Actinomorphic vs Zygomorphic Flower: Symmetry with Examples
Biology · Morphology of Flowering Plants · NEET
An actinomorphic flower has radial symmetry: you can cut it into two equal halves through the centre in any plane (like a wheel or a star). A zygomorphic flower has bilateral symmetry: you can cut it into two equal halves in only ONE vertical plane (like your face). Memory hook: "Actino = Any plane, Zygo = one Zone (single plane)."
Actinomorphic flowers (left) split into equal halves along many planes through the centre, like mustard. Zygomorphic flowers (right) split equally along only one vertical plane, like a pea flower.
Your doubts, answered
Is mustard flower actinomorphic or zygomorphic?
Mustard is ACTINOMORPHIC (radial symmetry). You can cut a mustard flower into two equal halves through many planes passing through the centre. NCERT lists mustard, datura and chilli as the three standard actinomorphic examples. Do not confuse it with pea, which is zygomorphic.
Which flowers are zygomorphic according to NCERT?
NCERT names exactly four zygomorphic examples: pea, gulmohur (gulmohar), bean and Cassia. All four are legumes or legume-like. A zygomorphic flower can be divided into two similar halves in only ONE particular vertical plane. NEET often mixes these into match-the-following questions, so memorise this list.
What is the difference between radial and bilateral symmetry in a flower?
Radial symmetry (actinomorphic) means MANY planes through the centre give equal halves, like a star or a wheel. Bilateral symmetry (zygomorphic) means only ONE vertical plane gives equal halves, like a mirror-image face. Radial = actinomorphic; bilateral = zygomorphic.
Is a pea flower actinomorphic?
No. A pea flower is ZYGOMORPHIC (bilaterally symmetrical). Its petals are unequal (one large standard, two wings, two fused keel petals), so only one vertical plane divides it into equal halves. This is why pea appears as the correct 'zygomorphic' answer in NEET 2024 and 2025.
What is an asymmetric flower and give an example?
An asymmetric (irregular) flower cannot be divided into two equal halves by any plane. NCERT's example is Canna. So the three symmetry types are: actinomorphic (radial), zygomorphic (bilateral) and asymmetric (no plane works).
⚠️ The NEET trap ✗ Cassia is actinomorphic because it has 5 free spreading petals that look star-like. ✓ Cassia is ZYGOMORPHIC. Even though petals look spread out, they are unequal, so only one vertical plane divides it equally. NCERT's zygomorphic list is pea, gulmohur, bean, Cassia. 🧠 If a flower is a legume (pea, bean, Cassia, gulmohur, Sesbania, Pisum, Trifolium), assume ZYGOMORPHIC in NEET unless proven otherwise.
Real NEET questions
NEET 2016 Phase 2
Radial symmetry is found in the flowers of
A · Brassica ✓
B · Trifolium
C · Pisum
D · Cassia
Solution: Radial symmetry = actinomorphic = the flower can be divided into equal halves in any radial plane through the centre. NCERT gives mustard (Brassica) as the example. Trifolium, Pisum and Cassia are leguminous flowers that are zygomorphic (bilateral). So the answer is Brassica.
NEET 2024
Which of the following is an example of actinomorphic flower?
A · Cassia
B · Pisum
C · Sesbania
D · Datura ✓
Solution: An actinomorphic flower can be cut into two equal halves by any radial plane through the centre. NCERT's actinomorphic examples are mustard, datura and chilli. Here Datura is actinomorphic, while Cassia, Pisum and Sesbania are zygomorphic legumes. Answer = Datura.
NEET 2024 / 2025
Which of the following is an example of a zygomorphic flower?
A · Pea ✓
B · Chilli
C · Petunia
D · Datura
Solution: Zygomorphic flowers can be divided into two similar halves in only one vertical plane. NCERT lists pea, gulmohur, bean and Cassia. Among the options only Pea is zygomorphic; chilli, Petunia and Datura are actinomorphic. Answer = Pea.
Solved Morphology of Flowering Plants NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Datura is ACTINOMORPHIC (radial). NCERT's three actinomorphic examples are mustard, datura and chilli. It appeared as the correct actinomorphic answer in NEET 2024.
Is chilli flower actinomorphic?
Yes. Chilli is one of NCERT's three actinomorphic examples, along with mustard and datura. It shows radial symmetry.
What is an example of an asymmetrical flower?
Canna is the NCERT example of an asymmetric (irregular) flower. It cannot be divided into two equal halves by any plane at all.
Why is a legume flower zygomorphic?
Legume flowers (pea, bean, Cassia, gulmohur) have unequal petals arranged in a papilionaceous or Cassia-type pattern, so only one vertical plane can divide the flower into two equal mirror halves. That single-plane rule makes them zygomorphic. This matters for NEET family questions on Fabaceae.
How is flower symmetry shown in a floral formula?
The symbol for an actinomorphic flower is the encircled plus sign, and the symbol for a zygomorphic flower is a slash or percentage-type sign. NEET 2025 tested this exact notation, so learn the actinomorphic symbol carefully.
