叶绿素

Chlorophyll

The leaves are beginning to turn yellow.

树叶开始发黄。

In autumn leaves turn yellow.

秋天树叶变黄。

The leaves have turned yellow.

树叶枯黄了。

In autumn the leaves change from green to yellow.

秋天，树叶由绿变黄。

The leaves of the tree were turning yellow and red.

树叶变成黄色和红色。

Why green leaves change to bright red, yellow, or orange？

为什么树叶会由绿变红，变黄，或者变橙？

The green of the leaves is because it contains a lot of chlorophyll.

叶子的绿色是因为含有大量的叶绿素，

It also contains carotene (yellow) and anthocyanin (red).

同时也含有胡萝卜素（黄色）和花青素（红色）。

In autumn the sunshine is reduced and the temperature is reduced.

秋天日照减少，气温降低，

Chlorophyll decreased significantly in the unsuitable photosynthesis.

不适宜光合作用叶绿素明显降低，

At this time the yellow pigment, the red pigment appears and is colourful.

这时黄色色素、红色色素就突显而呈色彩斑斓。