Ion gradients in xylem exudate and guttation fluid related to tissue ion levels along primary leaves of barley |
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| Authors: | MAKIKO NAGAI MIWA OHNISHI TAKEO UEHARA MUTSUMI YAMAGAMI EIKO MIURA MAI KAMAKURA AKIRA KITAMURA SHU‐ICHI SAKAGUCHI WATARU SAKAMOTO TERUO SHIMMEN HIDEHIRO FUKAKI ROBERT J REID TETSURO MIMURA |
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| Institution: | 1. Department of Biology, Graduate School of Science, Kobe University, , Kobe, 657‐8501 Japan;2. Department of Biological Science, Faculty of Science, Nara‐Women's University, , Nara, 630‐8506 Japan;3. Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), , Tokyo, 113‐0027 Japan;4. Institute for Environmental Science, , Rokkasho‐mura, Aomori, 039‐3212 Japan;5. Research Institute for Bioresources, Okayama University, , Okayama, 710‐0046 Japan;6. Department of Marine Engineering, Graduate School of Maritime Sciences, Kobe University, , Kobe, 658‐0022 Japan;7. Department of Life Science, Graduate School of Life Science, University of Hyogo, , Hyogo, 678‐1297 Japan;8. School of Earth and Environmental Sciences, The University of Adelaide, , Adelaide, South Australia, 5005 Australia |
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| Abstract: | The concentration of ions in plant cells and tissues is an essential factor in determining physiological function. In the present study, we established that concentration gradients of mobile ions exist in both xylem exudates and tissues within a barley (Hordeum vulgare) primary leaf. For K+ and NO3?, ion concentrations generally decreased from the leaf base to the tip in both xylem exudates and tissues. Ion gradients were also found for Pi and Cl? in the xylem. The hydathode strongly absorbed Pi and re‐translocated it to the rest of the plant, whereas Cl? was extruded. The ion concentration gradients developed early during leaf growth, increased as the tissue aged and remained under both high and low transpiration conditions. Measurement of the expression profiles of Pi, K+ and NO3? transporters along the longitudinal axis of the leaf revealed that some transporters are more expressed at the hydathode, but for most transporters, there was no significant variation along the leaf. The mechanisms by which longitudinal ion gradients develop in leaves and their physiological functions are discussed. |
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| Keywords: | epithem cell hydathode ion nutrition phosphate vascular bundle xylem fluid |
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