The leaves of the green flowering plant are so wonderful that they feed not only the plant itself, but also humans and animals. It can be said that without green leaves, there is almost no biological world.
How much mystery are there in the leaves? This article chooses to talk about, and it is enough to dazzle you.
<h2 class="pgc-h-arrow-right" > the "specific function" of the leaf</h2>
We say that the leaves of green plants have "specific functions", which is not an exaggeration. As we all know, the leaves of green plants can use the chlorophyll they contain, absorb water and carbon dioxide, and photosynthesis through sunlight to produce carbohydrates. Carbohydrates are able to be converted into starch, which provides a food source for humans and animals.
Curiously, although human beings have figured out the process of plants making carbohydrates, they have not been able to artificially produce starch and produce grain, and the mystery of this has not yet been revealed. Because the leaves of green plants have the "specific function" of making carbohydrates, and are known as "first producers", they produce starch from scratch for human and animal enjoyment, and cattle, sheep, etc. in livestock can grow up and be used by humans by eating grass.
Imagine what the world would have become without greenery.
So, how do the leaves of green plants get water and carbon dioxide? In fact, the reason is very simple. The water obtained by the leaves and the dissolved nutrients in the water, such as nitrogen, phosphorus, potassium, etc., are absorbed from the soil through the roots, and due to the root pressure function, the water is absorbed and directly transported to the leaf cells through the stem and branches. Carbon dioxide gas enters the leaf from the pores on the epidermis of the leaf. In general, there are more than 100 stomata on a square millimeter of leaf area, and as many as 10 million stomata on a cabbage leaf. It can be seen that the stomata creates an unimaginable convenience for the entry of carbon dioxide.
Botanists have studied and calculated that green plants on Earth produce up to 400 million tons of carbohydrates a day, and these leaves can also release oxygen when photosynthesis occurs. Botanists have calculated that global green plants can release nearly 500 million tons of oxygen a day. Oxygen is necessary for humans and animals to maintain breathing, without which there is no life.
It can be said that green plants are the benefactors of human beings.
Because plants exchange gases with the outside world through leaves, the leaves will be directly affected by pollutants in the air, so many plants reflect harmful gases much more sensitively than humans and animals, as long as they are slightly affected by pollutants, their leaves will have obvious symptoms.
If the damage is light, there will be spots on the leaves, and the green will become lighter; in the serious victims, the leaves will turn yellow, wilt, and even the whole plant will die. The amount of stratum corneum, fur, scales and other protective substances on the surface of the leaves, as well as the distribution of stomata, will affect the plant's resistance to pollutants. For example, the leaves of mosses and lichens are generally monolayer cells, without a protective layer, and external gases can easily invade the cells directly. When the concentration of sulfur dioxide in the air reaches 5 parts per 10 million, their leaves turn yellow or black-brown and quickly dry up and die.
In addition to plants such as mosses and lichens that are sensitive to sulfur dioxide pollution, we can also find many other plants that are also sensitive to air pollution. For example, tomatoes, tobacco, spinach, etc. are sensitive to nitrogen dioxide pollution: sunflowers, cabbage, larch are sensitive to chlorine pollution; plums, peaches, grapes, etc. are sensitive to fluoride pollution: tobacco, peanuts, onions, etc. are sensitive to ozone pollution. Using the sensitivity of plants to air pollution, we only need to observe the leaf conditions of sensitive plants in a certain area to know the type and extent of atmospheric pollution there.
<h2 class="pgc-h-arrow-right" > single and compound leaves</h2>
The leaves are divided into single and compound leaves. The so-called single leaf, refers to a petiole only 1 leaf, the plant's "bud" is born on the branch of the inner base of the petiole, usually the middle axillary bud (that is, the bud of the leaf axilla), for example, the leaves of cotton are single leaves, the leaves of sunflowers are also single leaves, the leaves of melon crops are single leaves, plums, peaches, plums, cherries, cherry blossom leaves are single leaves, poplars, willow leaves are also single leaves, apples, pear trees are single leaves...
What is compound leaf? Compound leaves are more than one leaf on the petiole, which are arranged on a total petiole. The buds of the plant grow on stem branches at the base of the inner part of the total petiole. These leaves should be called "leaflets", with no buds on the inside of the base of the leaflets. For example, the leaves of the locust tree are compound leaves, and the leaves of the locust are also compound leaves, because their two columns of leaflets are arranged in a feathery manner, so they are also called pinnate compound leaves, and because their number of leaflets is mostly odd, they are also called odd pinnate compound leaves. If the number of leaflets is double, it is called an even pinnate compound leaf, such as the pinnate compound leaf of the soap pod tree is even.
Sometimes the small leaves of the compound leaves can be seen in two rows, but are radial from the top of the total petiole, such as palm-shaped, it is called palm-like compound leaves, such as horse chestnut trees, kapok trees, and the leaves of fortune trees are palm-shaped compound leaves.
