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Front. Plant Sci. | doi: 10.3389/fpls.2019.00688

Thermal benefits from white variegation of Silybum marianum leaves

 Oren Shelef1*, Liron Summerfield2,  Simcha Lev-Yadun3,  Santiago Villamarin-Cortez4, Roy Sadeh5, Ittai Herrmann5 and  Shimon Rachmilevitch2
  • 1Department of Natural Resources, Institute of Plant Science, Agricultural Research Organization (ARO), Israel
  • 2French Associates Institute for Agriculture and Biotechnology of Drylands, Ben-Gurion University of the Negev, Israel
  • 3Department of Biology and Environment, University of Haifa Oranim, Israel
  • 4University of Nevada, Reno, United States
  • 5The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Israel

Leaves of the spiny winter annual Silybum marianum express white patches (variegation) that can cover significant surface areas, the outcome of air spaces formed between the epidermis and the green chlorenchyma. We asked: 1) what characterizes the white patches in S. marianum and what differs them from green patches? 2) Do white patches differ from green patches in photosynthetic efficiency under lower temperatures? We predicted that the air spaces in white patches have physiological benefits, elevating photosynthetic rates under low temperatures. To test our hypotheses we used both a variegated wild type and entirely green mutants. We grew the plants under moderate temperatures (20°/10° C d/n) and compared them to plants grown under lower temperatures (15°/5° C d/n). The developed plants were exposed to different temperatures for one hour and their photosynthetic activity was measured. In addition, we compared in green versus white patches, the reflectance spectra, patch structure, chlorophyll and dehydrin content, stomatal structure, plant growth, and leaf temperature. White patches were not significantly different from green patches in their biochemistry and photosynthesis. However, under lower temperatures, variegated wild-type leaves were significantly warmer than all-green mutants – possible explanations for that are discussed These findings support our hypothesis, that white variegation of S. marianum leaves has a physiological role, elevating leaf temperature during cold winter days.

Keywords: Patch, Silybum marianum (L) Gaertn, Leaf color, thermoregulation, IRGA, plant physiology, heat balance

Received: 15 Dec 2018; Accepted: 07 May 2019.

Edited by:

Éva Hideg, University of Pécs, Hungary

Reviewed by:

Georgios Liakopoulos, Agricultural University of Athens, Greece
Knut Asbjørn Solhaug, Norwegian University of Life Sciences, Norway  

Copyright: © 2019 Shelef, Summerfield, Lev-Yadun, Villamarin-Cortez, Sadeh, Herrmann and Rachmilevitch. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Oren Shelef, Agricultural Research Organization (ARO), Department of Natural Resources, Institute of Plant Science, Rishon LeZion, Israel, shelef@volcani.agri.gov.il