How does Paclobutrazol as a plant growth regulator affect plants?
What is paclobutrazol Cas 76738-62-0?Paclobutrazol is the ISO common name for an organic compound that is used as a plant growth retardant and triazole fungicide.Cas 76738-62-0 It is a known antagonist of the plant hormone gibberellin, acting by inhibiting gibberellin biosynthesis, reducing internodal growth to give stouter stems, increasing root growth, causing early fruitset and increasing seedset in plants such as tomato and pepper. paclobutrazol has also been shown to reduce frost sensitivity in plants.
Moreover, paclobutrazol can be used as a chemical approach for reducing the risk of lodging in cereal crops. paclobutrazol has been used by arborists to reduce shoot growth and shown to have additional positive effects on trees and shrubs. Among those are improved resistance to drought stress, darker green leaves, higher resistance against fungi and bacteria, and enhanced development of roots. Cambial growth, as well as shoot growth, has been shown to be reduced in some tree species.
Paclobutrazol Mechanism of action Cas 76738-62-0
Paclobutrazol is an inhibitor of enzymes which use cytochrome P450 as a co-factor. Their active site contains a heme center which activates oxygen from the air to oxidise their substrates. The (2S,3S) isomer inhibits the enzyme ent-kaurene oxidase which is on the main biosynthetic pathway to gibberellins, which are important plant hormones.A secondary effect arising from the inhibition of ent-kaurene oxidase is that its precursor, geranylgeranyl pyrophosphate accumulates in the plant and some of this is diverted into additional production of the phytol group of chlorophyll and the hormone abscisic acid. The latter is responsible for controlling transpiration of water through the leaves and hence paclobutrazol treatment can lead to better tolerance of drought conditions. The (2R,3R) isomer is a better fit to the active site of the fungal cytochrome P450 14α-demethylase. This inhibits the conversion of lanosterol to ergosterol, a component of the fungal cell membrane, which is lethal for many species. Many other azole derivatives including propiconazole and tebuconazole show this type of activity, so the main commercial opportunity for paclobutrazol was as a plant growth retardant
Nature of paclobutrazol Cas 76738-62-0
The plant growth regulator, [(2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol] (paclobutrazol; PP333) with chemical formula C15H20ClN3O, is a triazole derivative and has been shown to inhibit shoot growth on apple trees. The ancymidol blocks the oxidative steps with high specificity leading from ent-kaurene to ent-kaurenoic acid in the pathway of GA biosynthesis. The same oxidative steps are thought to be inhibited by the active triazol derivatives. Paclobutrazol has been reported to inhibit GA biosynthesis in plants by inhibiting kaurene oxidase, a Cyt P-450 oxidase, thus blocking the oxidation of kaurene to kaurenoic acid . The inhibitory activity of paclobutrazol can be reversed by GA. Besides reducing gibberellins level, paclobutrazol increases cytokinin contents, root activity and C:N ratio, whereas its influence on nutrient uptake lacks consistency. Paclobutrazol was also shown to shift assimilate partitioning from leaves to roots, increase carbohydrates in all parts of apple seedlings, increase chlorophyll content, soluble protein and mineral element concentration in leaf tissue, increase root respiration and reduce water use.investigated the effect of paclobutrazol on the translocation of endogenous IAA (indol-3-acetic acid) in Doyenne du Comice pear cultivar and found that paclobutrazol caused a slower movement of IAA in shoot tips. The usual application of paclobutrazol has been either by foliar spray or soil drenching. With foliar spray applications, absorption through mature leaves was limited and paclobutrazol may be taken up through stem absorption or from excess dripping onto the soil. have reported that protecting the soil from foliar drip reduced the paclobutrazol-induced inhibition of extension growth in apples. When applied to the soil, a continuous supply of paclobutrazol taken up by the roots is translocated acropetally via the xylem, thus maintaining the concentration of paclobutrazol above the threshold required for the inhibition of gibberellins biosynthesis, although phloem translocation has also been reported.
The effects of paclobutrazol Cas 76738-62-0
One method to manipulate flowering is to use the plant growth regulator, paclobutrazol. The post- harvest
application of a small amount of paclobutrazol to the soil significantly promotes flowering and fruiting in the following year. Trials over the last two years have shown the following benefits from the treatment:
• A significant increase in flowering leading to increased yields.
• The early flowering considerably enhanced fruit maturity. Treated trees flowered three to four weeks early, which reduced the time to fruit maturity by at least two weeks.
• Visually, the fruit developed a better external colour.
How does paclobutrazol act Cas 76738-62-0?
