How to remedy orchids after paclobutrazol phytotoxicity?

Paclobutrazol is effective for domesticating wild orchids and optimizingorchidplant shape. However, some people causeorchidphytotoxicity through improper use of paclobutrazol. Here is an introduction to the remedial measures. Paclobutrazol is a plant retardant. Its effects are to delay vertical elongation, enhance lateral growth, promote more tillering, thicken stems, and make plants dwarfed and compact. Its physiological effects are to increase the content of chlorophyll, protein and nucleic acid, reduce the content of gibberellins and indoleacetic acid in the plant, and increase ethylene release. Paclobutrazol is mainly absorbed through the root system, with very little absorbed by the leaves. When paclobutrazol is used on gramineous plants, the concentration is 100-300 PPM, with a dosage of 30-40 grams per mu. Exceeding this concentration often causes phytotoxicity. To control excessive growth, the concentration used is generally 100 PPM. When used onorchids, overdose phytotoxicity is of course serious. To control excessive growth in plants, paclobutrazol is generally used only 1-2 times, with an interval of 7-10 days. If it is used repeatedly on the same plant many times, it is of course extremely dangerous. Originally, when paclobutrazol is used within the normal range, for crops such as rice, its retardant effect can be released on its own once they develop to a certain extent, but in woody crops, the goal of controlling growth is achieved through lignification and cutinization of stems and leaves. When used on orchids, it can control excessive leaf length and make them short and sturdy, but if too much is used, the orchid plants stop growing or the leaves become unsightly, and the harm becomes the opposite. The remedial measures for phytotoxicity in orchid plants can be carried out in the following aspects. 1. Repot and use fresh growing medium, because paclobutrazol is mainly absorbed through the root system, so repotting and changing to fresh growing medium is the primary measure. Second, when repotting, wash the orchid roots clean and let them dry, to remove residual paclobutrazol in the roots. 2. Appropriately supplement nitrogen fertilizer. When the temperature is above 15°C, depending on the situation, spray the leaves with nitrogen fertilizer such as urea at a concentration of 0.1% to promote tender green leaves. 3. When necessary, spray gibberellin (920): for leaves already affected by phytotoxicity, use gibberellin at a dilution of 5000-10000 times for foliar spraying. If the effect is poor, carefully increase the concentration as appropriate. After using gibberellin, the effect can be seen in 5 days. If there is still no effect after two uses, continued use should be stopped. After adopting the above measures, new shoots will grow normally. Address: Plant Protection Station, Longquan City, Zhejiang Province Postal code: 323700 (Zhejiang - Zhu Xiongguan)