Haustoria, also called sucking roots, are characteristic of which of the following parasitic plants that absorb nutrients from a host?

Introduction / Context:
Roots perform various specialised functions in different plants, and one important modification is the haustorium or sucking root found in parasitic species. Such roots penetrate host tissues and absorb water and nutrients directly from them. This question asks which plant among the options possesses haustoria as a characteristic feature. Recognising that Cuscuta, commonly known as dodder or amarbel, is a parasitic plant that uses haustoria, is a fundamental concept in plant morphology and ecology.

Given Data / Assumptions:
– The structure under discussion is haustoria or sucking roots.
– These structures are associated with parasitic plants that depend on host plants for nutrients.
– The options are wheat, mango, chestnut, and Cuscuta.
– We assume standard textbook descriptions of root modifications and parasitic plants.

Concept / Approach:
Haustoria are specialised organs of parasitic plants that attach to and penetrate host tissues, often into the vascular system, to extract water and dissolved nutrients. Cuscuta is a well known total stem parasite that lacks chlorophyll and cannot perform sufficient photosynthesis on its own. It produces thin, thread like yellow or orange stems that coil around host plants. At points of contact, Cuscuta forms haustoria that enter the host stem and connect to its conducting tissues. Wheat, mango, and chestnut are free living, non parasitic plants that have normal root systems for absorbing water and minerals from soil, not haustoria that invade other plants. Therefore, haustoria or sucking roots in the sense described are characteristic of Cuscuta.

Step-by-Step Solution:
Step 1: Recall that haustoria are specialised absorbing organs produced by parasitic plants to tap into host plants. Step 2: Identify Cuscuta as a classic example of a parasitic plant that wraps around host stems and is commonly shown in textbooks. Step 3: Remember that wheat is a cereal crop with a normal fibrous root system and is not parasitic. Step 4: Recognise that mango and chestnut are trees with their own root systems and do not produce haustoria to invade other plants. Step 5: Conclude that haustoria or sucking roots are found in Cuscuta.

Verification / Alternative check:
Botany textbooks on plant morphology often include diagrams of Cuscuta twining around a host plant and forming haustoria. The accompanying text explains how these structures penetrate the host's vascular bundles, allowing Cuscuta to draw nutrients and water directly from the host. Lists of root modifications mention haustorial roots specifically under parasitic plants like Cuscuta and Viscum. In contrast, the sections on wheat, mango, and chestnut discuss tap root or fibrous root systems without any reference to haustoria. This confirms that Cuscuta is the plant associated with haustoria in school level botany.

Why Other Options Are Wrong:
Wheat: Wheat is a non parasitic cereal plant with a fibrous root system and does not form haustoria on other plants.
Mango: Mango trees have deep tap root systems to absorb water and nutrients from the soil; they do not act as parasites using haustorial roots.
Chestnut: Chestnut trees also develop normal roots in soil and are not parasitic; they lack haustoria that invade host plants.

Common Pitfalls:
Students may confuse haustoria with other root modifications such as prop roots or pneumatophores if they do not carefully read the term sucking roots and the mention of parasitism. Another mistake is to select a familiar crop like wheat just because it is well known, without checking whether it is parasitic. To avoid such errors, remember that haustoria are always associated with parasitic relationships, and Cuscuta is one of the most famous total parasites described in school books. Linking haustoria directly with Cuscuta in memory makes this type of question easy to answer.

Final Answer:
Haustoria or sucking roots are characteristic of the parasitic plant Cuscuta, which absorbs nutrients from its host using these structures.