Many studies have shown the effects of boron (B) application on various crops; however, results on roses are scarce. The aim of this experiment was to evaluate the effects of B on the production and quality of roses (Rosa hybrida Shiny Terrazza®) under controlled conditions. Treatments consisted of five rates of B (0, 1, 4, 8 and 16 mg kg-1) applied in the substrate in a randomized block design with five replicates. We evaluated the cycle; number of flowers per plant; number of leaves per flower stem; dry matter production of roots, leaves and flowers; plant height; length of the floral bud; and flower diameter and longevity. In addition, total chlorophyll and B content in the leaves and symptoms of B toxicity in the plants were also determined. There was a significant effect of B application rates on most of the variables, with the exception of plant height, number of flowers per plant, flower longevity, and root dry matter production. Leaf B content increased in a linear manner with increasing application rates of B in the range of 0 to 16 mg kg-1. There was an increase in flower production and quality with the application of B, and a reduction in the number of days to flowering. Boron toxicity symptoms were observed at B rates higher than 4 mg kg-1. These symptoms were characterized by soaked spots beginning at the edges of the leaf blade, with the spots evolving to chlorosis and subsequent necrosis. At the highest rate of B application, there was dropping of leaves. This leaf dropping was responsible for the decreased number of leaves per floral stem at the end of the cycle as of B application rates of 8 mg kg-1. Plants showing symptoms of toxicity had leaf B contents above 200 mg kg-1, while healthy plants (control) had B contents ranging from 65 to 89 mg kg-1.
Rosa hybrida; micronutrient; boric acid; floriculture
