(1) blade
The epidermis of leaves consists of a layer of closely arranged colorless transparent cells. The outer wall of epidermal cells has cuticle or wax layer, which plays a protective role. There are many paired half-moon guard cells on the epidermis.
The green parenchyma between the upper and lower epidermis is always called mesophyll, which is the main place for photosynthesis of leaves, and its cells contain a large number of chloroplasts. The leaves of most plants are planted horizontally on the branches, and the leaves are divided into upper and lower parts. The upper surface (paraxial surface and ventral surface) is light-receiving surface, dark green. The lower surface (far-axis surface and back surface) is a backlight surface, light green. Because of the different light conditions on both sides of the leaf, the mesophyll tissue on both sides often differentiates, which is called heterophyllous leaf. The leaves of many monocotyledons and some dicotyledons are planted almost upright, and the light on both sides of the leaves is uniform, so the mesophyll tissue inside is relatively uniform and there is no obvious tissue differentiation. This kind of leaf is called isosurface leaf, such as corn, wheat, Populus euphratica and so on. In heterophyllous leaves, mesophyll tissue cells near the upper epidermis are long columns, which are arranged closely and neatly, and their long axis is often perpendicular to the leaf surface, which is called palisade tissue. The number of palisade tissue cells varies with plant species, usually 1 ~ 3 layers. The mesophyll cells near the lower epidermis contain less chloroplasts, are irregular in shape, loosely arranged, and have large and numerous intercellular spaces, which are spongy, so they are called spongy tissues.
(2) Petiole
Petiole is the joint between leaf and stem, with the upper end connected to leaf and the lower end planted on stem. Usually the petiole is located at the base of the leaf blade. The petiole of a few plants is inserted in the center or slightly below the leaves, which is called shield-shaped insertion, such as lotus and Stephania. Petiole is usually thin cylindrical, flat or grooved.
(3) Leaf disk (leaf disk)
Stipules are tiny green or membranous sheets attached to the base, side or axils of petioles. Stipules usually grow before leaves and play a role in protecting young leaves and buds at an early stage. Stipules are generally very small, and the shape and size of stipules vary greatly among different plant species. In some plants, the existence of stipules is transient. With the growth of leaves, the stipules will fall off quickly, leaving only a little unnoticed stipules scar, which is called premature stipules, such as the stipules of heather. The stipules of some plants can accompany the leaves throughout the growing season, which is called stipules persistence. For example, Rubia and Agrimonia have a pair of leaflike stipules at the base of the petiole.
Leaf morphology
Just like people's looks are different, the leaves of plants have various shapes, such as scales, needles, wedges, ellipses, circles, sickles, diamonds, spoons, fans, violins, kidneys and so on. There are no two identical leaves in the world. Leaves not only have different shapes, but also have different edges. The edge of a leaf is called a leaf crack. Lu Ban, an inventor in ancient China, was inspired by cracked teeth and invented a saw.
In the process of adapting to various living environments, the leaves of some plants have undergone metamorphosis, the most typical of which is the cactus plant in the desert. In order to preserve water in the body and control transpiration, their leaves have degenerated into tiny needle-like leaves.
Autumn rain-tall buildings long for dusk, and there is rustling rain on the leaves of plane trees.
Autumn night-in my sleep, the autumn sound is nowhere to be found, and the leaves are full of steps.
Autumn sound-I didn't feel the dream of spring grass in the pond, but the leaves in front of the steps had autumn sound.
Autumn leaves-the wind blows bamboo in the middle of the night, and all the leaves are hate.
Autumn color-the rain invades the urn and the new moss is green, and the autumn leaves are red when entering the cross forest.
Autumn moon-the moonlight is flooded and the emptiness echoes.
Autumn chrysanthemum-it is better to die holding incense in the branches than to be blown down in the north wind.
Wan Li, an old friend, has never been heard from, and plans to ask Jiangtou to break the flood.
Autumn sorrow-don't say that you are always idle, and write clear sorrow every night.
Autumn is prosperous-the west wind blows all over the lake leaves, and it is unique to change your autumn clothes for the first time.
Autumn bosom-a fleeting sigh went out, and I saw konoha flying by the lake.
Qiu Meng —— Back in the autumn night at the beginning of my dream, Eden was still sleeping.
