Abstract
Key messageElement profile signatures of needle tissues differentiated four tissues: epidermis (main contributor: calcium), endodermis (main contributors: magnesium, sulphur and manganese), mesophyll (main contributor: potassium), and transfusion parenchyma (main contributor: zinc).Distribution of elements in cross-sections of Scots pine (Pinus sylvestris L.) needles was investigated using micro-proton-induced X-ray emission. Tissue-specific distributions of magnesium (Mg), sulphur (S), calcium (Ca), phosphorus (P), potassium (K), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), aluminium (Al) and silicon (Si) were resolved in a quantitative manner. Distribution maps and tissue-specific concentrations revealed the largest concentration of Ca in epidermis, of Mg, S and Mn in endodermis, of K in mesophyll and phloem and of Zn in transfusion parenchyma. Phosphorus, Cl, Fe, Al and Si did not exhibit apparent tissue-specific distribution. Inverse allocation of P and Ca was observed, a likely mechanism to prevent their precipitation. Taking the area of tissues into account, relative element distribution calculations indicated that mesophyll contained the majority of the elements studied, except Ca, which predominated in the epidermis (79% of total Ca concentration) and Mn, which predominated in the endodermis (40% of total Mn concentration). When considering a complete element profile of a particular tissue, four clusters were differentiated, which generally supported single-element observations. The first cluster differentiated mesophyll, xylem, phloem, transfusion tracheids and Strasburger cells with predominance of K, the second cluster differentiated epidermis on the basis of Ca, the third cluster differentiated endodermis with contributions from Mg, S and Mn, and the fourth cluster differentiated transfusion parenchyma with contribution from Zn. Information on tissue-specific-element allocations will complement structural and functional knowledge of needle tissues and advance our understanding of element/nutrient transfers in Scots pine.
Highlights
Leaf morphologies and anatomies differ substantially between plant species as a consequence of their phylogenetic origin and adaptation to environmental pressures
In a whole-needle cross-section, the areas of epidermis, mesophyll, endodermis and central cylinder were distinguished and element concentrations were extracted by encircling selected tissues
Relative element distribution in particular tissue was calculated on the basis of element concentration in this tissue and the relative area proportion of this tissue in the needle, which were determined by measuring area of particular tissue in ImageJ to be: epidermis 29%, mesophyll 41%, endodermis 10% and central cylinder 17%
Summary
Leaf morphologies and anatomies differ substantially between plant species as a consequence of their phylogenetic origin and adaptation to environmental pressures. In majority of gymnosperm leaves (needles), two distinctive structures separate centrally positioned vascular bundles from mesophyll: endodermis and transfusion tissue (Liesche et al 2011). Endodermis is a layer of cells, whose cell walls sometimes contain Casparian strip (Lersten 1997) and functions to endodermal barrier in roots, namely preventing uncontrolled apoplastic. Transfusion tissue comprises specialised cells of transfusion tracheids and transfusion parenchyma cells. Gymnosperm needles are characterised by a variable number of resin ducts positioned on the periphery of the thick-walled cells of mesophyll and epidermal cells with thick cutinized outer walls (Liesche et al 2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
