dias de medições. As reduções em A com o aumento da idade foliar também ocorreram nas plantas alagadas, apenas nos dias 4 e 18. O alagamento induziu alterações significativas em gs (P <0,05), alcançando 65% em relação ao controle no dia 4 e 152% em relação ao controle no dia 56. Com base nos resultados obtidos foi possível concluir que as elevadas taxas de sobrevivência e de crescimento de plântulas de A. glabra estão diretamente relacionadas com a capacidade de manter elevados valores de condutância estomática e de taxa fotossintética líquida em condições de alagamento do solo. Palavras-chave:Annonaceae, condutância estomática, floresta atlântica, taxa fotossintética líquida, tolerância ao alagamento ASTRACT -(Some photosynthetic and growth responses of Annona glabra L. seedlings to soil flooding). An experiment was conductedwith the aim to analyze the effects of soil flooding and leaf position on net primary productivity and whole plant carbon balance of Annona glabra L. (Annonaceae) seedlings, a highly flood-tolerant tree, native to the tropical Americas. All seedlings survived a period of 56 days of flooding without symptoms of stress. Flooding induced significant increments in root, stem and whole-plant biomass (P <0.01), and in the root:shoot mass ratio (P <0.05). Measurements of leaf gas exchange were conducted at days four, 11, 18 and 56 after flooding, on the first (L1), fourth (L4) and seventh (L7) fully expanded leaves from the apex of each seedling. The mean values of stomatal conductance to water vapour (g s ) and net photosynthetic rate ( , respectively. Significant reductions (P <0.05) in A were observed from L1 to L7 in controls at all four days of measurements. Reductions in A with increasing leaf age also ocurred for flooded plants, but only at days four and 18. Flooding induced significant changes in gs (P <0.05), reaching 65% of controls at day four but 152% of controls at day...

The wild grass species Brachypodium distachyon (L.) has been proposed as a new model for temperate grasses. Among the biotechnological tools already developed for the species, an efficient induction protocol of somatic embryogenesis (SE) using immature zygotic embryos has provided the basis for genetic transformation studies. However, a systematic work to better understanding the basic cellular and molecular mechanisms that underlie the SE process of this grass species is still missing. Here, we present new insights at the morpho-histological, histochemical, and molecular aspects of B. distachyon SE pathway. Somatic embryos arose from embryogenic callus formed by cells derived from the protodermal-dividing cells of the scutellum. These protodermal cells showed typical meristematic features and high protein accumulation which were interpreted as the first observable steps towards the acquisition of a competent state. Starch content decreased along embryogenic callus differentiation supporting the idea that carbohydrate reserves are essential to morphogenetic processes. Interestingly, starch accumulation was also observed at late stages of SE process. Searches in databanks revealed three sequences available annotated as BdSERK, being two copies corresponding to SERK1 and one showing greater identity to SERK2. In silico analysis confirmed the presence of characteristic domains in a B. distachyon Somatic Embryogenesis Receptor Kinase genes candidates (BdSERKs), which suggests SERK functions are conserved in B. distachyon. In situ hybridization demonstrated the presence of transcripts of BdSERK1 in all development since globular until scutellar stages. The results reported in this study convey important information about the morphogenetic events in the embryogenic pathway which has been lacking in B. distachyon. This study also demonstrates that B. distachyon provides a useful model system for investigating the genetic regulation of SE in grass species.

Polyploidy is widely recognized as a major evolutionary force in plants and has been reported in the genus Lippia (Verbenaceae). Lippia alba, the most studied species, has been documented as a polyploid complex involving at least four ploidal levels. L. alba presents remarkable chemical and genetic variation and represents a model for understanding genome organization. Although the economic and medicinal importance of the species has been widely described, no established polyploid induction protocol has been reported so far. Here, we describe the production of synthetic polyploid plants of L. alba using colchicine. The ploidal levels were estimated by flow cytometry and chromosome counting. In addition, FISH and molecular markers approaches were used to confirm the stability of the synthetic polyploids. The major component of the essential oils was estimated by GCMS to compare with the natural individuals. Tetraploids and triploids were produced providing new opportunities for investigating medicinal, pharmacological, and economic applications as well as addressing intrinsic questions involved in the polyploidization process in tropical plants.

No abstract

No abstract