Preference of Silicon Accumulation on the Shaded Foliage of Tree Crowns and its Implications for Juniperus chinensis L

Abstract

Abstract The passive accumulation of silicon (Si) generally depends on the regulation of plant transpiration rates. It is challenging to comprehend how plants use Si to adapt to shaded habitats where they have low transpiration rates. Therefore, we hypothesized that Si accumulation is partly due to physiological demand rather than being entirely dependent on transpiration regulation. To test this hypothesis, the concentrations of Si and total minerals at various positions of shaded foliage and branches within the crowns of Juniperus chinensis L. trees were examined to determine whether shaded foliage and branch had a physiological demand allocation to resist shade. The concentrations of total minerals and Si in the foliage were consistently higher in shaded areas than in sunny areas within the same crown, regardless of the position within the crown or foliar age. However, foliar Si accumulation displayed more dependent on available light, which is linked to crown orientation. Additionally, branch Si accumulation displayed a weak dependence on the available light. These results suggested that Si, an energy-saving element that supplements cell walls, could also supplement carbon-based components in photosynthetic organs to balance energy limitations in shaded habitats. Thus, the high Si accumulation in shaded foliage, not in shaded branches, was explained by the physiological demand to make up for the decreased energy supply caused by shade.