What plants have the highest concentration of chloroplasts in their leaves?

Question

Does a square foot of grass produce the same amount of oxygen as a square foot of tree leaves?

According to the Wikipedia page on photosynthesis, leaves can contain 'between 450,000 and 800,000 chloroplasts for every square millimeter of leaf."

The presence of the range would presuppose that different species develop differing concentrations.

Answer 1

I don't know that the matter has ever been settled, since the answer to the question has no practical use.  However, when we harvested chloroplasts from cell material in my college plant lab, we used spinach leaves.  While cost/availability of the plant may have been a consideration in the material selection, I bet that spinach leaves are relatively high in chloroplast concentration of owing to their deep-green color.