A hydrophyte lives in or on water, so its problems are different from a dry-land plant: staying afloat, getting light, and getting oxygen for parts in water.
This lesson is part of plant adaptations. The opposite problem is in relating xerophyte features to water conservation.
What problems do aquatic plants face?
- Staying afloat so leaves reach light.
- Getting oxygen to parts under water, where gas diffuses slowly.
- Staying supported when water, not stiff tissue, holds the plant up.
Water loss is not a problem for them, so a thick waterproof layer is not needed.
Worked example: a floating-leaf plant
An original description: a plant grows in a pond. Its leaves float on the surface, its leaf tissue has large air spaces, stomata are on the upper surface, the cuticle is thin and the stem is long and flexible.
Air spaces. They make the leaf buoyant, so it floats in the light. They also carry oxygen to submerged stems and roots.
Stomata on the upper surface. The upper surface touches air, so gases can be exchanged.
Thin cuticle. Water loss is not a problem, so a thick waxy layer is not needed.
Flexible stem. Water supports the plant, and flexibility reduces damage from water movement.
The mistake that mixes up the two plant types
A student writes that a hydrophyte has “a thick waxy cuticle to reduce water loss”. That is a xerophyte feature. A plant in water does not lose water in the same way.
Check each answer by asking: is the problem too little water or too much? The features follow from that answer.
How do I write the explanation?
Use the same frame as for xerophytes: feature, problem and solution. For example: “Large air spaces make the leaf buoyant, so it floats near the surface and receives light for photosynthesis.”
Adding the link to photosynthesis gives the answer a second idea.
A self-check question
A submerged plant has thin, finely divided leaves. Suggest how this helps it.
Answer
Thin, finely divided leaves have a large surface area compared with their volume, and a short diffusion distance. This increases the uptake of dissolved gases, such as carbon dioxide and oxygen, from the water, and the thin shape lets light reach the cells.
Gas movement ideas are covered in gas exchange. The biological data interpretation trainer offers practice with data.
Next, see salt tolerance in explaining halophyte adaptations. If these answers still feel vague, SPM Biology one-to-one tuition lets a teacher ask problem-first questions.