Here's why:
* Isotonic point for a cell: This refers to the solute concentration where a cell neither gains nor loses water. For a freshwater plant cell, the isotonic point is close to the low solute concentration of freshwater. For a saltwater plant cell, it's closer to the higher solute concentration of seawater.
* Isotonic point for the plant as a whole: This is more complex. Plants have mechanisms to regulate water movement and solute concentration in their tissues. While individual cells may have different isotonic points, the plant as a whole needs to maintain an internal environment suitable for survival.
So, in the context of individual cells:
* Yes, the isotonic point of a saltwater plant cell is higher than a freshwater plant cell. This is because saltwater plants need to maintain a higher internal solute concentration to prevent water loss to the surrounding salty water.
However, when considering the whole plant:
* It's not accurate to compare their "isotonic points" directly. Both types of plants need to regulate their water and solute balance to survive. The specific mechanisms they use will differ depending on their environment.
Key points to remember:
* Saltwater plants have evolved adaptations to live in a high-salt environment, including mechanisms to regulate their internal water and solute balance.
* Freshwater plants have different adaptations for a low-salt environment.
Therefore, while the isotonic point of individual cells may differ between saltwater and freshwater plants, it's not a simple comparison for the whole plant.
