Morphological and physiological differences in Scots pine seedlings of six seed origins

Abstract

Summary One-year-old seedlings of Scots pine (Pinus sylvestris L.) of four native seed origins (Loch Maree Islands, Glengarry/Glen Morriston, Glen Affric and Abernethy), a commercial British seedlot, and a seedlot from Hedesunda, in middle Sweden, were compared at monthly intervals from October 1993 to April 1994. Seedling morphology, root condition, root frost hardiness and bud dry matter were determined at each date. There were clear morphological differences among seed origins. Seedlings raised from the commercial seedlot (A70) were larger but had a poorer root:shoot ratio than the other seed origins. Of the native pines tested, the Loch Maree Islands origin allocated a larger proportion of its photosynthate to fine roots and needles and smaller proportion to woody structures. Seedlings raised from the commercial British seedlot tended to have poorer bud lignification than the other origins and also, in autumn, higher electrolyte leakage rates from its fine roots. During winter, the Swedish origin had the lowest fine root electrolyte leakage. Seedlings of all origins showed a progressive increase in fine root hardiness towards mid-winter with maximum hardiness (—7°C) in January. Dehardening occurred over subsequent months reaching -3°C in April. Differences among origins were evident. The Swedish seedlot developed greater frost resistance than the other origins, hardening began earlier in autumn and dehardening began later in spring. The commercial seedlot hardened later than the other origins but reached a similar level of frost hardiness by January. Of the native pines, seedlings of the Loch Maree Islands origin were slowest to develop root hardiness.