MORPHOLOGY AND ROOT GROWTH POTENTIAL OF Pinus patula PRODUCED IN TRAYS WITH ROOT PRUNING

Abstract

Plants grown in trays develop spiraling lateral roots that affect their later growth. The objective of the study was to evaluate root morphology and growth of Pinus patula Schiede ex Schltdl. et Cham. produced in three types of trays with 170 cm³ cavities. Two trays were plastic and one polystyrene, with and without copper coating to prune the plant root. The hypothesis was that the plant produced in trays with 7% Cu(OH)₂ coating would have better root growth than those produced without coating when transplanted to larger containers. The experimental design was completely randomized with a factorial array of 3 × 2 (three types of tray, with and without Cu coating) and four replications per treatment. An additional treatment, a tray designed to air-prune roots, was included to compare the two types of pruning. Statistical differences between treatments were detected with an ANOVA, using the GLM procedure and the Tukey test for comparison of means (p≤0.05). After nine months in the nursery, plants produced in trays with copper coating and those designed for air root pruning developed fewer spiraling lateral roots than those produced in the same trays without this treatment or design (0.1 vs. 3.3 and 0.2 vs. 3.5). Root growth potential test was conducted in 13.2-L pots for 1.5 months. Plants whose roots were pruned, by effect of copper and air, developed higher monthly relative root growth rates than plants whose roots had not been pruned: horizontal (0.28 vs. 0.15 and 0.18 vs. 0.12 g g^-1 per month) and total root growth (0.37 vs. 0.29 and 0.30 vs. 0.25 g g^-1 per month). Plants produced in polystyrene trays had better morphological and root quality traits than plants grown in plastic trays.