虛擬句型

So we know that plants make their own food through photosynthesis.

是以，我們知道植物通過光合作用製造自己的食物。

But how does a plant get together the ingredients it needs for this?

但是，植物是如何獲得所需的成分的呢？

Sunlight, carbon dioxide and water, and then combine those to create glucose and oxygen?

陽光、二氧化碳和水，然後將它們結合起來產生葡萄糖和氧氣？

A leaf is like a plant's food factory, and its parts work together to get the reactants into one place so that photosynthesis can happen.

葉片就像植物的食物工廠，它的各個部分相互配合，將反應物送到一個地方，以便進行光合作用。

The top of it is exposed to the most light, so the cells specialized for trapping light are on top.

頂部受到的光照最多，是以專門捕捉光線的細胞位於頂部。

These cells are called palisade mesophyll, and they're packed full of chlorophyll, the green chemical that plants use to absorb light.

這些細胞被稱為葉綠體間質，它們充滿了葉綠素，葉綠素是植物用來吸收光線的綠色化學物質。

That's why the top side of the leaf is darker than the bottom side.

這就是為什麼葉子的上半部分比下半部分顏色更深的原因。

You should also note that most leaves have a large surface area, so they can trap as much sunlight as possible.

您還應該注意的是，大多數樹葉的表面積都很大，是以可以儘可能多地吸收陽光。

That's where the bottom of the leaf comes in, it's got these little pores called stomata, which open up so carbon dioxide can diffuse into the leaf.

這就是葉片底部的作用，它有一些被稱為氣孔的小孔，這些小孔打開後，二氧化碳就能擴散到葉片中。

They're controlled by sausage shaped guard cells, which open up to let carbon dioxide in, but they can also close the stomata to prevent other things like water from escaping.

這些氣孔由香腸狀的防護細胞控制，防護細胞張開讓二氧化碳進入，但它們也可以關閉氣孔，防止水等其他物質漏出。

So the carbon dioxide comes in through the stomata, makes its way through the gaps in an airy layer of cells called the spongy mesophyll at the bottom part of the leaf, and then heads up to the palisade layer for photosynthesis.

是以，二氧化碳從氣孔進入，穿過葉片底部稱為海綿狀中葉的多空氣細胞層的縫隙，然後進入柵欄層進行光合作用。

Leaves are thin so that the carbon dioxide won't have too far to travel.

樹葉很薄，這樣二氧化碳就不會飄得太遠。

So we've got sunlight and carbon dioxide now, what's left?

現在我們有了陽光和二氧化碳，還剩下什麼？

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.

水從根部和莖部湧出，通過維管束進入葉片，維管束中有一條用於輸送水分的中空管道，稱為木質部。

Look at how the vascular bundle spreads out in the leaf to form veins so that it can spread water throughout.

看看維管束是如何在葉片中舒展開來形成葉脈，從而將水分擴散到整個葉片的。

So now the leaf's palisade cells have water, carbon dioxide and sunlight, all they need to photosynthesize and make glucose, their food, and oxygen.

是以，現在葉片的柵欄細胞有水、二氧化碳和陽光，它們可以進行光合作用，製造葡萄糖、食物和氧氣。

But how does the leaf prevent unwanted intruders like bacteria from getting in and stop important reactants from escaping?

但是，葉子如何防止細菌等不速之客進入，並阻止重要反應物逃逸呢？

Above the palisade mesophyll and below the spongy mesophyll are epidermis cells, which produce a waxy coating called the cuticle.

在柵格中葉的上方和海綿中葉的下方是表皮細胞，表皮細胞產生一層稱為角質層的蠟質塗層。

So that the only way in and out is through the stomata, which are regulated by those guard cells.

是以，進出的唯一途徑就是通過氣孔，而氣孔是由這些防護細胞調節的。

Now let's go back through the parts of a leaf.

現在，讓我們來回顧一下樹葉的各個部分。

We've got the thin waxy cuticle, then the epidermis cells.

我們有薄薄的蠟質角質層，然後是表皮細胞。

這些基本上構成了葉子的表皮。

Then comes the chlorophyll rich palisade mesophyll, where the bulk of photosynthesis occurs.

然後是富含葉綠素的葉枕中葉，光合作用主要在這裡進行。

Below that's the spongy mesophyll, which have plenty of space in between them for reactants to move through.

下面是海綿狀的葉肉，葉肉之間有足夠的空間供反應物通過。

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

木質部和韌皮部的維管束穿過這些空間，木質部負責輸送水分，韌皮部負責在光合作用後輸送糖分。

And below that, we've got another layer of epidermis and cuticle.

Space around the lower epidermis and the cuticle.

Are the stomata with guard cells on either side, leaves come in all different shapes and sizes, look at a cabbage leaf and an oak tree leaf, but most of them have these same parts in common, which allow them to get their reactants in and perform photosynthesis.

葉片有各種不同的形狀和大小，看看捲心菜葉和橡樹葉就知道了，但大多數葉片都有這些相同的部分，這些部分可以讓葉片吸收反應物並進行光合作用。

For more great videos visit the virtual school, www.thevirtualschool.com.

如需瞭解更多精彩視頻，請訪問虛擬學校 www.thevirtualschool.com。

字幕列表影片播放

葉的結構 | 植物 | 生物 | The FuseSchool (Structure Of The Leaf | Plant | Biology | The FuseSchool)

basically

plenty

common

bacteria