Available evidence strongly suggests that flower initiation depends on the presence of an unknown flowerpromoting factor or factors synthesised in the leaves. At the same time, there are other factors in the shoots。
which work against the flowering factor or factors. It is believed that a group of plant hormones called gibberellins act as inhibitors to flowering. When paclobutrazol is applied to the soil, it moves up through the roots into the shoots and, due to its anti-gibberellin properties, blocks the synthesis of flowering inhibitors, thereby allowing the flower-promoting factor(s) to work.
How and when to apply paclobutrazol Cas 76738-62-0?
The application of paclobutrazol to soil as a drench around the tree trunk (collar drench) is the most effective method, as it ensures proper uptake by the tree. The required quantity is mixed in approximately one litre of water and poured onto the soil around the trunk in a circular band. In the Top End, the ideal time to apply paclobutrazol is from soon after harvest to early January. In dry conditions, a light irrigation is recommended after application. Foliar sprays have been ineffective.
What is paclobutrazol used for Cas 76738-62-0?
Paclobutrazol is widely used to advance harvest maturity in various fruit crops and it improves fruit quality in terms of accelerated colour development, delayed and synchronized fruit maturation and control of preharvest fruit drop. It is known to improve fruit physical and fruit chemical characteristics.
Paclobutrazol Usage Cas 76738-62-0
As an antagonist of gibberellin biosynthesis, paclobutrazol has a growth retardant effect on most plant species.It is absorbed by plant tissues and transported via the xylem to the growing parts, where the rate of cell division is reduced compared to untreated plants and the new cells do not elongate.
Ornamental crops
paclobutrazol is used in horticulture, especially for glasshouse-reared perennial plants.
Trees and shrubs
The ability of paclobutrazol to reduce the growth of trees and shrubs means that it has found use in areas where there is a need to moderate such growth, for example under electric power lines and where a right-of-way is to be maintained. A single application of the growth regulator can give season-long control.
Fruit and vegetables
paclobutrazol is used to increase the quantity and quality of orchard fruit and of vegetables. The quality is measured by elevated amounts of carbohydrates, total soluble solids (TSS), the TSS/titratable acidity ratio and a decreased acidity. It stimulates the growth of roots and stems and maintains the number of the leaves but suppresses the height of the plants
Turf management
paclobutrazol has been extensively used as a means to improve the quality of turf on golf courses, where it reduces the need for mowing and by increasing chlorophyll content has the effect of greening the grass.
Cereal crops
paclobutrazol is demonstrated to increase grain yields and reduce lodging, demonstrated The same mechanism is responsible for modern high-yield semi-dwarf crops such as the IR8 rice variety 2014 also describe better lodging tolerance.They find that winter wheat undergoes reduction of internode length, thickened internodes, increased lateral growth, increased lignin synthesis enzyme activity and therefore increased lignification with application of this compound.Although this does not reduce lodging it does make lodging less harmful.
Response of Growth Inhibitor Paclobutrazol in Fruit Crops Cas 76738-62-0
Paclobutrazol IUPAC name: (2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1, 2, 4-triazol-1-yl) pentan-3-ol) is a triazol derivative and an antagonist of gibberellins. It has been shown to inhibit shoot growth in various perennial fruit trees. Paclobutrazol application reduced the number of shoots, transforming trees into a more desirable, spur-type growth habit as the vegetative sink was reduced. This compound induces an early and intense flowering, diminishing vegetative growth and reducing the extension of buds, allowing for ripening and the initiation of apical buds inflorescence. Besides, it also increases fruit set, the years following application as a carryover effect. An increase in return bloom is a common response to paclobutrazol treatment and has been reported for various fruit crops. Paclobutrazol is widely used to advance harvest maturity in various fruit crops and it improves fruit quality in terms of accelerated colour development, delayed and synchronized fruit maturation and control of preharvest fruit drop. It is known to improve fruit physical and fruit chemical characteristics. Fruit calcium is increased for 2–3 years due to carry over effect. It helps in the maintenance of better fruit quality during storage and influences nutrient uptake in various fruit crops including stone fruits. It has been characterized as an environmentally stable compound in soil and water environments with a long half-life under both aerobic and anaerobic conditions.
