Species ecology determines the role of nitrogen nutrition in the frost tolerance of pine seedlings

Abstract

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.

Rooting big and deep rapidly: the ecological roots of pine species distribution in southern Europe

“…The spatial segregation of these pine species can be explained in part by their capacity to withstand frost events. Pinus halepensis, P. pinea and to a lesser extent P. pinaster are less frost-tolerant than the high-mountain pines P. sylvestris and P. nigra (Climent et al 2009;Fernández et al 2017;Toca et al 2017). However, the fact that P. sylvestris and P. nigra do not occur at low-altitude locations where summers are dry and hot could be explained by a lower capacity to survive water stress than Mediterranean pines in the early life stages (Salazar-Tortosa et al 2018).…”

Chemical products for crop protection against freezing stress: A review

“…Chemical protection for crops or trees includes the use of different products that can be classified as conventional agrochemicals (e.g. nutrients or fertilizers, such as nitrogen (Scagel et al., 2010; Toca et al., 2018), potassium (Centinari et al., 2016; Ma et al., 2019), and calcium (Marosz & Nogowska, 2018; Vega et al., 1996)), biostimulants or growth regulators (Dwyer et al., 1995; Tsipouridis et al., 2006; Yang et al., 2019), pesticides (Robinson et al., 2015; Tsipouridis et al., 2006), and products whose main objective is to protect the crop or plant against freezing (Anderson, 2012; Francko et al., 2008, 2011; Hernández et al., 2016; Starkutė et al., 2017).…”

“…nitrogen, potassium, and calcium) to protect crops against low‐temperature stress have been evaluated; however, the effectiveness of nutrients has been variable and depends on the kind of nutrient (Table 2). Among evaluated nutrients, nitrogen exhibited a negative or marginal crop protective effect (Scagel et al., 2010; Toca et al., 2018), which is probably ascribable to plants receiving nitrogen at greater doses than required, which increases their growth (biomass and stems) and, consequently, their susceptibility to stress, which decreases their low‐temperature tolerance. This is possible because under nitrogen excess, plants employ non‐structural carbohydrates for their growth, especially under conditions of stress, hence protection gave by those carbohydrate is reduced (Huber & Watson, 1974; Palacio et al., 2007).…”

“…and depends on the kind of nutrient (Table 2). Among evaluated nutrients, nitrogen exhibited a negative or marginal crop protective effect (Scagel et al, 2010;Toca et al, 2018) gave by those carbohydrate is reduced (Huber & Watson, 1974;Palacio et al, 2007).…”

El rol del nitrógeno orgánico en el desarrollo de mecanismos de resistencia a estrés en especies del género Pinus.

“…Sin embargo, las plantas con baja dosis de N, que tuvieron mayores concentraciones de azucares solubles en todas las fechas, no mostraron mayor resistencia al frío (LT50). En este sentido, recientes trabajos no muestran un claro vínculo de los azúcares totales con la tolerancia al frío en distintas especies de pinos mediterráneos (Toca et al, 2018;Fernández-Pérez et al, 2018). Esta discrepancia podría explicarse si sólo algunos de los azúcares u otros compuestos estuvie-Figura 5.…”