Germination and Growth of Spinach under Potassium Deficiency and Irrigation with High-Salinity Water

Understanding the salt overly sensitive pathway in Prunus: Identification and characterization of NHX, CIPK, and CBL genes

Salinity is a major abiotic stress factor that can significantly impact crop growth, and productivity. In response to salt stress, the plant Salt Overly Sensitive (SOS) signaling pathway regulates the homeostasis of intracellular sodium ion concentration. The SOS1, SOS2, and SOS3 genes play critical roles in the SOS pathway, which belongs to the members of Na+/H+ exchanger (NHX), CBL-interacting protein kinase (CIPK), and calcineurin B-like (CBL) gene families, respectively. In this study, we performed genome-wide identifications and phylogenetic analyses of NHX, CIPK, and CBL genes in six Rosaceae species: Prunus persica, Prunus dulcis, Prunus mume, Prunus armeniaca, Pyrus ussuriensis × Pyrus communis, and Rosa chinensis. NHX, CIPK, and CBL genes of Arabidopsis thaliana were used as controls for phylogenetic analyses. Our analysis revealed the lineage-specific and adaptive evolutions of Rosaceae genes. Our observations indicated the existence of two primary classes of CIPK genes: those that are intron-rich and those that are intron-less. Intron-rich CIPKs in Rosaceae and Arabidopsis can be traced back to algae CIPKs and CIPKs found in early plants, suggesting that intron-less CIPKs evolved from their intron-rich counterparts. This study identified one gene for each member of the SOS signaling pathway in P. persica: PpSOS1, PpSOS2, and PpSOS3. Gene expression analyses indicated that all three genes of P. persica were expressed in roots and leaves. Yeast two-hybrid-based protein-protein interaction analyses revealed a direct interaction between PpSOS3 and PpSOS2; and between PpSOS2 and PpSOS1C-terminus region. Our findings indicate that the SOS signaling pathway is highly conserved in P. persica.

Physiological and biochemical effects of biochar nanoparticles on spinach exposed to salinity and drought stresses

The utilization of nanobiochar in agricultural practices has garnered substantial interest owing to its promising potential. Its nano-size particles possess an enhanced ability to infiltrate plant cells, potentially instigating biochemical and physiological responses that augment stress tolerance. In our study, we aimed to assess the impact and extent of exogenously applied nanobiochar on the growth dynamics and antioxidative responses in Spinacia oleracea L. (spinach) plants subjected to salt stress (50 mM NaCl) and drought stress (maintained at 60% field capacity) compared with respective controls (0 mM NaCl and 100% field capacity). Following a 15-day exposure to stress conditions, nanobiochar solution (at concentrations of 0, 1, 3, and 5% w/v) was sprayed on spinach plants at weekly intervals (at 14, 21, and 28 days after sowing). The foliar application of nanobiochar markedly improved biomass, net assimilation rate, leaf area, and various other growth parameters under drought and salinity stress conditions. Notably, the application of 3% nanobiochar caused the most significant enhancement in growth traits, photosynthetic pigments, and nutrient content, indicating its efficiency in directly supplying nutrients to the foliage. Furthermore, under drought stress conditions, the application of 3% nanobiochar elicited a notable 62% increase in catalase activity, a two-fold rise in peroxidase activity, and a 128% increase in superoxide dismutase activity compared to the control (without nanobiochar). Additionally, nanobiochar application enhanced membrane stability, evidenced by reduced lipid peroxidation and electrolyte leakage. The foliar application of 3% nanobiochar was found as a promising strategy to significantly enhance spinach growth parameters, nutrient assimilation, and antioxidative defense mechanisms, particularly under conditions of drought and salinity stress.

Foliar Application of Potassium Mitigates Salinity Stress Conditions in Spinach (Spinacia oleracea L.) through Reducing NaCl Toxicity and Enhancing the Activity of Antioxidant Enzymes

Agronomic biofortification is the purposeful utilization of mineral fertilizers to increase the concentration of desired minerals in edible plant parts for enhancing their dietary intake. It is becoming crucial to enhance the dietary intake of K for addressing hidden hunger and related health issues such as cardiac diseases and hypertension. This study was designed to enhance the potassium concentration in edible parts of spinach through its foliar application under saline environment. The salinity levels of electrical conductivity (EC) = 4, 6, and 8 dS m−1 were applied using sodium chloride (NaCl) along with control. The levels of K for foliar sprays were 5 and 10 mM, along with control. The present experiment was performed under two factorial arrangements in a completely randomized design (CRD). After 60 days of sowing, the crop was harvested. Data regarding growth, ionic, physiological, and biochemical parameters, i.e., shoot dry weight, relative water content, electrolyte leakage, total chlorophyll content, tissue sodium (Na) and K concentration, activities of superoxide dismutase (SOD), and catalase (CAT) were recorded and those were found to be significantly (p ≤ 0.05) affected by foliar application of K on spinach under saline conditions. The highest growth, physiological and biochemical responses of spinach were observed in response to foliar-applied K at 10 mM. It is concluded that agronomic bio-fortification by foliar use of K can be a useful strategy to increase tissue K intakes and minimize Na toxicity in the vegetables studied under saline conditions.