2020/2/13CharacteristicsofMonocotyledonousRootsBotanyICELLULARROOTHAIRCUTICLEEPIDERMISCORTEX(PARENCHYMA)AIRSPACESENDODERMISERICYCLEPASSAGECELLPROTOXYLEMPHLOEMMETAXYLEMJUNCTIVETISSUEPITH(SCLERENCHYMA)Fig.42.22.Theroot.T.S.ofmonocotrootofOryza sativa (rice)showing air-spaces in cortexandsclerenchymatous pith.MonocotyledonousRoots:AnatomicalCharacteristics#7.Pericycle:It isusuallyuniseriate and composed ofthin-walledparenchymatous cells. In the monocotyledons, the pericycleoften undergoes sclerification in older roots,partlyorentirely. In many monocotyledons (e.g., some Gramineae,Smilax,Agave,Dracaena,palms)thepericycleconsists ofseveral layers.The pericycle may be interrupted by the differentiation ofxylem(manyGramineaeandCyperaceae)orphloemelements (Potamogetonaceae)nextto theendodermis(Guttenberg, 1943).Here, the pericycle gives rise to lateralroots only.www.biologydiscussion.com/root/characteristics-of-monocotyledonous-roots-botany/206926/19
2020/2/13 Characteristics of Monocotyledonous Roots | Botany www.biologydiscussion.com/root/characteristics-of-monocotyledonous-roots-botany/20692 6/19 Monocotyledonous Roots: Anatomical Characteristics # 7. Pericycle: It is usually uniseriate and composed of thin-walled parenchymatous cells. In the monocotyledons, the pericycle often undergoes sclerification in older roots, partly or entirely. In many monocotyledons (e.g., some Gramineae, Smilax, Agave, Dracaena, palms) the pericycle consists of several layers. The pericycle may be interrupted by the differentiation of xylem (many Gramineae and Cyperaceae) or phloem elements (Potamogetonaceae) next to the endodermis (Guttenberg, 1943). Here, the pericycle gives rise to lateral roots only
2020/2/13CharacteristicsofMonocotyledonousRootsBotanyNUCELHAASUTICLEEPIDERMISHYPODERMISCLEDENEHYMAPACRENTESMACHYENDODERMISPERICYCLEPACEAGEMETAXYLEMAETATIONEALPROTOXYLEM(SCLERENCHYMA)Fig.42.23.TherooLT.S.olmontAaeus pith anadditional metaxylem vessels.The cellsofcorticalregionarebeing arranged in distinctradialrowsCUTICLEEPIDERMSEXODERMISCORTEXASSAGECELINDODERMISRICYCLEPHLOEMROTOXYLEMMETAXYLEMCONJUNCTIVETISSUEFig.42.24.Theroot.T.S.ofmonocotyledonousroot(grass)MonocotyledonousRoots:AnatomicalCharacteristics#8.VascularTissue:Thevasculartissueconsists ofalternatingstrandsofxylemandphloem.Thephloemoccursintheformofstrandsneartheperipheryofthevascularcylinder,beneaththepericycle.Thexylemformsdiscretestrands,alternatingwiththephloem strands.The centre is occupied bylarge pith whichmaybeparenchymatous or sclerenchymatous.Bundles are numerous and referred as polyarch. TheadventitiousrootsofPalmaeandPandanaceaehaveconsiderably higher number of vascular bundles, as many as1oo or more. In some roots (e.g., Hydrilla, Triticum), asinglevessel occupiesthecentreandisseparatedbynon-tracheary elements from the peripheral strands. In otherwww.biologydiscussion.com/root/characteristics-of-monocotyledonous-roots-botany/206927/19
2020/2/13 Characteristics of Monocotyledonous Roots | Botany www.biologydiscussion.com/root/characteristics-of-monocotyledonous-roots-botany/20692 7/19 Monocotyledonous Roots: Anatomical Characteristics # 8. Vascular Tissue: The vascular tissue consists of alternating strands of xylem and phloem. The phloem occurs in the form of strands near the periphery of the vascular cylinder, beneath the pericycle. The xylem forms discrete strands, alternating with the phloem strands. The centre is occupied by large pith which may be parenchymatous or sclerenchymatous. Bundles are numerous and referred as polyarch. The adventitious roots of Palmae and Pandanaceae have considerably higher number of vascular bundles, as many as 100 or more. In some roots (e.g., Hydrilla, Triticum), a single vessel occupies the centre and is separated by nontracheary elements from the peripheral strands. In other