Auxin helps form vascular tissue that carries water and nutrients throughout the plant.

生长素帮助形成维管组织，在整个植物中输送水分和营养。

But there were still many more plant attributes that had yet to evolve, one of them being vascular tissue.

但还有更多的植物属性有待进化，其中之一就是维管组织。

Next up: Vascular tissue, which forms the circulatory system, or the veins, of the plant.

接下来是维管组织，它构成了植物的循环系统，或者说是静脉。

Please welcome: dermal tissue, the plant's skin; vascular tissue, the plant's veins; and ground tissue — everything in between.

表皮组织，植物的皮肤；维管组织，植物的脉络；还有基本组织——介于两者之间的一切。

And they don't contain vascular tissue, the water and transport system found in all other plants, which developed later with seedless vasculars.

它们不含维管组织，这是所有其他植物中发现的水和运输系统，这些植物后来发展出无籽维管。

And scattered throughout the ground tissue are the vascular tissue bundles, or veins, which look weirdly like they're screaming.

分散在地面组织中的是维管组织束，或静脉，它们看起来很奇怪，就像在尖叫一样。

It's got a similar vibe to the stem, except its vascular tissue is clustered in the center of the root.

它和茎有相似的感觉——除了它的维管组织聚集在根的中心。

The vascular tissue is surrounded by a thick layer of ground tissue, and the epidermis wraps around the whole thing.

维管组织被一层厚厚的地面组织包围着，表皮包裹着整个维管组织。

And there are two main types of cells that make up that vascular tissue: xylem and phloem.

构成维管组织的细胞主要有两种：木质部和韧皮部。

But, they were the first plants to form true roots, stems, and leaves that contain vascular tissue, so they're considered the first vascular plants.

但是，它们是第一批形成真正的根、茎和含有维管组织的叶子的植物，所以它们被认为是第一批维管植物。

Particles with a diameter of 2.5 microns or smaller, or PM2.5, are especially dangerous: because of their tiny size, they can penetrate vascular tissue.

直径为 2.5 微米或更小的微粒（ PM2.5）尤其危险：由于其尺寸极小，它们可以穿透血管组织。

Vascular tissue began to carry water and minerals around the plants, supporting the growth of much bigger plants.

维管组织开始在植物周围携带水和矿物质，支持更大的植物生长。

Stems are typically, though not always, found above-ground and contain vascular tissue that supports the plant and transports water and sugar throughout its body.

茎通常（虽然不总是）长在地上，含有维管组织，这些维管组织支持植物，并在整个身体中运输水和糖。

Their epidermis, or outermost layer of tissue, produces billions of tiny hairs that absorb water and nutrients, and their vascular tissue transports the nutrients up to the stem and leaves.

它们的表皮，或最外层的组织，产生了数十亿根微小的毛发，这些毛发吸收水分和营养，它们的维管组织将营养物质运送到茎和叶。

By this time, many plants had developed  a kind of vascular tissue called " xylem." This helped move water from the  bottom to the top of the plant.

到这个时候，许多植物已经发育出一种叫做“木质部”的维管组织。这有助于将水从植物底部输送到植物顶部。