Silicon accumulation and distribution in petunia and sunflower grown in a rice hull-amended substrate

Authors: Boldt, Jennifer; Locke, James; Altland, James

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2017
Publication Date: 5/25/2018
Citation: Boldt, J.K., Locke, J.C., Altland, J.E. 2018. Silicon accumulation and distribution in petunia and sunflower grown in a rice hull-amended substrate. HortScience. 53:698-703. https://doi.org/10.21273/HORTSCI12325-17.
DOI: https://doi.org/10.21273/HORTSCI12325-17

Interpretive Summary: Silicon (Si) is a plant beneficial element associated with mitigation of abiotic and biotic stresses (e.g., high or low temperatures, salt stress, nutrient deficiency or toxicity, drought, insects, or fungal pathogens). Plants are classified as low-Si or high-Si accumulators based on foliar Si concentration, and as such, most greenhouse-grown ornamentals are considered low-Si accumulators. However, Si accumulates throughout the plant, and plants with low foliar Si may accumulate high concentrations of Si in other tissues. There is little published data on the distribution of Si in plants, and this knowledge will be useful in using Si to mitigate tissue-specific plant stresses. We quantified Si accumulation and distribution in petunia ‘Dreams Pink’ (a low-Si accumulator) and sunflower ‘Pacino Gold’ (a high-Si accumulator). We grew the plants with or without Si, and it was supplied by amending the growing medium with rice hulls (20% of the total volume). We determined that the Si concentration in sunflower was greatest in the leaves, and the roots, stems, and flowers had similar concentrations of Si; in petunia, however the roots accumulated more Si than the stems or flowers, but less than the leaves. Also, we the Si concentration in sunflowers increased more than 5-fold in all of the plant tissues when they were grown in a rice hull-amended growing medium, but in petunia it only increased substantially in the roots. This is one of the first reports to provide Si accumulation in roots, stems, and flowers, as well as leaves, of greenhouse-grown ornamentals. Also, it shows that classifying a species as a low- or high-Si accumulator solely on the basis of foliar concentration does not necessarily provide a complete picture of total plant Si accumulation and uptake capacity.

Technical Abstract: Silicon (Si) is a plant beneficial element associated with mitigation of abiotic and biotic stresses. Most greenhouse-grown ornamentals are considered low Si accumulators based on foliar Si concentration. However, Si accumulates in all tissues, and there is little published data on the distribution of Si in plants. This knowledge may be critical to using Si to mitigate tissue-specific plant stresses, e.g., pathogens. Therefore, we quantified Si accumulation and distribution in petunia (Petunia ×hybrida Hort. Vilm.-Andr. ‘Dreams Pink’), a low-Si accumulator, and sunflower (Helianthus annuus L. ‘Pacino Gold’), a high-Si accumulator. Plants were grown in a sphagnum peatmoss : perlite substrate amended with 0% (-Si) or 20% (+Si) parboiled rice hulls. Aboveground dry mass was greater in non-amended petunia (13%) and sunflower (18%), compared to rice-hull amended plants, but days to flower was unaffected. Sunflowers grown in the rice-hull amended substrate had the greatest Si concentration (10,909 mg/kg) in leaves, while roots (895 mg/kg), stems (303 mg/kg), and flowers (252 mg/kg) had lower, but similar, Si concentrations. In petunia, Si concentration was greatest in leaves (2,036 mg/kg), then roots (1237 mg/kg), followed by stems (301 mg/kg) and flowers (247 mg/kg). The addition of rice hulls to the substrate increased Si concentration in sunflower 5.1-fold in roots, 6.1-fold in flowers, 7.1-fold in stems, and 8.6-fold in leaves. In contrast, Si concentration in petunia increased only 1.1-fold in flowers and 2.1-fold in leaves and stems, but increased 7.9-fold in roots. In rice hull-amended sunflower, the distribution of Si was 91% in leaves, 3% in stems, 3% in roots, and 3% in flowers, and in petunia, it was 72% in leaves, 17% in stems, 6% in roots, and 5% in flowers.