Forest Ecology and Restoration Group, Departamento de Ciencias de la Vida, Apdo 20, Universidad de Alcalá, E-28805, Alcalá de Henares, Madrid, Spain.
Hardwood Tree Improvement and Regeneration Center, Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA.
Tree Physiol. 2018 Jan 1;38(1):96-108. doi: 10.1093/treephys/tpx165.
Frost determines the evolution and distribution of plants in temperate and cold regions. Several environmental factors can influence frost acclimation of woody plants but the magnitude and direction of the effect of nitrogen (N) availability is controversial. We studied the effect of N availability on root and shoot frost tolerance in mid-fall and in winter in seedlings of four pines of contrasting ecology: Pinus nigra J.F. Arnold, P. pinaster Ait., P. pinea L. and P. halepensis Mill.. Organ N and soluble sugar concentration, and timing of cessation of shoot elongation were measured to assess the physiological mechanisms underlying frost acclimation. Nitrogen was supplied at high and low rates only during the pre-hardening period and at a moderate N rate during hardening in the fall. Shoot frost tolerance increased over winter while root frost tolerance did not change in any species. Pre-hardening N availability affected the frost tolerance of both roots and shoots, although the effect was species-specific: high N reduced the overall root and shoot frost tolerance in P. pinea and P. halepensis, and increased the frost tolerance in P. nigra, but had no effect in P. pinaster. Nitrogen supply in the fall consistently increased frost tolerance in all species. Differences in frost tolerance among species and N treatments were not explained by variations in organ N or soluble carbohydrate concentration, nor by timing of cessation of shoot elongation; however, the most frost tolerant species ceased elongation earlier than the least frost tolerant species. Despite the close phylogenetic relatedness of the studied species, the effect of N availability on seedling frost tolerance differed among species, indicating that species ecology (especially frost acclimation physiology) and timing of N supply drives the effect of N availability on frost tolerance of pine species.
霜决定了温带和寒带地区植物的进化和分布。有几个环境因素可以影响木本植物的抗霜性，但氮（N）供应的影响程度和方向存在争议。我们研究了 N 供应对四个不同生态松树（黑松 J.F. Arnold、欧洲赤松 Ait.、地中海松 L. 和欧洲山松 Mill.）幼苗秋季和冬季根和茎抗寒性的影响。为了评估抗霜性的生理机制，我们测量了器官 N 和可溶性糖浓度以及茎伸长停止的时间。仅在预硬化期间以高和低的速率提供氮，而在秋季硬化期间以中等 N 速率提供氮。冬季茎的抗寒性增加，而在任何物种中，根的抗寒性都没有变化。预硬化氮供应影响根和茎的抗寒性，尽管影响是特定于物种的：高氮降低了 P. pinea 和 P. halepensis 的整体根和茎的抗寒性，增加了 P. nigra 的抗寒性，但对 P. pinaster 没有影响。秋季氮供应一致增加了所有物种的抗寒性。物种和 N 处理之间抗寒性的差异不能用器官 N 或可溶性碳水化合物浓度的变化来解释，也不能用茎伸长停止的时间来解释；然而，最耐寒的物种比最不耐寒的物种更早停止伸长。尽管研究物种具有密切的系统发育关系，但 N 供应对幼苗抗寒性的影响在物种之间存在差异，表明物种的生态（尤其是抗霜性生理）和 N 供应的时间驱动了 N 供应对松树种抗寒性的影响。
