Development of the prickly pear cactus Opuntia stricta (Haw.) Haw. (Cactaceae) in vitro in response to the replacement of potassium nitrate for a commercial kno 3 fertilizer

ABSTRACT: In micropropagation, potassium nitrate (KNO3), an ACS reagent grade chemical, used in the preparation of growing mediums is expensive and its procurement depends on bureaucratic procedures, as it is controlled by the Brazilian Army. This research to assessed the effect of replacing the ACS KNO3 for a commercially available fertilizer (KNO3- based) on the micropropagation of the prickly pear cactus (Opuntia stricta (Haw.) Haw. cv. Elephant Ear. Treatments used six different fertilizer concentrations (0, 0.5, 1, 1.5, 2 and 2.5 g L-1) and a control consisting of 1.9 g L-1 KNO3, as shown in the MS salts. The survival, size and number of sprouts and the value of fresh biomass were evaluated. After seedling acclimation, we assessed the survival, number of sprouts, length, and number of roots, racket formation, average fresh biomass mass, macronutrient absorption and morphological changes of the seedlings. Explants inoculated with fertilizers at concentrations of 0.0; 2.0 and 2.5 g L-¹ did not grow. The response of explants at concentrations of 0.5 and 1.5 g L-1 of the fertilizer were the same as those developed in a KNO3 medium, and at a concentration of 1.0 g L-1, in all variables, the means were higher than those of the control medium. Therefore, it showed the feasibility of using fertilizers in the in vitro cultivation of the prickly pear cactus, which may remove bureaucratic barriers and reduce product costs by 99.12%.摘要：在植物微繁殖（micropropagation）过程中，用于配制生长培养基的ACS试剂品级硝酸钾（potassium nitrate, KNO3）成本高昂，且因其受巴西陆军管控，采购需遵循繁琐的官僚审批流程。本研究旨在评估用市售硝酸钾基肥料替代ACS品级硝酸钾，对梨果仙人掌（Opuntia stricta (Haw.) Haw. cv. Elephant Ear，品种名译为“象耳”）微繁殖的影响。试验设置6种不同肥料浓度梯度（0、0.5、1、1.5、2、2.5 g·L⁻¹），并以1.9 g·L⁻¹硝酸钾配制的MS培养基为对照。测定指标包括外植体存活率、芽体大小、芽数及鲜生物量。幼苗经炼苗处理后，进一步测定其存活率、芽数、根长、根数、球拍状茎片形成情况、平均鲜生物量、大量元素吸收量及幼苗形态变化。结果显示，肥料浓度为0.0、2.0和2.5 g·L⁻¹时，接种的外植体均未生长；浓度为0.5和1.5 g·L⁻¹时，外植体的生长表现与ACS硝酸钾培养基中培育的外植体一致；而浓度为1.0 g·L⁻¹时，所有测定指标的均值均高于对照培养基。综上，本研究证实了在梨果仙人掌离体培养中使用该市售肥料的可行性，可规避官僚审批壁垒，并将产品成本降低99.12%。