Memories of autumn-the anvil pestle knocks on the deep lane, and the phoenix tree shakes down the autumn hometown.
Enlightenment of autumn-everyone is explaining the sad autumn, not knowing it thoroughly like a poet.
The smell of autumn-crickets only know that autumn is early and there is a lot of rain on the banana.
Ancient poems and famous sentences describing autumn
Autumn wind blows gently, and Dongting waves under the leaves.
Curly wind: describes the breeze blowing. Dongting: Dongting Lake, in the north of Hunan Province. Waves: microwave flooding. Muye: Yellow leaves.
Qu Yuan's "Nine Songs, Lady Xiang" in Chu Ci of Warring States Period
Sad autumn is also angry! Bleak, vegetation withers and decays. Travel far, and return to the mountains near the water.
Desolate: loneliness and depression. Liao Li: Desolate. If you travel far away: It seems that people travel far away.
Nine Debates on Chu and Song Yu in Warring States Period
The autumn wind rises in Bai Yunfei, the plants and trees fall yellow, and the geese return to the south.
Che's autumn wind poem
The autumn wind is bleak, the weather is cool, and the vegetation is shaken and exposed to frost.
Song of Yan comes from Cao Wei Pi in The History of the Three Kingdoms.
There are many fallen leaves in Lu Ting, so I know it's autumn.
Green court: green fragrant courtyard.
Tao Jin Yuanming's Reward to Liu Chaisang
In the new autumn, the elegant moon will be round.
Jump: describe the length of the night. Tingting: It's far away.
Tao Jin Yuanming's "Fire in June in Wushen"
The lotus is exposed, and the willow is sparse in the moon.
Lotus: Lotus.
Xiao Qi Yan's Qiu Si in the Southern Dynasties
The cold city wants to overlook, and Pingchu is bleak.
Cold city: The cold has invaded the city. Look: Look into the distance. Pingchu: Ye Ping. Cangran: The appearance of lush vegetation. Write two sentences about the scene of early autumn.
Looking at Xuancheng County in Southern Dynasties
The leaves under the pavilion are high, and it is the first autumn in Gansu.
Gao Ting: The water is flat. Konoha: Leaves. Dragon Head: The mountain name is between Shaanxi and Gansu today.
Yi Dao Poems of Liang and Liu Hun in Southern Dynasties
Grass is low, golden city is foggy, and Yumen is under the wind.
Grass is low: hay withers. Under the tree: leaves are falling. Jincheng: the name of an ancient county, between Yuzhong, Gansu and Xining, Qinghai. Yumen: Yumen Pass, in the west of Dunhuang, Gansu. Write two sentences about the cold autumn scenery in the northwest.
The uniqueness of clouds in the southern dynasties
Trees and trees sing in autumn, and the colors of mountains and mountains are very cold.
Autumn sound: in autumn, the west wind works, the vegetation is scattered and it is chilly.
Epitaph of Lady Brugu, Duke of Zhouqiaocheng, Yuxin, Northern Zhou Dynasty
In September, the sequence belongs to Sanqiu.
V: auxiliary words are meaningless. Foreword: season.
Tang, Preface to the Autumn Knee King Pavilion.
Sunset and lonely Qi Fei, autumn waters and sky are the same color.
Raccoon: Bird name, wild duck. Qi Fei: The sun sets from the sky, and I am lonely from bottom to top, competing with Qi Fei. A color: the water in autumn is blue, and the sky is blue, reflecting the water and forming a color.
Tang, Preface to the Autumn Knee King Pavilion.
Trees are all autumn, and mountains only have light.
Don Wang Ji's Wild Hope
Hanging forest scenery is different, and autumn is like Luoyangchun.
Tang Song Wen Zhi "Autumn in the Early Years of Anchou".
The mountain is cold and blue now, and the autumn water has flowed for a day.
Ripple: the sound of running water.
I wrote a letter to Wei in Wangchuan's cabin.
The white stone in the west of Beijing is cold and the red leaves are thin
These two sentences describe the scenery in late autumn: streams dripping, white stone dew and red leaves falling, leaving little.
Wei's Two Poems of Magpie Criing in the Mountain
Autumn sounds like bamboo, and cool colors like Wuling pine.
Tang "Looking at Qinchuan"
The golden well phoenix tree has yellow autumn leaves, and the bead curtain does not roll frost at night.
