Question:The Gemorah speaks of the time for a replanted plant to take root as being three days. One would imagine that the determining factor would be the time duration of the replanting. However the Gemorah in its first answer uses the legalistic principal of "a partial day is like a Whole day at both ends" In its second answer the Gemorah uses both the time principal and the legalistic principal at one end. This I find most difficult to understand for if one recognizes that time is the determining factor, that how can the legalistic principal have any effect? Let me point out that it is quite possible to have a longer period of time via the Gemoras first answer than the second
When the Chachamim determined the amount of time it takes for the plant to take root, they based the amount of time on their experience and observations. However, when they *expressed* that amount of time and taught it to the people for Halachic purposes, they expressed it in a way that even people who -- upon hearing the Chachamim's determined amount of time -- would apply the previously known rules of time (such as a partial day is like a whole day). Therefore, when they said that it takes three days, they already took into consideration that a partial day is like a whole day (and, in reality, they knew that a plant takes root in just over two days). One who interpreted the Chachamim literally, and waited three days, would not lose, but would merely be acting more stringently (for this Halachah is used exclusively for deriving a lenient ruling).