Effect of calcium manganese interaction on the growth and nutrient uptake in Scots pine and black pine seedlings
Acid soil infertility has been associated with excess of Al, either Mn toxicity or deficiency, deficiencies or toxicities of one or more other trace elements, or deficiencies of certain major nutrients such as Ca, Mg, P and K. Studies on the influences of these factors on the tree growth are useful in identifying the mechanisms and the genetic sources of tolerance to acid soil. A series of five culture experiments, under controlled conditions, were carried out using Greek and British Scots (Pinus sylvestris L.) seedlings as well as black pine seedlings of Greek (Pinus nigra Arnold var. nigricans Host) and 'British' (Pinus nigra var. maritima (Ait.) Melville) origin. Nine major and trace elements (N, P, K, Ca, Mg, Fe, Mn, Zn and Cu) were determined in the growth components of pine seedlings. The Mn and Ca requirements of the pine seedlings of all growth components were assessed. Foliar values found for the Mn (ppm) and Ca (%) concentrations associated with 90% of maximum yield were: a) Greek-derived Scots pine: Mn 84-855 and Ca 0.34-1.00, b) British-derived Scots pine: Mn 77-1,450 and Ca 0.43-0.87, c) Austrian pine: Mn *-2,100 and Ca 0.27-*, and d) Corsican pine: Mn *-1,400 and Ca 0.30-0.73 (* denotes not estimated). The results suggested that under conditions of low Ca availability, excessive Mn uptake could result in toxicity in Greek pines and the feed solution Ca/Mn concentration ratio is an important factor in determining the ability of British pines to tolerate adverse Mn conditions. The relative tolerance of Corsican pine to Mn toxicity is related both to immobilisation of Mn in roots by increased Ca uptake, particularly at low solution Ca availability, and to inhibition of Mn translocation from roots to the foliage, while that of British P.sylvestris is associated to its ability to withstand high Mn concentration in shoots. The characteristic nutritional behaviour of Corsican pine (exclusion of some essential elements from the foliage) appeared to be partly responsible for the induced Mg and Fe deficiencies by excess Mn availability. Furthermore, the adverse influence of increasing solution Mn availability on Ca concentration of pine seedlings is dependent on the availability of Ca in the nutrient solution, on the component part analysed, on the genotype and on the experimental conditions. The presence of two absorption mechanisms for Mn and a close functional relationship between Ca and Mn in foliage of seedlings is suggested.