Preference of Silicon Accumulation on the Shade Foliage of Tree Crown and its Implication in Juniperus chinensis L.

Purpose The passive accumulation of silicon (Si) generally depends on the regulation of plant transpiration rates after its uptake. It is challenging to comprehend how plants use Si to adapt to shady habitats where they have low transpiration rates and photothermal energy. Therefore, we speculated that Si accumulation is not entirely dependent on the transpiration rate.Methods To test this speculation, the concentrations of Si and total minerals and water status at various positions of shady shoots (stems and their foliage) and stems within the crown of Juniperus chinensis L. were examined to determine whether shady shoots or stems had a preferred allocation to resist shade.Results The concentrations of total minerals and Si in the shoots were consistently higher in shady areas than in areas within the same crown, regardless of the position within the crown or shoot age. However, shoot Si accumulation displayed a greater dependence on available light or photothermal supply, which is linked to crown orientation. Additionally, stem Si accumulation displayed a weak dependence on available light. Compared with the bound water content, the water potential and free water content of shady shoots were higher than those of sunny shoots. In light of the fact that water prefers to move readily towards regions with low water potential, these results demonstrate that the movement of minerals and water is not fully coupled in the same crowns.Conclusion Therefore, the accumulation of Si and minerals in shady foliage is partially independent of water flow, which helps to offset the low-carbon supply due to the photothermal decrease in the shady crown area.