Changes in anatomy and chlorophyll synthesis in orchids propagated in vitro in the presence of urea/Alteracoes anatomicas e sintese de clorofila em orquidea propagada in vitro na presenca de ureia

The environmental and nutritional conditions during plant growth can influence cell differentiation, resulting in anatomical and physiological adaptations. The objective of this study was to investigate the anatomical characteristics and chlorophyll content of L. purpurata during in vitro propagation when different concentrations of urea were applied. After 120 days of culture in a greenhouse, the growth characteristics, chlorophyll content, leaf anatomy and root features were assessed. Plants cultivated in a medium containing 75% urea exhibited modifications in their growth, increase in the number of leaves and roots, changes in the leaf and root dry matter content. There was an increase in the contents of "a" and "b" chlorophyll in plants treated with 50, 75 and 100% urea. An increase in the ratio of chlorophyll a to chlorophyll b ("a/b") was observed in plants treated with 25% urea compared with the controls. In plants treated with 75% urea, increases in the thicknesses of the mesophyll and the leaf blade were observed, and reductions in the number of layers of root cells, the velamen thickness, the exodermis and the vascular cylinder were observed. These results indicate that this species has a tolerance to urea and exhibits higher growth in vitro. Keywords: Laelia purpurata, cultivation in vitro, sources of organic nitrogen. O ambiente assim como as condicoes de cultivo e tipo de nutricao podem influenciar na diferenciacao celular, resultando em adaptacoes anatomicas e fisiologicas. O objetivo foi estudar caracteristicas anatomicas e o teor de clorofila de L. purpurata "carnea" propagadas in vitro quando aplicado diferentes concentracoes de ureia. Apos 120 dias em sala de crescimento, foram avaliadas caracteristicas de crescimento, teor de clorofila, aspectos anatomicos foliares e radiculares. Ocorreram modificacoes nas caracteristicas de crescimento das plantas cultivadas em meio com 75% de ureia, resultando em aumento do numero de folhas, raizes, teor de massa seca foliar e radicular. Houve aumento no teor de clorofila "a" e "b" nos tratamentos com 50, 75 e 100% de ureia. Foi observado aumento da razao de clorofilas "a/b" no tratamento com 25% de ureia, quando comparado com o controle. Na concentracao de 75% de ureia foi observado aumento da espessura do mesofilo, limbo foliar, reducao do numero de camada de celulas radiculares, espessura do velame, exoderme e cilindro vascular. Tais resultados indicam que a especie possui tolerancia a ureia, possib