Answer: I suggest you consider amending your experiment to see how overall temperature affects seed germination. It's a little hard to investigate the water temperature alone, because, unless you apply boiling water and kill the seed's embryo, the effect of the water temperature will lessen once it hits the room-temperature soil. Also, I think you'll find more info on optimum germination temperatures with respect to room temperature. You may have seen heating mats for sale that are placed under newly planted pots. The bottom warmth helps the seeds to germinate. Once the plants are growing, they tend to prefer slightly cooler temps.
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