Tree rings are made of tissue called xylem.

构成年轮的组织被称为。

Xylem cells transport water and nutrients from the roots to the leaves.

将水和营物从根输送到叶。

Through that space stretches the vascular bundle, with xylem to transport water and phloem which transport sugars after photosynthesis.

通过这个空间，延伸出维管束，负责运输水，韧皮负责在光合作用后运输糖。

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

构成维管组织的要有两种：和韧皮。

So these are xylem sap feeders.

所以这些是汁液饲者。

And xylem is just 95% water.

只有 95% 是水。

Phloem cells, on the other hand, transport stuff mostly in the opposite direction as xylem cells.

另一方面，韧皮与的运输方向相反。

And pro-tip, xylem is one of my favorite scrabble words.

专业提示，是我最喜欢的拼字游戏之一。

Right beside the phloem is the tree’s other tissue type: the xylem.

韧皮旁边是树的另一种组织类型：。

And if we zoom in, we'll notice its xylem and phloem cells snuggled together, just like they were in the stem.

如果我们放大，我们会注意到它的和韧皮依偎在一起，就像它们在茎中一样。

Carbon and water, more than 1,000 liters of water, in fact, flow freely through the phloem and xylem tubes carry it along.

碳和水，实际上超过 1000 升的水，自由流动于韧皮和的管道中。

Sclerenchyma supports organs that are fully mature, and similar to xylem, it has cells that are dead inside (physically, not emotionally) .

厚壁组织支持完全成熟的器官，与相似，它有从内死亡的（我指的是身体上，而不是情感上）。

After water flows from the roots to the leaves through the xylem, it can exit the plant through the tiny stomata mouths.

水通过从根流向叶后，再通过小的气孔口排出植株。

As the plant grows, stem cell clusters called meristems generate new xylem cells, which form bigger pipes to suit the plant's needs.

随着植物的生长，被称为分生组织的干簇产生新的，这些形成更大的管道以适应植物的需要。

The earliest wood seems to have been a mechanism for transporting water more effectively than one layer of xylem could on its own.

最早的材似乎是一种比一层更有效地输送水的机制。

But that new species of plants had  more than one layer of xylem - it had what's called secondary xylem, also known as wood.

但是这种新植物有不止一层的——它有所谓的次生，也被称为材。

Water comes up through the roots and stem and enters the leaf through a vascular bundle, which contains a hollow tube for water transport called the Xylem.

水从根和茎上来，通过维管束进入叶子，维管束包含一个空心管，用于运输水，称为。

Xylem and phloem are bundled together to form the veins of a plant — the subway map that connects the leaves, stem, and roots.

和韧皮捆绑在一起形成植物的脉络——连接叶子、茎和根的地铁地图。

The pith is encircled by a ring of xylem, and xylem is encircled by a ring of phloem… phloem, and pith growth is usually pale in color.

髓被一圈包围，又被一圈韧皮… … 韧皮包围，髓生长通常呈浅色。

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“”的维管组织。这有助于将水从植物底输送到植物顶。