Drought and salinity: A comparison of their effects on the ammonium‐preferring species Spartina alterniflora

Abstract

Drought and salinity are the most serious environmental factors affecting crop productivity worldwide; hence, it is important to select and develop both salt-and droughttolerant crops. The perennial smooth cordgrass Spartina alterniflora Loisel is unusual in that it is highly salt-tolerant and seems to prefer ammonium (NH 4 + ) over nitrate (NO 3 − ) as an inorganic N source. In this study, we determined whether Spartina's unique preference for NH 4 + enhances performance under salt and drought stress. Greenhouse experiments were conducted to compare the interactive effects of N source, salinity, and low water availability on plant performance (growth and antioxidant metabolism). Drought significantly reduced growth and photosynthetic activity in S. alterniflora, more so with NH 4 + than NO 3 − ; in contrast, NH 4 + enhanced growth under high salinity. The increased tolerance of S. alterniflora to salt stress in the presence of NH 4 + was linked to a high level of antioxidant enzyme activity, combined with low MDA content, EL, and H 2 O 2 production. In contrast, drought stress negated the growth advantages for S. alterniflora exposed to salt stress in the presence of NH 4 + . The susceptibility of S. alterniflora to drought was partly due to reduced antioxidant enzyme activities, thereby reducing the defense against the oxidative damages induced by osmotic stress. In conclusion, in contrast to salt stress, drought stress negates the beneficial effects of ammonium as an N source in the C 4 plant Spartina alterniflora.1 | INTRODUCTION Drought and salinity are the most serious environmental factors affecting crop productivity worldwide (Sabagh et al., 2019). With the scarcity of precipitation and increase in evapotranspiration resulting from global warming and potential climate changes, farmers turn to irrigation practices. However, unplanned and reckless anthropogenic activity in the use of low water quality adds to existing osmotic stresses from other environmental hazards, such as salinity, soil degradation, mineral deficiency, and environmental pollution (Ben Hamed et al., 2013; Hessini et al., 2019a). Studies have shown that about half of existing irrigation systems are under the influence of alkalization, salinization, or waterlogging (Munns, 2002). Munns et al. (2020) defined saline soil as having an ECe above 4 dS m −1 , equivalent to 40 mM NaCl (mainly Na +and Cl − salts), and about twice that for well-drained soil (80 mM NaCl).Such levels would diminish the productivity of most crops (Munns et al., 2020). Likewise, drought is a composite abiotic stress, occurring at any period of plant development to varying degrees (Hessini et al., 2009a;Al-Yasi et al., 2020). Drought can reduce annual crop yields by more than 50% (Boyer, 1982;Farooq et al., 2009). However, in their natural biotope or in farms, plants are unavoidably exposed to multiple stresses, including salinity and drought, which can be more destructive to crop production than a single stress (Ben Hamed et al., 2013;Matthaei and Piggott, 2019). One s...

Salinity Duration Differently Modulates Physiological Parameters and Metabolites Profile in Roots of Two Contrasting Barley Genotypes

“…Thus, recent photosynthates continued to be exported and accumulated into the roots as sucrose, hexoses and starch, contributing to supply carbon skeletons and energy for the synthesis of compatible metabolites. As consequence, in the roots of the wild species at 30 DAS the concentration of proline, GABA and glycine betaine increased, supporting a high RWC, protein synthesis and growth, notwithstanding the decrease of nitrate and potassium [5,26]. This allowed H. maritimum stressed plants to increase sap osmolality, suggesting the development of an active osmotic adjustment [22,62].…”

“…In fact, around 20% of irrigated land worldwide providing one-third of food is affected by salt [4]. Salinity limits plant growth and development by disturbing ions and water uptake, affecting nitrogen metabolism and causing oxidative stress [5,6]. The detrimental impact on plant performance depends on the stage of application, plant species and salinity dose and duration among other [7,8].…”

Drought, Salinity, and Low Nitrogen Differentially Affect the Growth and Nitrogen Metabolism of Sophora japonica (L.) in a Semi-Hydroponic Phenotyping Platform

“…In our study, all three stresses increased the ratios of NH 4 + and NO 3 − with the exception of leaves under salinity ( Figures 3G , H ), which may have been because NH 4 + assimilation requires less energy than NO 3 − ( Guerrero et al, 1981 ). Higher NH 4 + concentrations could promote root growth and enhance stress resistance in plants ( Fernández-Crespo et al, 2014 ; Zhang et al, 2014 ; Ding et al, 2015 ; Meng et al, 2016 ; Miranda et al, 2016 ; Hessini et al, 2020 ). The reasons for the increase in the ratio of NH 4 + and NO 3 − in plants may be increases in NO 3 − assimilation or NH 4 + uptake and reductions in NH 4 + assimilation or NO 3 − uptake.…”

Different Sensitivity Levels of the Photosynthetic Apparatus in Zea mays L. and Sorghum bicolor L. under Salt Stress

“…Changes have been shown in both the donor and acceptor sides of PSII, as well as changes in the PSII heterogeneity with respect to the antenna size [23,24]. The high salt concentrations influence the photosynthetic electron transport chain and decrease the photosynthetic activity [13,16,25]. Moreover, the influence of salt stress has been shown on the interaction between Q A and plastoquinone (PQ), as well as on PSI antenna size [26,27].…”