ALLOCATION OF DRY MATTER AND CARBON IN Pinus taeda L. SEEDLINGS SUBJECTED TO THIGMOMORPHOGENESIS

Abstract

The present study aimed at quantifying the effects of thigmomorphogenesis induced by stem bending in the hardening phase of seedlings of Pinus taeda L. on the partitioning of dry matter and carbon. Seedlings of Pinus taeda 22 cm high grown in tubes were subjected to five intensities of stem bendings (0, 5, 10, 20 and 40 bendings) performed daily using a mechanical device, for 60 days. Subsequently we quantified the leaf area and the increments in height and diameter. Afterwards, it was determined the increments in dry weight of roots and shoots, which were subdivided into five components: taproot, lateral roots, needles, bark and wood. Along with the resulting dry matter, we determined the carbon concentration and content. The experiment followed a completely randomized design with four replications. The obtained data were subjected to regression analysis at 5% error probability. The thigmomorphogenesis induced by stem bendings resulted in a reduced height growth, leaf area and shoot dry weight, but with up to 20 stem bendings increased the growth rate in diameter and the root dry weight. The changes in primary and secondary growth was a result of the redistribution of carbon and dry matter content in the stem and root system, especially in lateral roots through of reduced leaf area, in terms of area and dry matter. The results suggest that on mechanically disturbed seedlings increase in leaf area ceases to be the preferred sink of carbon, predominating the growth of stem and root.