Soil-Induced Manganese Deficiency Modulates Growth, Chlorophyll Stability, Redox Homeostasis, and Mn Partitioning in Maize

Manganese (Mn) deficiency is an increasingly relevant abiotic stress in alkaline, carbonate-rich soils, where limited manganese (Mn2+) availability disrupts plant physiological functions. This study investigated how contrasting oasis soils, collected beneath date palms representing previously characterized Mn nutritional states, including Mn-sufficient, asymptomatic Mn-deficient, and symptomatic brittle leaf disorder (BLD), affect growth, pigment stability, redox metabolism, and Mn allocation in maize (Zea mays L.). A 100-day greenhouse experiment with five sampling dates (20–100 days after sowing [DAS]) assessed shoot and root traits, chlorophyll pigments, hydrogen peroxide (H2O2), peroxidase (POX) activity, and Mn concentrations in soils and tissues. Strong temporal effects (η2 = 0.56–0.91, p < .001) and clear soil-dependent differences were observed. Plants grown in symptomatic Mn-deficient soil showed pronounced stress, including 18–32% reductions in root length, 32–45% declines in chlorophyll a and total chlorophyll, and intensified oxidative pressure, with H2O2 increasing 1.4–1.8-fold and POX activity 45–70% above the Mn-sufficient control. Extractable soil Mn displayed significant Treatment × DAS interactions (η2 = 0.71), and Mn partitioning shifted with deficiency severity. Multivariate analyses distinguished three coherent physiological signatures aligned with soil categories. Overall, maize exhibited rapid and coordinated changes in growth, pigment integrity, redox balance, and Mn homeostasis, supporting its potential as a sensitive bioindicator of soil conditions associated with Mn availability.