Sulfate Nutrition Modulates the Oxidative Response against Short-Term Al³⁺-Toxicity Stress in <i>Lolium perenne cv. Jumbo</i> Shoot Tissues

Al³⁺-toxicity in acidic soils is among the main abiotic stress factors that generate adverse effects in plant growth; in leaves, it affects several physiological parameters such as photosynthesis and ROS balance, leading to limited crop production. On the other hand, sulfur is a macronutrient that has a key role against oxidative stress and improves plant growth in acidic soils; however, the implication of sulfate nutritional status in the modulation of short-term Al³⁺-toxicity tolerance mechanisms in plant leaves are barely reported. This study is focused on the role of sulfate on the leaf response of an Al³-sensitive perennial ryegrass (<i>Lolium perenne cv. Jumbo</i>) after 48 h of exposure. <i>Lolium perenne cv. Jumbo</i> seeds were cultivated in hydroponic conditions with modified Taylor Foy solutions supplemented with 120, 240, and 360 μM sulfate in the presence or absence of Al³⁺-toxicity. The <i>L. perenne cv. Jumbo</i> leaves were collected after 48 h of Al³⁺-toxicity exposure and processed to evaluate the effects of sulfate on Al³⁺ toxicity, measuring total proteins, mineral uptake, photosynthesis modulation, and ROS defense mechanism activation. The plants exposed to Al³⁺-toxicity and cultivated with a 240 µM sulfate amendment showed a recovery of total proteins and Ca²⁺ and Mg²⁺ concentration levels and a reduction in TBARS, along with no changes in the chlorophyll A/B ratio, gene expression of proteins related to photosynthesis (Rubisco, ChlAbp, and Fered), or ROS defense mechanism (SOD, APX, GR, and CAT) as compared with their respective controls and the other sulfate conditions (120 and 360 µM). The present study demonstrates that adequate sulfate amendments have a key role in regulating the physiological response against the stress caused by Al³⁺ toxicity.