Tang Wang Changling's "Long Letter in Autumn" includes five poems: "Golden well, phoenix tree, yellow autumn leaves, and the bead curtain does not roll frost at night. The smoked jade pillow has no color, and you can listen to the Nangong for a long time. "
The cold pool reflects Bai Yue, and the autumn rain grows moss.
Liu Tang Changqing's You Xiu Zen Master Shuangfeng Temple
The south is a wilderness, because leaves are falling, and the wind from the north makes the water cold.
Tang Menghao's early Leng Jiang got pregnant.
There is no distance in autumn, and it is cold to go out.
Tang Li Bai's "Gift to Lu"
The rain in Qiu Lai is very cold, and the wind is cool and clear.
Tang Li Bai's "Rewarding Pei for Love Rain"
Autumn geese are escorted by Changfeng, and I treat them in this villa and drink my wine.
Han: Drink to your heart's content.
Tang Libai bid farewell to Minister Shu Yun at Xie Tiao Villa in Xuanzhou.
A cold orange pomelo and an old phoenix tree in autumn
People smoke: people cook and smoke. Cold orange pomelo: The cold smoke in autumn makes the orange sleeves chilly. The two sentences are written about human beings, orange pomelo is dark blue, and phoenix tree is yellowish, showing a late autumn scenery.
Tang Li Bai Qiu Deng Xuancheng Xie Tiao North Building
At dusk in Huang Yun, birds fly high in the sky, and in autumn, the trees are very cold.
Tang Du Fu's Late Autumn, Changsha Cai Wufeng gave a royal banquet to send Liu Yin back to Fengzhou to visit the province.
The fisherman who lives in the lodge is still vague, and the swallow flies in the clear autumn.
Shinjuku: Two nights. So: still.
Tang Du Fu's Eight Poems of Autumn Prosperity
Zhaitang Xiakou Qujiang Head, Wan Lifeng Smoke meets Suqiu.
Tang Du Fu's Eight Poems of Autumn Prosperity
The far shore is white in autumn and sandy, and even the mountains shine red at night.
Tang Du Fu's Five Poems of Akita
Autumn is near in the sky, and the moon is bright on the ground.
Tang Du Fu's Moon
In August and autumn, the wind roared and rolled up my three hairs.
Tang Du Fu's Autumn Wind Breaking the Cottage
Changfeng blows cogongrass rhizome, and wild fire withers mulberry.
Imperata; Thatched grass describes the scene of vilen in late autumn: the wind blows thatched grass on the vilen, and the wild fire burns withered mulberry trees.
Tang Cen Can's "Send the Lord of Kuangcheng to the Girder"
The autumn wind moves in Wan Li, and the setting sun is yellow.
Don Cen Can's Gongbeiqiu Jixing Cui Mingyun
The return of light is chaotic, cold and empty.
Flight: Late photo, sunset photo. Turbulence: A criss-crossing river. Zhang: A steep mountain peak.
Qi "Mid-Autumn Festival Nanshan Xifeng Title Master Lan Ruo"
In the Voice of Ye Qiu, when thousands of people took pictures.
Sunset: The sun sets.
Qi's Su Ting
Suyu dynasty came to rest, empty mountains and clear autumn.
Su Yu: It rained last night.
Tang Li Duan's Maoling Mountain Travel Companion Wei and Jin Department
The rain is green and the frost garden has many red leaves.
Green grass: green grass. Closed: full. It means that after the rain, the path in the yard is covered with green grass, and the garden is covered with red leaves after frost, and the courtyard is desolate and lonely.
Tang Bai Juyi's Sima Zhai
Beautiful scenery, with frost at night, a few trees are dark red and light yellow.
Two Autumn Poems of Yuxi, Liu Tang
Try to go to the bottom of the building, but I'm afraid of spring fever.
Clear to the bone: the autumn scenery is clear to the bone. Hey: Encourage.
Liu Yuxi's two autumn poems
How many violets depend on each other and hate each other, looking back at the west wind for a while
Describe the lotus leaf slanting eastward in the autumn wind, which hurts autumn.
Two Occasional Problems of Mu in Qi 'an County
Red candle cold painting screen, light Luo small fan flapping fireflies
Small fan: A thin round fan. These two sentences describe that the red candle emits cold light in autumn night. According to the picture, the girl is chasing firefly mountain with a delicate round fan.
