Miyoshi Yuta, Hidaka Kota, Yin Yong-Gen, Suzui Nobuo, Kurita Keisuke, Kawachi Naoki
Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology (QST), Takasaki, Japan.
Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Kurume, Japan.
Front Plant Sci. 2021 Jul 14;12:688887. doi: 10.3389/fpls.2021.688887. eCollection 2021.
The efficiency of photosynthate translocation from leaves to fruits directly affects dry matter partitioning. Therefore, controlling photosynthate translocation dynamics is critical for high-yield and high-quality fruit production. Accordingly, photosynthate translocation changes must be characterized using data obtained at a higher spatiotemporal resolution than those provided by conventional methods. In this study, C-photosynthate translocation into strawberry ( × Duch.) fruits in individual plants was visualized non-invasively and repeatedly using a positron emission tracer imaging system (PETIS) to assess the spatiotemporal variability in the translocation dynamics in response to increasing daylight integrals (i.e., 0.5-, 4.5-, and 9-h exposures to 400 μmol m s at the leaf surface). Serial images of photosynthate translocation into strawberry fruits obtained from the PETIS confirmed that C-photosynthates were translocated heterogeneously into each fruit on the same inflorescence. The amount of translocated C-photosynthates and the translocation rate into each fruit significantly increased as the integrated light intensity at the leaf surface increased. An analysis of the pedicel of each fruit also confirmed that the photosynthate translocation rate increased. The cumulated photosynthesis in leaves increased almost linearly during the light period, suggesting that an increase in the amount of photosynthates in leaves promotes the translocation of photosynthates from leaves, resulting in an increase in the photosynthate translocation rate in pedicels and enhanced photosynthate accumulation in fruits. Additionally, the distribution pattern of photosynthate translocated to fruits did not change during the light period, nor did the order of the sink activity (C radioactivity/fruit dry weight), which is the driving force for the prioritization of the C-partitioning between competing organs, among fruits. Thus, this is the first study to use C-radioisotopes to clarify the spatiotemporal variability in photosynthate translocation from source leaves to individual sink fruits in response to increasing daylight integrals at a high spatiotemporal resolution.
光合产物从叶片向果实的转运效率直接影响干物质分配。因此，控制光合产物转运动态对于高产、优质水果生产至关重要。相应地，必须使用比传统方法提供的数据更高时空分辨率的数据来表征光合产物转运变化。在本研究中，使用正电子发射示踪成像系统（PETIS）对单株草莓（× 杜克斯）果实中C光合产物的转运进行了非侵入性和重复性可视化，以评估转运动态响应日积分增加（即叶片表面400 μmol m s下0.5、4.5和9小时暴露）时的时空变异性。从PETIS获得的光合产物转运到草莓果实中的系列图像证实，C光合产物以不均匀的方式转运到同一花序上的每个果实中。随着叶片表面积分光强的增加，转运到每个果实中的C光合产物量和转运速率显著增加。对每个果实的果梗分析也证实光合产物转运速率增加。叶片中的累积光合作用在光照期几乎呈线性增加，这表明叶片中光合产物量的增加促进了光合产物从叶片的转运，导致果梗中光合产物转运速率增加以及果实中光合产物积累增强。此外，转运到果实中的光合产物的分布模式在光照期没有变化，果实之间作为C分配优先顺序驱动力的库活性（C放射性/果实干重）顺序也没有变化。因此，这是第一项使用C放射性同位素以高时空分辨率阐明光合产物从源叶向单个库果实转运的时空变异性以响应日积分增加的研究。
