Brief Analysis of Paclobutrazol Plant Growth Regulator
What is paclobutrazol?
Paclobutrazol is a triazole plant growth regulator and an inhibitor of endogenous gibberellin synthesis. It can also increase the activity of rice indole acetic acid oxidase and reduce the level of endogenous IAA in rice seedlings. Significantly weaken the top growth advantage of rice seedlings and promote the growth of side buds. The appearance of the seedlings is short and thick, and the leaves are dark green. The root system is well developed. Anatomical studies have shown that paclobutrazol can reduce the cells of rice seedling roots, leaf sheaths, and leaves, and increase the number of cell layers in various organs. Paclobutrazol can be absorbed by rice seeds, leaves and roots. Most of the paclobutrazol absorbed by leaves stays in the absorption part, and rarely transported outward. Low concentration of paclobutrazol improves the photosynthetic efficiency of rice seedling leaves; high concentration inhibits photosynthetic efficiency, increases the respiration intensity of roots, reduces the respiration intensity of aerial parts, increases stomatal resistance of leaves, and reduces leaf transpiration.
Paclobutrazol is a plant growth regulator, which has the effects of delaying plant growth, inhibiting stem elongation, shortening internodes, promoting plant tillering, increasing plant stress resistance, and increasing yield. Paclobutrazol is suitable for crops such as rice, wheat, peanuts, fruit trees, tobacco, rapeseed, soybeans, flowers, lawns, etc., and the use effect is remarkable.
paclobutrazol environment
Aquatic organisms: LC50 (96 hours mg/L) rainbow trout 27.8, no effect dose 3.3mg/L
Bees: acute oral no effect dose>0.002mg/bee, acute percutaneous no effect dose>0.041mg/bee
Natural enemies: acute oral LD50 mallard>7900mg/kg
Water and soil conservation: half-life in soil is 0.5-1 year, <42 days in calcareous clay soil (pH8.8, 14% organic matter), coarse sandy loam (pH6.8, 4% organic matter)
The role of paclobutrazol
1. Regulating plants
Paclobutrazol can inhibit gibberellin synthesis, delay growth, shorten internodes, and dwarf plants. It reduces the synthesis or metabolism of indole acetic acid, promotes the increase of endogenous abscisic acid content in plants, and can also regulate the release of ethylene in plants.
2. Improve anti-aging ability
Paclobutrazol can make plant leaves dark green, increase the content of photosynthetic pigments such as chlorophyll, increase the content of nucleic acid and protein in the plant, improve the anti-aging ability of plants, and make plants have strong vitality.
3. Improve anti-bacterial ability
Paclobutrazol can improve the ability of plants to resist adversity and bacteria. It can make the plant epidermal cells expand, causing the stomata to be squeezed and subsidence, resulting in increased stomatal resistance, reduced transpiration, and reduced water loss.
4. Improve plant kangda ability
The application of paclobutrazol can improve the ability of plants to resist chilling and freezing damage. After the application of paclobutrazol, the content of the stress hormone abscisic acid in plants is increased, and the damage of low temperature to the leaf cell membrane is reduced.
5. Inhibition of plant apical dominance
Paclobutrazol can inhibit apical dominance and promote the germination and growth of lateral buds. For example, the application of paclobutrazol can make rice seedlings tiller early and more tiller, the plant becomes shorter, and the base of the stem becomes thicker.
6. Inhibitory activity to control weed damage
Paclobutrazol was first developed as a fungicide. It has inhibitory activity against more than 10 pathogenic bacteria such as rapeseed sclerotinia, wheat powdery mildew, rice sheath blight and apple anthracnose. It can control weed damage, dwarf weeds, and slow growth. Hazard mitigation.
Altered levels of endogenous hormones
Paclobutrazol can inhibit gibberellin synthesis, delay growth, shorten internodes, and dwarf plants. It reduces the synthesis or metabolism of indole acetic acid, promotes the increase of endogenous abscisic acid content in plants, and can also regulate the release of ethylene in plants.
Increase chlorophyll content
Paclobutrazol can make plant leaves dark green, increase the content of photosynthetic pigments such as chlorophyll, increase the content of nucleic acid and protein in the plant, improve the anti-aging ability of plants, and make plants have strong vitality.
Improve plant resistance
Paclobutrazol can improve the ability of plants to resist adversity and bacteria. It can make the plant epidermal cells expand, causing the stomata to be squeezed and subsidence, resulting in increased stomatal resistance, reduced transpiration, and reduced water loss. By alleviating water loss, the stress on plant cells is reduced, normal growth and development can be carried out, and the plant's own drought resistance ability is enhanced. The application of paclobutrazol can improve the ability of plants to resist chilling injury and freezing injury. The application of paclobutrazol increases the content of the stress hormone abscisic acid in plants and reduces the damage of low temperature to leaf cell membranes.