<h2 class="pgc-h-arrow-right" > diverse leaf shapes</h2>
The leaves are varied, round, oval, lanceolate, spoon-shaped, sickle-shaped, and violin-shaped. The edges of the leaves are smooth, wavy, serrated, shallow, deep or fully lobed, and some palmate splits of varying shades. Such as palm, castor, etc., there are obvious splits at the edges of the leaves, resulting in many gaps in the whole leaf.
Why does the leaf of the plant change in appearance?
We know that green leaves are the main organs of plants that make nutrients. In the process of photosynthesis, sunlight is a necessary condition. In addition to the flat structure of the plant, which can increase the absorption of light energy on the surface, the leaves of the plant have produced palm-shaped split leaves due to long-term evolution. This leaf shape can not only make the leaves absorb the largest amount of light energy, but also the gap left by the split will not completely cover the leaves below to receive light, so it can ensure the full performance of photosynthesis of the whole plant.
In addition, when the round palm-shaped leaves encounter strong winds, they are easily blown due to the large windward area, and with these splitting gaps, the harm of strong winds can be greatly reduced. In this way, the leaves of the plant undergo long-term natural selection and appear palm-like division.
There is a tree leaf often makes many people unable to distinguish whether it is a compound leaf or a single leaf, more people at a glance, said that it is a pinnate compound leaf, this plant is called Metasequoia.
Some people think that the leaves of Metasequoia are arranged in a plane, pinnate, that is, pinnate compound leaves; in fact, this is the key to not clearly distinguishing between single leaves and compound leaves, the key should be to see whether there are "buds" at the base of the leaves, if there are buds, the buds will produce short branches, and there can be leaves on the short branches, if there is no bud, there will be no short branches from the leaf axils. Metasequoia leaves have small buds in the leaf axils, some of which can produce new short branches, and some of which have not yet produced new short branches, but this does not mean that there are no buds, but the conditions are not yet suitable. Therefore, Metasequoia belongs to the monolear plant.
<h2 class="pgc-h-arrow-right" > a variety of leaves</h2>
In nature, the leaves of green plants are all kinds of colorful.
In the alpine environment, the temperature is low, the air is thin, the light is strong, and there is snow all year round. The biggest problem faced by plants in this environment is the contradiction between too strong sunlight and too low temperature. Therefore, the leaves of the alpine snow lotus are close to the ground and have flocculent white skin hair, which can not only prevent the alpine wind from blowing, but also absorb the heat of the ground, prevent heat loss, and also reflect off strong ultraviolet rays. Relying on this metamorphosis and structure, they tenaciously live in harsh environments.
In the tropics, things change. The temperature is high, the sun is strong, and the moisture is abundant, so the leaves of the plant are larger, mostly round, oval or shield-shaped, and the leaf surface is smooth. This leaf can not only enhance the evaporation of water, reduce the leaf surface temperature, but also reflect strong sunlight because the leaf surface is smooth. In addition, the leaf tips of tropical plants are mostly pointed and convex shapes, and the water that falls on the leaf surface can fall quickly, which can prevent the leaf surface caused by rain from being invaded and covered by parasitic plants; at the same time, it is also convenient for rainwater to wash away the larvae and eggs on the leaf surface to reduce pests and diseases.
Some green plants have leaves that are both large and playful, such as Wang Lian. King Lotus belongs to the water lily family, born in the Amazon River in South America, the leaves are disc-shaped, surrounded by upward rolls,
There are notches to prevent rain and water, the leaf diameter can reach 2 meters, and the leaf surface can support a small child without sinking.
There are also plants whose leaves catch insects. There are many species of this type of plant, the most famous being Nepenthes. Its leaves are metamorphosed into a pocket, there is sweet juice at the mouth of the bag, there is digestive juice in the bag, and when the insect comes to the mouth to find the sweet juice, it falls into the bag and drowns, and is digested and absorbed.
There are also many species of insectivorous plants that rely on leaves to catch insects, which will not be repeated here.
The leaves of some plants turn into tendrils, such as the leaflets of peas and wild peas. The leaves of the pea are even pinnate compound leaves, and there are tendrils at the top, which are metamorphosed from the leaflets, and the function is to facilitate the use of tendrils to roll on other things, so that the peas stand up, expand the space, and facilitate their growth. This is also true of the fact that the leaves of wild peas become tendrils.
The yellow essence of the lily family, the stem is upright, the impeller is born, each leaf is narrow and long, the apex is metamorphosed into a curl hook, it is formed by the extension of the middle vein of the leaf, it can roll other things, let the stem grow upright upwards, the whole body stands steadily, grows tall, expands the living space, and is more favorable to its own survival.
