Phosphorus deficiency in soils is a major problem for sustainable crop production worldwide. Silicon is a beneficial element that can promote plant growth, development and responses to stresses. However, the effect of silicon on tomato growth, photosynthesis and mineral uptake under phosphorus deficit conditions and underlying mechanisms remain unclear.
Researchers showed that low phosphorus supply inhibited tomato growth as revealed by significantly decreased fresh and dry weights of shoots and impaired root morphological traits. Low phosphorus -induced growth inhibition was associated with decreased photosynthetic pigment content, net photosynthetic rate, stomatal conductance, transpiration rate and water use efficiency.
However, exogenous silicon application alleviated low phosphorus-induced decreases in growth and physiological parameters. In particular, silicon increased photosynthetic rate by 65.2%, leading to a significantly increased biomass accumulation.
Biochemical quantification and in situ visualization of reactive oxygen species (ROS) showed increased ROS (O2−· and H2O2) accumulation under low phosphorus stress, which eventually elevated lipid peroxidation. Interestingly, exogenous Si decreased ROS and malondialdehyde levels by substantially increasing the activity of antioxidant enzymes, including superoxide dismutase, peroxidase, and catalase. In addition, silicon increased concentrations of osmoregulatory substances, such as proline, soluble sugar, soluble proteins, free amino acids, and organic acids under low phosphorus stress.
Analysis of major element concentrations revealed that exogenous silicon application under low phosphorus stress not only increased silicon uptake but also enhanced the concentrations of most essential elements (K, Na, Ca, Mg, Fe, and Mn) in different tissues (roots, leaves, and stems). These results reveal that silicon mitigates low phosphorus stress by improving photosynthetic capacity, antioxidant potential, and nutrient homeostasis and that it can be used for agronomic management of vegetable crops in phosphorus-deficient soils.