Promote the growth of lateral buds
Paclobutrazol can inhibit apical dominance and promote the germination and growth of lateral buds. For example, the application of paclobutrazol can make rice seedlings tiller early and more tiller, the plant becomes shorter, and the base of the stem becomes thicker.
Certain bactericidal effect
Paclobutrazol was first developed as a fungicide. It has inhibitory activity against more than 10 pathogenic bacteria such as rape sclerotinia, wheat powdery mildew, rice sheath blight and apple anthracnose. It has broad-spectrum antibacterial properties and can also control weed damage. Weeds are dwarfed, their growth is retarded, and their harm is reduced.
1. Spraying paclobutrazol on fruit trees can reduce the extension of extended branches, shorten the length of internodes, promote the development of side branches and short fruit branches, reduce the number of leaves and increase the thickness of leaves. Paclobutrazol also affects the growth of roots, which is manifested in inhibiting the growth of main roots, increasing the thickness of absorbing roots, and increasing the ratio of lateral roots and absorbing roots to the total number of roots.
2. Paclobutrazol can significantly inhibit the synthesis of gibberellins. Foliar spraying of gibberellin can restore the effect of paclobutrazol on the growth of seedlings of apple, peach, citrus kiwifruit and other seedlings. The test results prove that the main mechanism of action of paclobutrazol on the vegetative growth of fruit trees is to inhibit the synthesis of endogenous gibberellins.
3. The elongated growth of fruit trees treated with paclobutrazol was inhibited, but the lateral branches and short fruiting branches were greatly increased, which indicated that paclobutrazol not only inhibited the synthesis of endogenous gibberellin, but also reduced the synthesis of indole acetic acid IAA.
4. Spraying paclobutrazol can increase the leaf green, leaf chlorophyll content and soluble protein content of kiwifruit, apple, peach, hawthorn, etc. Paclobutrazol increases the carbohydrate content of various organs of fruit tree seedlings such as apple and jujube kiwi. This indicates an increased transport of carbohydrates to the root system. Thus, paclobutrazol significantly increased the photosynthetic efficiency of fruit trees and promoted the export of carbohydrates from leaves. The increase of photosynthetic intensity of fruit trees manifested in two aspects: A paclobutrazol increased chlorophyll content and increased photosynthetic efficiency. B-paclobutrazol reduces the vegetative growth and makes the canopy ventilated and light-transmitting, thereby indirectly increasing the light intensity.
5. Paclobutrazol increased the concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, manganese, copper, boron and zinc in leaves of seedlings. The effect of paclobutrazol on the level of plant mineral nutrition is related to its increase in the activity of ATPase in roots, and it is also related to its increase in root/shoot ratio, promotion of lateral root and absorption root growth, and changes in transpiration intensity.
Dosage of paclobutrazol
Applicable crops Application scope Application period Dosage and usage
Three-wheat corn soaking should be shallow sowing, soaking for 10-12 hours before sowing, adding 1.5 grams of medicine per kilogram, soaking for 3-4 hours and stirring once
One leaf one heart stage of wheat seedlings, the wheat rises up to before the festival, one leaf and one festival before the festival, 20 grams of medicine mixed with 15 kilograms of water, 40 grams of medicine mixed with 50 kilograms of water and sprayed
Cultivate short-legged and strong seedlings of rape. The seedbed has a high level of fertilizer and water, sows early, and the density of the seedbed is 3-4. Spray 40 grams of medicine with 50 kg of water at the leaf stage
Spray 50 grams of medicine per mu in flowering period of peanuts and cotton mixed with 50 kilograms of water
Cultivate strong seedlings of rice to prevent lodging. Seedling age is about 35 days. In a single season, late rice seedlings are sprayed with 175-200 grams of water and 100 kg of water 25 days before transplanting.
For high-yield fields, local prosperous long-stem and high-stem varieties that are easy to lodging are sprayed with 150-175 grams of water and 100 kg of water 30-40 days before heading
15-20 grams of medicine soil fence per plant under the apple autumn branch exhibition
When the new shoot grows to 5-10 cm, mix it with 500-700 times of water and spray it once every 10 days, a total of three times
Pear shoots grow to 5-10 cm, mixed with 500-700 times of water and sprayed once every 10 days, a total of three times
Apply 10-15 grams of medicinal soil per plant under branches of peaches and hawthorns in autumn or spring
Soybean and potato flowering period: Spray with 60 grams of medicine per mu and 50 kg of water
Citrus summer shoot stage 150 times watered liquid foliar spray fence
Apply 4-6 grams of soil to each cherry plant, spray 150-300 times the water solution
Mango: 15-20 per plant, 15-20 kg of water mixed with water in the first ten days of May.
