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Preferential freezing avoidance localized in anthers and embryo sacs in wintering Daphne kamtschatica var. jezoensis flower buds visualized by MRI
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  • Masaya Ishikawa,
  • Hiroyuki Ide,
  • Tetsuya Tsujii,
  • Timothy Stait-Gardner,
  • Hikaru Kubo,
  • Norihisa Matsushita,
  • Kenji Fukuda,
  • William Price,
  • Yoji Arata
Masaya Ishikawa
The University of Tokyo Graduate School of Agricultural and Life Sciences Faculty of Agriculture Department of Forest Science

Corresponding Author:isikawa.masaya5127@mail.u-tokyo.ac.jp

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Hiroyuki Ide
Ajinomoto Co Inc Institute for Innovation
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Tetsuya Tsujii
PerkinElmer Japan Co., Ltd.
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Timothy Stait-Gardner
Western Sydney University
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Hikaru Kubo
The University of Tokyo Graduate School of Agricultural and Life Sciences Faculty of Agriculture Department of Forest Science
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Norihisa Matsushita
The University of Tokyo Graduate School of Agricultural and Life Sciences Faculty of Agriculture Department of Forest Science
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Kenji Fukuda
The University of Tokyo Graduate School of Agricultural and Life Sciences Faculty of Agriculture Department of Forest Science
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William Price
Western Sydney University
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Yoji Arata
Water Research Institute
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Abstract

To explore diversity in cold hardiness mechanisms, high resolution magnetic resonance imaging (MRI) was used to visualize freezing behaviors in wintering flower buds of Daphne kamtschatica var. jezoensis, which have no bud scales surrounding well-developed florets. MRI images showed that anthers remained stably supercooled to -14 ∼ -21°C or lower whilst most other tissues froze by -7°C. Freezing of some anthers detected in MRI images at ∼ -21°C corresponded with numerous low temperature exotherms and also with the “all-or-nothing” type of anther injuries. In ovules/pistils, only embryo sacs remained supercooled at -7°C or lower, but slowly dehydrated during further cooling. Cryomicroscopic observation revealed ice formation in the cavities of calyx tubes and pistils but detected no ice in embryo sacs or in anthers. The distribution of ice nucleation activity in floral tissues corroborated the tissue freezing behaviors. Filaments likely work as the ice blocking barrier that prevents ice intrusion from extracellularly frozen calyx tubes to connecting unfrozen anthers. Unique freezing behaviors were demonstrated in Daphne flower buds: preferential freezing avoidance in male and female gametophytes and their surrounding tissues (by stable supercooling in anthers and by supercooling with slow dehydration in embryo sacs) whilst the remaining tissues tolerate extracellular freezing.
04 Aug 2021Submitted to Plant, Cell & Environment
11 Aug 2021Submission Checks Completed
11 Aug 2021Assigned to Editor
30 Aug 2021Reviewer(s) Assigned
07 Oct 2021Review(s) Completed, Editorial Evaluation Pending
13 Oct 2021Editorial Decision: Revise Minor
23 Nov 20211st Revision Received
23 Nov 2021Submission Checks Completed
23 Nov 2021Assigned to Editor
23 Nov 2021Reviewer(s) Assigned
11 Dec 2021Review(s) Completed, Editorial Evaluation Pending
13 Dec 2021Editorial Decision: Accept
05 Jan 2022Published in Plant, Cell & Environment. 10.1111/pce.14255