title: Calcium delivery and storage in plant leaves: exploring the link with water flow.
abstract: Calcium (Ca) is a unique macronutrient with diverse but fundamental physiological roles in plant structure and signalling. In the majority of crops the largest proportion of long-distance calcium ion (Ca(2+)) transport through plant tissues has been demonstrated to follow apoplastic pathways, although this paradigm is being increasingly challenged. Similarly, under certain conditions, apoplastic pathways can dominate the proportion of water flow through plants. Therefore, tissue Ca supply is often found to be tightly linked to transpiration. Once Ca is deposited in vacuoles it is rarely redistributed, which results in highly transpiring organs amassing large concentrations of Ca ([Ca]). Meanwhile, the nutritional flow of Ca(2+) must be regulated so it does not interfere with signalling events. However, water flow through plants is itself regulated by Ca(2+), both in the apoplast via effects on cell wall structure and stomatal aperture, and within the symplast via Ca(2+)-mediated gating of aquaporins which regulates flow across membranes. In this review, an integrated model of water and Ca(2+) movement through plants is developed and how this affects [Ca] distribution and water flow within tissues is discussed, with particular emphasis on the role of aquaporins.
authors.affiliation: Waite Research Institute, School of Agriculture, Food and Wine, University of Adelaide, PMB1, Glen Osmond, SA, 5064, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Gilliham
authors.forename: Maclin
authors.initials: M
authors.lastname: Dayod
authors.forename: Bradleigh J
authors.initials: BJ
authors.lastname: Hocking
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Conn
authors.forename: Brent N
authors.initials: BN
authors.lastname: Kaiser
authors.forename: Roger A
authors.initials: RA
authors.lastname: Leigh
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Tyerman
mesh_terms: D020346:Aquaporins / Q000378:metabolism; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D014867:Water; D002118:Calcium