ROOT MORPHOLOGY, GROWTH AND UPTAKE OF PHOSPHORUS AND NITROGEN OF PINUS-RADIATA FAMILIES IN DIFFERENT SOILS

Ten Pinus radiata D. Don families were grown in pots in the glasshouse for 1, 2 and 4 months. The 1- and 2-month-old seedlings were used for P-32 uptake experiments. The 4-month-old seedlings were grown in two different soils, Mt. Buff Sand and Terra Rossa, and their growth, root morphology and P and N uptake were measured. The uptake of P-32 varied significantly between families and seedling age, and between the main root apex and laterals. The uptake by the laterals was significantly greater than that of the main root apex. There were also significant differences in the root morphology of the seedlings used in the P-32 uptake. When the seedlings grew in different soils, both root and shoot growth varied significantly with family and soil. Shoot growth was correlated with root growth in both soils (Mt. Buff Sand, r=0.90; Terra Rossa, r=0.80; combined soils, r=0.92). There were significant differences between the families in the uptake of P and N from different soils and in the efficiency of utilization of these elements. The family which was best in these respects in one soil was not necessarily the best in the other. The Tallaganda Seed Orchard family was the best in growth and efficiency in Mt. Buff Sand and family 80 055 was best in Terra Rossa. The root morphology, as expressed by number of first- and second-order laterals, was correlated to the oven dry weight of plants, and the root oven dry weight was significantly correlated to the uptake of N and P.