How to remedy the yellowing of Phyllostachys pubescens leaves

The original turquoise young leaves become lighter and appear yellow or light green, while the old leaves are more normal or gradually change from green to yellow.

Cause analysis:

In fact, this situation is rare, and the yellowing of fertilizer-deficient leaves is chronic. Flower friends can observe the leaves. If the leaves yellowed quickly, it will not be because of lack of fertilizer, and do not apply fertilizer blindly, because if something goes wrong with the roots, fertilization will aggravate the rot.

Solution:

If it is determined that the lack of fertilizer is caused by the yellowing of leaves, we can apply fertilizer with snacks and meals and add some alum at the right time. (note: Phyllostachys pubescens is a foliage plant and should be fertilized mainly with nitrogen fertilizer.)

Identification and Prevention of freezing injury of Flowers and trees

When potted or planted flowers and trees suddenly encounter a cold wave and go south in late autumn and early winter, or because of the sudden arrival of the "first frost", it is easy to cause flowers and plants to suffer cold injury or frost injury; when potted flowers leave the room or facility cultivation in spring to remove the covered film, suddenly encounter the belated "late frost" or "late spring cold", it is also very likely to cause the flowers and plants to suffer cold injury or frost injury again. Whether it is large-scale productive cultivation, or a small number of potted plants by flower lovers, great attention must be paid to the prevention of cold injury, otherwise it will bring you serious losses and long-term "remorse".

Cold injury is a kind of physiological disease, which is not an infectious disease caused by pathogenic bacteria. It generally refers to the injury caused by the direct action of low temperature on flower plants, including cold injury and freezing injury, but does not include indirect winter drought, freezing and other winter injuries.

Winter drought and freezing are indirect damage caused by low temperature. Winter drought refers to: some evergreen flowers, under some special weather conditions in winter, such as long-lasting and strong wind sweeping or sunny days that are not too cold but sunny, the transpiration rate is relatively high, but because the soil temperature is low and the root absorbs water slowly, the water in the body can not maintain a normal balance, so that leaves and other tissues are dehydrated, dried and damaged, which is essentially a kind of drought damage. Such as wood incense, Jasminum and other leaves suddenly dried up in dry, cold and sunny days. Frozen pull refers to: when the water of melting snow seeps into the soil and freezes again, some plants, especially seedlings or herbaceous flowers, are often lifted together with the frozen soil, thus destroying the close contact between the root system and the soil, or even tearing off the root group; before the root system has time to recover, it encounters weather conditions that promote strong transpiration, causing the plant to wither and die. If the wintersweet planted in the flowerpot is placed in a very cold place in winter and freezes because the pot soil is wet, lift the root block to separate it from the basin wall, if it can not be found in time, and replant it, or move it to a warmer environment, it is also likely to die due to the loss of water in the root system, resulting in plant death.

I. types and causes of cold injury

As the causes of cold injury are different, the harmfulness is also different. The difference between cold injury and general infectious diseases lies in: first, it is not contagious, the injured site will not appear pathogens; second, the same kind of flowers and trees placed in the same environment tend to have diseases at the same time overnight, and young shoots and new leaves are the most serious. Third, it occurs in low temperature or very cold weather conditions, and the harmfulness is related to the types of flowers and trees, the duration of low temperature, the speed of temperature recovery, the lower limit of low temperature and so on.

Bamboo taro chilling injury poinsettia chilling injury pocket turtle back bamboo chilling injury petunia chilling injury concomitant fruit taro chilling injury Marianne powder leaf chilling injury

1. Causes of chilling injury

Some ornamental plants native to the tropics or subtropics are seriously damaged or killed by the low temperature above freezing point (0 ℃ ~ 5 ℃ or higher) for a few days or even only a few hours. This kind of cold injury, which does not reach the degree of freezing in the tissue, is called "cold injury". It is caused by the disturbance of normal metabolism in cells and tends to be disordered, resulting in the production of toxic substances. Different physiological activities and metabolic processes of flower plants have their own highest, lowest and optimum temperatures. when the environmental temperature changes, their physiological activities and metabolic processes will be affected differently; if beyond a certain range, it will destroy the coordination between them and produce a large number of substances that will not be produced and accumulated under normal conditions. Further study found that under the condition of chilling injury, the rate of protein hydrolysis was 4 / 9 times higher than that under normal conditions, and the metabolism of nucleic acid was seriously interfered. In addition, cooling also affected the oxidation activity of sensitive mitochondrial membrane in plant somatic cells.

