The melon crop is of great socioeconomic importance in Brazil and some species from the Caatinga biome show allelopathic effects on other species. The aim of this study was to assess leaf and seed extracts of cumaru (Amburana cearensis (Allemao) A.C. Sm.), the jujube tree (Zizyphus joazeiro Mart.), Jucá (Caesalpinia ferrea Mart. Ex. Tul. Var. Ferrea) and mulungu (Erythrina velutina Willd.) on the emergence of melon seeds (Cucumis melo L.). Leaves and seeds were used to produce extracts for each species at concentrations of a) 1%, b) 0.5% c) 0.25%, d) 0.125% and e) 0% (control). The experiment was conducted with each extract type and its respective concentrations in a completely randomized design, with four replicates, each of 20 seeds. The percentage emergence and rate index, percentage of abnormal seedlings, seedling dry matter and seedling shoot and root length were assessed. Seed extracts of A. cearensis prevented melon germination, whereas the other extracts had no effect on this variable. Leaf extracts of A. cearensis and leaf and seed extracts of Z. joazeiro, C. ferrea and E. velutina resulted in abnormal melon seedlings. The percentage of abnormal melon seedlings exceeded 30% when treated with C. ferrea seed extract at the highest concentration. Most extracts did not affect seedling dry matter, but E. velutina leaf and seed extract increased the dry matter accumulation of melon seedlings and Z. joazeiro seed extract decreased dry matter accumulation at a concentration of 0.25%. The highest concentrations of mulungu and jucá leaf extracts promoted the shoot growth of melon seedlings. The extract from E. velutina seeds negatively affected root length compared to the control, similar to the effect of C. ferrea and E. velutina leaf extracts at the highest concentrations. Extracts of different organs of Caatinga plants can affect the emergence and characteristics related to seedling growth, depending on the concentration. Most extracts did not affect germination or the emergence rate index, but affected seedling growth. Key words: Cucumis melo L. Amburana cearensis. Ziziphus joazeiro. Caesalpinia férrea. Erythrina velutina.
ResumoA cultura do melão tem grande importância socioeconômica no Brasil e algumas espécies do bioma Caatinga têm ação alelopática sobre outras espécies. O objetivo do trabalho foi avaliar os extratos de folhas e sementes de cumaru (Amburana cearensis (Allemao) A.C. Sm.), juazeiro (Zizyphus joazeiro Mart.) jucá (Caesalpinia ferrea Mart. ex. Tul. var. ferrea) and mulungu (Erythrina velutina Willd.) na emergência de sementes de melão (Cucumis melo L.). Os tipos de extratos foram os de folhas e sementes para cada espécie em concentrações de a) 1%, b) 0,5%, c) 0,25%, d) 0,125% e e) 0% (testemunha). Cada tipo de extrato com suas respectivas concentrações constituiu um experimento que foi conduzido em delineamento experimental inteiramente casualizado com quatro repetições de 20 sementes. Foram avaliadas a porcentagem e índice de velocidade de emergência, porcentagem de plântulas anormais...