Abstract

Black cohosh (Actaea racemosa Nutt., Syn. Cimicifuga racemosa) roots were traditionally used by Native North Americans to treat female complaints and today are used to treat menopausal problems. From root wild populations in the eastern USA 95% of it is exported. Wild populations are declining and there is an urgent need to conduct research in the propagation and cultivation of this species to supply the increasing demand. The objectives of this research were (i) to characterize black cohosh growth and development under artificial shading, (ii) to determine the minimum root size that can be used for vegetative propagation, and (iii) to determine the CO2 assimilation rate and content of carbohydrates, peroxidases and esterases during one season of growth. The experiment was conducted in Chillán, Chile. Rhizomes for propagation were imported from North Carolina, USA, in 2001. There were planted, at 30 cm × 30 cm distance between plants and 5-cm deep, with a polypropylene shading net of 80% light absorption, in July 2003. The experimental design was a randomized complete block design with four replicates. Different rhizome sizes and rhizome ages were used to obtain seven treatments, that included the whole rhizome containing roots and buds (T1), basal segment of rhizome (T2), apical segment of rhizome (T3), transversally dimidiated basal segment of rhizome (T4), transversally dimidiated apical segment of rhizome (T5), underground stolon bearing four buds (T6), and a single bud (T7). The evaluations included the number of buds and stems, plant height, total leaf area and leaf area index, leaf nitrogen content, CO2 assimilation rate (AR) and stomatal conductance (SC), root weight and root relative growth rate (RGR). Plants derived from the rhizome containing roots and buds (T1) and apical segment of the rhizome (T3) had greater number of initial buds and produced more stems. A close relationship was found between initial rhizome weight and plant height, total leaf area and rhizome growth. All treatments showed similar AR and SC (6.01 μmol CO2 m-2 s-1 and 1.54 cm s-1, respectively), and leaf nitrogen content. The RGR of rhizomes was significantly different among treatments with the highest value for T5. Vegetative propagation of black cohosh is possible using fragments of rhizomes and the most efficient is using the transversally dimidiated apical segment of the rhizome. Differences in the peroxidases isozyme patterns were observed between 232 DAP and 353 DAP for T2, T4 compared to T3 and T5. © 2006 Elsevier B.V. All rights reserved.