Thus it can be seen that: first, the species of ornamental plants that cause chilling injury are usually plants native to the tropics or subtropics; second, the temperature condition of chilling injury is higher than that of freezing point; third, the time of causing chilling injury is long and short, usually a few days, or even just a few hours. Generally in late autumn and early winter or early spring, sudden changes in temperature are most likely to lead to chilling injury to flowers and foliage plants originating in the tropics or subtropics. Usually the young leaves of the tender shoots are "purple", "brown", "yellowing", "wilting", "necrotic" and so on, such as a string of red, green bamboo leaves, longevity flowers, leaf cotyledons, purple bamboo leaves, and so on, all belong to this category.

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2. The cause of freezing injury.

Freezing injury refers to the damage caused by freezing in the tissue of ornamental plants when the temperature is below 0 ℃ or when they encounter ultra-low temperature for a long time.

There are two kinds of ice crystals in plant tissue, one is freezing in cells, the other is freezing between cells. The former means that when plant tissue freezes quickly, ice crystals form in vacuoles and protoplasts, destroying the structure of protoplasts and causing protein denaturation, and some membranes in protoplasts are also scratched, usually causing tissue to be killed. therefore, the result of this "freezing injury" is very serious and irreversible. For example, the cold wave in the north suddenly went south in early winter, causing a sharp drop in temperature in a short time, and in the winter of 2004, a large number of foliage plants in southern China died of freezing injury; in early December 2005, the temperature in Hefei suddenly dropped from 12 ℃ ~ 15 ℃ to-3 ℃ ~-5 ℃, resulting in a large number of magnoliaceae flowers and trees, such as Magnolia mandshurica, Magnolia mandshurica, Magnolia safflower, Magnolia ruyuanensis and other leaves and young stems seriously frozen. The latter refers to the gradual formation of ice crystals in plant tissues with the gradual decrease of ambient temperature. because the concentration of solution in the intercellular space is generally lower than that of protoplasts and vacuoles, the cooling rate is not too fast. the water in the intercellular space reaches the freezing point and freezes first than inside the cell, and the formation of ice crystals causes the water in the protoplast to move outward. This leads to cell liquid concentration, protoplast dehydration, protein precipitation, cell membrane degeneration and cell wall rupture. When ice crystals are formed in the intercellular space, whether the cell tissue is killed depends on the freezing resistance of the cell and the speed and times of freezing and thawing; one of the mechanisms of freezing injury is the dehydration of protoplasts, which has the same consequences as dehydration under drought conditions. that is, due to the mechanical stress caused by the deformation of the cell wall, the structure of the protoplast has been irreversibly destroyed. After the cell fluid is concentrated, the concentration of salt ions and organic acids increases, which may also be toxic to the protoplasm. The serious degree of freezing injury is related to the speed of freezing, the faster the freezing, the more serious the injury, this is because the faster freezing, the greater the possibility of intracellular freezing; if the freezing is limited to the intercellular space, then the faster the freezing, the faster the water loss and contraction of the cell. the greater the destructive effect of mechanical stress. The serious consequences caused by freezing injury are also related to the rate of thawing of frozen tissue. Generally, in the case of intracellular freezing, it will inevitably lead to tissue necrosis, which has nothing to do with the rate of freezing; while in the case of freezing between cells, the faster the melting rate, the greater the harm. This is because the cell wall rapidly absorbs the water produced by melting ice and expands, but the protoplast attached to the cell wall absorbs water slowly, resulting in tearing and damage. For example, after the red bell flower and triangular plum were severely frozen, the temperature rose rapidly, resulting in the bark being torn and died.

II. Specific manifestations of cold damage suffered by ornamental plants

1. Blackening of xylem

Among the various tissues of mature branches of woody flowers, the cambium is the most cold-resistant, followed by the skin, and the xylem and pith are the least cold-resistant. Therefore, mild frostbite only showed pulp discoloration, xylem discoloration in moderate frostbite, and frostbite phloem in severe frostbite. If the cambium in the stem or branch changes color, it will lose its resilience and may lead to the death of the whole plant.

