以下是小编整理的7篇经典英语作文：秋天叶子为什么会变颜色，仅供参考，希望能够帮助到大家。
经典英语作文：秋天叶子为什么会变颜色
Why do leaves change color in the fall? asks Patricia Brown, of New York City.
Autumn's cool days are trimmed with deep blue skies and golden light, and brilliant leaves of yellow, orange and red. Leaves changing color in the fall are a tree's way of preparing for long winter, rather like we put up storm windows and pull warm clothes and blankets out of storage.
In summer, the leaves on trees like pin oaks and sugar maples are green because they are chock-full of the green pigment chlorophyll.
Trees need sunlight to produce chlorophyll. In turn, chlorophyll uses sunlight's energy to split water (H2O) into hydrogen and oxygen. Meanwhile, leaves also absorb carbon dioxide gas from the air. The end products of leaf chemistry: carbohydrates (homemade plant food for the tree), and oxygen, released into the air (the gas we need to breathe). The whole process is called photosynthesis.
Along with green chlorophyll, most leaves also contain yellow, orange and red-orange pigments celled carotenoids. Trees don't need light to make carotenoids. Botanists call them “helper pigments,” because carotenoids absorb some sunlight and (nicely) pass the energy along to chlorophyll. We don't see much of these deputy pigments (carotene, lycopene, and xanthophyll) in summer, because they are masked by abundant green chlorophyll.
But the ever-shortening days of fall mean less daylight and colder weather. The average tree is rushing to save all the nutrients it can for its winter hibernation. Nitrogen and phosphorus are pulled from leaves for storage in branches. A layer of corky cells grows between the leaves' stems and their branches, reducing the leaves' supply of nutrients and water.
With diminished sunlight, water, and nutrients, chlorophyll synthesis slows. Old, worn-out chlorophyll breaks down at the usual rate--ironically, sunlight destroys it--so each leaf's stock gradually dwindles. And as the green fades, yellow and orange emerge from hiding.
Unlike the green and yellow pigments, red and purple pigments (anthocyanins, part of the flavonoid class) actually form in leaves in the autumn, tinting leaves scarlet and burgundy.
Botanists have long wondered why some trees are genetically programmed to manufacture anthocyanins in the fall. New research indicates that anthocyanins may be a tree's own sunscreen.
Anthocyanins are made in a leaf's sugary sap, with the help of lots of sun and cool temperatures. Botanists think that anthocyanins shield the leaves' fading photosynthesis factories from too much sunlight, rather like the pigment melanin protects our skin from the sun. While the red pigments act as a shield, the tree feverishly breaks down and pulls nutrients out of leaves and into its limbs and trunk before leaves drop or die.
Anthocyanins may also act like Vitamin C or E, scavenging so-called “free radicals” before they can do oxidizing damage to a fall leaf's fragile structure.
Upper and outer leaves tend to be reddest, since they are most exposed to sunlight and cold. In some trees, like sugar maples, the reds of the anthocyanins combined with the yellows of the carotenoids make especially brilliant orange leaves.
Why do leaves change color in the fall? asks Patricia Brown,of New York City.
Autumns cool days are trimmed with deep blue skies and golden light,and brilliant leaves of yellow,orange and red.Leaves changing color in the fall are a trees way of preparing for long winter,rather like we put up storm windows and pull warm clothes and blankets out of storage.
In summer,the leaves on trees like pin oaks and sugar maples are green because they are chock-full of the green pigment chlorophyll.
Trees need sunlight to produce chlorophyll.In turn,chlorophyll uses sunlights energy to split water (H2O) into hydrogen and oxygen.Meanwhile,leaves also absorb carbon dioxide gas from the air.The end products of leaf chemistry: carbohydrates (homemade plant food for the tree),and oxygen,released into the air (the gas we need to breathe).The whole process is called photosynthesis.
Along with green chlorophyll,most leaves also contain yellow,orange and red-orange pigments celled carotenoids.Trees dont need light to make carotenoids.Botanists call them “helper pigments,” because carotenoids absorb some sunlight and (nicely) pass the energy along to chlorophyll.We dont see much of these deputy pigments (carotene,lycopene,and xanthophyll) in summer,because they are masked by abundant green chlorophyll.
But the ever-shortening days of fall mean less daylight and colder weather.The average tree is rushing to save all the nutrients it can for its winter hibernation.Nitrogen and phosphorus are pulled from leaves for storage in branches.A layer of corky cells grows between the leaves stems and their branches,reducing the leaves supply of nutrients and water.
With diminished sunlight,water,and nutrients,chlorophyll synthesis slows.Old,worn-out chlorophyll breaks down at the usual rate--ironically,sunlight destroys it--so each leafs stock gradually dwindles.And as the green fades,yellow and orange emerge from hiding.
