炼苗期烟草苗床是传毒介体有翅蚜着落的靶子中心，是烟田蚜传病毒病的主要初侵染源，为防治烟草蚜传病毒病的关键时期。

During the tobacco hardening period bed of tobacco seedling was the falling target of alate aphids and was the main resource of tobacco virus spread by aphids.

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箭舌豌豆根瘤为杆形，主要由皮层细胞和一个体积很大，含有分生组织、侵染组织，有时还有衰老组织的中心区域所组成。

Vicia sativa root nodule is usually rod-shaped, it is mainly composed of many cortex cells and a very large central zone which contains meristem, infected tissue and senescent tissue.

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