Effect of Salinity and Nitrogen Sources on the Leaf Quality, Biomass, and Metabolic Responses of Two Ecotypes of Portulaca oleracea

Maria Camalle,Majed Bsoul,Moshe Sagi,Yvonne Ventura,Nidal Bader,Dominic Standing,Aigerim Soltabayeva,Mohammed Jitan,Rana Muhaisen

doi:10.3390/agronomy10050656

Maria Camalle, Majed Bsoul + Show 7 more

Open Access

https://doi.org/10.3390/agronomy10050656

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Abstract

Halophytic plants are, by definition, well adapted to saline soils. However, even halophytes can face nutritional imbalance and the accumulation of high levels of compounds such as oxalic acid (OA), and nitrate (NO3−). These compounds compromise the potential nutritional health benefits associated with salt-tolerant plants such as Portulaca oleracea or Purslane. Purslane has long been known to be a highly nutritious leafy vegetable particularly with respect to high levels of omega-3 fatty acids. Thus, preventing the accumulation of non-nutritional compounds will allow plants to be grown in saline conditions as crops. Two ecotypes (ET and RN) of Portulaca oleracea plants were grown under growth room conditions with two levels of salinity (0, 50 mM NaCl) and three ratios of nitrate: ammonium (0:100%; 33:66%; 25:75% NO3−:NH4+). The results show that both ecotypes, when exposed to elevated NO3−, showed severe leaf chlorosis, high levels of OA, citric acid, and malic acid. Compared to ecotype RN, ecotype ET, exposed to elevated NH4+ concentrations (33% and 75%) and 50 mM NaCl, displayed a marked reduction in OA content, increased total chlorophyll and carotenoid contents, crude protein content, total fatty acid (TFA) and α-Linolenic acid (ALA), enhancing leaf quality. This opens the potential to grow high biomass, low OA P. oleracae crops. Lastly, our experiments suggest that ecotype ET copes with saline conditions and elevated NH4+ through shifts in leaf metabolites.

Highlights

Soil salinity is increasing around the world, especially in arid and semi-arid ecosystems, due to high evaporation and insufficient ion leaching [1]
Plants of ecopyte RN exposed to 75% and 66% NO3 − ammonium under saline conditions showed curling leaves, necrosis on the edges of the leaves, leaf chlorosis and necrotic spotting
The higher levels of total chlorophyll were found in plants grown either with 33% or 75% of ammonium without salinity compared with plants exposed to elevated NO3 − in both ecotypes (Figure 1Aa,Ba)

Summary

Introduction

Soil salinity is increasing around the world, especially in arid and semi-arid ecosystems, due to high evaporation and insufficient ion leaching [1]. An estimated 45 million hectares (20%) of the soils of irrigated agriculture are affected by salinity [2]. Salinity is a significant abiotic stress that can induce physiological, chemical, and molecular changes in plants [3]. Plant physiological processes such as growth are affected by salinity by inhibiting root growth, which, in turn, limits the uptake of water and nutrients [4], leading to water deficiency and nutrient imbalances, causing a shift in the plant growth rate [5]. The use of halophyte species (salt-tolerant plants) could be a promising solution for increasing agricultural production in saline zones [6]

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