I am a PhD student from the University of Toronto in Helene’s Wagner lab and I am doing my thesis work with natural populations of Heliconia tortuosa in Costa Rica. In a general way, for my PhD thesis we want to know the effect of fragmentation on pollination, seed dispersal and the natural populations of Heliconia tortuosa in Las Cruces, Costa Rica. In one part of the PhD thesis I will do germination experiments, in which we will collect seeds of Heliconia tortuosa from fecal samples. These seeds will be germinated and then the germination rates will be compared with experimental treatments we will make using different chemical and/or manual scarification processes and a control in which the pulp will be washed off to obtain Heliconia tortuosa seeds. The aim of this experiment is to obtain germination rates as similar as possible as the germination rates from fecal samples and to observe if gut passage time has an effect on germination. The main reason for doing this is because we are limited for doing field germination experiments by the amount of seeds obtained from fecal samples, so we want to test if germination rates from seeds with chemical scarification would be similar to the germination rates from those from fecal samples. If so, then we could chemically scarify seeds in the future to use them for germination experiments in the field. So I have some general questions that would help me to plan my experiment:
1. For doing the chemical scarification, I have read that H2SO4 is more commonly used than HCl, but I do not know why. What is the difference between both acids? 2. I have not found any information about the pH of the acids in the proventriculous of Turdus grayi (which is the bird species that we will use in our gut passage experiment) or any other birds. Do you know more or less which would be a good pH to use for the chemical scarification experiment? I have found some vague information that the pH in a bird’s proventriculous is between 0.5 and 3. 3. For the chemical scarification treatment, we are going to submerge the seeds in the acid for 5, 10 and 15 minutes. These times were set because I read an article that the gut passage time of another Turdus species is between 20 minutes and an hour (although they had low sample sizes). So I am assuming that naturally the seeds would be exposed to acid in the proventriculous for ¼ of the total gut passage time. So setting the 5, 10 and 15 scarification treatments would translate in 20, 40, and 60 minutes gut passage time. However, I do not know if this assumption is true. Do you have any knowledge of an average time that a seed remains in the proventriculous of a bird? I would appreciate if you could help me with any information you know, like references, books, articles, your knowledge or if you know someone that could help me to clarify these questions. Thanks, Luis
