Inhibition and recovery of symbiotic N2 fixation by peas (Pisum sativum L.) in response to short-term nitrate exposure

Abstract

The design of more sustainable cropping systems requires increasing N-input from symbiotic N 2 fixation (SNF). However, SNF can be inhibited by nitrate exposure (e.g., soil N-mineralization). Although the effect of nitrate on SNF has been extensively investigated at the cell scale, few studies have highlighted the impact of nitrate exposure on nodule number and biomass, nodule activity of the SNF apparatus or its ability to recover. Pea plants were grown in greenhouse conditions in a N-free nutrient solution and exposed to nitrate (5 mM NO 3 − L −1 ) for one week during either early vegetative growth, flowering or seed filling. After nitrate removal, the plants were grown either under natural light or shade. Nitrate exposure reduced the rate of nodule establishment during vegetative growth, whereas it caused damage to existing nodules when applied during the reproductive stages. Nitrate decreased the specific activity of nodules regardless of the stage of the exposure. After nitrate removal, an extra wave of nodulation was observed on plants grown under natural light but only when nitrate exposure occurred before the seed filling stage. The recovery of SNF activity after nitrate removal depended on the amount of carbon available to nodules.

An RNA Sequencing Transcriptome Analysis Reveals Novel Insights into Molecular Aspects of the Nitrate Impact on the Nodule Activity of Medicago truncatula

“…In addition, there may be a shoot-mediated mechanism of down-regulating nitrogen fixation dependent on a phloem mobile signal reflecting the nitrogen satiety status of the leaves (Naudin et al, 2011). Such a signal might contain nitrogen as nitrogen travels quickly from leaves to nodules (less than 15 min; Fischinger et al, 2006).…”

Differences for traits associated with early N acquisition in a grain legume and early complementarity in grain legume–triticale mixtures

“…Sowing depth was 1.0 cm for lupin and 0.5 cm for triticale. All seeds were then inoculated with Bradyrhizobium lupini at an estimated rate of 10 8 cells per plant to allow for N 2 fixation in lupins (Naudin et al 2011). After seedling emergence, a 1-cm-thick layer of sand was added to the surface of the rhizotron to limit water evaporation from the soil.…”

Selection and Breeding of Suitable Crop Genotypes for Drought and Heat Periods in a Changing Climate: Which Morphological and Physiological Properties Should Be Considered?

“…This ability naturally enhances the nitrogen content in soils and reduces the need for nitrogen fertilizers, which makes their cultivation a sustainable practice in soil fertility maintenance and organic farming [72]. The legumes, such as soybean, common bean, broad bean, pea, chickpea and cowpea are widely cultivated as a valuable nutrition source [73,74] or offer a large potential for sustainable biofuel production [75]. However, the symbiotic relationships are highly vulnerable to extreme environmental conditions [76].…”