An annual Echinochloa with plagiotropic tillers (semi‐erect type) was found on a paddy levee in Miyagi prefecture in Japan. This semi‐erect type had tetraploid chromosome numbers (2n = 36) and would be expected to be E. oryzicola. However, its appearance was distinct from that of E. oryzicola. To collect seed samples and clarify its distribution and habitat, exploration and collection surveys were carried out in the northern part of Honshu, the main island of Japan in 2014, 2017, and 2018. Thirty‐two populations that were assumed to be the semi‐erect type were found and their mature seeds were collected. Based on the results of chromosome counts and growth form analyses, all of them were confirmed to be the semi‐erect type. The 32 populations were distributed in the prefectures of Aomori, Iwate, Akita, Miyagi, Yamagata, Fukushima, and Niigata, and located in paddy fields, abandoned paddy fields, paddy levees, roadsides, vacant land, and scree slopes. Our surveys indicated that the semi‐erect type grew in wet and dry disturbed habitats at an early stage of secondary succession including paddy fields in the northern part of the main island of Japan.

中文翻译：

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具有斜向分蘖的四倍体稗草：它在日本本岛北部的分布和栖息地

在日本宫城县的一个稻田堤坝上发现了一种一年生具有斜向分蘖（半直立型）的稗子。这种半直立型具有四倍体染色体数 (2n = 36)，预计为 E. oryzicola。然而，它的外观与 E. oryzicola 不同。为收集种子样本并明确其分布和栖息地，于 2014 年、2017 年和 2018 年在日本本州岛北部进行了探索和收集调查。发现直立型并收集其成熟种子。根据染色体计数和生长形态分析结果，均确认为半直立型。32个种群分布在青森县、岩手县、秋田县、宫城县、山形县、福岛县和新泻县，位于水田、废弃水田、水堤、路旁、空地、碎石坡地。我们的调查表明，半直立型在次生演替的早期阶段生长在潮湿和干燥的干扰生境中，包括日本本岛北部的稻田。