Unlike the green and yellow pigments,red and purple pigments (anthocyanins,part of the flavonoid class) actually form in leaves in the autumn,tinting leaves scarlet and burgundy.
Botanists have long wondered why some trees are genetically programmed to manufacture anthocyanins in the fall.New research indicates that anthocyanins may be a trees own sunscreen.
Anthocyanins are made in a leafs sugary sap,with the help of lots of sun and cool temperatures.Botanists think that anthocyanins shield the leaves fading photosynthesis factories from too much sunlight,rather like the pigment melanin protects our skin from the sun.While the red pigments act as a shield,the tree feverishly breaks down and pulls nutrients out of leaves and into its limbs and trunk before leaves drop or die.
Anthocyanins may also act like Vitamin C or E,scavenging so-called “free radicals” before they can do oxidizing damage to a fall leafs fragile structure.
Upper and outer leaves tend to be reddest,since they are most exposed to sunlight and cold.In some trees,like sugar maples,the reds of the anthocyanins combined with the yellows of the carotenoids make especially brilliant orange leaves.
Unknowingly,Miss Qiu came to our side.There are many fruits on the fruit trees,and there are unique scenes everywhere.In Xingyang,at this time,the most beautiful scenery is the ginkgo trees on both sides of Suohe road!
From a distance,the road is lined with ginkgo trees,solemn and majestic,just like a famous soldier guarding our city.Closer look,some ginkgo trees also hang a string of ginkgo fruit,round toot,like ice sugar gourd,lovely! Listen to my mother,ginkgo fruit or a kind of traditional Chinese medicine!
A gust of autumn wind blowing,ginkgo leaves like a beautiful butterfly flying in the air,and then slowly fall on the ground,I cant help but pick up a ginkgo leaf,carefully observe,found that its shape is very unique,like a small fan,it seems that these small fans,blowing autumn is particularly cool,and then I continue to observe other ginkgo leaves,some of them like small goldfish The tail! Some are like my brothers little hands! They are all kinds of things!
In addition to their different shapes,their colors are also different.Some are green with yellow,some are gray yellow on the edge of the leaves,and some are pure yellow.They are so beautiful! In addition to the color,if you look closely,you will find that each leaf has vertical stripes,but it feels smooth and smooth,and it smells like a fragrance!