2. Cracking and necrosis of dry skin

Some flowers and trees native to tropical and subtropical regions with high water content in dried bark, such as Fusang, red bell flower, cinnamon, rich tree, big flower tiger thorn plum, golden banyan and so on. When the ambient temperature drops to about-3 ℃, not only the leaves and branches will be frozen to death, but even the outer bark of the stem, especially the root neck, will form ice crystals, cold expansion and hot shrinkage due to water in the tissue, resulting in bark cracking and necrosis, or even death of the whole plant. White orchid chilling injury purple bamboo grass chilling injury Amorphophallus chilling injury longevity flower chilling injury keel freezing injury 3, tender shoot new leaf color change one of them is "yellowing", in the cold season, because the temperature is too low, some flower leaves that require high overwintering temperature will also turn yellow or even fall off due to cold injury, such as Anthurium andraeanum, hanging branch green apple, watermelon pepper grass and so on. The second is "whitening", such as hanging orchids placed or planted in the open field, Zhu Dinghong, flower and leaf hanging bamboo plums, etc., when they encounter lower temperatures, the new shoots and young leaves will lose their original luster and appear abnormal changes of "whitening and losing green"; third, "scorched", the new shoots and leaves of some ornamental plants are "scorched" due to frost, such as Cymbidium, Junzi orchid, star anise gold plate and so on. Fourth, "purple", some ornamental plants, in the case of low temperature, the leaf tip or leaf edge "purple brown" phenomenon, such as money tree, ink orchid, camellia (new leaves) and so on. 4. Ornamental plants with high water content in leaves, shoots or stems scalded by boiling water, including some succulent plants, such as green apple, ash, mulberry, Rieger begonia, flower vine, orchid, taro, aloe, longevity flower, palm bamboo, Canadian jujube (seedling), Washington sunflower, money tree, hulk, etc., when the ambient temperature suddenly drops from 5 ℃ ~ 8 ℃ to-3 ℃ ~-5 ℃. And lasted for a long time, its new twigs and leaves, as if they had been scalded or cooked by boiling water, all died in a short time, and the dry skin cracked and peeled off. 5. New shoot young leaves brown and dead some underdeveloped ornamental plants, such as golden banyan, ten meritorious works, star anise gold plate, oleander, rich tree, Phoenix tail iron, etc., like a fire, very ugly. 6. plant necrosis hollow succulent plants, when encountered with frost injury, often lead to plant dryness and hollow, and necrosis of the whole plant. Such as cactus, cactus, unicorn, three-angled arrow and so on. 3. Prevention and treatment of cold injury of ornamental plants 1. Prevention of cold injury of ornamental plants (1) choose more cold-resistant flower species. Flower lovers should choose flowers and trees for foliage, flowers or fruit according to the lowest temperature in normal years in your area or the highest room temperature that can be maintained in winter in your home (usually 5 ℃ ~ 6 ℃). Located in the general home in the Yangtze River basin, without heating equipment, camellia, tea plum, jasmine, magnolia, gentleman orchid, Belgian rhododendron, plum blossom, wax plum, bergamot, dai dai, red palm, cycad, etc., can not choose variable leaf wood, bamboo taro, reticulate grass, desert rose, rhododendron, flutong, Phalaenopsis, Mariandai powder, taro, money tree and so on. (2) Cold resistance training in general potted plants, such as five-needle pine, black pine, red pine, Huangshan pine, papaya, elm, triangular maple, plum blossom, camellia, ginkgo, dragon cypress, Platycladus orientalis, cypress, etc., can be considered for overwintering, and it is best to carry out anti-freezing exercise in several stages after the end of their growth in the current year. The first stage is 0 ℃ ~ 6 ℃, which takes several days to weeks and is given sufficient light. Evergreen can convert starch in leaves into sugar, large vacuoles into several small vacuoles, and some fat tree species can convert starch into fat. The second stage is-3 ℃ ~-5 ℃, the fine structure and enzymes in the protoplast are recombined so that the cells can tolerate the dehydration caused by freezing, and the third stage is between-10 ℃ ~-15 ℃, which makes the protoplast have strong freeze tolerance and survive the cold winter. And some cold-resistant succulent plants, such as long-term balcony or open field maintenance, have a gradual adaptation process, such as rat tail palm, 12 rolls, sedum tree, gemstone flower and so on, which can be raised from 0 ℃ to-5 ℃ ~-7 ℃. Zhu Dinghong freeze injury Camellia, rich coconut, king coconut, coconut, aloe, aloe, goose palm wood, spring plum, plum, orchid, kumquat, butterfly orchid, beautiful needle sunflower, sweet-scented osmanthus, palm bamboo, turtle back, bamboo, anise iron, star anise, golden plate, red bell, oleander, fish-tail, palm, rich trees, cycads, dried cycads.

