From memory Passionfruit Seed is fairly tough and to get them to germinate 'on time'. you may need to scarify the seed. This is done in 3 ways. Firstly, nick the outer coating with a blade. Secondly, try rubbing the outer coating back to expose the inner. Thirdly, you can soak it in hot water for a while - no hard and fast rules on this. Some aussie natives are so immune to these shortcuts you really have to get serious. Along the lines of exposure to fire and smoke..
I am not a horticuluturist but all seeds have 3 levels, an outer hard case and inner skin [a hormone layer] and the inner bit which grows. Sometimes we can intervene and rupture the hormone layer to induce immediate germination. Good examples of this which we most of us are aware are nut seeds like almond and walnut. The 3 layers are quite distinctive.
Having ''attacked'' very many mango seeds I now know you can literally cut the top 10% off the seed with secaturs and away they go.
In your case I would think if you rubbed the passionfruit seed on a bit of fine sandpaper till the inner was exposed you would find your germination rates would be excellent..
It is very much worthwhile experimenting when you get a batch of seed to see what works for you. Say with 10 seeds, plant 2 direct and experiment on the other 8. Seeds have encapsulated a genetic message which tells them to GO GO GO whenever most of the conditions have been met. The reason for the 3 layers is so that seeds dont fall and germinate at the wrong time - or in the case of non-annuals.. all at once. It gives the mother plant some longevity. The inner hormone layer is what gives seeds their longevity so that only a few will germinate at any time making sure the species survive. The above processes are designed to circumvent that.
Past this point normal plant specific seed germination rules apply.
