Silicon absorption, partitioning, chlorophyll fluorescence, and gas exchange in passion fruit seedlings fertilized with different silicon sources

The objective of this work was to evaluate the effect of fertilization with different sources of silicon on key physiological traits and the pattern of absorption and distribution of the silicon element in passion fruit seedlings. A randomized block design was used with eight treatments (control; Agrosilicon Plus®; pure silicic acid; pure silicic acid + calcium oxide; pure silicic acid + magnesium oxide; pure silicic acid + calcium oxide + magnesium oxide; calcium oxide; magnesium oxide) x four replications and two pots per plot. Quantum yield of photosystem II, photosynthetic index, stomatal conductance, transpiration rate and water use efficiency were assessed. Moreover, the contents of Si in shoot, roots and soil, as well as its absorption efficiency and distribution within plants were evaluated. Although the supplementation with pure silicic acid reduced net photosynthetic rates and transpiration, the other physiological traits were not significantly changed when compared to the control. In addition, higher silicon content was found in both shoots and root system of plants treated with pure silicic acid. Silicon sources altered silicon accumulation patterns, with greater root accumulation under pure silicic acid, indicating limited internal distribution under the evaluated conditions.