The environment role in the incomplete reproductive cycle of Tropaeolum pentaphyllum Lam. (crem) in Brazilian Mixed Ombrophilous Forest: implications for conservation and cultivation

The herbaceous vine Tropaeolum pentaphyllum (crem) is an endangered geophyte with great economic potential as its tubers and flowers are used for human nutrition. The aim of this study was to evaluate the phenophases of T. pentaphyllum under the influence of the climatic conditions of southern Brazil, contributing to its conservation and cultivation. The study was conducted on a natural population from Brazilian Mixed Ombrophilous Forest (Sertão municipality, Southern Brazil) and 130 tubers were planted and kept under field conditions in an area close to the natural population. We monitored phenology on a weekly basis throughout the growing season and analysed the relationship between phenology and environmental parameters (temperature, day-length and precipitation). We quantified the activity and intensity indices of the following phenophases: tuber sprouting, flower bud, flower, unripe fruit, and ripe fruit. In order to test the seasonality of phenophases, we analysed each one using Rayleigh test statistics. The species showed very similar activity and intensity peaks for all phenophases. All phenophases occurred once a year and were seasonal. Tuber sprouting and the number of shoots were associated with photoperiod (less than 13 h) and temperature (between 13.2 and 20.2°C). The life cycle of T. pentaphyllum was short, with average duration of only 17.5 ± 4.7 weeks, from tuber sprouting to aerial stem senescence. The plant senescence occurred before fruit ripening compromising its sexual reproduction. Based on our findings, we recommend planting the tubers in January, collecting tubers in December and collecting flowers in September.