Leaf ontogeny and meristem activity of Typha domingensis Pers. (Typhaceae) under different phosphate concentrations

Phosphorus eutrophication may promote increased growth, photosynthesis, and shoot investment in cattail (Typha domingensis). However, its influence in early leaf development and meristem traits remains unclear. Therefore, this work aimed to evaluate the effects of phosphate levels on meristem structure and activity as well as tissue differentiation during the leaf development of T. domingensis. Plants were subjected to modified nutrient solutions containing three phosphate concentrations. The leaves were collected daily for 7 days, and were used to evaluate growth, meristem characteristics and tissue differentiation. In addition, phosphorus content was measured in roots and rhizomes exposed to phosphate treatments. The leaf primordia cultured in 0.4 and 0.8 mM phosphate levels showed a larger proportion of ground meristem than those grown in 0.1 mM. The procambium proportion was higher under 0.8 mM phosphate when compared to other concentrations. However, the proportion of protodermis was greater in 0.1 mM phosphate when compared to 0.4 and 0.8 mM. In addition, leaf primordia submitted to 0.4 and 0.8 mM phosphate increased meristem cell production. These primordia also showed fewer dividing cells and shorter cell cycle as compared to 0.1 mM phosphate. The development of aerenchyma and palisade parenchyma was promoted by greater phosphate concentrations. Higher aerenchyma proportion was found in plants from 0.8 mM phosphate treatment. Phosphorus content was higher in root than rhizomes for plants grown at 0.4 and 0.8 mM of phosphate. Likewise, the higher phosphate concentrations increased P levels in both roots and rhizomes. Therefore, optimal phosphorus levels promote the development of leaves with a higher photosynthetic potential, which may contribute to the uncontrolled growth of cattail under phosphorus eutrophication. (C) 2016 Elsevier B.V. All rights reserved.