It's impossible to say definitively what the "second most important" part of a plant cell is. That's because all parts of a plant cell are essential for its function.

However, we can consider some strong contenders:

* Chloroplasts: These organelles are responsible for photosynthesis, the process that converts sunlight into energy. Without chloroplasts, plants wouldn't be able to produce their own food.

* Cell Wall: This rigid structure provides support and protection to the plant cell, giving it its shape and allowing plants to grow upright.

* Vacuole: This large organelle stores water, nutrients, and waste products, helping to regulate the cell's internal environment.

Ultimately, the importance of each part depends on the specific function of the cell. For example, in cells involved in photosynthesis, chloroplasts might be considered the most important. In cells providing structural support, the cell wall would be paramount.

It's best to appreciate the interconnectedness of all these parts and their vital roles in the life of a plant cell.