Irrigation frequency and salinity levels' impact on biomass production and nutritional value in Sarcocornia fruticosa and Arthrocaulon macrostachyum.

Salinity and water deficit are known to impair biomass production and affect the regulation of physiology and metabolism. The impact of irrigation frequency and salinity levels on biomass production, physiological, and antioxidant responses in Sarcocornia (Megadim ecotype) and Arthrocaulon macrostachyum (AM) was investigated. Plants were subjected to irrigation intervals of 2, 6, and 10 days and salinity levels of 50, 150, and 250mM NaCl for Sarcocornia, and 150 and 250mM for AM. Frequent irrigation significantly increased plants' biomass across salinity treatments, with the highest biomass under 250mM NaCl in AM and at 150 and 250mM in Megadim. Under 6- and 10-day irrigation, 150mM NaCl maintained higher biomass than lower or higher salinity levels. In Megadim, biomass decreased by 28.9-43.8%, 23.1-42.7%, and 37-56.2% at 50, 150, and 250mM NaCl, respectively, under six- and ten-day irrigation. Similarly, AM biomass declined by 32.3-59% at 150mM and 58.1-79.4% at 250mM NaCl. AM showed higher levels of flavonoids, polyphenols, radical-scavenging activity (RSA), oxygen radical absorbance capacity (ORAC), and protein levels, especially with 6-day irrigation. Megadim showed higher polyphenol, RSA, and ORAC under frequent irrigation at 150-250mM NaCl, while flavonoids peaked under 10-day irrigation, and polyphenol, RSA, and ORAC peaked at 50mM NaCl with 6-day irrigation. Photosynthetic pigments, total soluble solids, and electrical conductivity increased under 10-day irrigation, whereas anthocyanins, relative water content, and malondialdehyde were highest under frequent irrigation. Overall, irrigation frequency regulated salinity responses, with frequent irrigation enhancing biomass production and moderate water limitation improving antioxidant capacity.