Seed dormancy and germination of two cultivated species of Passifloraceae

Colombia is the country with the highest number of species of Passiflora in the world and most species have edible fruits and are cultivated. This investigation aims to better understand the range of seed dormancy exhibited in the fleshy fruits of Passifloraceae species, and to determine how to break this dormancy efficiently and reliably. Thus, in this investigation seed germination of Passiflora edulis and P. maliformis were studied. Seeds were extracted, conditioned, dried and scarified. Several chemical pre-treatments were applied (e.g. GA3 500, 1000, 2000 ppm, KNO3 1%, KNO3 1.5% - KH2PO4 1.5%). Illuminated germinators were used with constant temperature (i.e. 25, 30 ºC) and alternate temperature (i.e. 15/25, 15/30, 19/33, 20/30, 20/35 ºC). Germination was recorded as radicle protrusion. Removing the seed aril with water allowed a clean germination test in both species. For P. edulis the greatest germination was obtained at 20/30 ºC, while the poorest germination was found at constant temperature. Manuallyscarifi ed seeds provided the most rapid germination in all temperatures. For P. maliformis the highest germination was obtained for non-manually scarifi ed seeds treated with boiling water and tested at 20/35 ºC. Pre-treatment with GA3 or KNO3 did not promote germination in both species. It is concluded that seeds of P. edulis and P. maliformis have physical dormancy. Scarifying seeds of Passiflora spp. enabled the water potential of the embryo to increase and for seeds to germinate. Meanwhile, the chemical pre-treatmeant of seeds showed no additional benefit. Thus, physiological dormancy does not occur, and physical barriers are the only factor preventing germination of viable seeds of the two Passiflora species studied.