Dwarfing Effects of Plant Growth Regulators on Banana Plants

【Objective】The study was conducted to screen plant growth regulators that could shorten the plant height of banana without affecting the yield, and explore the dwarfing effects of their application times on banana plants. Furthermore, appropriate concentrations of uniconazole were detected for identifying the changes in the activities of several defensive antioxidant enzymes, and the contents of soluble protein, potassium, calcium, magnesium and phosphorus in banana leaves, to further analyze the positive auxiliary effect of uniconazole on banana plant growth in addition to dwarfing effect, which would provide references for the safe and rational use of plant growth regulators in banana production.【Method】The dwarfing effects of several plant growth regulators including uniconazole (XX), paclobutrazol (DX), chlormequat chloride (AZ), mepiquat (JP), compound agents 0802 and 0501 on banana plants were evaluated by root spraying method. The contents of polyphenol oxidase (PPO), superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia lyase (PAL), soluble protein, potassium, calcium, magnesium and phosphorus in banana leaves were determined after 15, 20 and 25 days of 0.3 g/plant XX treatment.【Result】According to the evaluation standard of dwarfing effect, banana plant could grow normally in the 3-5 level of internode distance after dwarfing. Under one dwarfing treatment, the banana plant heights of XX1, DX1, 0501, XX3, JP2, 0802, AZ1 and JP4 treatments were decreased by 11.67-24.00 cm. The banana plant heights of JP2, DX1, JP4, 0802, AZ1, 0501 and XX3 under two dwarfing treatments were decreased by 29.67-39.00 cm with normal growth. It found that the banana plant height was shortened with the increase of the concentrations and application times of these grow regulators. XX3, 0802 and 0501 treatments could promote the early bud shooting of banana, and the duration periods were 8-19 days earlier than that of the control; The plant shooting was neat. The shooting rate of XX3 under two drarfing and 0802 treatment was 62.01% and 89.32%. The yield per plant showed decreasing trends with the increase of XX concentration. The plant yields of banana were 27.26, 25.62 and 23.45 kg for the one time treatment of XX1, XX3 and XX5, respectively. Of which, the yields per plant of XX3 and XX5 treatment were significantly decreased compared with that of the control (27.45 kg). The yields per plant of banana treated with 0802 and 0501 were 27.37 and 26.99 kg, respectively, and there was no significant difference with that of the control. It was found that the yield performance of banana plants was similar under the two dwarfing treatments of different plant grow regulators. Under the treatment with low concentrations of chlormequat chloride and paclobutrazol, the early shooting of banana could be promoted. Whereas the shooting of banana was delayed when the treating concentration was above 0.2 g per plant, and the plant yield was greatly affected or even reduced. The uniconazole treatment could increase the activities of PPO, CAT and PAL in banana leaves as well as the contents of soluble protein, calcium, magnesium, phosphorus and potassium, and enhance plant resistance.【Conclusion】It is recommended to use uniconazole, compound agents 0802 and 0501 as banana dwarfing agents with concentration ranging of 0.2-0.3 g/plant in banana production, and the newly planted banana could be dwarfed once. Banana is more susceptible to paclobutrazol (DX) and chlormequat chloride (AZ), which are not recommended.