What do mature red blood cells lack so that they can hold as much hemoglobin as possible?

one is through turgidity. this occurs before ground tissue ( collenchyma

and sclerenchyma cells) become well

developed to give structural support to the plant as it grows bigger. the xylem

tissue (composed of rigid tissue) of the young

plant render this support and also maintaining osmotic turgidity of the surrounding

plant cells.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added