Mesophytes
Mesophytes live in environments where there is water in abundance most of the times but is not completely surrounded by it at all times. This means that the mesophytes have to rely on their stem and xylem to provide mechanical support and transport water and minerals throughout the plant. Therefore, the stem and xylem of mesophytes have adapted to not be flexible or store water, but to support the plant and transport water around the plant.
The stem can provide mechanical support to the cell as it goes through secondary growth unlike the stems of hydrophytes. But for the stem cells to provide support to the plant, the cells need to be turgid and they need water in abundance to do this. Therefore, mesophytes wouldn’t be able to survive well in xerophytic conditions where there is hardly no water in abundance. (MooreMelissa, 2015)
The xylem is developed well for the transportation of water unlike hydrophytes as mesophytic plants are not completely surrounded by water at all times meaning that they are not able to absorb water and nutrients directly from their surroundings. Therefore it has a well developed vascular system and xylem which acts as a vascular sclerenchyma with thick secondary cell walls. These thick secondary cell walls of xylem cells contain lignin which makes the cells waterproof that consequently causes the cells to die. This causes the cell contents and walls to decompose leaving a hollow tube of dead cells. However, the lignin that is left behind strengthens the hollow tube, preventing it from bending or snapping easily or collapsing in on itself. The xylem tubes are also narrow making it more stable and enhancing the capillary action in the tubes. (mhhe, 2015) (vaultexam, 2015 ) (HenryEllen, 2015)
Capillary action is a part of transpiration where water can travel from the roots to the top of the plant due to the cohesive forces between the water molecules and the adhesive forces between the water molecules and the walls of the xylem tube. The adhesive forces are caused due to the polar water molecules being attracted to the polar cellulose which is a component in the cell wall. (SterlingTracy, 2015) (NinErrin, 2015 ) |
The developed xylem is perfect for mesophytic environments but not for hydrophytic environments as the developed xylem will stiffen the stem of the plant making it easier to break in the water which is moving at all times as it is unable to move with the water. It is also not desirable for xerophytic conditions as the developed xylem enhances capillary action which would increase the rate of transpiration. This is great in for mesophytes and hydrophytes where water is in abundance, but not for xerophytes as there is no water in abundance.