TREE ROOT ARCHITECTURE, ROOT DYNAMICS AND RHIZOSPHERE PROCESSES

Lead scientists: M. Toselli, G. Tonon , M. Tagliavini, B. Marangoni and A.D. Rombolà

Co-workers: L. Cantoni, F. Ponti, E. Baldi, D. Malaguti, G. Marcolini, M. Quartieri

Introduction: Improving tree root efficiency is an important goal for sustainable management of plantations. Besides having marked influence on fruit quality, water and nutrient supplies are increasingly found at sub-optimal levels, whereas the root system needs conditions for optimal uptake. The knowledge of root architecture can provide information on the most appropriate way to place water and nutrients. Root architecture and physiology are quite difficult to study and it is often necessary to develop new approaches, including the use of stable isotopes. Changes in rhizosphere pH have important consequences on soil-plant relationships, including effects on the availability of such nutrients as P, Fe, Mn, Cu and Al.

Aims: The research focuses on root architecture, root spatial distribution and development through the soil profile as affected by genotype and soil conditions; seasonal root growth, root turnover and rhizodeposition, and the effects of root activity on the rhizosphere environment.

Results: Root excavations of mature peach and apricot trees on different rootstocks and subjected to several irrigation regimes were carried out. Underneath a 1-m wide tree row almost all the roots were recovered. When water and nutrients were localized by dip irrigation higher root density was promoted in the soil surrounding the emitters. Quantification of C fluxes and nutrients from the roots to the soil are approached by following the changes over time occurring in soil 15N and 13C abundance. Both studies using natural abundance and enriched material are being conducted. Rhizosphere pH in alkaline and calcareous soils was always lower than that in bulk soil, but the form of nitrogen nutrition affects rhizosphere pH, which is generally higher when plants are supplied with NO3--N than with NH4+-N. Localization of key enzyme activity indicates that Fe reductase takes place preferentially in root tips.

Publications
Tagliavini, M., Masia, A. and M. 1995. Quartieri. Bulk soil pH and rhizosphere pH of peach trees in calcareous and alkaline soils as affected by the form of nitrogen fertilizers. Plant and Soil, 176(2): 263-271.
Tagliavini, M., Neilsen, D., Hogue, E.G. and Neilsen, G.H. 1997. Effects of nitrogen- fertilizer form on rhizosphere pH and growth of apple in soils with different soil buffer capacity capacity. Acta Horticulturae, 448: 297-302.
Govi, G., Toselli, M., Gaspari, N. and Scudellari, D. 1996. Effetti dell'irrigazione localizzata sull'apparato radicale dell'albicocco, Irrigazione e Drenaggio, 43(4): 13-19.
Marangoni, B. and Toselli, M. 2000. "La radice delle dicotiledoni arboree". In "Obiettivo radice. Metodi di studio e risultati ottenuti in ambiente mediterraneo", a cura di G. Mosca e T. Vamerali, p. 13-19. Consiglio Nazionale delle Ricerche, CLUEP, Padova.
Marangoni, B., Toselli, M. and Amato, M. 2000. "Accrescimento ponderale e rapporto 'parte aerea/parte radicale'. In "Obiettivo radice. Metodi di studio e risultati ottenuti in ambiente mediterraneo", a cura di G. Mosca e T. Vamerali, p. 73-75. Consiglio Nazionale delle Ricerche, CLEUP, Padova.