Silicon-Induced Changes in Viscoelastic Properties of Sorghum Root Cell Walls

Abstract

;Silicon is deposited in the endodermal tissue in sorghum (Sorghum bicolor L. Moench) roots. Its deposition is thought to protect vascular tissues in the stele against invasion by parasites and drying soil via hardening of endodermal cells. We studied the silicon-induced changes in mechanical properties of cell walls to clarify the role of silicon in sorghum root. Sorghum seedlings were grown in nutrient solution with or without silicon. The mechanical properties of cell walls were measured in three separated root zones: basal, apical and subapical. Silicon treatment decreased cell-wall extensibility in the basal zone of isolated stele tissues covered by endodermal inner tangential walls. The silicon-induced hardening of cell walls was also measured with increases in elastic moduli (E) and viscosity coefficients (h). These results provided new evidence that silicon deposition might protect the stele as a mechanical barrier by hardening the cell walls of stele and endodermal tissues. In contrast to the basal zone, silicon treatment increased cell-wall extensibility in the apical and subapical zones with concomitant decrease in E and h. Simultaneously, silicon promoted root elongation. When root elongation is promoted by silicon, one of the causal factors maybe the silicon-enhanced extensibility of cell walls in the growing zone.

Effect of salinity and silicon on root characteristics, growth, water status, proline content and ion accumulation of purslane (Portulaca oleraceaL.)

“…Hattori et al (2003) also reported that Si promoted root elongation in sorghum. The Si-enhanced cell-wall extensibility in the growing zone of the roots is probably one of the causal factors promoting root elongation.…”

Silicon leaf application and physiological quality of white oat and wheat seeds

“…It is already known that Si decreases cell wall thickness in leaves, by increasing its extensibility and thus general growth (HOSSAIN et al, 2002a); therefore, it is plausible to state that this may also be effective other plant organs. Hattori et al (2003) studied some changes induced by Si on mechanical properties in cell walls of sorghum roots and found that this element improved their expansion capacity in apical and subapical regions. Findings from those authors emphasize Si role in root growth, as also observed in this study (Table 2).…”

Study of silicon effects on antioxidant enzyme activities and osmotic adjustment of wheat under drought stress

“…Silicon plays two separate functions in root cell walls, strengthening the endodermal cell walls in the mature basal region and keeping the young expanding cell walls extensible in the apical region of the roots (Hattori et al 2003). The application of silicon seems to be quite beneficial to plants grown under drought conditions by encouraging the development of a big root system and providing protection to roots against soil drying.…”

“…Si benefits to drought tolerance in wheat (Gong et al 2005), maize (Li et al 2007;Yong et al 2007), sorghum (Hattori et al 2003(Hattori et al , 2005 and salt tolerance of barley, tomato and cucumber (Liang et al 2003;Al-Aghabary et al 2004;Zhu et al 2004) have been related to its effect on the antioxidant enzyme activity. Gong et al (2005) reported that application of Si increased the activities of SOD, CAT and GR, the fatty acid unsaturation of lipids, and the contents of photosynthetic pigments and soluble proteins as well as total thiols under drought stress on wheat, whereas the content of H 2 O 2 , activity of acid phospholipase (AP) and oxidative stress of proteins were decreased by applying Si compared with those of non-Si treatments under drought stress.…”