Tree growth and vigour
Paclobutrazol when applied during early summer has been observed as effective suppressant of stem growth in sweet cherry . reported that paclobutrazol when sprayed on ‘Redhaven’ cultivar of peach reduced terminal growth and advanced leaf fall. tree−1 paclobutrazol to cherry trees followed by 0.8 g a. paclobutrazol in next year inhibited extension growth of young trees on either colt or FB22 rootstocks.stated that 1000–4000 ppm of paclobutrazol on ‘Canino’ apricot cultivar decreased the lateral shoot length. Foliar spray of 1000 ppm paclobutrazol to sweet cherry trees suppressed shoot growth and delay in fruit colour.stated that paclobutrazol decreased the shoot development of ‘Crimson Gold’ nectarines.observed that application of paclobutrazol decreased shoot elongation in cherries when applied on the vegetative and reproductive parts. Shoot extension growth was reduced by 57% at stone hardening and by 47.6% at harvest following soil and collar drench of cultar (2.0 g a.i. PP333/tree) applied in autumn in peach cv.observed that 250 ppm of paclobutrazol decreased the shoot growth by about 34.1–42.4% in apricot. Leaf chlorophyll of almonds was increased with the application of 50 and 100 ppm paclobutrazol. Arzani and Roosta [35] reported that paclobutrazol significantly reduced vegetative growth in apricot. They also reported that the total pruning dry weight, shoot growth and trunk cross sectional area (TCSA) of treated trees were lower than those of the control. reported that the application of different concentrations of paclobutrazol and chloromequat at 250, 500, 1000 and 5000 ppm to ‘Red Delicious’ apple decreased the extension growth and leaf area of trees. applied paclobutrazol through soil to the basin of tree on trunk diameter basis. The investigation was carried out under two independent experiments. In one experiment, treatments were applied for two years consecutively and in another during first year only in order to assess carryover effect during second year. Application of paclobutrazol decreased yearly increment of tree trunk cross-sectional area, tree spread, volume and internodal length in sweet cherry.noticed that soil application of paclobutrazol @ 10 ml/lit on high density pear plantation effectively controlled the excessive and vigorous growth. They also observed that the vegetative growth was inhibited by paclobutrazol.observed that paclobutrazol resulted in shortest shoot length in pear. recorded reduced extension growth, plant height and plant spread with paclobutrazol in nonpareil almond plants.reported that paclobutrazol reduced vegetative growth by reducing both fresh and dry weights of shoots and the leaf area was also significantly decreased in strawberry cv.reported that paclobutrazol significantly retarded the shoot growth, shoot diameter and trunk cross-sectional of ‘Roundel’ apricot trees growing under low density planting system. revealed that apple trees cv. Red Delicious treated with paclobutrazol @ 750 ppm and summer pruning resulted in minimum vegetative growth and vigour in terms of tree height, trunk diameter, annual shoot extension growth, tree spread and leaf area in comparison to control and other treatments. Reduction in growth is attributed to paclobutrazol, which is a triazol that inhibits gibberellin biosynthesis especially three steps in the oxidation of the GA precursors ent-kaurene to ent-kaurenoic acid
Fruit colour
Application of paclobutrazol @ 0.33, 0.50, 0.66 and 1.32 g a.i. as soil application to ‘Flavorcrest’ peach hastened the fruit colour than control. that paclobutrazol either sprayed once with 1000 ppm or twice with 500 ppm concentration to ‘Lambert’ cherry displayed less red colour as indicated by juice anthocyanin concentration or by visual rating of skin colour and 500 mg l−1 paclobutrazol within 5 weeks after full bloom to ‘Mclntosh’ apples gave high percentage of fruit with acceptable red colour at harvest. with 500 ppm paclobutrazol once at full bloom and repeated at pit hardening stage recorded maximum anthocyanin content (0.299 OD units) which was significantly higher than control. hat fruit colour was enhanced by the application of paclobutrazol in sweet cherry. Continuous application of paclobutrazol significantly reduces vegetative growth characters of the trees, thereby exposing fruits to direct sunlight which significantly increased red colouration of the fruits. The soil application of paclobutrazol in ‘Red Delicious’ apple fruits increased the fruit anthocyanin by the increasing dose of paclobutrazol.
What are the side effects of paclobutrazol Cas 76738-62-0?
Phytotoxic effects resulting from paclobutrazol include leaf necrosis and crinkling, hardening of the growing point and stunting, particularly if applied to sensitive plants, such as Begonia.
How does paclobutrazol induce flowering Cas 76738-62-0
When paclobutrazol is applied to the soil, it moves up through the roots into the shoots and, due to its anti-gibberellin properties, blocks the synthesis of flowering inhibitors, thereby allowing the flower-promoting factor(s) to work.
Does paclobutrazol affect flowering Cas 76738-62-0?
The most important effects of paclobutrazol in fruit quality are related to the repression of senescence in plant tissues by decreasing ethylene production. It improves the concentration of photosynthetic pigments, minerals, and carbohydrates. It is highly involved in flowering and, consequently, in fruit yield.
How do you mix paclobutrazol Cas 76738-62-0?
Paclobutrazol 23% SC is much effective when used with Collar Drench method. With the recommended quantity of PEP STAR with 0.5 – 2 ltr of water per tree, apply this on soil or trunk crack line around the base of the trunk. Or, apply PEP STAR as Soil Drench.
plant growth regulators paclobutrazol price Cas 76738-62-0
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plant growth regulators paclobutrazol supplier Cas 76738-62-0
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