Questions: How many stems grew on the plant that was kept at 6°C for 60 days?

To answer the question about how many stems grew on the plant that was kept at $6^{\circ} \mathrm{C}$ for 60 days, I need more specific information about the plant's growth conditions and any experimental data or results that might be provided.

Since the question does not provide any additional context or data, I cannot determine the exact number of stems that grew on the plant under these conditions. Typically, such information would be derived from an experimental study or a growth chart that details the plant's response to different temperatures over a specified period.

If you have any additional data or context related to the plant's growth under these conditions, please provide it so I can give a more accurate answer.