Variable P supply affects N metabolism in a legume tree, Virgilia divaricata, from nutrient-poor Mediterranean-type ecosystems

Abstract

Virgilia divaricata is an indigenous forest margin legume growing in nutrient richer soils, but it is also known to invade the N and P poorer soils of the mature fynbos.This implies that the legume has a functional tolerance for variable soil N and P levels. It is not known how the legume utilizes inorganic N from soil and atmospheric sources under variable P supply. Moreover, very little is known about how P deficiency affects root nodule metabolic functioning of V. divaricata and their associated energy costs of N assimilation. Therefore the aim of this study was to determine whether the P deficiency affects the metabolic status of root and nodules and the consequent impact on the routes of N assimilation in a Fynbos legume, V. divaricata. Our results show that V. divaricata had a reduced biomass, plant P concentration and BNF during P deficiency. Based on the adenylates data, P stressed nodules maintained their P status better than P stressed roots. Furthermore V. divaricata was able to alter C and N metabolism in different ways in roots and nodules, in response to P stress. For both roots and nodules, this was achieved via internal cycling of P, by possible replacement of membrane phospholipids with sulpholipids and galactolipids and increased reliance on the PPi-dependant metabolism of sucrose via UDPG and to Fru-6-P. P stressed roots exported mostly ureides as organic N and recycled amino acids via deamination glutamate dehydrogenase (GDH). In contrast, P stressed nodules largely exported amino acids.Compared to roots, the nodules showed a greater degree of P conservation during low P supply, this resulted in the roots and nodules of V. divaricata, metabolising N differently during P stress, this meaning that these organs may contribute differently to the success of this plant in soils ranging from forest to fynbos.

Adaptation of the symbiotic Mesorhizobium –chickpea relationship to phosphate deficiency relies on reprogramming of whole-plant metabolism

“…S3 and Dataset S2). Our results confirmed the role of NADH-GDH in detoxification of NH 4 + and also, the supply of glutamate for glutamine synthesis (42).…”

Phosphorus and Nitrogen Modulate Plant Performance in Shrubby Legumes from the Iberian Peninsula

“…In the four species, in the water treatment, the greatest number of nodules was observed in the Inoc + low P treatment and the highest N accumulation occurred in the Inoc + high P plants (Figure 5), which coincides with a peak in plant biomass production in the four species (Figure 1). However, in the water-stressed plants, N and P accumulation did not differ between Inoc + high P and Inoc + low P and that can only be explained by a more efficient nodulation in the water-stressed plants following the same pattern as in other leguminous species [4,34,35,36,37]. This behavior has been already described in other species in the Genistea family under several stresses [38,39].…”

Roots and Nodules Response Differently to P Starvation in the Mediterranean-Type Legume Virgilia divaricata

“…It was shown that nitrate impacts negatively on Rhizobium -infection as well as on the ratio of the nodule dry mass to the whole plant mass (Luciñski et al, 2002). As BNF is a costly process, it may be more beneficial for legumes from low nutrient ecosystems to take up N via its roots and to reduce energetically costly BNF (Magadlela et al, 2015). Similar trends were also observed in white clover where N concentration was unaffected by P deficiency.…”