Assertion (A): The underground stem in potato (Solanum tuberosum) is modified to store food. Reason (R): Potato belongs to the family Solanaceae, which is characterized by the presence of underground stems in all its members.
The underground stem of potato is modified for food storage. However, underground stems are not a characteristic feature of all members of the family Solanaceae. Many members, such as tobacco and brinjal, possess aerial stems.
Question 262 of 300
📘 CLASS XI
Assertion (A): Stems can be easily distinguished from roots by the presence of multicellular hairs on their surface. Reason (R): Root hairs are unicellular epidermal elongations, whereas stem trichomes or hairs are typically multicellular.
Stems possess multicellular epidermal hairs (trichomes), whereas roots bear unicellular root hairs in the region of maturation. This difference serves as a useful morphological feature for distinguishing stems from roots. Therefore, Reason (R) correctly explains Assertion (A).
Question 263 of 300
📘 CLASS XI
Assertion (A): Leaves originate from shoot apical meristems and are arranged in a basipetal order on the stem. Reason (R): Leaves are the most important vegetative organs for photosynthesis.
Leaves originate from the shoot apical meristem but are arranged in an acropetal, not basipetal, order. Leaves are the primary vegetative organs responsible for photosynthesis.
Question 264 of 300
📘 CLASS XI
Assertion (A): In some leguminous plants, the leaf base becomes swollen, and this swollen leaf base is called a pulvinus. Reason (R): In monocotyledons, the leaf base expands into a sheath covering the stem partially or wholly.
Both Assertion and Reason are true. A pulvinus is the swollen leaf base found in many leguminous plants, while monocotyledons possess a sheathing leaf base. However, the sheathing leaf base of monocots does not explain the occurrence of a pulvinus in legumes.
Question 265 of 300
📘 CLASS XI
Assertion (A): Long, thin, flexible petioles allow leaf blades to flutter in the wind. Reason (R): Fluttering of the leaf blade cools the leaf and brings fresh air to the leaf surface.
Long, thin, and flexible petioles allow the leaf blade to flutter in the wind. This fluttering cools the leaf surface and improves air circulation around the lamina, thereby facilitating efficient gaseous exchange. Hence, Reason (R) correctly explains Assertion (A).
Question 266 of 300
📘 CLASS XI
Assertion (A): The prominent middle vein in the lamina of a typical leaf is known as the midrib. Reason (R): Veins provide rigidity to the leaf blade and act as channels of transport for water, minerals, and food materials.
Both Assertion and Reason are true. The prominent middle vein of the lamina is called the midrib. Veins provide rigidity to the leaf blade and serve as channels for the transport of water, minerals, and food. However, these general functions of veins do not explain why the prominent central vein is specifically termed the midrib.
Question 267 of 300
📘 CLASS XI
Assertion (A): Leaves of dicotyledonous plants generally possess parallel venation, while reticulate venation is characteristic of monocotyledons. Reason (R): Parallel venation is defined as the pattern where veins run parallel to each other within the leaf lamina.
The Assertion is false because dicotyledonous plants generally possess reticulate venation, whereas parallel venation is characteristic of most monocotyledons. The Reason is true because parallel venation is defined by veins running parallel to one another within the lamina.
Question 268 of 300
📘 CLASS XI
Assertion (A): In both simple and compound leaves, a bud is present in the axil of the petiole. Reason (R): A bud is always absent in the axil of the leaflets of a compound leaf.
Both statements are true. A bud is present in the axil of the petiole in both simple and compound leaves, whereas buds are absent in the axils of the individual leaflets of a compound leaf. The absence of buds in leaflets is a diagnostic feature but does not explain the presence of the bud in the axil of the petiole.
Question 269 of 300
📘 CLASS XI
Assertion (A): Neem possesses pinnately compound leaves where multiple leaflets are present on a common axis called the rachis. Reason (R): The rachis in a pinnately compound leaf represents the midrib of the leaf.
Neem has pinnately compound leaves in which leaflets are borne on a common axis called the rachis. The rachis represents the midrib of the leaf, which explains why numerous leaflets are attached along it.
Question 270 of 300
📘 CLASS XI
Assertion (A): In alternate phyllotaxy, a single leaf arises at each node in an alternate manner. Reason (R): Alternate phyllotaxy is seen in plants like Calotropis and guava.
Alternate phyllotaxy consists of a single leaf arising at each node in an alternate manner. However, Calotropis and guava exhibit opposite phyllotaxy. Alternate phyllotaxy is characteristic of China rose, mustard, and sunflower.
