Observations on the Root Anatomy of Rice (Oryza Sativa L.)

Abstract

Rice plants were grown hydroponically and roots were prepared for light and electron microscopy using standard techniques. The roots are bounded by an epidermis, exodermis, and fibrous layer. The exodermis has a suberin lamella along its inner tangential wall. The fibrous layer is composed of thick‐walled lignified cells with little pitting. The cortical parenchyma is compact when young, but expands and separates to form a zone of cell walls and air spaces in a spoked arrangement. Supporting columns of living parenchyma cells are occasionally present, particularly near lateral roots. The endodermis is typical for grasses with Casparian strips, suberin lamellae, and tertiary state walls with numerous pits. The pericycle and pith become sclerified. Protoxylem elements alternate with protophloem in the young root; later, early metaxylem, late metaxylem, and metaphloem proliferate. The exodermis, fibrous layer, lacunate cortex, and endodermis appear to present a formidable barrier to radial ion movement in the mature portions of the root.

Lysigenous aerenchyma formation involves non-apoptotic programmed cell death in rice (Oryza sativa L.) roots

“…in barley (John 1977) and maize (Jackson et al 1985a;Drew et al 2000). However, in root of rice, aerenchyma formation is constitutive type which takes place even in aerobic conditions (John 1977;Clark and Harris 1981), although the extent of aerenchyma formation is triggered by soil waterlogging (Das and Jat 1977;Justin and Armstrong 1991). Furthermore, studies on root aerenchyma formation in rice have also shown enhanced formation of aerenchyma, when O 2 deficiency was imposed in hydroponics (Colmer et al 1998;Colmer 2003a).…”

“…However, mitochondrial destruction is observed in anaerobic conditions, which is found to be absent under aerobic conditions in rice roots (Vartapetian and Andreeva 1986). Aerenchyma formation in rice occur due to separation of cell walls from adjacent cells so that the radial walls from the collapsing cells aggregate together, forming "forks", leaving a large gas-filled space or lacuna between them (Clark and Harris 1981).…”

“…2d). Outermost rhizodermis surrounding exodermis is single layered dead sclerenchyma fibre below exodermis and innermost unmodified cortical cell layer adjacent to aerenchyma are separated from each other by radial, monolayered walls, which appeared as spokes in crosssections (Clark and Harris 1981).…”

Development of Casparian strip in rice cultivars

“…[1][2][3] In roots of most species, the sequence of development of the endo-and exodermis is roughly the same and involves two consecutive developmental stages: (1) formation of CSs in radial and transverse walls impregnating the primary cell wall pores with lipophilic and aromatic substances and (2) deposition of suberin lamellae to the inner surface of anticlinal and tangential cell walls. [4][5][6] A major function of the CS is to block the non-selective apoplastic bypass flow of water and ions into the stele.3 Therefore, the structure, 7-9 chemical nature, [10][11][12] and physiological function 13,14 of endo-and exdodermal CSs in roots have been the focus of many investigations. Although oxygen loss, drought and salinity can influence the development and chemical nature of CSs in different rice cultivars, [15][16][17][18][19] few investigations have considered the development and formation of endo-and exdodermal CSs in the roots of rice cultivars with different salt tolerance under normal growing conditions.…”

Morphoanatomy of the underground system of Androtrichum trigynum (Cyperaceae)

“…Regarding root ontogeny in general, studies related to meristematic activity of the endoderm (Williams 1947;Melo-de-Pinna & Menezes 2002, 2003Rodrigues & Estelita 2004;Alonso &Moraes-Dallaqua 2004 andMenezes et al 2005); and to the development of the aerenchyma in the cortical region are especially noteworthy in the literature, by authors such as Beckel (1956); Heimsch (1960); Clarck & Harris (1981); Seago & Marsh (1989); Drew et al (2000) and Seago et al (1999aSeago et al ( , 2000Seago et al ( , 2005. These studies show that the inner cortex of the roots is originated by periclinal divisions of the meristematic endoderm, which may form aerenchyma at maturity.…”