Fig 1.
Shoot (A) and root (B) dry weight and root growth rate (C) of rice, maize and onion plants as affected by Si supply.
Data are mean ± s.e., n = 4. Different letters indicate a significant difference between Si treatments of a species; t-test with p < 0.05.
Fig 2.
Silicon concentration in shoot (A) and root (B) of rice, maize and onion plants as affected by Si supply.
Data are mean ± s.e., n = 4. Different letters indicate a significant difference between Si treatments of a species; t-test with p < 0.05.
Fig 3.
Development of Casparian bands (CB) in the exodermis of rice (A), maize (B) and onion (C) roots as affected by Si supply.
Root zone where the formation of CB initiated was defined as root zone A, which was at 0–2 cm drt for rice and onion, and at 2–4 cm drt for maize. Root zone B started 2 cm behind root zone A. Exodermal CB were classified into stages I-IV according to 0, 0–25, 25–50 or > 50% of the length of the anticlinal cell wall with developed CB. n = 4. Different letters indicate significant difference between Si treatments and root sections of a species; cumulative link mixed models with p < 0.05.
Fig 4.
Total, aliphatic and phenolic suberin amounts in the outer cell layers comprising the exodermis of root zone B in rice (A), maize (B) and onion (C) as affected by Si supply.
Amounts were determined via GC-FID. Root zone B was at 4–6 cm drt in rice and onion and at 6–8 cm drt in maize roots. Data are mean ± s.e., n = 4. Different letters indicate a significant difference between Si treatments of a suberin fraction; t-test with p < 0.05. nd = not detected.
Fig 5.
Concentration of lignin and lignin-like polymers in the outer cell layers of the root comprising the exodermis and the sclerenchyma in rice, and the exodermis in maize and onion as affected by Si supply.
Amounts were determined photometrically. Root zone B was at 4–6 cm drt in rice and onion and at 6–8 cm drt in maize roots. Data are mean ± s.e., n = 4. Different letters indicate a significant difference between Si treatments of a plant species; t-test with p < 0.05.
Fig 6.
Distribution of Si in the root zone B of rice (A), maize (B) and onion (C).
The values indicate the relative Si abundance relating to a maximum value of 1.0. Root zone B was at 4–6 cm drt in rice and onion and at 6–8 cm drt in maize roots. Data are mean ± s.e., n = 4. The black bar indicates 100 μm. EX, exodermis; SCL, sclerenchyma; EN, endodermis; CC, central cylinder. The formation of an aerenchyma was observed not only in rice but also in maize roots, which was reported before for well-aerated maize plants [61].