Frost Hardiness of Nutrient-loaded Two-Year-Old Picea Abies Seedlings in Autumn and at the End of Freezer Storage

The effects of nutrient loading (NLOAD) on the frost hardening and dehardening of Picea abies (L.) Karst. seedlings were investigated under nursery conditions. Before NLOAD. second-year container seedlings were either short-day (SD) treated for 3 weeks in July or left for the natural photoperiod (CO). By mid-September. after 5 weeks of NLOAD. the fertilization of three foliar nutrient concentration levels (low = L-SD, medium = M-SD, and high = H-SD) for the SO-treated seedlings and one (medium = MCO) for the CO-seedlings was completed. The NLOAD resulted in foliar nitrogen concentration 10.6, 16.1. 223. and 17.5 g kg-1 for L-SD, M-SD, H-SD and M-CO seedlings, respectively. The NLOAD had no effects on the morphology or dry mass variables of the seedlings, while SO-treatment reduced the dry mass of shoots. but not that of roots. The frost hardiness (FH) of different batches of the seedlings was assessed by the visual scoring of damage in their needles. stems and buds after their controlled exposure to freezing during frost hardening and dehardening. The low nutrient concentration in the SO-treated seedlings (L-SD seedlings) resulted in poor FH, to an even lower extent than that of theMCO seedlings. The NLOAD did not affect the dehardening of the seedlings at the end of the freezer storage in the following spring. Keywords Frost hardiness · Morphology · Nitrogen · Norway spruce · Short day treatment

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Author(s): Jaana Luoranen, M. Lahti, Risto Rikala

Section: Seedling Physiology and Morphology

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