I love autumn,more love so colorful ginkgo leaf!
大部分叶子之所以是绿色是因为树叶中含有大量叶绿素。但除了叶绿素之外，还有花青素、叶黄素和倍他胡萝卜素，只是数量很少而已。秋天温度下降时胡萝卜素的分泌增多，而胡萝卜素是橙色的，所以树叶会变黄或者变红。
在植物的叶子中储藏有光合作用产生的淀粉，淀粉只有转化成葡萄糖，才能输送到植物的各部分去。但是到了深秋季节，天气变冷，叶子在白天制造的淀粉由于输送作用的减弱，到了晚上也不能完全变为葡萄糖运出叶子，同时叶子内的水分也逐渐减少，于是葡萄糖就留在叶子里，浓度越来越高，而葡萄糖的增多和秋天低温有利于花青素的形成。所以，花青素含量逐渐增多而叶绿素含量逐渐降低，花青素是一种不稳定的有机物，本身没有颜色，当它遇到酸性物质时变成红色，遇到碱性物质时会变成蓝色。这样，花青素在酸性的叶肉细胞中就变成了红色，所以树叶就变成了鲜红色。
1、换季：由于植物的生长素调节，当植物叶片衰老的一定成度时，植物分泌大量脱落酸，植物叶片脱落加快增多。换季时，有些植物只生活一个生长季，每当冬寒来临时树叶会枯黄并全部脱落。
2、长期干旱缺水：当植物缺水时会减少水分传输到叶子中，这时树叶自然就枯黄了。
3、害虫危害：夏季是植物病虫害的高峰期，随着气温的逐渐升高，许多植物病虫害进入繁殖高峰期，多种虫害孵化成幼虫，大量食取叶片，吮吸叶液，导致树木病死。
4、根部积水：当一棵植物根部积水时就很容易烂根，植物根部被泡烂，无法吸取足够的养分导致树叶枯黄。
家里养的植物叶子发黄是为什么呀
1、旱黄：缺水的黄与水多的黄不一样，缺水之黄为叶梢或边缘发枯、发干，老叶自下而上枯黄脱落，但新叶生长比较正常。
2、缺肥黄：表现在嫩叶颜色变淡，呈黄或淡绿色，而老叶比较正常或逐渐由绿转黄。
3、缺光黄：长时间置荫蔽环境，叶片得不到足够阳光，不能形成叶绿素，整株叶片变黄继而脱落。
4、肥黄：施肥过多或浓度过大引起的花卉发黄，表现在新叶顶尖出现干褐色，一般叶面肥厚而无光泽，且凹凸不舒展，老叶片焦黄脱落。
5、灼黄：强烈阳光直射到一些喜阴的花卉上，易引起花卉叶梢、叶缘发枯，叶片朝阳部分出现黄斑。
6、水黄：嫩叶暗黄且无光泽，老叶无明显变化，枝干细小黄绿，新梢萎缩不长，表明浇水过多。
叶片发黄缺什么元素
叶子变黄多是因为缺少铁元素，硫元素以及镁元素，应根据实际情况来分析，之后采取具体措施来救治补充，这样才可变会绿油油的状态。此外，还可能是因为土壤的碱性过大，要及时补充酸性元素，使其变绿。
如果说叶子发黄缺什么肥的话，主要是缺少氮肥、磷肥、钾肥、钙肥，还有缺少铁元素、镁元素、硫元素和土壤碱分过多，只需要根据叶子发黄的不同情况，进行细致分析，随后对症下药施加合适的肥料，对植物进行元素补充。
秋天树上的叶子会变黄，主要原因是：树的叶片里含有叶绿素、叶黄素和胡罗卜素等物质。在春天和夏天，叶绿素在叶片中的含量比其他色素要丰富得多，所以叶子呈现出叶绿素的绿色，看不出其他色素的颜色。 当秋天气温下降，光照时间缩短，影响了根系
秋冬时节叶子缺少阳光的照射，叶子中的叶绿素合成量不及分解量，便露出了植物里其他色素的颜色，于是就呈现出黄、红等颜色。
秋天来临后，树木感受到来自秋天的气候的变化，从而使自身大量的叶红素把绿油油的叶绿素遮盖住，人们自然看到树叶变成红色或的了。一到秋天，落叶树停止生长，只需少量养料就可存活。 在落叶前，树干先分解叶绿素，分解产生的物质从叶子输送
秋天树叶变黄的原因
在春天的时候，树叶会进行光合作用，从而出现大量的叶绿素，而秋天光照变弱，树木生长放缓，叶子里面的胡萝卜素就会浮现出来。
其实黄色是叶子原本隐藏的颜色，之所以会呈现绿色，是因为叶子中含有大量叶绿素的缘故，但是除了叶绿素之外，叶子里面还含有红色素、黄色素等，秋天天气转凉的时候，输液停止工作，树叶里面的营养无法传输到树枝、树干上，就会慢慢沉淀到叶子上，变成黄色。
秋天树叶会变黄，是因为树叶中含有叶绿素、叶黄素和胡萝卜素，平时叶绿素含量较多，到了秋天，树木的根、茎就不再向叶输送养料和水分，并且会分解叶片中的叶绿素，叶绿素的分解速度远大于类胡萝卜素的分解速度，新的叶绿素由于天气寒冷又无法形成。当叶绿素被分解完，只剩下类胡萝卜素，于是就呈现出叶黄素和胡萝卜素所具有的黄色，所以我们就看到秋天树上的树叶是黄色的。
秋天树叶会变黄的原因
1、其实黄色是叶子原本隐藏的颜色，之所以会呈现绿色，是因为叶子中含有大量叶绿素的缘故，但是除了叶绿素之外，叶子里面还含有红色素、黄色素等，秋天天气转凉的时候，输液停止工作，树叶里面的营养无法传输到树枝、树干上，就会慢慢沉淀到叶子上，变成黄色。
2、秋天叶子会变黄的树木有很多，常见的有梧桐、银杏、石榴、合欢等。一般来说植物的叶子里面主要含有叶绿色、叶黄素和胡萝卜素，而这三种色素会因为温度的变化而发生变化，所以叶子也会呈现出不同的颜色了。
为什么秋天来了叶子会变黄
1、叶子绿的时候，叶子里充满了叶绿素，到了秋天，植物会分泌叶黄素;
2、秋天来临后，树木感受到来自秋天的气候的变化，从而使自身大量的叶红素把绿油油的叶绿素遮盖住，人们自然看到树叶变成红色或黄色;
3、到了秋天，落叶树停止生长，只需少量养料就可存活。在落叶前，树干先分解叶绿素，分解产生的物质从叶子输送到树恨，作为过冬养料。叶绿素分解后，树叶里就剩下叶红素，所以能看到树叶由绿变黄;
4、树叶中除了有绿色素外，还有红色素、黄色素等许多色素，只是数量少。到了秋天，绿色素慢慢褪去，红色素、黄色素便露出来;
5、新生叶子所含的叶绿素，其数量大约是叶黄素的八倍。春季和夏季黄色被绿色掩盖，随着叶子老化，虽然叶子含有的所有色素都会被分解，但叶黄素的分解速度比较慢，于是叶子就逐渐变成黄色。