Nitrogen nutrition and drought hardening exert opposite effects on the stress tolerance of Pinus pinea L. seedlings

Abstract

Functional attributes determine the survival and growth of planted seedlings in reforestation projects. Nitrogen (N) and water are important resources in the cultivation of forest species, which have a strong effect on plant functional traits. We analyzed the influence of N nutrition on drought acclimation of Pinus pinea L. seedlings. Specifically, we addressed if high N fertilization reduces drought and frost tolerance of seedlings and whether drought hardening reverses the effect of high N fertilization on stress tolerance. Seedlings were grown under two N fertilization regimes (6 and 100 mg N per plant) and subjected to three drought-hardening levels (well-watered, moderate and strong hardening). Water relations, gas exchange, frost damage, N concentration and growth at the end of the drought-hardening period, and survival and growth of seedlings under controlled xeric and mesic outplanting conditions were measured. Relative to low-N plants, high-N plants were larger, had higher stomatal conductance (27%), residual transpiration (11%) and new root growth capacity and closed stomata at higher water potential. However, high N fertilization also increased frost damage (24%) and decreased plasmalemma stability to dehydration (9%). Drought hardening reversed to a great extent the reduction in stress tolerance caused by high N fertilization as it decreased frost damage, stomatal conductance and residual transpiration by 21, 31 and 24%, respectively, and increased plasmalemma stability to dehydration (8%). Drought hardening increased tissue non-structural carbohydrates and N concentration, especially in high-fertilized plants. Frost damage was positively related to the stability of plasmalemma to dehydration (r = 0.92) and both traits were negatively related to the concentration of reducing soluble sugars. No differences existed between moderate and strong drought-hardening treatments. Neither N nutrition nor drought hardening had any clear effect on seedling performance under xeric outplanting conditions. However, fertilization increased growth under mesic conditions, whereas drought hardening decreased growth. We conclude that drought hardening and N fertilization applied under typical container nursery operational conditions exert opposite effects on the physiological stress tolerance of P. pinea seedlings. While drought hardening increases overall stress tolerance, N nutrition reduces it and yet has no effect on the drought acclimation capacity of seedlings.

Effect of controlled release fertilizer type and rate on mineral nutrients, non-structural carbohydrates, and field performance of Chinese pine container-grown seedlings

“…Studies with Picea abies L. and Pinus pinea L. seedlings, using low and high fertilization rates, indicated that NSC contents were positively and negatively correlated with fertilization rates, respectively (Kaakinen et al 2004;Villar-Salvador et al 2013). Stored N and NSC are functional attributes, indicative of seedling quality and a substantive body of evidence in the literature concludes that over-fertilization retards N storage (Millard and Grelet 2010;Villar-Salvador et al 2015).…”

Combined pre-hardening and fall fertilization facilitates N storage and field performance of Pinus tabulaeformis seedlings

“…In recent years, there has been a trend to determine nursery fertilization in light of field performance on a specific site condition as well as seedling biomass and nutrient reserves accumulated during nursery growth (Hawkins et al 2005, Heiskanen et al 2009, Oliet et al 2009, Jonsdottir et al 2013, Villar-Salvador et al 2013. For example, in very dry Mediterranean environments some studies showed that seedlings with low nutrient concentration or content performed better (Trubat et al 2008, Cortina et al 2013, whereas other studies indicated that increased tissue nutrient reserves improves seedling field performance (Luis et al 2009, Cuesta et al 2010, Villar-Salvador et al 2012, Oliet et al 2013.…”

Manejo hídrico na rustificação em mudas de Maytenus ilicifolia [(Schrad.) Planch.]

“…O extravasamento de eletrólitos de células é uma reposta isiológica característica em vegetais submetidos aos diferentes tipos de estresse (RÄISÄNEN et al, 2009;VILLAR-SALVADOR et al, 2013;VOLKWEIS et al, 2014). Esse fenômeno é amplamente usado como um indicativo do nível de dano ou da tolerância ao estresse, sendo que menores valores para o extravasamento de eletrólitos indicam a maior integridade das membranas biológicas.…”

“…Alterações na condutância estomática, ajustamento osmótico, assimilação líquida de carbono e redução no crescimento da parte aérea com maior percentual de raízes são algumas evidências em estudos de condicionamento à deiciência hídrica (BAÑON et al, 2006;THOMAS, 2009;VILLAR-SALVADOR et al, 2013). Na produção de mudas por sementes de espécies lenhosas da flora brasileira, a heterogeneidade do crescimento aéreo é corriqueiramente observada dada a variabilidade genética das matrizes assim como o manejo no viveiro, gerando mudas com diferentes padrões de qualidade e onerando a classiicação antevendo a expedição (VOLKWEIS et al, 2014).…”