How do several plant growth hormones promote budding and flower bud formation?

Inorchidssprouting, growing, and floweringofthe various growth and development processes, using plant growth hormones to treat different parts oforchidplants can achieve good results. In particular, it plays a special role in the preservation, continuation and development of some rare or endangered famous varieties; it also has an extraordinary effect on accelerating the speed of propagation, enhancing variety exchanges with the outside world, and improving economic benefits. ① Breaking dormancy and stimulating the germination of dormant latent buds on pseudobulbs (lu tou). Separate the old pseudobulbs left over year by year from the plant, in groups of 2 to 3 connected together, then clear away the remaining old leaves, wash clean and let dry, but throughout the whole process never injure the latent bud eyes. The hormone treatment steps are: first use 0.05% (500 ppm) gibberellin (GA3) to dab and coat the latent bud eyes, and after drying use 0.1% (1000 ppm) indolebutyric acid (IBA) to treat the root crown of the remaining old roots of the pseudobulb and the base of the pseudobulb. After treatment, plant into pots according to the conventionalcultivationmethod, depending on the variety. Trials have shown that after treatment, the number of sprouted shoots per orchid plant is clearly higher than in the control. ② Promoting more shoots and fast growth. For rare and fine varieties, in order to increase the propagation coefficient, the main approach at present is through division of clumps. In a large clump of orchids, only a few new shoots from the previous year can produce new seedlings; old plants of many years produce no or very few new seedlings, and propagating by dividing into single plants affects growth vigor, and the new shoots produced become smaller, and may even cause the mother plant to die. Treatment and regulation with plant growth substances can induce new shoots and promote growth. The method is: take the orchid clump out of the pot, wash clean the remaining roots and the soil between the plants, and let dry until the fleshy roots become soft and no longer brittle; separate plant by plant with a sharp knife, then soak for a moment in a 0.08% (800 ppm) carbendazim solution; after it is slightly dry again, use a cotton swab dipped in 0.01% (100 ppm) 6-benzyladenine to coat the pseudobulb; then use 0.1% (1000 ppm) indolebutyric acid, soaking from the root crown down to the root base. Practical use shows that combining the three treatments results in fewer pseudobulb deaths, more shoots, and good growth vigor. ③ Promoting flower bud emergence and blooming.Orchidflower bud differentiation, besides being constrained bycultivationmanagement (including light hours, the carbon-nitrogen nutrient ratio in the plant's life cycle, the degree of division, and fertilizer and water conditions, etc.), is importantly regulated by varietal characteristics and exogenous hormones. TakingCymbidium goeringiias an example, under generally normal conditions, by the end of July and beginning of August the orchid plant has gradually grown complete and mature. At this time, spraying 0.03% (300 ppm) paclobutrazol (PP333) on the orchid leaves can promote pseudobulb swelling and provide the material basis for flower bud differentiation in August and September. When applying paclobutrazol by leaf spray, the pot surface must be covered, and the solution must never be poured directly onto the soil. From practical use, orchid leaves sprayed with paclobutrazol only show thickened leaf texture and deeper leaf color; it has no effect in controlling leaf length; but if the solution is sprayed onto the soil, at flowering time the flower stalk is clearly shorter than normal, and the orchid loses the ornamental value it should have. When using plant growth hormones, the following two points must be noted: ① Plant growth hormones should all be used during the orchid plant's growing season and at the physiological development stage of the treated part, so as to facilitate the transport and metabolism of substances. The temperature during treatment should not be lower than 15°C. ② Plant growth hormones can only regulate the plant's growth and development; they cannot replace management and fertilizer. Only by applying plant growth substances on the basis of careful management conditions and reasonable fertilization measures can the effect of doing twice the result with half the effort be achieved. (Zhejiang - Chen Hantao, Yu Huaiyun)