Monitoring copper-induced changes in fine root geometry of birch (Betula pendula) using nutrient film technique (NFT)

Effects of copper on fine root geometry (number, length) and K and Cu content in birch ( Betula pendula Roth) were studied. After pre-cultivation, the plants were grown in a nutrient film technique (NFT) system and exposed to additional 0–5 μ M for a period of 8 days. The NFT system permitted undisturbed growth of the roots during monitoring. Copper experiments were carried out in a split-root setup both with a uniform and differentiated Cu supply to investigate growth responses of roots grown in a homogeneous and heterogeneous root environment, respectively. At uniform external Cu supply, average root length was affected by increased Cu concentration during the first four days while the next four days only the overall root length (product of root length and root number) was significantly reduced. During the first four days in the split-root experiments with differentiated Cu supply, additional Cu primarily reduced root number on the Cu-treated parts of the root system but at stronger Cu concentration the overall root length was also significantly reduced. In contrast, number and average root length of the part of the root system not exposed to Cu increased when 1, 2 and 5 μ M Cu was added to the other side. Growth parameters were affected differently in the beginning of the heavy metal exposure compared to later stages of exposure, which may indicate acclimatisation to Cu stress.