停止製造葉綠素
In many places around the world, people love to travel to mountains and forests to view the beautifully colored foliage in autumn.
在世界上許多地方，人們喜歡去山上和森林欣賞秋天色彩繽紛的樹葉。
colored (adj.)彩色的,有顏色的
As the days become shorter, trees’ leaves turn brilliant yellows, oranges and reds before they drop to the ground.
隨著白天愈來愈短，樹葉轉變為鮮豔的黃色、橘色和紅色，之後才掉落至地上。
brilliant (adj.)鮮豔的,明亮的
This is part of the natural cycle of trees, and is directly affected by the changing of the seasons.
這是樹木自然週期的一部分，直接受到季節變化的影響。
cycle (n.)週期,循環；the cycle of the seasons 四季的週期；the menstrual cycle月經週期
As summer becomes fall, there is less sunlight due to the shorter days.
隨著夏季進入秋季，陽光因為白天時間縮短的關係而減少。
For trees, this signals leaves to prepare for winter and stop making chlorophyll, which is a pigment in leaves that creates the green color we associate with spring and summer.
對樹木來說，這表示樹葉將要開始為冬天作準備並停止製造葉綠素，葉綠素是樹葉中的色素，能呈現出我們與春天和夏天聯想在一起的綠色。
signal (n.)信號,號誌 (v.)打信號,示意pigment (n.)色素associate A with B 將A與B聯想在一起
Chlorophyll is a key element of photosynthesis—a process which helps almost all plants make energy from sunlight.
葉綠素是進行光合作用的重要元素─這是一種幫助幾乎所有植物將陽光轉換成能量的過程。
photosynthesis (n.)光合作用
Once trees stop producing chlorophyll and the green color fades away, other pigments in the leaves become more visible: xanthophylls turn leaves yellow, carotenoids make them orange, and anthocyanins turn them red.
樹木一旦停止製造葉綠素，綠色漸漸褪去，樹葉中的其它色素也就變得更清晰：葉黃素將葉子變成黃色、類胡蘿蔔素將葉子變成橘色、而花青素將葉子變成紅色。
fade (v.)褪色visible (adj.)可以看見的
In addition to light, weather can also affect these changes, with rain, snow and falling temperatures either making leaves turn from green to other colors more quickly or making the different colors last longer.
除了光照之外，天氣也會造成這些變化，降雨、降雪和氣溫的下降會使樹葉更快從綠色轉變成其它顏色，或使其它顏色持續更長一段時間。
in addition to 除……之外=besides=apart fromeither A or B 不是A就是Blast (v.)持續
Therefore, seasonal and weather conditions affect why and for how long leaves change color, creating the beautiful foliage many people associate with fall.
因此，季節和天氣狀況會影響樹葉顏色變化和其時間長度，帶來許多人在秋天所見的美麗樹葉。