Autumn Night by Tang Du Mu
During the day, the order is as cool as water at night, lying and watching morning glory and Vega.
Day order: steps in the palace.
Autumn Night by Tang Du Mu
Autumn cloudy frost flies late, leaving the lotus to listen to the rain.
Cloudy in autumn: Although it was autumn, it was cloudy for several days, so there was no serious frost landing. The dry load in the later period also came out from this. Listen to Yuji: The rain withered lotus, monotonous and desolate.
Tang Shangyin's "Love in the Snail Pavilion, Ode to Cuizhou"
In autumn, when Shan Ye was drunk, he was 100 feet tall and half a month old.
Tang Jianwu's Mountain Residence on Autumn Night: "Who weaves new snow when the geese go silent?" Shan Ye is drunk in autumn, and half a month is full. "
The old tree is autumn, and the empty pool is soaked in the moon.
Liu Tang Deren sleeps in the swimming pool.
The moonlight in autumn is better than the spring night, and the days in first frost, Wan Li are quiet and lonely.
Tang Rongyu's Autumn Moon (also known as: autumn moon wins spring night, Wan Li is quiet and lonely)
A night of violet frost shearing made him lose the autumn rain.
Flying frost breaks the lotus leaf, and autumn rain falls on the broken leaf and can no longer form water droplets.
Two occasional poems by Tang Laigu
Midnight wine makes people awake unconsciously, and the lotus leaves by the pool are swaying in the autumn wind.
Unconsciously; No sleep.
Tang Dougong's Autumn Night
Xiang Lian sells green leaves, while the west wind worries about green waves.
Lotus: another name for lotus.
South Tang Li Jing's Huanxisha
Blue sky, yellow leaves, autumn waves, cold smoke on the waves.
Song Fan Zhongyan's Su Mu Man
Good years must be remembered, especially when they are orange and green.
Orange, orange and green: refers to the season at the turn of autumn and winter.
A gift from stone.
You don't have to go home when you meet, and Huang Die will be sad tomorrow.
Tomorrow's yellow flowers: refers to the gradual fading of chrysanthemums after Chongyang. Butterflies are also sad: chrysanthemums wither and butterflies have nowhere to find flowers, so they are called "sad".
Stone's "Nine Days Rhyme" in Wang Gong
Whispering trees flow out of the forest, and the autumn mountains have a sunset.
Pavilion wall on Zhunshu River in Songkou
Autumn sometimes flies alone, and the sunset has nothing to do with cold smoke.
Song Su Lin's Seeing the Master's Room at the End of Gushan Temple
Sprinkle rainy dusk on the river and wash the autumn.
Xiaoxiao: The way the light rain falls.
Song Liu Yong's Klang Ganzhou
The frost and wind are getting cold and tight, the river is cold, and the sunset is a hug.
Frost wind: autumn wind. Guanhe: Guansai River. Afterglow: the afterglow of sunset.
Song Liu Yong's Klang Ganzhou
Red flowers wither everywhere, and all the beautiful scenery gradually disappears. Only the Yangtze river water, speechless east.
Everywhere: everywhere. Decline: Flowers wither and leaves fall. Hengheng: Gradually. Wuhua: Beautiful scenery.
Song Liu Yong's Klang Ganzhou
Broken rainbow rain, clear autumn sky, dyed mountains and trimmed eyebrows and new green.
Broken rainbow: the remaining rainbow. Yuji: The rain has stopped. Eyebrow trimming: long eyebrows that describe the beauty of the mountain.
Song and Huang Tingjian's Niannujiao
The desert is lighter than the small building, and the hooligans are like poor autumn.
Rogue: Boring. Poor autumn: late autumn.
Guan's "Huanxisha"
There are no fallen leaves in Xiao Xuan, but caterpillars spit autumn silk.
Xiao Xuan; A small room with a windowsill.
Guan's Autumn Day
Autumn is full of old hibiscus gardens, and the frost on the grass is even like a headland.
What autumn looks like: the color of autumn. Old: deep.
Guan's Magnolia
How many violets are there in the sunset? Who knows who hates who supports the west wind?
Who; Who is it? Back to the west wind: back to the autumn wind.
Refers to the lotus leaf bent by the autumn wind.
