What is Thidiazuron？
Thidiazuron (TDZ) is a highly effective plant growth regulator belonging to the phenylurea class of compounds. In agricultural production, it serves a dual role: at low concentrations, it exhibits extremely potent cytokinin activity (exceeding that of conventional cytokinins by more than 1,000-fold), while at high concentrations, it functions as a defoliant.
Core Mechanism of Action
The uniqueness of Thidiazuron lies in the dual nature of its mechanism of action:
1.Extremely Potent Cytokinin Activity: Its capacity to induce plant cell division and callus formation is more than a thousand times greater than that of conventional cytokinins. It promotes the synthesis and balance of endogenous plant hormones, while simultaneously enhancing photosynthesis and metabolic processes.
2.Promotion of Abscission Layer Formation: At high concentrations, it can induce the natural formation of an abscission layer between the petiole and the stem, thereby leading to leaf abscission.
Key Application Areas of Thidiazuron
1. Cotton Defoliation (Core Application)
Thidiazuron serves as an indispensable defoliant in mechanized cotton harvesting; its application efficacy directly impacts cotton quality and harvesting efficiency.
| Application Parameters | Specific Details |
| Application Timing | Approximately 20 days prior to the first frost, or when 60% of the cotton bolls have cracked open. In the Xinjiang cotton-growing region: late August to early September in Northern Xinjiang; early to mid-September in Southern Xinjiang. |
| Application Method | Whole-plant spraying facilitates the shedding of leaves across the entire plant. In regions where cotton is harvested in batches, spraying may be limited to the middle and lower leaves only, thereby retaining the top leaves, buds, and bolls to enhance ventilation and light penetration. |
| Defoliation Efficacy | When applied scientifically, the defoliation rate can reach between 95.89% and 98%. |
| Yield Enhancement | When used in combination with Diuron, yields can reach 6,156.33 kg/hm²; additionally, fiber breaking tenacity increases by 2.27%, and the uniformity index improves by 1.33%. |
| Harvest Advancement | Enables cotton harvesting to commence approximately 10 days earlier, thereby reducing the incidence of frost-damaged bolls and improving cotton grade. |
2. As a Broad-Spectrum Growth Regulator (Promoting Fruit Setting, Fruit Enlargement, and Yield Increase)
Thidiazuron is registered for growth regulation across a wide variety of crops, boasting an extremely broad scope of application.
| Application Focus | Major Crops | Core Functions & Effects | Application Timing / Concentration Reference |
| Promoting Fruit Setting | Tomatoes, Wax Gourds, Zucchini, Melons, Grapes, etc. | Increases fruit setting rate (exceeding 90% in wax gourds); induces parthenocarpy (seedless fruit formation). | Tomatoes: During the flowering stage and the fruit enlargement stage of the first fruit cluster; Wax Gourds: Dip flowers 1–2 days prior to blooming. |
| Fruit Enlargement & Yield Increase | Mangoes, Grapes, Kiwifruit, Apples, Kumquats, Strawberries, etc. | Increases individual fruit weight; significantly boosts yield. | Spray during the young fruit enlargement stage. Mango yield increases can reach 44.92%–55.60%, with individual fruit weight increasing by 43.63%–53.04%. |
| Improving Fruit Quality | Apples, Mangoes, Kumquits, Grapes, etc. | Increases fruit size; improves fruit surface smoothness; increases soluble solids and Vitamin C content; reduces acidity. | Apples: Apply once when 10–20% of the central flowers have opened, and again during the full bloom stage. |
| Promoting Vegetative Growth & Stress Resistance | Wheat, Rice, Maize, Potatoes, Tobacco, etc. | Enhances photosynthesis; delays leaf senescence; improves resistance to environmental stresses. | Spray during key growth stages, such as tillering, booting (ear formation), or pre-flowering. |
| Regulating Plant Architecture & Yield Components | Cotton, Wheat | When combined with growth retardants, it inhibits excessive vegetative growth (lodging), increases the Leaf Area Index (LAI), increases the number of bolls per plant, and significantly boosts yield. | Cotton: Spray before or after chemical topping; seed cotton yield increases by 11.23%. |
| Tissue Culture | Horticulture, Scientific Research | Induces callus formation and bud differentiation in plant tissue culture. | Used as an additive in culture media. |
3. Applications in Tissue Culture
Thidiazuron holds significant value in plant tissue culture:
- Induces callus formation and bud differentiation
- Promotes bud regeneration and plant regeneration
- Suitable for use with a wide range of horticultural crops and for research purposes
4. Herbicidal Activity
Thidiazuron exhibits inhibitory effects against certain weeds:
- Target Weeds: Barnyard grass, Bermuda grass, large crabgrass, annual ryegrass, creeping wheatgrass, cleavers, etc.
- Dosage: At an application rate of 3 kg/hm², control efficacy approaches 100%.
Distinctions from Other Plant Growth Regulators
| Comparison Criteria | Thidiazuron | Gibberellin | Sodium Nitrophenolate |
| Primary Functions | Cell division, defoliation, fruit setting, fruit enlargement | Cell elongation, dormancy breaking | Cytoplasmic streaming, rooting, growth promotion |
| Activity Characteristics | Extremely high cell division activity (1,000 times greater) | Promotes stem and leaf elongation | Broad-spectrum, fast-acting, effective at low temperatures |
| Typical Applications | Cotton defoliation, grape enlargement, mango yield enhancement | Seedless grapes, celery, rice | Foliar fertilizer synergist, rooting for cuttings |
Thidiazuron is a versatile plant growth regulator; it serves as a defoliant for cotton to facilitate mechanized harvesting, while also acting as a highly effective cytokinin to promote fruit setting, fruit enlargement, and yield increases across a wide range of crops, offering broad prospects for future application. When using this product, one should strictly adhere to the registered label instructions and local agricultural technical guidelines to ensure optimal efficacy and safety.