Question

Flowers are monochlamydeous in
A. Malvaceae
B. Fabaceae
C. Liliaceae
D. Polygonaceae

Answer 1

The term 'mono' means 'one' and 'chlamydeous' means 'floral structure'. Therefore, as the name describes a monochlamydeous flower has only one of the members of perianth or floral structure, that is, either calyx or corolla.

Complete answer:
Amongst the options given above, Polygonaceae is the monochlamydeous flower. It has 3 - 6 sepals of calyx but has no petals of corolla, thus, having only one member of perianth. It is a bisexual flower therefore, absence of petals (the attractive part of flowers which is very important for pollination) does not affect pollination.
Therefore, option d, is the correct answer.

Additional information
Following are a few characteristics of a monochlamydeous flowering plants:
Vegetative Characters:
Root: This family has a tap root system.
Stem: Stem is generally herbaceous having swollen nodes, surrounded by a stipular sheath.
Leaves: They have simple leaves having alternate phyllotaxy.
Floral Characters:
Inflorescence: The inflorescence is generally variable ranging from racemose to cymose. It is often present as umbellate clusters.
Flower: They have small, bisexual flowers that are usually trimerous rarely dimerous, having radial symmetry (actinomorphic).
Androecium: Stamens are usually 6 to 9, arranged in two whorls having the six outer ones often introrse and the three inner extrorse.
Gynoecium: The gynoecium is generally tricarpellary, syncarpous, ovary superior, and unilocular with basal placentation. The ovary has a characteristic nectariferous disc having as many as 8 lobes.
Fruit: The fruit is a dry nut having a single seed that may be three-sided or biconvex having lateral wings, or an achene with wings which may be furnished in bristles or hooks.
Seed: Seeds are copious.

Note:
Calyx is nothing but the green leafy envelope (sepals) at the top of the stalk that holds petals of flowers whereas corolla is another term used to collectively refer to petals. In perianth, sometimes the inner sepals are enlarged resulting in membranous wings known as Rumex or rarely the outer ones can enlarge known as Triplaris. These might get modified as hooks, spines, or bristles and aids in the distribution of the fruit.