Silicon increases cell wall thickening and lignification in rice (Oryza sativa) root tip under excess Fe nutrition

• Published in: Plant physiology and biochemistry 2019-11, Vol.144, p.264-273
• Main Authors: Mehrabanjoubani, Pooyan, Abdolzadeh, Ahmad, Sadeghipour, Hamid Reza, Aghdasi, Mahnaz, Bagherieh‐Najjar, Mohammad B., Barzegargolchini, Behrouz
• Format: Article
• Language: English
• Subjects: Cell Wall - metabolism; Cell wall thickness; Fe excess; H2O2; Hydrogen Peroxide - metabolism; Iron - metabolism; NADPH oxidase; Oryza - metabolism; Plant Roots - metabolism; Silicon; Silicon - metabolism; SOD
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2019.09.047

Iron (Fe) as a micronutrients and silicon (Si) as a cell wall element are important in plant cell wall extension and integrity. While the interaction of exogenous Si and excess Fe on root cell wall modifications is known, the effects of these nutritional parameters on the spatial changes in the activities of genes and/or enzymes involved in the lignification of root cell walls are not well studied. Thus, these parameters were investigated in the root apical part (AP) and basal part (BP) of rice (Oryza sativa L.) plants supplied with and without Si (1.5 mM) under normal (10 mg/L) and excess Fe (150 mg/L) nutrition for 7 days. Beside growth retardation, excess Fe increased the activities of phenylalanine ammonia lyase (PAL), superoxide dismutase and NADPH–oxidase and PAL and cell wall peroxidase (POD) genes expression, along with the increased phenols and H2O2 contents in the root AP. Furthermore, the increased thickening of endodermal, exodermal and metaxylem cell walls in the root AP by excess Fe was attributed to the enhanced POD activity. POD expression, endodermal and exodermal cell wall thickenings were not affected by excess Fe in the root BP. Si application under excess Fe exaggerated the effects of excess Fe on root cell wall thickening, increased POD activity but reduced H2O2 content in the root AP. Thus, Si application under excess Fe nutrition promotes earlier initiation of lignin polymerization closer to and toward the root tip and hence restricts the entry of excess Fe into the plant. •Interaction of Si and excess Fe on rice root cell wall lignification was studied.•Excess Fe increased PAL and cell wall peroxidase (POD) expression in root apical part.•Cell wall thickening in the root apical part was attributed to POD activity.•Si exaggerated the effects of excess Fe on root cell wall thickening.•Si promoted earlier initiation of lignin polymerization closer to and toward the root tip under excess Fe.