title: Spectral and dose dependence of light-induced ion flux responses from maize leaves and their involvement in leaf expansion growth.
abstract: Two types of segments (intact leaf tissue and isolated mesophyll tissue respectively) were isolated from basal (still growing) and tip (non-growing) maize leaf regions. The leaf segments were exposed to different light qualities (blue or red light) and quantities, and net fluxes of K+, Ca2+ and H+ were measured non-invasively using ion-selective vibrating microelectrodes (the MIFE technique). A clear dose dependency of all ion flux responses on both red (RL) and blue (BL) light fluence rate was found. We provide evidence that light-induced K+ flux kinetics are different between growing and non-growing tissues and attribute this difference to the direct involvement of RL-induced K+ flux in turgor-driven leaf expansion growth controlled by the epidermis, as well as to the charge-balancing role of K+ in the leaf mesophyll. Generally, BL was much more efficient in stimulating K+ uptake in the growing basal region compared with RL. We also show a much stronger influence of RL on Ca2+ fluxes in the basal region compared with BL, which argues in favor of the importance of RL in Ca2+ signaling during leaf growth.
authors.affiliation: School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, Australia.
authors.forename: Branka Dusan
authors.initials: BD
authors.lastname: Zivanović
authors.forename: Tracey Ann
authors.initials: TA
authors.lastname: Cuin
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
mesh_terms: D002118:Calcium / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D017136:Ion Transport / Q000528:radiation effects*; D008027:Light; D018515:Plant Leaves / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects*; D011188:Potassium / Q000378:metabolism; D011522:Protons; D003313:Zea mays / Q000378:metabolism*
chemical_list: D011522:Protons; D011188:Potassium; D002118:Calcium