Phosphate and nitrate movement in the clonal plants Lycopodium annotinum L. and Diphasiastrum complanatum (L.) Holub

Abstract

summaryThe uptake and movement of phosphate by Lycopodium annotinum L. in the field was studied using 32P‐labelled orthophosphate. Although over 90% of the phosphate taken up was retained in the incubated roots, the phosphate transported to the aboveground tissues showed extensive movements both distally and proximally along the horizontal branch system. Root systems up to 12 years old could transport phosphate as far as the stolon apex over one metre distally along the horizontal branch. The movement of phosphate is preferentially to the main sinks for phosphorus, the current year's horizontal and vertical branch segments.Nitrate uptake and movement was studied in Diphasiastrum complanatum (L.) Holub by measuring the induction of in vivo nitrate reductase activity in current year's growth in different parts of the clone. There was equal induction of in vivo nitrate reductase activity in 1–4 year old root systems incubated in nitrate, but absorption by 3 and 4 year old root systems induced the highest activities in the vertical branches. Nitrate movement to the stolon apex was only detectable from root systems up to 3 years old. There was considerable induction of nitrate reductase activity in vertical branch apices proximal to the 3 and 4 year old root systems supplied with nitrate. L. annotinum and D. complanatum show considerable inter‐module integration for nitrate and phosphate supply. This means that the plant can adopt an effective ‘foraging’ strategy for nutrients. The movement of resources from sites of absorption to their sites of utilisation means that there is extensive recycling of nutrients spatially, as well as temporally, within the habitats colonised by these plants.