title: Net sodium fluxes change significantly at anatomically distinct root zones of rice (Oryza sativa L.) seedlings.
abstract: Casparian bands of endodermis and exodermis play crucial roles in blocking apoplastic movement of ions and water into the stele of roots through the cortex. These apoplastic barriers differ considerably in structure and function along the developing root. The present study assessed net Na+ fluxes in anatomically distinct root zones of rice seedlings and analyzed parts of individual roots showing different Na+ uptake. The results indicated that anatomically distinct root zones contributed differently to the overall uptake of Na+. The average Na+ uptake in root zones in which Casparian bands of the endo- and exo-dermis were interrupted by initiating lateral root primordia (root zone III) was significantly greater than that at the root apex, where Casparian bands were not yet formed (root zone I), or in the region where endo- and exo-dermis with Casparian bands were well developed (root zone II). The measurement of net Na+ fluxes using a non-invasive scanning ion-selective electrode technique (SIET) demonstrated that net Na+ flux varied significantly in different positions along developing rice roots, and a net Na+ influx was obvious at the base of young lateral root primordia. Since sodium fluxes changed significantly along developing roots of rice seedlings, we suggest that the significantly distinct net Na+ flux profile may be attributed to different apoplastic permeability due to lateral root primordia development for non-selective apoplastic bypass of ions along the apoplast.
authors.affiliation: Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijng 100093, China.
authors.forename: Qingyuan
authors.initials: Q
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Xia
authors.initials: X
authors.lastname: Cai
authors.forename: Di
authors.initials: D
authors.lastname: Wang
authors.forename: Xuejun
authors.initials: X
authors.lastname: Hua
authors.forename: Leqing
authors.initials: L
authors.lastname: Qu
authors.forename: Jinxing
authors.initials: J
authors.lastname: Lin
authors.forename: Tong
authors.initials: T
authors.lastname: Chen
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D002463:Cell Membrane Permeability; D002473:Cell Wall / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D012275:Oryza / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D018517:Plant Roots / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D036226:Seedlings / Q000033:anatomy & histology / Q000378:metabolism*; D012964:Sodium / Q000032:analysis / Q000378:metabolism*; D013054:Spectrophotometry, Atomic
chemical_list: D000584:Amiloride; D012964:Sodium