Tobacco 5-7 leaf stage Spray with 60 grams of water per mu and 50 kg of water [1]
Litchi In mid-November, spray 750 times the water on the leaves
Dosage form: 95% paclobutrazol technical material, 10% paclobutrazol wettable powder, 15% paclobutrazol wettable powder, 25% paclobutrazol suspension concentrate
How to use paclobutrazol
1. Rice In long seedling fields, use 10% wettable powder 300g/667m2 at the stage of 1 leaf and 1 heart, and spray 50L of water to control the height of seedlings and cultivate strong seedlings with many tillers and strong rooting ability. After transplanting, at the panicle differentiation stage, use 10% wettable powder 180g/667m2 and spray 50-60L of water to improve the plant type, make it dwarf, and reduce lodging.
2. Fruit trees Applied to apple, pear, peach and cherry trees, the effect is remarkable, and it can be used for soil treatment, trunk coating and foliar spray. Soil treatment works best. For soil treatment, use 10-15g of 10% wettable powder per cubic meter of crown, in the form of a ring-shaped fertilization ditch, 30cm wide and 20cm deep. The principle is to expose the roots without damaging the roots. Sprinkle the medicine into the ditch and cover with soil. Water before and after application to maintain soil moisture. Use 15% WP 150-300 times liquid to dry. Use 15% wettable powder 75-150 times liquid foliar spray, for young trees, can make the canopy dwarf, compact, early flowering and fruit; for adult trees, can inhibit the growth of new shoots, increase yield, improve quality.
3. Soybeans, rape seedlings, cotton, flowers, wheat The whole soybean plant is sprayed with 10% WP 500 times liquid at the initial flowering stage, which can dwarf soybean plant height, promote branching and increase production. Spray 500-1000 times liquid of 10% wettable powder when rape seedlings have 2 leaves and 1 heart to 3 leaves and 1 heart, which can prevent tall seedlings and antifreeze. Applying it to cotton seedlings can prevent the occurrence of tall seedlings and frost damage. Applied on flowers, it can make the plant type tall and straight. Beautiful posture. Applied on wheat, it can increase tillering and resist lodging. the
Tangerine
Germination period of summer shoots: Spray 15% paclobutrazol 300 times, and use it with sapicide and phosphorus and potassium fertilizers to control the germination of summer shoots. After the autumn shoots are mature: spray 15% paclobutrazol 300 times, potassium dihydrogen phosphate, etc., to improve tree nutrition and promote flower bud differentiation.
Grape
Spray 1000-2000mg/L liquid medicine on the leaves at the end of full flowering. It can inhibit the excessive growth of main shoots and auxiliary shoots and increase yield.
apple
Spring or autumn: apply 15-20g of 15% paclobutrazol wettable powder to each plant, or spray 15% paclobutrazol wettable powder with 500-700 times of water every 10 days for new shoots growing to 5-10cm, a total of 3 times.
mango
Generally, when the leaves turn green and are not fully mature, the first use of paclobutrazol 15% wettable powder is about 600 times, and the second time the amount is gradually increased. Each time the dosage is 450 catties of water plus 100 grams of 15% wettable powder Paclobutrazol, - Control shoots once every 10 days or so. After controlling the shoots 1-2 times, the shoots begin to mature.
Paclobutrazol application method
Commonly used methods in flower production include soaking (bulbs), soil application, leaf spraying and drying. Among them, soaking, soil application, and leaf spraying have the best effects, and the drug effect is long-lasting and stable. There are two methods of soil application. One is to plant foliage and flowering plants on the ground, dig a ring-shaped ditch about 5 cm deep around the crown of the tree, sprinkle it evenly into the ditch and then irrigate in time; the other is to plant indoor potted flowers in the pot soil Water in time after drilling holes. Leaf spraying is mostly carried out in the early stage of growth. Different flowers, soil quality, and nutritional management levels have different spraying time and concentration. The spraying method is the same as the general fertilizer spraying method, but care should be taken to make the growing point evenly sprayed.
Dosage and concentration of paclobutrazol
It varies with variety, growth, age, soil quality and other factors. The soil application rate is generally 0.25 grams per square meter, the concentration of the liquid medicine is 800 to 1500 ppm when spraying leaves, and the concentration of soaking roots (bulbs) is 70 to 90 mg / L, soaking for 5 to 8 hours. The dosage and concentration of woody flowers can be slightly higher, and the dosage of herbaceous flowers should be lower. Use with caution on orchids.
Paclobutrazol use time
Different application methods have different application times. Soil application is generally carried out before flower buds germinate in spring (spring flowers); leaf spray is generally used when new shoots grow about 10-15 cm that year. Deciduous flowers and trees can be used some time in advance to ensure timely efficacy.