(3) strengthen the cultivation and management of cold resistance.

After the Mid-Autumn Festival, control the water and fertilizer supply of potted ornamental plants, appropriately increase the application of phosphorus and potassium fertilizer, promote the Lignification and tissue development of branches, and enhance their cold resistance, such as pouring or spraying 0.3% potassium dihydrogen phosphate solution. Pruning or manual removal of some leaves (such as Magnolia) in winter to reduce transpiration area can have a good effect on the prevention of low temperature injury. Strengthen the prevention and control of diseases and insect pests and promote the growth of plants without autumn shoots or tender shoots.

(4) to protect the tree from freezing.

For tall camellia, sweet-scented osmanthus, Michelia, Magnolia, Canadian jujube, cycad, etc., the trunk can be bundled with grass rope or film, the trunk can be white or the crown can be whitened (7% 10% lime milk); the crown mask can be bound with plastic film, and can also be sprayed with wax or liquid plastic, which can have a certain anti-freezing effect.

(5) artificial warming to ward off cold

Potted plants shelved in the greenhouse can be heated in the greenhouse with electric heaters or coal stoves in especially cold weather, especially in the coldest part of the day from 5: 00 a.m. to 6 o'clock in the morning. Cover the greenhouse with straw curtains or blankets to keep warm. Generally, plants can be covered with double-layer plastic bags at home; potted flowers placed indoors, if conditions permit, can turn on the air conditioner from 6 a.m. to 10:00 to avoid chilling damage to Anthurium andraeanum, Amorphophallus, Magnolia, Phalaenopsis, Oncidium, Cymbidium, Cymbidium, etc. Camellia, sweet-scented osmanthus, Michelia and other flowers and trees planted on the ground can spray water on the canopy at the dawn of frost or ignite anti-frost smoke before frosting in the morning, which can effectively prevent "radiation frost".

(6) postpone germination and prevent night frost.

The use of growth regulators or other methods to prolong plant dormancy and delay germination can avoid frost caused by cold wave in early spring. For example, spraying B9, ethephon, penicillin, potassium naphthylacetate (250mg/kg~500mg/kg), or maleic dihydrazide (0.1%-0.2%) solution before germination or at the end of autumn has a good effect. Such as potted flowers encounter "night frost" after coming out of the room. It can be covered with double-layer large plastic film and will be removed after the temperature picks up during the day.

2. Treatment of cold injury of ornamental plants.

(1) reasonable pruning

Reasonable pruning measures should be taken for plants suffering from cold injury, and heavy pruning should not be carried out, otherwise it will produce harmful side effects. So how to control the amount of pruning? It is necessary to cut the damaged organs to healthy parts to promote the renewal and growth of branches, and to ensure the relative balance of underground and aboveground organs. Generally pruning immediately after the injury, the damaged part of the branch 1cm~2cm can be retained to prevent the healthy part of the branch from drying down again; if it is pruned after the beginning of spring, it can be cut to a healthy place to facilitate wound healing; practice has proved that the recovery speed of the damaged plant after reasonable pruning is faster than that of re-pruned and non-pruned plants.

For general evergreen potted woody flowers and foliage plants, all dead parts should be cut off in time and moved to a warmer environment.

(2) protect and repair wounds

For the thick flower plants that are only partially frozen on the dry base (northwest), the necrotic part can be gouged out, the wound healing agent can be smeared, and then protected by thin film, so as to create a warmer small environment for it; for some damaged bonsai plants, it can be remedied by bridging or changing roots.

(3) strengthen the prevention and control of diseases and pests

After being harmed by low temperature, ornamental plants are vulnerable to diseases and insect pests because of their weak tree potential, so chemical agents can be applied in combination with the prevention and control of freezing injury. Among them, the effect of fungicide plus moisturizing adhesive is better, followed by fungicide and high fat film, which is better than simple fungicide or whitening agent. Because the main fungicide can only play the role of surface disinfection and sterilization, the auxiliary moisturizing viscose and high-fat film not only play the role of moisturizing, but also play the role of warming, which are conducive to the formation of frostbite callus and promote the healing of frostbite.

(4) careful fertilization

For freeze-damaged plants, high concentration chemical fertilizer should not be applied immediately after overwintering, but should be sprayed or irrigated with low concentration liquid fertilizer after the temperature rises and the root system resumes its absorption function, such as 0.3% potassium dihydrogen phosphate and 0.3% urea solution, alternately spraying or pouring, the effect is very good.