Environmental factors' action on the germination process and initial growth of weeds of Rubiaceae family

Knowledge of factors that influence the germination process and their interactions allows estimating the initial development of a species in a particular environment and optimizing the weed management decisions. The objectives of this study were to evaluate the effect of environmental factors on the germination and initial growth of the weed species Borreria latifolia, Galianthe chodatiana and Richardia brasiliensis. Five trials were conducted using a completely random experimental design, in factorial design, with five repetitions, each one evaluating effects of temperature, irradiance, aluminum, salinity and pH. The germination was assessed daily, and germination speed index and the length of radicle and epicotyl were determined. Temperatures between 20 and 30 °C maximized final germination and germination speed index of the three species. B. latifolia showed low germination with 15 °C temperature. G. chodatiana and R. brasiliensis did not germinate well at temperatures between 30 and 35 °C. B. latifolia and R. brasiliensis did not germinate in the dark condition, whereas G. chodatiana were indifferent to photoperiod. Seeds from B. latifolia and G. chodatiana were more tolerant to aluminum concentration in the germination than R. brasiliensis, while G. chodatiana were tolerant in germination and early growth. Low NaCl concentration inhibits the seed germination of the three species. B. latifolia showed higher adaptation at low pHs, while the other species at pHs close to neutrality. The responses of the species to environmental factors can be used in the planning of strategies for their management.