biology

Leaf size

Leaf size is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Leaf size rather than just read about it. In short: Leaf size of plants can be described using the terms megaphyll, macrophyll, mesophyll, microphyll, nanophyll and leptophyll (in descending order) in a classification devised in 1934 by Christen C. Raunkiær and since modified by others.

Key takeaways

Leaf size belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Leaf size to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Leaf size from memory before moving on to harder problems.

Reference excerpt

Leaf size of plants can be described using the terms megaphyll, macrophyll, mesophyll, microphyll, nanophyll and leptophyll (in descending order) in a classification devised in 1934 by Christen C. Raunkiær and since modified by others. Definitions vary, some referring to length and others to area. Raunkiaer's original definitions were by leaf area, and differed by a factor of nine at each stage. Some authors have simplified the system to make it specific to particular climates, and have introduced extra terms including notophyll, picophyll, platyphyll and subleptophyll. In ecology, microphyll and similar terms based on blade size of the leaf are used to describe a flora, for example, a "microphyll rainforest" is often defined as a forest where the dominant trees have leaves less than 7.5 cm in length.

Raunkiaer's work Christen C. Raunkiaer proposed using leaf size as a relatively easy measurement that could be used to compare the adaptation of a plant community to dryness. We have for a long time been aware of a series of different adaptations in the structure of plants enabling them to endure excessive evaporation, and thus allowing them to live in place where the environment determines intense evaporation, or where the conditions of water absorption of the ground are unfavourable either physically or physiologically. Examples of such structures are: (1) covering of wax, (2) thick cuticle, (3) sub-epidermal protective tissue, (4) water tissue, (5) covering of hairs (6) covering of the stomata, (7) sinking of the stomata, (8) inclusion of the stomata in a space protected from air currents, (9) diminution of the evaporating surface, &c. The matter however is so complicated that it is very difficult to reach an exact appraisal of these adaptations in characterizing the individual plant communities biologically. ... In general we must content ourselves with showing the most frequently occurring adaptations, without going farther into the statistical investigation. ... A preliminary direct consideration of a series of evergreen phanerophytic communities, ... show that amongst the adaptations named, diminution of the transpiring surface, diminution in leaf size, is one of the adaptations generally in evidence; and since this adaptation is easy to observe and comparatively easy to measure, it is convenient to begin with it if we wish to use the statistical method on this domain. Raunkiaer used the following size classes:

Leptophyll: less than 25 square millimetres Nanophyll: 25–225 square millimetres Microphyll: 225-2,025 square millimetres Mesophyll: 2,025-18,225 square millimetres Macrophyll: 18,225-164,025 square millimetres Megaphyll: greater than 164,025 square millimetres Later authors have modified the classes and have sometimes used leaf length as a simpler measure than leaf area if the leaf shape is approximately an ellipse. For example, L.J. Webb used size classes:

Microphyll: less than 2,025 square millimetres Notophyll: 2,025–4,500 square millimetres Mesophyll: greater than 4,500 square millimetres

Examples of definitions

Single vegetable organisms with large leaves Gunnera manicata, giant ornamental rhubarb; leaves 2 m × 3.4 m (6 ft 7 in × 11 ft 2 in); Raphia regalis, composed leaves 25.11 m × 3 m (82.4 ft × 9.8 ft); Manicaria saccifera, Amazonian palm; partially composed leaves 8 m (26 ft); Marojejya darianii, big-leaf palm; leaves 5 m (16 ft); Johannesteijsmannia altifrons, Joey palm; undivided leaves 4 m (13 ft) long; Amorphophallus titanum, titan arum; leaves area 3.2 m2 (34 sq ft); Victoria amazonica, giant Amazonian waterlily; aquatic plant with leaves 2.4 m (8 ft) long; leaves area 4.6 m2 (50 sq ft).

Worked examples

Example 1 — a first encounter with Leaf size

Start with the simplest possible case. Write down what Leaf size claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Leaf size before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Leaf size ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Leaf size

In research: Leaf size appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Leaf size in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Leaf size is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ecological metrics, Leaf morphology, so understanding it makes those chapters shorter.
In everyday life: Look for Leaf size outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Leaf size in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Leaf size means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Leaf size out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Leaf size in simple terms?

Why does Leaf size matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Leaf size?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Leaf size.