Silicon Compensates Phosphorus Deficit-Induced Growth Inhibition by Improving Photosynthetic Capacity, Antioxidant Potential, and Nutrient Homeostasis in Tomato

Abstract

Phosphorus (P) deficiency in soils is a major problem for sustainable crop production worldwide. Silicon (Si) is a beneficial element that can promote plant growth, development and responses to stresses. However, the effect of Si on tomato (Solanum lycopersicum L.) growth, photosynthesis and mineral uptake under P deficit conditions and underlying mechanisms remain unclear. Here, we showed that low P (LP) supply inhibited tomato growth as revealed by significantly decreased fresh and dry weights of shoots and impaired root morphological traits. LP-induced growth inhibition was associated with decreased photosynthetic pigment content, net photosynthetic rate (Pn), stomatal conductance, transpiration rate and water use efficiency. However, exogenous Si application alleviated LP-induced decreases in growth and physiological parameters. In particular, Si increased Pn 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 LP 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, Si increased concentrations of osmoregulatory substances, such as proline, soluble sugar, soluble proteins, free amino acids, and organic acids under LP stress. Analysis of major element concentrations revealed that exogenous Si application under LP stress not only increased Si 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 Si mitigates LP stress by improving photosynthetic capacity, antioxidant potential, and nutrient homeostasis and that it can be used for agronomic management of vegetable crops in P-deficient soils.

Phosphorus (P) use efficiency in rice is linked to tissue-specific biomass and P allocation patterns

“…Organic pools of P in plant tissues mainly exist as nucleic acids, phospholipids, phosphorylated proteins and P-ester metabolites 15 . Under P deficiency, phospholipids have greater potential to serve as an alternate source of P which remobilizes towards young growing plant tissues 46 . This phenomenon of replacing phospholipids in cell membranes with sulfolipids and galactolipids is known as membrane-lipid remodeling 43 .…”

The Halotolerant Rhizobacterium—Pseudomonas koreensis MU2 Enhances Inorganic Silicon and Phosphorus Use Efficiency and Augments Salt Stress Tolerance in Soybean (Glycine max L.)

“…The judicious application of silicon, phosphorus, and plant growth promoting rhizobacteria is considered pivotal in the mitigation of such abiotic stresses [ 43 ]. It has been reported that Si maintains plant strength through the regulation of the internal physiology [ 50 ] and compensating P deficiencies in plants [ 51 ]. It has also been reported that PGPB engineers the root system of plants, thereby facilitating nutrient uptake [ 52 ].…”

Role of Silicon in Mediating Phosphorus Imbalance in Plants

“…Excess-P stress is also observed in some greenhouse soils subjected to heavy application of P fertilizer or in hydroponic culture where a high P concentration is supplied [ 9 ]. The beneficial effect of Si on P deficiency or excess stress has been reported for a number of plant species [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. To the best of our knowledge, however, no review has discussed the roles and mechanisms of Si in alleviating P-imbalance stress in plants.…”