Compared root system architectures in seedlings and in vitro plantlets of Hevea brasiliensis, in the initial years of growth in the field

In vitro culture of Hevea was undertaken to propagate selected clones on th eir own roots. The challenge was to overcome the failure of cuttings due to the poor conformity of regenerated root systems. Trees of several juvenile or mature genotypes were propagated either by in vitro microcutting, or by somatic embryogenesis, and planted in the field. Certain static and dynami c components of the root system were observed at different growth stages, f rom 0 to 3 years, and compared to those of seedlings of the same age used i n the trial as a reference. A simple method was designed for measuring the vigour and balance of the root system. The in vitro plantlets had a well-de veloped taproot and lateral root system, with an architecture similar to th at of plants obtained from seed. Moreover, clear differences occurred betwe en selected clones for the relative vigour of the tap roots, lateral roots and trunk.