Silicon uptake by wheat: Effects of Si pools and pH

Abstract

Silicon (Si), although not considered essential, has beneficial effects on plant growth which are mostly associated with the ability to accumulate amorphous (phytogenic) Si, e.g., as phytoliths. Phytogenic Si is the most active Si pool in the soil-plant system because of its great surface-tovolume ratio, amorphous structure, and high water solubility. Despite the high abundance of Si in terrestrial biogeosystems and its importance, e.g., for the global C cycle, little is known about Si fluxes between soil and plants and Si pools used by plants. This study aims at elucidating the contribution of various soil Si pools to Si uptake by wheat. As pH affects dissolution of Si pools and Si uptake by plants, the effect of pH (4.5 and 7) was evaluated. Wheat was grown on Si-free pellets mixed with one of the following Si pools: quartz sand (crystalline), anorthite powder (crystalline), or silica gel (amorphous). Silicon content was measured in aboveground biomass, roots, and soil solution 4 times in intervals of 7 d. At pH 4.5, plants grew best on anorthite, but pH did not significantly affect Si-uptake rates. Total Si contents in plant biomass were significantly higher in the silica-gel treatment compared to all other treatments, with up to 26 mg g -1 in aboveground biomass and up to 17 mg g -1 in roots. Thus, Si uptake depends on the conversion of Si into plant-available silicic acid. This conversion occurs too slowly for crystalline Si phases, therefore Si uptake from treatments with quartz sand and anorthite did not differ from the control. For plants grown on silica gel, real Si-uptake rates were higher than the theoretical value calculated based on water transpiration. This implies that Si uptake by wheat is driven not only by passive water flux but also by active transporters, depending on Si concentration in the aqueous phase, thus on type of Si pool. These results show that Si uptake by plants as well as plant growth are significantly affected by the type of Si pool and factors controlling its solubility.

Release of Silicon From Silicate Materials and Its Uptake by Rice Plant

“…As Si accumulates at the places of respiratory water losses and consequently Si concentrates in the leaves (Gocke et al 2013), thus we analyze Si concentration in above ground biomass. The effect of JSG and steel slag on increasing Si uptake is presented in Figure 5.…”

Plant Silicon and Phytolith Contents as Affected by Water Availability and Herbivory: Integrating Laboratory Experimentation and Natural Habitat Studies

“…High water availability and transpiration are expected to promote Si uptake and deposition, since plants take up Si from the soil and mobilise it within the plant through their internal water stream in the form of monosilicic acid (H 4 O 4 Si) [5][6][7][8]. However, species that grow in arid environments may employ various mechanisms to reduce water losses or to otherwise cope with low water availability [9].…”

“…In our literature search for papers on the effects of water availability and herbivory on plant Si accumulation, we found that out of 165 relevant papers, only 12 report results of studies conducted in natural habitats, suggesting that relatively little is known about long-term effects of a multitude of environmental variables on Si uptake and accumulation and their significance in plant ecology. This imbalance is problematic because laboratory and field experimentation often control soil or growth medium properties that affect water and Si availability [2][3][4][5], but such controls are unrealistic in nature. Laboratory and field experiments provide important understanding of physiological processes and functions of various plant components and how trait values change in response to manipulations, but do not always properly reflect the natural reality in which plants have evolved over the centuries.…”

Acidity neutralization and silicon availability using calcium silicate in soil cultivated with wheat (Triticum aestivum L.)

“…Lima Filho and Tsai (2007) and Zanão Júnior et al (2010) also observed greater Si absorption by wheat when fertilized with this element. According to Lima Filho and Tsai (2007), wheat is highly efficient in absorbing Si, becoming bigger in soils with high content of this element, and it is regarded as a Si accumulating plant (Gocke et al, 2013). Data demonstrate that wheat absorbed this element and, along with other factors, it has led to improved plant growth, resulting in a more efficient grain yield.…”

“…Si is not regarded as a crucial element for plants, because it is dispensable for their life cycle (Gocke et al, 2013). However, it is seen as a beneficial element, due to the fact that it is related to increased resistance to attack by pests and diseases; it also improves absorption and use of nutrients and decreases the stress caused by toxicity or deficiency of some elements (Ma and Yamaji, 2008;Tripathi et al, 2014).…”