Guan The Mermaid
The mountain rubs Wei Yun, the sky sticks to the grass, and the painting breaks the door
Rotting grass: hay. Horn painting: a horn used in the army. Breakthrough: Do it. Bridge Gate: Drum Tower on the city, used to watch the enemy.
Write three sentences about the isolated city of autumn scenery.
Qin Song Guanman Fang Ting
The west wind falls, and people are sparse.
Song Xin Qi Ji's Revenge of Zhao Jun
Sleeping in the world, everything goes to Qiu Lai, and everything is shaken.
Song Xin Qi Ji's "Man Jiang Hong You Nan Yan Fan Kuoyun"
Autumn is not an inevitable sadness, but a pleasant cold. The green pools are all red, but the leaves still have the smallest money.
Karen: This is desirable. Red-violet (pronounced "Canal"): Lotus. But: open them all. Minimum money: the new lotus leaf is as big as a small copper coin.
Song Yang Wanli's Walking in Late Autumn
Don't fold Hà Thu in the garden, because it covers the sunset with fish.
Song Zhou Mi's Xiheng Waste Garden (also known as Xiheng Waste Garden). Rolfe: Soil stalks in the field. )
The sky is blue, and a river is dyed in autumn.
Dye it: dye it.
Song Zhou Mi's "Wen Que Xiwushan Viewing Pottery"
There is only one blade, and I don't know how many autumn sounds.
Yan's Qing Ping Le
The sound of spring is loose, and rows of autumn geese come.
Valley (sound the same as "harmony"): Valley.
Two Poems of Yuan's Climbing Dreams
Autumn wind blows Bai Bo, and autumn rain beats lotus. Pinghu is thirty miles away, and there are many passers-by in autumn.
No load: residual load.
Yuan's Nine Poems of Crossing Gaoyou Sheyang Lake
The sunset in the lonely village, the light smoke from the old tree in the west of Western jackdaw, and the shadow of Hong Fei.
Sunset: Sunset. Western Western jackdaw: Crows returning to the forest in cold weather. Hong Fei: Goose.
Pu's Jing Tian Sand Ball
There are many yellow geese crossing the river in the cold wave at night.
On the River by Wang Qing Shi Zhecun
The mountains are shallow and deep with the setting sun, and the rivers become autumn day and night.
Autumn Sound: The river changes its sound when it flows to Qiu Lai in summer.
Qing Dynasty and Song Dynasty Bowl "On the 9th, Jiang Rulong,, and Cheng went to Huiguangge Bamboo Garden for drinking".
There are three pigments in plant mesophyll cells: chlorophyll, lutein and carotene.
The synthesis of these three pigments is related to temperature. When the temperature drops in autumn, the secretion of carotene increases, and carotene is orange, so the leaves will turn yellow.
Why do trees lose their leaves in autumn?
Because autumn means the coming of winter, trees need to sleep for self-protection, and hibernating trees themselves need nutrients. In order to adjust the internal balance, many trees need to shed leaves, reduce the loss of water and nutrients, and conserve energy until the conditions are suitable. And some trees, such as pine and cypress, can remain evergreen because their leaves are like needle tips, and there is little loss of water and nutrients.
People often use "autumn wind sweeping leaves" to describe autumn scenery in temperate regions. Autumn has come, and the leaves of broad-leaved trees such as poplar and locust tree are gradually aging. With the rustling autumn wind, the yellow leaves fall quietly. You may feel sorry for the fallen leaves, but have you ever thought that the fallen leaves are just the self-protection of trees?
It's cold, people put on stoves and cotton-padded clothes. But what about trees? They can only spend the winter safely by shedding all the leaves to minimize water transpiration. Otherwise, due to the freezing weather and whistling wind, it is difficult for the roots to absorb water, and the transpiration of the leaves will proceed as usual. Think about it, what is waiting for the trees besides death?
Petiole used to grow stiff on branches. In autumn, as the temperature drops, several layers of fragile parenchyma cells form at the base of petiole. Because these cells can be easily separated from each other, it is called stratification. After the separation layer is formed, it will break when a slight breeze blows, so the leaves will fall.
Leaves are broad-leaved trees in temperate regions, which is a skill to reduce transpiration and prepare for safe winter.
And it has a lot to do with abscisic acid contained in trees.