Paclobutrazol application frequency
Since paclobutrazol has a long-lasting effect, it is generally applied once and the effect can last for 3-5 years, so the frequency of application should be strictly controlled. Soil application is at most once every 3 years, and leaf spray is once a year. If it is used in consecutive years, the concentration should be reduced year by year. If you find that the growth is extremely weak, you should stop using it. If necessary, you can spray gibberellin to help restore the growth.
Paclobutrazol lag period
Since there is a period of time from the application of the drug to the exertion of the drug effect—that is, the sluggish period of the drug effect, it is easy to be mistaken for "ineffective" in production, so that the drug is repeatedly applied, resulting in excessive dosage. Before spraying, this factor should be fully considered to avoid losses.
Paclobutrazol can be mixed with most insecticides and foliar fertilizers. However, it should be used with caution when mixed with copper preparations. Paclobutrazol is a growth inhibitor, which is a relatively conventional technical means in fruit tree cultivation. However, if the dosage is too high, it will cause short plants, deformed leaves, curling, dumb flowers, premature fruit fall, and deformed fruits. It is recommended to appropriately increase fertilizer and water after phytotoxicity occurs, and topdress organic nutrient fertilizers Jiamei Hongli and Hailibao in time, or spray 920 (gibberellin), Jiamei Jindian, nitrogen fertilizer, etc. to eliminate phytotoxicity as soon as possible.
Symptoms of paclobutrazol injury
The plants are short, the roots and tubers are small, deformed, the leaves are curled, dumb flowers, the old leaves at the base fall off early, and the young leaves are twisted and shrunk. For cotton, the plants are seriously dwarfed, the fruit branches cannot be stretched, the leaves are deformed, the buds are clustered, and the buds and bells drop. For peanuts, the leaves are small, the plants do not grow, the peanuts are small, and prematurely senescent. Because paclobutrazol has a long drug effect time, it will also cause phytotoxicity to the next crop, resulting in no seedlings, late emergence, low emergence rate, seedling deformity and other symptoms of phytotoxicity. To alleviate the damage of the medicine, attention should be paid to the compound use of Zhongwei Chunyu No. 1 and so on.
paclobutrazol toxicity
Acute oral administration of the original drug to male male LD50 is 2000mg/kg
Female acute oral LD50 is 1300mg/kg
Rat and rabbit acute percutaneous LD50>1000mg/kg
Slightly irritating to the skin and eyes of rats and rabbits. The subacute oral no-effect dose for rats is 250mg/L, and the chronic oral no-effect dose for rats is 75mg/kg.
No teratogenic, carcinogenic, mutagenic effects.
Trout LC50 dose (96 hours) is 27.8mg/L;
Wild duck acute oral LD50>7900mg/kg;
Bee exposure LD50>0.002mg/head.
paclobutrazol environment
Aquatic organisms: LC50 (96 hours mg/L) rainbow trout 27.8, no effect dose 3.3mg/L
Bees: acute oral no effect dose>0.002mg/bee, acute percutaneous no effect dose>0.041mg/bee
Natural enemies: acute oral LD50 mallard>7900mg/kg
Water and soil conservation: half-life in soil is 0.5-1 year, <42 days in calcareous clay soil (pH8.8, 14% organic matter), coarse sandy loam (pH6.8, 4% organic matter)
Paclobutrazol precautions
1 This product shall not be mixed with food, feed and seeds.
2 This product should be stored in a cool and dry place.
3 Strictly follow the instructions for use to avoid drug damage.
4 If the dosage is too much and the crop growth is excessively inhibited, it can be rescued by adding nitrogen fertilizer or spraying gibberellin.
5. This product is a plant growth retardant with low toxicity. There is no special antidote. If it is poisoned by mistake, it should be sent to the hospital for symptomatic treatment.
When paclobutrazol is sprayed, the focus is on the stems of the plants, followed by the leaves. At the same time, the degree of spraying should be controlled. It is not suitable to use excessive liquid and drip it into the soil, causing excessive inhibition of plant growth.
Paclobutrazol remains in the soil for a long time, and it moves very slowly in the soil. After the application field is harvested, it must be plowed. Reduce the impact on the growth of subsequent crops.
The concentration and dosage of paclobutrazol are related to the temperature during processing. When the temperature is high, the concentration of paclobutrazol is slightly higher, and the dosage is slightly more; when the temperature is low, the concentration of paclobutrazol is also low, and the dosage is reduced. This is the opposite of the general use of growth hormone.
Although the dosage of paclobutrazol is low, it has a long duration of drug effect, so it should not be used continuously on fruit trees. And pay attention to the timing of use, so as not to cause disturbance of endogenous hormones in fruit trees.
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