Felipe Fogaroli Corrêa

Typha domingensis Pers. (cattail) is a globally widespread aquatic plant that causes significant impacts as an invasive species; this ability is dependent on its photosynthetic capacity that is related to leaves. Thus, understanding leaf development is essential for interpreting shoot growth and the formation of its photosynthetic area. This study investigates leaf ontogeny in T. domingensis from early stages until complete development of primary tissues. Plants were collected from natural wetlands and cultivated in a greenhouse. Rhizomes were then selected, and leaves were removed to enable the emergence of new shoots. Rhizome fragments containing leaves were collected at 1-day intervals until day 7 and were subjected to routine procedures in plant microtechnique. New leaves emerged from lateral buds located along the rhizome. The anatomy of scale leaves differs from that of photosynthetic leaves since they contain solid inclusions without palisade parenchyma. Leaf primordia arose laterally from the shoot apical meristem, which was organized as a tunica-corpus. Final leaf shape was influenced by different meristematic zones: the leaf apical meristem, the marginal meristem, the rib meristem, and intercalary meristems. Most leaf tissues developed basipetally, except for xylem and phloem. Within seven days following leaf initiation, all primary tissues were developed and morphologically functional. Leaf formation of Typha domingensis is similar to that of other monocot species. Leaves of T. domingensis develop very early, providing fully functional photosynthetic tissues, which may have implications for its invasive capacity.

Aim The capacity of macrophytes to colonize large areas is often referred to as dependent of the investment in root system and its capacity to uptake nutrients. This work aimed to evaluate the phosphorus (P) effects on the root growth and anatomy as well as its capacity to uptake this nutrient by the aquatic macrophyte Typha domingensis. Methods Plants were grown for 60 days in nutrient solution containing 0, 0.2, 0.4, 0.6 or 0.8 mM of phosphorus. At the end of the experiment, the root length and P root content as well as the root anatomy at the maturation and meristematic zones were evaluated. Results Higher P concentrations increased the uptake of this nutrient and plant dry mass. However, the root length was reduced by higher phosphorus levels. In addition, P increased the proportion of the root cap while reduced the proportion of the procambium at the meristematic zone. Higher phosphorus concentrations reduced the xylem vessel diameter and the proportion of the vascular cylinder at the maturation zone, whereas increased phloem proportion was observed under this condition. Furthermore, higher phosphorus levels reduced the endodermis and exodermis thickness as well as the aerenchyma proportion. Conclusions Therefore, the T. domingensis P requirement is fulfilled at 0.4 mM of this nutrient and hypertrophic conditions promote the development of unfavorable root anatomical traits and reduction of the root growth.

Byrsonima coccolobifolia Kunth. (Malpighiaceae) é citada como planta apícola, forrageira, produtora de frutos comestíveis e como planta medicinal, podendo ser utilizada como diurética (uso interno, em infusão) a partir das cascas dos caules e dos frutos. O objetivo deste trabalho foi realizar um estudo quali-quantitativo das características anatômicas da folhas desta espécie que ocorre em áreas de cerrado e campo rupestre. As observações anatômicas foram realizadas em folhas de material fresco ou fixado, tratadas segundo metodologias usuais em anatomia vegetal. Foram observadas as seguintes características: epidermes do pecíolo e da lâmina foliar uniestratificadas; estômatos do tipo paracítico presentes somente na face abaxial da folha; mesofilo com parênquima paliçádico de uma só camada de células; parênquima lacunoso com sete a nove camadas celulares com formas irregulares e tamanhos variados; idioblastos cristalíferos, observados em todos os parênquimas do pecíolo e lâmina foliar; feixes vasculares, do tipo colateral; colênquima observado, subepidermicamente, no pecíolo e nervuras de maior porte, nas duas faces; o padrão geral de nervação da espécie é pinado, camptódromo, broquidódromo. As análises micromorfométricas revelaram diferenças significativas em todos os itens quantitativos analisados, sendo as médias mais elevadas encontradas nas folhas das plantas crescendo no cerrado. Isto sugere que a influência de fatores ambientais pode ter modulado respostas morfológicas nas plantas, visto que o tipo e distribuição qualitativa dos tecidos não sofreram alterações nos dois ambientes.

1. INTRODUCTION AND OBJECTIVES

The seeds of Schinus molle are referred to as displaying physical dormancy because of their water-impermeable endocarp. Therefore, this work aimed to evaluate the germination of S. molle seeds as related to environmental conditions, scarification, storage time and seed anatomy. Various experiments were conducted to test the alleviation of dormancy in newly collected and stored seeds. Acid-scarified seeds incubated under continuous light at 25°C showed greatest vigour and germination. The separation of seeds by specific gravity revealed a higher germination percentage for those seeds that sank. In addition, dry storage alleviated dormancy with a remarkable increase in the various germination parameters. Overall, germination traits decreased after prolonged storage, but even after 12 months the means for germination parameters for stored seeds were still higher than those of newly collected ones. S. molle seeds remain attached to parts of the fruit mesocarp and endocarp. The mesocarp contains several layers of parenchyma showing secretory cavities. The endocarp consists of three layers of sclereids surrounding the embryo. Acid scarification strongly changed the structure of the external layers in the mesocarp, digesting parenchyma cells and removing the contents from both parenchyma cells and the secretory cavities; this improved water uptake during imbibition, which occurred only at the carpellary hilar slit. In conclusion, S. molle seeds are positively photoblastic and show physiological dormancy which can be alleviated by acid scarification and dry storage. Seeds can be stored for over 12 months without significant losses in germination parameters compared to newly collected seeds.