Abstract
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 .
Highlights
The flower production sector has increased in Brazil during recent years and has reached significant importance in the international market
We evaluated the anatomical changes in the root tissue and analyzed the chlorophyll content of leaves to evaluate the nitrogen requirements in the orchid species Laelia purpurata “carnea”
Laelia purpurata “carnea” plants that were 1 cm in length after in vitro germination were inoculated in MS culture medium (MURASHIGE; SKOOG, 1962) that was supplemented with 2.68 μmol of naphtalenacetic acid (ANA) + 13.72 μmol of gibberellic acid (GA3) + 2 g L-1 of activated carbon + 100 g L-1 of banana nanica pulp solidified with 6 g L-1 of agar
Summary
The flower production sector has increased in Brazil during recent years and has reached significant importance in the international market. In Brazil, the in vitro production of flowers is essential to produce plants with higher quality and higher commercial value (MATA-ROSAS et al, 2011). Due to the destruction of the Laelia habitat as a result of intense exploration activities, some species are at risk of extinction. Biotechnological techniques such as in vitro culture provide essential tools (RODRIGUES et al, 2009; RODRIGUES et al, 2012) to aid in the preservation and production of these plants (SILVA JÚNIOR et al, 2012)
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