TRACHELIUM CAERULEUM ON ANCIENT WALLS OF THE CITY OF BRAGA: A LEGACY FROM THE PAST TO THE FUTURE

A. Freitas, C.A. Alves, A. Cunha
Trachelium caeruleum L. plants can often be found on mortars of walls of the historic centre of Braga, a city of north-western Portugal. These plants spontaneously colonize some ancient walls, but they are absent from others apparently similar in structure and conditions, as well as from modern areas. This species was not found either in other urban or country areas of the same province. This study aimed at investigating the reasons underlying this plant habitat and distribution pattern and at establishing in vitro cultures of this species that can be seen as a city floristic patrimony to preserve. A sampling plan was delineated considering colonised and non-colonised places and different sun orientations and exposure levels. Mortar samples were taken and analysed by chemical spot tests (carbonates, alkalinity), x-ray diffraction, water and organic matter contents and chemical characteristics of the water-soluble fraction (pH and Ca, Mg, and Fe levels by ICP-AES). Seeds were collected in situ to establish in vitro cultures protocols. ANOVA and Principal Component Analysis results showed that shading level and substrate characteristics (hardness, presence of clay minerals, pH values and calcium and water content) were significant factors in explaining the plant distribution. This multifactor explanation, based on the interaction between chemical characteristics and wall structure, underlined the importance of substrate bioreceptivity in studying species distribution. High percentages of in vitro germination were obtained and in vitro seedling nodal segments used as primary explants induced highly productive in vitro shoot cultures with a profuse root system.
Freitas, A., Alves, C.A. and Cunha, A. (2009). TRACHELIUM CAERULEUM ON ANCIENT WALLS OF THE CITY OF BRAGA: A LEGACY FROM THE PAST TO THE FUTURE . Acta Hortic. 812, 153-160
DOI: 10.17660/ActaHortic.2009.812.16
https://doi.org/10.17660/ActaHortic.2009.812.16
in vitro culture, plant distribution pattern, mortars, bioreceptivity, shading level
English

Acta Horticulturae