Nitrogen Economy and Nitrogen Environmental Interactions in Conifers

Abstract

Efficient acquisition, assimilation and economy of nitrogen are of special importance in trees that must cope with seasonal periods of growth and dormancy over many years. The ability to accumulate nitrogen reserves and to recycle N determine to a great extent the growth and production of forest biomass. The metabolic relevance of two key amino acids, arginine and phenylalanine, as well as other processes potentially involved in the nitrogen economy of conifers are discussed in the current review. During their long life cycles, conifers not only cope with cyclical annual and long-term changes in the environment but also interact with other organisms such as herbivores and symbionts. The interactions of biotic and abiotic factors with conifer nitrogen metabolism will also be outlined in this review.

Inorganic Nitrogen Form Determines Nutrient Allocation and Metabolic Responses in Maritime Pine Seedlings

“…Depending on the species habitat, including climatic and soil conditions, conifers show preferences for the uptake and utilization of ammonium or nitrate [22]. Most of the conifers are tolerant to ammonium [20,30]. In the case of P. pinaster, its growth is higher with ammonium than with nitrate [21], although it is a conifer species with extensive families of nitrate transporters (NPF and NRT2) and transport regulators (NRT3) [28] and also lives in the Western Mediterranean region where climate conditions can promote high nitrification rates in the soil.…”

“…L-arginine is synthesized from L-glutamate and is an amino acid with an important role as an N reserve in pine. This amino acid is very abundant in storage proteins and is an important sink for assimilated N surplus [20,36]. Additionally, the metabolite profile in the roots indicates that the availability of C for metabolic processes was reduced in nitrate-fed seedlings ( Figure 6, Table S1).…”

“…while also conserving these ecosystems. As for all other plants, N is essential for conifer growth [20]. Most conifers prefer ammonium as the main inorganic N form for their growth [10,21,22].…”

“…In some cases, it has become an invasive species, particularly in South Africa [25]. This species grows better with ammonium than with nitrate nutrition [20]. Despite its high phenotypic plasticity and high tolerance to abiotic stresses [26,27], this tree is adapted to live in temperate regions where conditions favor soil nitrification, at least during the warm seasons.…”

Special Issue: Nitrogen Transport and Assimilation in Plants

“…Two review articles [5,6] contain extensive overviews of [4] N assimilation and management, as a function of various environmental cues in conifers and [5] the colonization of plants by AMF. A detailed characterization of two key nitrate transporters in the alga Chlamydomonas reinhardtii (P.A.…”