Growth and loss of distal tissue in blades of Lessonia nigrescens and Lessonia trabeculata (Laminariales)

Meristematic growth and loss of distal tissue from blades of two ecologically important species in the south-east Pacific, Lessonia nigrescens and Lessonia trabeculata, was evaluated during 1 year. Comparative growth was determined by a hole-punch method, loss of distal tissue from the blades was determined by subtracting final blade length (with loss) from expected blade lengths (without loss); growth and tissue loss were transformed to fresh biomass units for calculation of inter-algae differences. The results showed that blade elongation rate increased at the beginning of spring, and declined towards the end of summer, with mean values between 0.40 and 0.08 cm day−1 for L. nigrescens, and 0.65-0.17 cm day−1 for L. trabeculata. Loss of distal tissue varied seasonally when examined as length units for both species; with mean values between 0.24 and 0.10 cm day−1 for L. nigrescens, and 0.51-0.25 cm day−1 for L. trabeculata. Variations in fresh biomass units were only observed in Lessonia trabeculata, increasing in spring, with mean values to 0.13 g (fresh weight) day−1. Annual growth and loss of distal tissue were higher in L. trabeculata (0.41 and 0.39 cm day−1, respectively) than in L nigrescens (0.19 and 0.15 cm day−1). When growth and tissue loss were considered as fresh biomass, monthly gains significantly outweighed loss of distal tissue in both species, but parallel results based on length data followed a different trend. L. trabeculata released about 50% of its growth biomass as particulate organic matter, while the comparative value for L. nigrescens was about 20%.