Root- and foliar-applied silicon modifies C: N: P ratio and increases the nutritional efficiency of pre-sprouted sugarcane seedlings under water deficit

Abstract

Water deficit limits the establishment of sugarcane plants from pre-sprouted seedlings (PSS). Silicon (Si) can mitigate such stress, and your supply in plants with the active absorption mechanism is carried out through roots. However, foliar spraying has been practiced to supply Si in PSS production nurseries. Althought it is known that Si via roots can alter C: N: P ratios, nothing has been reported about its supply via foliar spraying, nor whether such changes interfere with structural nutrient use efficiency and with plant physiological responses. Thus, this study aimes to asses whether Si foliar spraying changes C: N: P ratios and increases the nutritional efficiency of PSS, as well as whether water deficiency interferes with such a relationships. For these purposes, three experiments were carried out. In experiment I, treatments consisted of two sugarcane cultivars (CTC 4 and RB 966928) and three Si supply forms (in nutrient solution via roots [SiR], via foliar spraying [SiL], and one control with the absence of Si [-Si]). The same Si supply forms were used in the other two experiments. In experiment II, a short-term water deficit was induced by polyethylene glycol addition to nutrient solution (-0.6 MPa) for three days. In experiment III, a long-term water deficit was imposed using levels of soil water retention capacity (70% [no water deficit], 50% [moderate water deficit], and 30% [severe water deficit] for 30 days. Our findings revealed that Si supply decreased C concentrations regardless of water conditions and that N and P concentrations varied with Si supply form and water deficit level. Moreover, root- and foliar-applied Si modified the C: N: P stoichiometry and increased C use efficiency in PSS, which thus increased N and P use efficiencies. Such an increased nutritional performance helped adjust physiological parameters and increase dry matter yield in PSS, both under water stress and non-stress conditions. Further, Si foliar spraying promoted structural effects on PSS regardless of water conditions, even if sugarcane has an active absorption via roots. In conclusion, foliar spraying can be used to supply Si in PSS production nurseries.

Silicon modifies C:N:P stoichiometry, and increases nutrient use efficiency and productivity of quinoa

“…3 ), suggesting a possible nutrient translocation from the root and stem to this tissue. A similar result was also reported for wheat 5 and sugar cane 35 , where adding Si in the nutrient solution increased P availability in the leaves while Si involvement in the metabolism of C and P was indicated, with subsequent changes in the nutrient stoichiometry and use efficiency. Studies in the literature suggest that Si changes the positive regulation of the expression of transporter genes for P uptake while increasing the exudation rates of organic acids that play a role in improving P uptake and availability 20 .…”

“…The energy cost for incorporating Si in structural compounds is less than the inclusion of C in organic compounds, due to the intrinsic permeability of the lipid bilayers 33 , also contributing to better plant growth. The decreasing C levels in different plant organs have not only been confirmed under normal growing conditions but also in plants grown under abiotic stress conditions, such as salinity 12 , 34 and water deficit 35 , which induces greater energy expenditure by the plant and Si can mitigate this consumption, benefiting these plants.…”

“…The use efficiency of C increased from 0.087 ± 0.003 (Si-0) to 0.120 ± 0.003 (Si-1), 0.154 ± 0.002 (Si-2) and decreased to 0.151 ± 0.00 (Si-3). This result is attributed to higher Si incorporation by the plant tissues that acted mainly in the photosynthetic process instead of replacing the C of the organic compounds 7 , 35 . The supplied Si also affected N use efficiency by increasing biomass production when N concentration in the plant organs was higher as well.…”

Silicon in the Soil–Plant Continuum: Intricate Feedback Mechanisms within Ecosystems

“…However, as N fixation being increased by better P nutrition [ 5 , 390 ] and Si increasing plants’ P nutrition (as shown for grasses, see above), the positive effect of Si on N fixation may be indirectly due to Si increasing plants P nutrition. For sugarcane, no positive effect of Si on P nutrition was found [ 391 ]. In contrast, Xu et al [ 91 ] found no positive effect of Si on N in legumes.…”

“…A large study revealed a negative relationship between Si and N/P ratios for wetland and submerged species and a negative relationship between Si and both C/N and C/P ratios for submerged species [ 289 ]. A study of the effect of Si fertilization on sugarcane found an increase in the C/N ratio by Si for different cultivars and a decrease in the C/P ratio for one cultivar [ 391 ]. A study analyzing grass species in China found an increase in C/N ratio with increasing Si and a decrease in both C/P and N/P ratios with increasing Si [ 393 ].…”