Abstract The effects of some short-term temperature regimes on tracheid production and tracheid dimensions of Pinus radiata D.Don plants (both seedlings and rooted cuttings) are described. Plants in low temperatures (day/night: 16°/6°c) produced cells with small diameter initially but, with time, cells with very large diameters were produced. Plants in low temperatures tended to produce cells with thicker walls than those in high temperatures. This difference could be due to the longer time cells spend in the wall-thickening zone in low temperatures, but could also be linked with increased carbohydrate availability. Changes in cell dimensions were not attributable to temperature-induced changes in any one of other variables such as water status and height growth.