Leaf adaptations
Both mesophytes and hydrophytes have leaves that vary in shape and size, while xerophytes tend to have leaves that are reduced to fur, spikes or spines and if there are leaves they are as small as possible to reduce surface area for transpiration and rolled to create an area where water vapour is trapped. Contrastingly mesophytic leaves tend to be large and thin to increase chance of sunlight rebounding of the spongy mesophyll layer for absorption, however this does mean that they are vulnerable during times of sunny dry weather. Hydrophytes can have multiple types of leaves on one plant (heterophylly - having dissimilar leaves on one plant) depending on whether the plant is fully submerged or partially submerged (submerged leaves are heavily divided to increase surface area for diffusion and floating leaves are large and wide to increase surface area for slight absorption). However mesophytes and xerophytes tend to have only one type of leaf per plant. Mesophytic and xerophytic leaves are both green in colour indicating chlorophyll, however xerophytic leaves are a very pale green (less chloroplasts) as sunlight reflects off more easily meaning that the plant is subjected to lower temperatures. Hydrophytes have many stomata located at the top of floating leaves, (upper epidermis) (stomata are generally not present or in lower quantity in submerged leaves because water, nutrients, gases etc can enter via diffusion and osmosis) they are located at the upper epidermis so that water does not block the stomata and prevent transpiration and gas exchange from happening. On the other hand, in mesophytes the stomata are generally located in the lower epidermis because the evaporation of water under the leaf helps the plant to stay cool. In xerophytes there are a much lower amount of stomata compared to mesophytes and hydrophytes, this is so the plant can conserve water, the stomata are sunken into the plant and are located within rolled leaves. The stomata can be covered in fur or hair to create an area where water vapour is trapped. Stomata in hydrophytes remain open constantly (abundance of water = no need to conserve water by closing stomata) while mesophytes and xerophytes stomata are not. During times of low water the stomata in mesophytes will close to prevent further water loss in cells (mesophytes partially rely on cell turgidity for the structure of the plant, high water loss = plant beginning to wilt) but during most seasons the stomata will remain open for efficient diffusion of gasses and so that new water, nutrients and minerals can be brought up into the plant. On the other hand xerophytes stomata are closed much of the time, this is because xerophytes tend live in climates with hot temperatures meaning that the water's kinetic energy is greater, resulting in a greater drive for transpiration. Some xerophytes will only open their stomata at night when it is cooler so that the plant will experience less water loss. Both mesophytes and hydrophytes have the traditional leaf cell structure, with one row of palisade cells, however xerophytes have two rows of palisade cells because they are subjected to a greater light intensity giving a better chance of sunlight absorption. Hydrophytic leaves tend to have very little or no waxy cuticle because water loss is not an issue, on floating leaves there is a thin waxy cuticle because it helps water roll off the leaf preventing it from blocking the stomata. This is similar to most mesophytic leaves as they generally only have a thin waxy cuticle (this can become a limitation during times of dry weather because it means that water is not as easily conserved). Contrastingly xerophytes have a very thick waxy cuticle on both the leaves and the stem, because the plant must be able to conserve water to survive, a thick waxy cuticle means that water is not as easily lost.
Root adaptations
Hydrophytes do not have well developed root systems, while both mesophytes and xerophytes do because they do not live in a climate with an abundance of water, therefore meaning that well developed root systems are essential for their survival. Hydrophytes will sometimes have a small root system, like the eel grass, (though generally undeveloped because it is not needed for the uptake of water and nutrients) for anchorage against strong currents, waves etc. Mesophytes and xerophytes tend to have a shallow root system or deep reaching roots and in some species of xerophytes both. This is so that the shallow roots, like the fibrous root system in many mesophytes, quickly absorb any water from the surface of the soil (when it rains), this is extremely important in xerophytes because due to rainfall being minimal there is a high competition for water. Deep reaching roots mean that the plants can absorb water in deeper soil - for mesophytes this is similar to the taproot system, means that the plants can survive better in dry times or droughts - while for xerophytes this is an essential root adaptation because without the roots being able to reach water deep within the soil the plant would die because of the minimal rainfall.
STem and xylem adaptations
Both mesophytes and xerophytes have well developed vascular tissues because they both rely on them for support and the transportation of nutrients, minerals and water around their cells. This is due to both these plant groups living in climates where water is not in abundance, so well developed vascular systems, particularly in xerophytes are used for support (because of the limited water cells will not always be turgid - cell turgidity helps to keep plants upright) and in mesophytes this means that water can be easily transported to the plant's cells to keep them turgid and the plant upright. However hydrophytes do not have well developed vascular systems because they do not require them for support, (water provides them with support) or for the transportation of water, minerals or nutrients because this is easily done by diffusion and osmosis.