Which of the following describes a perianth?
In some flowers like lily, the calyx and corolla are not distinct and are collectively called the perianth.
Ref: NCERT Class 11 Biology chapter - Morphology of flowering plants
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Flowers lacking perianth are called
Achlamydeous flowers completely lack perianth, sexual organs directly exposed to environment, typically associated with anemophilous pollination or highly reduced floral biology as in Piperaceae, some Euphorbia cyathium male flowers and Salicaceae catkins. Monochlamydeous retains single whorl usually interpreted as sepaloid, dichlamydeous possesses both calyx and corolla, perigynous refers to ovary position where hypanthium forms cup surrounding ovary. Achlamydeous condition results from evolutionary reduction maximizing pollen release efficiency and minimizing resource allocation to attraction, correlating with naked inflorescences, absence of nectaries and wind dispersal strategies.
Ref: Simpson Plant Systematics, Achlamydeous reduction; NCERT, Monochlamydeous achlamydeous flower types
Perianth is composed of
Perianth collectively denotes non-reproductive outer floral envelopes providing protection in bud and attraction during anthesis; normally differentiated into outer calyx of sepals typically green sepaloid and inner corolla of petals often coloured petaloid. In complete dicot flowers both present termed dichlamydeous, in monoclamydeous only one whorl evident. Androecium and gynoecium constitute sexual whorls internal to perianth. Carpel alone refers to gynoecium unit, stamen alone to androecium. Perianth differentiation into distinct calyx-corolla is hallmark of most dicots and advanced monocots, while Liliaceae shows undifferentiated tepals called perigonium.
Ref: NCERT Class 11, Perianth calyx corolla differentiation; Campbell Biology, Perianth organization
Perianth with tepals is characteristic of
Liliaceae exhibits homochlamydeous perianth where calyx and corolla are not distinguishable morphologically, segments called tepals, typically petaloid, six arranged in two trimerous whorls 3+3 forming perigonium, polyphyllous or slightly gamophyllous with valvate aestivation. This condition reflects monocot ancestry where differentiation into sepals and petals secondarily reduced. Fabaceae shows clear papilionaceous C with standard wings keel, Solanaceae gamosepalous and gamopetalous K(5) C(5), Brassicaceae 4 sepals and 4 petals. Presence of conspicuous coloured tepals hence diagnostically identifies lily, tulip, Gloriosa and Allium as lilioid monocots.
Ref: NCERT Class 11 Biology Chapter 5: Liliaceae perianth tepals; Simpson, Plant Systematics, Lilioid monocots
Tepals are characteristic of flowers where
Perianth segments termed tepals when calyx corolla differentiation absent, showing similar pigmentation, size and texture throughout, often both petaloid or sepaloid without clear distinction. Condition common in monocots Liliaceae where outer whorl not green sepaloid but showy, termed petaloid tepals, or in basal angiosperms like tulip, Magnolia where gradual transition from bracts to perianth evident morphologically. Sepals and petals indistinct genetically due to overlapping B-class MADS-box gene expression domain expansion. Presence only petals still corolla, only sepals calyx, absence achlamydeous, whereas tepal concept indicates undifferentiated perianth evolutionarily intermediate.
Ref: NCERT Class 11 Biology, Chapter 5: Perianth differentiation tepals monocot characteristic