Hidaka Kota, Miyoshi Yuta, Ishii Satomi, Suzui Nobuo, Yin Yong-Gen, Kurita Keisuke, Nagao Koyo, Araki Takuya, Yasutake Daisuke, Kitano Masaharu, Kawachi Naoki
Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, Kurume, Japan.
Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, Takasaki, Japan.
Front Plant Sci. 2019 Jan 9;9:1946. doi: 10.3389/fpls.2018.01946. eCollection 2018.
In protected strawberry ( × Duch.) cultivation, environmental control based on the process of photosynthate translocation is essential for optimizing fruit quality and yield, because the process of photosynthate translocation directly affects dry matter partitioning. We visualized photosynthate translocation to strawberry fruits non-invasively with CO and a positron-emitting tracer imaging system (PETIS). We used PETIS to evaluate real-time dynamics of C-labeled photosynthate translocation from a CO-fed leaf, which was immediately below the inflorescence, to individual fruits on an inflorescence in intact plant. Serial photosynthate translocation images and animations obtained by PETIS verified that the C-photosynthates from the source leaf reached the sink fruit within 1 h but did not accumulate homogeneously within a fruit. The quantity of photosynthate translocation as represented by C radioactivity varied among individual fruits and their positions on the inflorescence. Photosynthate translocation rates to secondary fruit were faster than those to primary or tertiary fruits, even though the translocation pathway from leaf to fruit was the longest for the secondary fruit. Moreover, the secondary fruit was 25% smaller than the primary fruit. Sink activity (C radioactivity/dry weight [DW]) of the secondary fruit was higher than those of the primary and tertiary fruits. These relative differences in sink activity levels among the three fruit positions were also confirmed by C tracer measurement. Photosynthate translocation rates in the pedicels might be dependent on the sink strength of the adjoining fruits. The present study established C-photosynthate arrival times to the sink fruits and demonstrated that the translocated material does not uniformly accumulate within a fruit. The actual quantities of translocated photosynthates from a specific leaf differed among individual fruits on the same inflorescence. To the best of our knowledge, this is the first reported observation of real-time translocation to individual fruits in an intact strawberry plant using C-radioactive- and C-stable-isotope analyses.
在保护地草莓（× 杜氏）栽培中，基于光合产物转运过程的环境控制对于优化果实品质和产量至关重要，因为光合产物转运过程直接影响干物质分配。我们使用一氧化碳和正电子发射示踪成像系统（PETIS）对光合产物向草莓果实的转运进行了非侵入性可视化。我们使用PETIS评估了完整植株中，从紧挨着花序下方的一片供给一氧化碳的叶片，到花序上各个果实的碳标记光合产物转运的实时动态。通过PETIS获得的一系列光合产物转运图像和动画证实，来自源叶的碳光合产物在1小时内到达库果实，但在果实内并非均匀积累。以碳放射性表示的光合产物转运量在各个果实及其在花序上的位置之间存在差异。即使从叶片到二级果实的转运路径是最长的，但光合产物向二级果实的转运速率比向一级或三级果实的转运速率更快。此外，二级果实比一级果实小25%。二级果实的库活性（碳放射性/干重[DW]）高于一级和三级果实。通过碳示踪测量也证实了这三个果实位置之间库活性水平的这些相对差异。花梗中的光合产物转运速率可能取决于相邻果实的库强度。本研究确定了碳光合产物到达库果实的时间，并证明转运物质在果实内并非均匀积累。来自特定叶片的实际光合产物转运量在同一花序上的各个果实之间存在差异。据我们所知，这是首次使用碳放射性和碳稳定同位素分析，在完整草莓植株中对单个果实的实时转运进行的报道观察。
