Silicon induced Fe deficiency affects Fe, Mn, Cu and Zn distribution in rice (Oryza sativa L.) growth in calcareous conditions

Abstract

A protective effect by silicon in the amelioration of iron chlorosis has recently been proved for Strategy 1 species,

at acidic pH. However in calcareous conditions, the Si effect on Fe acquisition and distribution is still unknown.

In this work, the effect of Si on Fe, Mn, Cu and Zn distribution was studied in rice (Strategy 2 species) under Fe

sufficiency and deficiency. Plants (+Si or-Si) were grown initially with Fe, and then Fe was removed from the

nutrient solution. The plants were then analysed using a combined approach including LA-ICP-MS images for

each element of interest, the analysis of the Fe and Si concentration at different cell layers of root and leaf cross

sections by SEM-EDX, and determining the apoplastic Fe, total micronutrient concentration and oxidative stress

indexes. A different Si effect was observed depending on plant Fe status. Under Fe sufficiency, Si supply in creased Fe root plaque formation, decreasing Fe concentration inside the root and increasing the oxidative stress

in the plants. Therefore, Fe acquisition strategies were activated, and Fe translocation rate to the aerial parts was

increased, even under an optimal Fe supply. Under Fe deficiency, +Si plants absorbed Fe from the plaque more

rapidly than –Si plants, due to the previous activation of Fe deficiency strategies during the growing period

(+Fe + Si). Higher Fe plaque formation due to Si supply during the growing period reduced Fe uptake and

could activate Fe deficiency strategies in rice, making it more efficient against Fe chlorosis alterations. Silicon

influenced Mn and Cu distribution in root.