Systematic production techniques for high quality of Japanese radish cv.Gensuke under summer-sown culture

在石川县，日本萝卜因其风味而在很大程度上被种植。然而，在7月份播种时，它往往在花柱中央形成纵向的中空间隙，从而降低了根的质量。本研究的目的是在夏播栽培条件下生产出优质的根癌根。在土壤温度较高的情况下，在根中心区靠近细胞间隙的薄壁细胞上可观察到木质素的形成，并明显观察到中空现象的发生。当植物在生长中期用高温和生长素处理时，细胞间的气隙结合成一个大的凹陷，这是因为缺乏大的薄壁细胞的增殖，防止了细胞由于与气隙毗邻的薄壁细胞上活跃的木质素形成而侵入气隙。细胞分裂素CPPU{N-(2-氯-4-吡啶)-N‘-苯基脲}处理抑制了木质素的形成和中空发育，这是因为即使在高温下，根部中部薄壁细胞的增殖也很活跃。当植物生长在低密度下时，根的生长加速，根部出现空心化。在高密度下生长时，根的生长受到抑制，不发生空心化，因此，根中心区细胞间隙的形成和毗邻细胞间隙的薄壁细胞壁上木质素的形成是根空心化发育所必需的。由此可见，在夏播条件下，叶面喷施CPPU是生产优质根的最实用的方法之一。

The Japanese radish cv.Gensuke has been largely cultivated in Ishikawa Prefecture for its flavor. When sown in July, however, it often develops a longitudinal hollow gap in the central style, thus lowering t he quality of the root. This study aimed to produce 'Gensuke' root of high quality under summer-sown culture.1. Under high soil temperature lignin formation was recognized on parenchymatous cells abutting on the intercellular air space in the central region of the root, and hollowing was clearly observed developing.2. When the plant was treated with high soil temperature and auxin during the middle growing stage intercellular air spaces coalesce into a large hollowing for want of proliferation of large parenchymatous c ells, which prevents the cells intruding into the air space as a result of active lignin formation on parenchymatous cells abutting on the air space.3. Lignin formation and hollowing development was repressed by the treatment of a kind of cytokinins, CPPU {N-(2-chloro-4-pyridyl)-N'-phenylurea} due to active proliferation of parenchymatous cells in the central region of the root even under high soil temperature.4. When plants were grown under low plating density, root growth was accelerated and hollowing developed in the root. When plants were grown under high planting density, root growth was sup-pressed and no hollowing developed.Therefore, genesis of intercellular air space in the central region of the root and lignin formation in the walls of parenchymatous cells abutting on the space are necessary for the development of hollowing in the root. From these results, it is reasonable to consider that foliar spraying of CPPU is one of the most practical means to produce 'Gensuke' root of high quality under summer-sown culture.