< h2 class="pgc-h-arrow-right" > degraded leaves</h2>
The leaves of some plants gradually degrade during evolution to adapt to the environment. Especially when the environmental conditions are too arid, the survival of plants is seriously threatened, in order to reduce the requirements for water, in order to ensure their own safety, their leaves become smaller, become small scales, and lose their green.
Some plants have degraded leaves that can replace leaves for photosynthesis due to their green stems, such as the false leaf trees of the lily family.
It appears that the false leaf tree has ovate "leaves", which are green, flattened, small and hard. People who don't understand it still think it's the leaves of the false leaf tree, but in fact, it's the flattened stem of the false leaf tree, and the real leaves have degenerated. Another example is the familiar cactus, its stem is also flat, green, and the real leaves are metamorphosed into thorns.
Wenzhu, also known as cloud bamboo, the dense leaf-like object is actually a small twig, with small, white degenerated leaves on the branches.
The single stick tree belongs to the Euphorbiaceae family, and there are many upright, slippery green stems and branches all over the body, not a single leaf is missing, and when it grows young branches, it will see a few small leaves, but it will soon fall off, and photosynthesis depends on these green branches.
According to scientists, none of the leaves of the world's plants are exactly the same. They come in all shapes and sizes. The largest leaf can build a small house, and the smallest is smaller than the scales of the fish. The length of the leaves also varies. The leaves of corn look relatively long, about 1 meter or so.
In the Palm of the Amazon in South America, a leaf with a stalk with a leaf is 24.7 meters long. Tropical long-leaf coconut, one leaf is 27 meters long and erected 7 stories high. This is the longest known leaf to date.
< h2 class= "pgc-h-arrow-right" > leaf lifespan</h2>
Animals and plants have a certain life cycle, and the leaves are the same. It does not grow on the plant body for a long time, but has a certain lifespan.
The life of the leaves is generally not long, such as deciduous trees, spring leaves, the autumn wind together, it will fall; evergreen trees, such as pine cypress, have green leaves throughout the year, but in fact, its leaves are not never withered, but also constantly have leaves to die, but the leaves of the pine are not all at once withered, but part of the change, when the old leaves die, the new leaves have come out, so the pine looks forever lush. The lifespan of pine leaves is indeed longer than the leaves of deciduous trees such as peaches and plums, and they can survive for 3 to 5 years, but not too long. The lifespan of fir leaves is 12 years.
Typically, annual plants, the leaves die along with the plant body. Perennial herbaceous plants and deciduous woody plants with leaves that live for only one growing season. Evergreen woody plants, the lifespan of the leaves can be several years.
When the plant is about to fall, there are great changes inside the leaves, and useful substances in the cells are gradually broken down and transported back into the stem. Chlorophyll in chloroplasts decomposes faster than lutein, so the leaves gradually turn yellow. Some plants produce anthocyanins in the cells before deciding, and the green leaves become red leaves. At the same time, at the base of the petiole there is a layer of cells to divide, the formation of several layers of small thin-walled tissue cells, this layer of structure is called the layer of separation, soon the middle layer of this layer of cells decomposition, and then the entire cell decomposition, the leaf gradually withered, and then due to mechanical forces such as wind and rain, the petiole breaks from the layer and the leaves fall off. The thrombosis of cells at the break of the layer plays a role in protecting the "wound". After the leaves fall off, there will be scars on the stems, which are called leaf marks.
Since the lifespan of leaves is long and short, which plant in the world has the shortest leaf lifespan? Which plant has the longest leaf lifespan?
The shortest-lived leaf in the world is the leaf of the short-lived chrysanthemum, which can only live for 3 to 4 weeks.
The longest-lived leaf in the world is the African centenary leaf. This plant belongs to the gymnosperm family Centaur family Centaur leaf genus, only one species, namely centaur leaf, also known as centipede orchid.
The 100-year-old leaves have a peculiar shape, the stem is short and thick, no more than 10 to 20 centimeters high, and the stem circumference is up to 4 meters, similar to the flat tires of large trucks. This plant has only two ribbon leaves in its lifetime, spread on the ground, and can live for hundreds of years.
The leaves of the centenarian leaves are soft when they are first born, and in order to adapt to the arid desert environment, they gradually become as hard as leather. The two leaves are 2 to 3 meters long and 30 centimeters wide, and the two leaves put together are much longer than a single straw mat. The apex of this leaf gradually withered, the flesh of the leaf rotted, the remaining woody part of the fiber reel was bent, and the thick and short stem, people looked at it from a distance and thought it was a monster on the ground.
There are leaves in the world that are larger than the centenarian leaf, and there are leaves that are more peculiar in shape than it, but there is no leaf that lives longer than the centenarian leaf.
Born on the sandy ground off the coast of Africa, he lives on the moist water vapor blown by the sea breeze.