Planting performance potential of Pinus sylvestris seedlings as evaluated by root growth capacity and triphenyl tetrazolium chloride reduction methods

Root growth capacity (RGC) and root viability by the reduction of triphenyl tetrazolium chloride (TTC) of Scots pine (Pinus sylvestris L.) seedlings were measured in the winter and spring after freeze‐induced stress (0, ‐10, ‐15, ‐20°C). After freezing, seedlings were also stressed with different storage temperatures, and drying. Field performance during two years at two sites was used to determine the prediction abilities of the two test methods. RGC and TTC differed between the winter and spring tests. Coefficients of variation (CV) for RGC were larger in the winter than in the spring. The opposite applied for TTC. RGC was significantly lower in the winter than in the spring. TTC reduction was lower in the spring than in the winter. RGC‐ and TTC‐values decreased as freezing temperatures were lowered. Correlation coefficients between treatment means of RGC and TTC were low. Coefficients of determination (r ²) of linear regressions of RGC to the field performance attributes, first and second year diameter increment, height increment, and survival, were between 0.30 and 0.40. For TTC the revalues ranged from 0.50 to 0.80. In general, the TTC‐method seemed to be a better indicator of Scots pine seedling performance in the field.