Abstract A somatic embryogenesis protocol was developed from the immature leaves of adult plants of the macaw palm. Leaf explants from different regions of the palm heart were used for callus initiation in a modified Y3 medium, supplemented with 2,4-D or Picloram at 450 μM. Calli were separated from the leaf explants at 6-, 9- and 12-month periods and transferred to a fresh culture medium of the same composition. They were multiplied for up to 120 days. Reduced concentrations of 2,4-D and Picloram were used to differentiate somatic embryos. They were then germinated in a medium without plant growth regulators. Morphological and anatomical analyses were conducted at different stages of the embryogenic process. The best results for callus induction were achieved by Picloram, when explants were maintained for up to 9 months on culture medium (64.9%). The farthest portions of the apical meristem were those that provided the biggest calli formation. The formation of the somatic embryos was observed from the calli multiplication phase. Reduction in concentrations of growth regulators failed to promote the formation of complete plants. Picloram at 450 μM promotes high callogenesis in leaf tissues of macaw palm, with a potential for somatic embryo formation.

Adaptabilidade e características anatômicas de folhas em mudas de dendezeiros produzidas pelo resgate de embriões e sementes pré-germinadas. Alterações na estrutura da folha de plantas crescidas em diferentes ambientes têm sido relatadas, como o aumento no tamanho e densidade dos estômatos e a redução no controle estomático, na quantidade de cera epicuticular e na espessura do mesofilo, com alta diversidade de espaços intercelulares. Entretanto, tais alterações são altamente variáveis em função das características fisiológicas e morfológicas próprias de cada espécie. O objetivo deste trabalho foi analisar a adaptabilidade e plasticidade anatômica foliar de mudas de dendezeiros produzidas pelo resgate de embriões e sementes pré-germinadas cultivadas num sistema in vitro ou em casa de vegetação. Cortes transversais e paradérmicos, além da dissociação de tecidos, foram preparados para obtenção dos dados morfométricos e anatômicos. Verificou-se que as condições ambientais do cultivo in vitro influenciaram negativamente os valores da densidade estomática, espessura da epiderme e hipoderme, e os valores obtidos para as células de expansão e do mesofilo foliar. Anatomicamente as folhas de dendezeiro apresentam a mesma composição tecidual em ambas condições de cultivo, com epiderme unisseriada, estômatos do tipo tetracítico de ocorrência em ambas as faces epidérmicas. As células epidérmicas das folhas de plantas in vitro são mais delgadas que as da casa de vegetação. Nas plantas de casa de vegetação a nervura principal é mais desenvolvida sendo formada por apenas um grande feixe vascular, enquanto que plantas cultivadas in vitro desenvolveram de três a quatro feixes vasculares.

Changes in the leaf structure of plants grown in different conditions have been reported, such as increase in size and density of stomata and reduction in stomatal control, amount of epicuticular wax, and mesophyll thickness, with a high diversity of intercellular spaces. However, these changes are highly variable depending on the physiological and morphological characteristics of each species. The objective of this work was to analyze the adaptability and anatomical plasticity of oil palm seedlings produced after embryo rescue and pre-germinated seeds. Expanded leaves were prepared for evaluation of morphometric data and anatomical structures. It was verified that the environmental conditions in vitro negatively influenced the stomata density, epidermal and hypodermal thickness, and the values for the expansion cells and leaf mesophile. Anatomically, the oil palm leaves present the same tissues composition in both growth conditions, with uniseriate epidermal cells, and tetracitic stomata occurring in both epidermal surfaces. Epidermal cells from in vitro plants are thinner than ones from greenhouse. The midrib of leaves from greenhouse plants are more developed and is composed by only one central vascular bundle, while plants from in vitro cultivation developed three to four collateral vascular bundles.