Mesophytes

Mesophytes

Mesophytes are plants of habitats where the water supply is neither excessive, as it is for hydrophytes, nor scarce, as it is for xerophytes, but moderate and reasonably reliable through most of the year. Ordinary garden plants, most trees of non-arid regions, and the majority of cultivated crop plants belong to this group, since farmland and typical garden soil generally provide a balanced, moderate water regime rather than the extremes of a pond or a desert.

Because their habitat does not impose either kind of stress, mesophytes show structural features that sit between the two extremes described for hydrophytes and xerophytes, rather than showing either set of specialised adaptations in an exaggerated form. Their root systems are moderately developed — neither reduced to almost nothing (as in hydrophytes, which can absorb water and minerals directly through submerged tissue) nor unusually extensive or deep (as in xerophytes, which must actively search out scarce water). Their cuticle is present and offers reasonable protection against water loss, but it is not nearly as thick or heavily waxed as the cuticle of a true xerophyte, since the risk of drying out is far lower. Stomata in mesophytes are typically distributed on both leaf surfaces, or concentrated on the lower surface away from direct sun, rather than being confined entirely to an upper floating surface (as in hydrophytes) or sunk into protective crypts (as in xerophytes).

Internally, mesophytes maintain a fairly standard balance of tissues: xylem is normally developed to support regular water transport from root to shoot, since (unlike a hydrophyte) a mesophyte cannot absorb water directly across most of its exposed surface and genuinely depends on root uptake and internal transport. Mechanical tissue is likewise present in typical amounts, since — again unlike an aquatic plant that is buoyed up by water — a mesophyte must support its own weight against gravity and wind using ordinary structural tissue, without needing either the minimal reinforcement of a hydrophyte or the extra-reinforced, water-conserving anatomy of a true desert xerophyte. …