Write the floral formula for Allium Cepa.

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Q. Write the floral formula for Allium Cepa.

Puducherry TnboardTamil Nadu HSC First Year (DGE) Board 2020Subjective· 2mImportance★★★★★

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Concept understanding — Family Liliaceae

The Lily Family — An Intuitive Start

Imagine a flower that is perfectly symmetrical, with parts arranged in neat groups of three. That is the signature of the lily family, Liliaceae. Think of the common lily you see in gardens — six petals (or what look like petals), six stamens, and a three-lobed ovary at the centre. That repeating pattern of three is the family's fingerprint.

Why three? It is a deep evolutionary trait. Monocot plants — the group that includes lilies, grasses, orchids, and palms — almost always have floral parts in multiples of three. Liliaceae is the classic example of this monocot floral plan.

The Precise Statement

Liliaceae is a family of monocotyledonous flowering plants. Its diagnostic features are:

Trimerous flowers — all floral whorls (sepals, petals, stamens, carpels) are in sets of three or multiples of three.
Tepals — sepals and petals are identical in colour and texture, so they are not called separate sepals and petals but collectively called tepals. They are arranged in two whorls of three each (3+3).
Androecium — six stamens, arranged in two whorls of three.
Gynoecium — a syncarpous (fused) ovary made of three carpels. The placentation is axile: the ovules are attached along the central axis where the carpels meet.
Ovary position — superior (above the attachment of other floral parts).

\oplus \ \P \ P_{3+3} \ A_{3+3} \ G_{\underline{(3)}}

Why These Features Matter

The trimerous plan and tepals together distinguish Liliaceae from many other families. Compare with a rose (family Rosaceae): a rose has five petals, many stamens, and separate green sepals — none of that matches the lily pattern.

Axile placentation means that if you cut a lily ovary crosswise, you see three compartments (locules) with ovules arranged around a central column. This is different from marginal placentation (as in peas) or parietal placentation (as in mustard).

Tip

To remember the lily family, think 3-3-6-3: 3 sepals (tepals), 3 petals (tepals), 6 stamens, 3 fused carpels. Everything comes in threes or sixes.

Common Examples

Lilium (true lily)
Tulipa (tulip)
Allium (onion, garlic — yes, they are lilies too!)
Asparagus (asparagus)
Aloe (aloe vera) …

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Allium cepa (onion, family Liliaceae) has a typical monocot flower: actinomorphic, bisexual, with 6 similar tepals (perianth not differentiated into sepals/petals), 6 stamens, and a 3-carpellary syncarpous superior ovary.

Allium cepa is the common onion, placed in family Liliaceae (the lily family) — a family characterised by trimerous flowers with an undifferentiated perianth.

Floral characters of Allium cepa:

Inflorescence: umbel (many small flowers borne on a single point, subtended by a spathe-like bract) — hence "Br" (bracteate) in the formula.
Symmetry: actinomorphic (regular, radially symmetric) — shown by the symbol %.
Sex: bisexual (both androecium and gynoecium present) — shown by ⚥.
Perianth: not differentiated into separate calyx and corolla; instead there are 6 similar tepals arranged in two whorls of 3 each — written P(3+3) or P3+3 (fused or free tepals, typically shown fused in this family: P(3+3)).
Androecium: 6 stamens, arranged in two whorls of 3, usually free — A(3+3) or A3+3. …

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Q.Write the floral formula for Allium Cepa.

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