NEET Biology Morphology of Flowering Plants MCQs Set 18

Answer: (a) Fusiform root

Explanation:
1. Fusiform roots are swollen in the middle and taper at both ends.
2. Radish is the standard fusiform example, whereas turnip and beet are napiform and carrot is conical.

Teacher's Note:
1. Fusiform means spindle shaped. Remember radish = fusiform, turnip = napiform, carrot = conical.

Answer: (c) Nodulated roots

Explanation:
1. Root nodules of legumes house Rhizobium, which fixes atmospheric nitrogen.
2. Fusiform, napiform and conical roots are only food storage modifications.

Teacher's Note:
1. Nodulated roots are typical of the family Fabaceae. The bacteria and plant live in mutualism.

Answer: (b) Modified tap root

Explanation:
1. Turnip is a napiform root, a swollen modification of the tap root.
2. It is not a stem, so options 3 and 4 are wrong, and it is not adventitious because it arises from the radicle.

Teacher's Note:
1. Tap root modifications (fusiform, napiform, conical) store food. Adventitious modifications include sweet potato and tuberous roots.

Answer: (d) Stilt root

Explanation:
1. Stilt roots arise from the lower nodes of the stem and give mechanical support, as in maize and sugarcane.
2. Napiform, fusiform and tuberous roots all store food.

Teacher's Note:
1. Supporting roots: stilt and prop roots. Respiratory roots: pneumatophores.

Answer: (b) Eichhornia

Explanation:
1. An offset is a short, thick lateral branch of an aquatic plant that gives a new plant, as in Eichhornia (water hyacinth) and Pistia.
2. Cynodon and Fragaria spread by runners and Mentha by suckers.

Teacher's Note:
1. Offsets are formed by mitotic division and are found in aquatic plants. Runners are found in grass and strawberry.

Answer: (b) It bears nodes and internodes

Explanation:
1. Nodes and internodes, with scale leaves and buds, are the defining features of a stem.
2. Roots can also bear adventitious roots, be underground and store food, so those features are not specific to stems.

Teacher's Note:
1. Always use nodes and internodes to prove that an organ is a stem. Ginger and turmeric are rhizomes.

Answer: (b) Grass

Explanation:
1. Grass is a monocot and its leaves show parallel venation.
2. Castor, gram and mustard are dicots with reticulate venation.

Teacher's Note:
1. Monocots usually have parallel venation and dicots reticulate venation. Calophyllum is a famous dicot exception.

Answer: (c) Phylloclade

Explanation:
1. In Opuntia the stem is flattened, green and fleshy (phylloclade), and the leaves become spines.
2. A phyllode is a modified petiole and a tuber is a swollen underground stem.

Teacher's Note:
1. Phylloclade is a stem modification for xerophytes. Cladode is a similar one-internode green branch, as in Ruscus.

Answer: (b) Calophyllum

Explanation:
1. Calophyllum is a dicot whose leaves have closely parallel lateral veins.
2. Smilax is a monocot with reticulate venation, so it is the opposite exception, while cotton and mango show normal reticulate venation.

Teacher's Note:
1. Learn both exceptions: Calophyllum (dicot with parallel venation) and Smilax (monocot with reticulate venation).

Answer: (d) Labiatae

Explanation:
1. A verticillaster is a cymose cluster arising in the axils of opposite leaves, giving a false whorl, as in Ocimum and Salvia of Labiatae.
2. The other families have racemose or other cymose types.

Teacher's Note:
1. Labiatae (Lamiaceae) means opposite leaves and verticillaster. Remember Ocimum (tulsi) as the example.

Answer: (b) One : Many

Explanation:
1. A cyathium has a single central naked female flower surrounded by many male flowers.
2. It is the characteristic inflorescence of Euphorbia.

Teacher's Note:
1. Cyathium is a type of cymose inflorescence. Look for one pistillate flower with many staminate flowers around it.

Answer: (b) Capitulum

Explanation:
1. In a capitulum, many sessile florets (ray and disc) are packed on a flat receptacle and appear as one flower, which is an advanced condition.
2. Corymb, spadix and catkin are simpler arrangements.

Teacher's Note:
1. Sunflower and marigold bear capitula. Capitulum is characteristic of Asteraceae.

Answer: (a) Umbel

Explanation:
1. In an umbel the flowers have pedicels of nearly equal length arising from a common point, as in coriander and onion.
2. A capitulum has sessile flowers and a verticillaster is a whorl-like cyme.

Teacher's Note:
1. Umbel = pedicellate flowers from one point. Capitulum = sessile flowers on a flat head.

Answer: (c) Providing support to the big tree

Explanation:
1. Prop roots hang from the branches, reach the ground and thicken into pillars that support the heavy branches.
2. They do not store food and do not carry out respiration.

Teacher's Note:
1. Prop roots arise from branches while stilt roots arise from the basal nodes of the stem. Both give mechanical support.

Answer: (c) Pitcher of Nepenthes

Explanation:
1. The pitcher of Nepenthes is a modified leaf.
2. Rhizome, corm and tuber are underground stem modifications that bear nodes and buds.

Teacher's Note:
1. Leaf modifications include spines, tendrils, pitcher and scales. Stem modifications include tubers, rhizomes, corms, bulbs and phylloclades.

Answer: (a) Phyllode

Explanation:
1. A phyllode is a flattened, leaf-like petiole, as seen in Australian Acacia.
2. Phylloclade and cladode are stems and a corm is an underground stem.

Teacher's Note:
1. In Australian Acacia the true leaves fall early and the phyllode performs photosynthesis. This reduces water loss.

Answer: (c) Euphorbia

Explanation:
1. Euphorbia (and Poinsettia) bear cyathia with a cup-like involucre.
2. Ficus has a hypanthodium, while Croton and Ricinus have racemes.

Teacher's Note:
1. Hypanthodium = Ficus; cyathium = Euphorbia. They are both specialised cymose types.

Answer: (a) Axillary bud

Explanation:
1. Eyes of potato are depressions on the tuber and are the axillary buds in the axils of scale leaves.
2. They grow into new shoots, which makes the tuber a stem.

Teacher's Note:
1. Presence of eyes proves that potato is a stem tuber. Each eye can sprout into a new plant.

Answer: (b) Cladode

Explanation:
1. In Ruscus the axillary branch is flattened, green and carries out photosynthesis; this is called a cladode (one internode long).
2. Phyllode is a petiole modification and offset and sucker are vegetative propagation organs.

Teacher's Note:
1. Cladode is short (1-2 internodes). Phylloclade, as in Opuntia, is many internodes long.

Answer: (c) Rhizome

Explanation:
1. Turmeric and ginger have thick, branched horizontal underground stems called rhizomes, with scale leaves and nodes.
2. Potato is a tuber, onion a bulb and Colocasia a corm.

Teacher's Note:
1. Rhizome grows horizontally and stores food. It also helps in vegetative propagation.