Legume Nitrogen Utilization Under Drought Stress

Abstract

Legumes, account for around 27% of the world's primary crop production and can be classified based on their use and traits into grain and forage legumes. Legumes can establish symbiosis with N-fixing soil

Nitric Oxide Metabolic Pathway in Drought-Stressed Nodules of Faba Bean (Vicia faba L.)

“…Under DS, the osmolarity increased by about 40% after 4 days of water deprivation and was four-fold increased to reach about 1080 ± 80 mOsm after 10 days. The N-fixation capacity, as measured by ARA, was strongly affected by DS, with 66%, 93%, and >98% inhibition after 4, 8, and 10 days, respectively ( Figure 2 B), confirming the high sensitivity of SNF to DS [ 6 , 24 ]. Over the course of the DS, the color of the nodules changed from pinky white at 0 and 4 days to brown at 8 days, and then to glassy black at 10 days (data not shown), indicating that after 10 days the tissues were strongly degraded.…”

“…It is responsible for 50–70% of crop productivity and yield losses [ 3 , 4 , 5 ]. Due to the importance of water in biological processes, drought stress (DS) affects all stages of plant growth, from germination to maturity, and induces profound disturbances that affect virtually all cellular functions [ 6 , 7 , 8 , 9 ]. DS leads to tissue dehydration and to a drop in water potential, which results in a reduction in cell expansion, cell wall synthesis, and organ growth [ 10 ].…”

“…For crop legumes, symbiotic N 2 fixation provides the plant with the nitrogen it needs without resorting to the use of nitrogen fertilizers. To understand the behavior of crop legumes during environmental stresses and to propose appropriate breeding strategies and agronomic practices, the effects of DS in legumes have been widely investigated in recent years [ 6 , 7 , 14 , 20 ]. Symbiotic N 2 fixation (SNF) is a function particularly sensitive to DS.…”

“…Symbiotic N 2 fixation (SNF) is a function particularly sensitive to DS. Thus, both infection, nodule development, and nodule function are impaired by DS [ 6 , 21 , 22 ], and in nodulated soybean plants, DS was shown to inhibit the SNF process before photosynthesis [ 23 ]. Several hypotheses, which are not mutually exclusive, have been proposed to explain the decline in SNF during drought [ 6 , 24 ]: (1) the local carbon-based feedback inhibition of SNF linked to the inhibition of sucrose synthase and subsequent sucrose accumulation and organic acid depletion in nodules [ 25 , 26 , 27 ]; (2) local nitrogen-based feedback regulation linked to the restriction on the export of nitrogen compounds in nodules and their inhibitory action against N 2 fixation [ 24 , 28 , 29 , 30 ]; (3) nitrogen-based systemic regulation linked to the inhibition of SNF by phloem-delivered nitrogen compounds [ 31 , 32 ]; and (4) a decline in oxygen (O 2 ) availability for bacteroid respiration linked to an increase in nodular O 2 diffusion resistance [ 23 , 33 ].…”

Drought Stress Response in Guar (Cyamopsis tetragonoloba (L.) Taub): Physiological and Molecular Genetic Aspects

“…To meet the plant demand for both amino acid and carbohydrate biosynthesis [79], the assimilation of carbon and nitrogen in irradiated leaves needs to occur simultaneously and in a well-coordinated way, i.e., the relevant metabolic pathways need to be tightly regulated. Thereby, the tissue levels of reduced nicotinamide adenine dinucleotide (NADH) are critical for successful nitrate and ammonia assimilation [80].…”