Assertion (A): In silk cotton, the leaflets are attached to a common axis called the rachis. Reason (R): Silk cotton possesses palmately compound leaves where leaflets are attached at a common point at the tip of the petiole.
The Assertion is false because in palmately compound leaves (like silk cotton), leaflets are attached at a common point at the tip of the petiole, and there is no rachis. The Reason is true as it correctly defines the attachment in silk cotton.
Question 122 of 300
📘 CLASS XI
Statement I: Leaves originate from the shoot apical meristem and are arranged in a basipetal order. Statement II: Leaves are the most important vegetative organs for photosynthesis. Select the correct option:
Statement I is incorrect because leaves are arranged in an acropetal order (youngest at the top, oldest at the base), not basipetal. Statement II is correct because leaves are indeed the primary photosynthetic organs in vascular plants.
Question 123 of 300
📘 CLASS XI
Assertion (A): Reticulate venation is an absolute and universal diagnostic key to identify dicotyledonous plants without exception in all plant groups. Reason (R): Parallel venation occurs in most monocotyledons, which show no overlap in anatomical characteristics with dicotyledons.
Both statements are false. The textbook states that dicotyledonous leaves "generally" possess reticulate venation, and parallel venation is characteristic of "most" monocotyledons. In biology, "generally" and "most" indicate that these are strong general rules, not absolute or universal diagnostic features without exceptions.
Question 124 of 300
📘 CLASS XI
Statement I: Stipules are small leaf-like structures that are borne laterally at the leaf base. Statement II: All flowering plants must possess stipules to protect the axillary buds in their early development. Select the correct option:
Statement I is correct; a leaf may bear two lateral small leaf-like structures called stipules at its base. Statement II is incorrect because stipules are not present in all plants; many leaves are exstipulate (such as Solanaceae family leaves).
Question 125 of 300
📘 CLASS XI
Assertion (A): Pinnately compound leaves and palmately compound leaves share the same basic structure of a midrib-like rachis. Reason (R): In both cases, leaflets are distributed along the entire length of the petiole axis.
Both statements are false. Only pinnately compound leaves possess a rachis (which represents the midrib) along which leaflets are distributed. Palmately compound leaves lack a rachis; their leaflets are attached at a single common point at the tip of the petiole.
Question 126 of 300
📘 CLASS XI
Statement I: The leaf base of monocotyledons expands into a sheath covering the stem. Statement II: In leguminous plants, the leaf base is always dry and contracted. Select the correct option:
Statement I is correct. Statement II is incorrect because in some leguminous plants, the leaf base becomes swollen (pulvinus), not dry and contracted.
Question 127 of 300
📘 CLASS XI
Assertion (A): Phyllotaxy is an adaptation to optimize light interception and minimize self-shading among leaves on a shoot. Reason (R): It is defined as the specific pattern of arrangement of leaves on the stem or branch.
Both statements are true. Phyllotaxy is the pattern of arrangement of leaves on a stem or branch. It is indeed an evolutionary adaptation that spaces out leaves to maximize light interception for photosynthesis and reduce self-shading, but the definition (R) is simply a description of what phyllotaxy is, not a causal explanation of why plants optimize leaf spacing (A).
Question 128 of 300
📘 CLASS XI
Statement I: In alternate phyllotaxy, a pair of leaves arises at each node in an alternating fashion. Statement II: In opposite phyllotaxy, a single leaf arises at each node opposite to the next leaf. Select the correct option:
Both statements are incorrect. In alternate phyllotaxy, a single leaf arises at each node in an alternate manner. In opposite phyllotaxy, a pair of leaves arises at each node and lies opposite to each other.
Question 129 of 300
📘 CLASS XI
Assertion (A): A flower is morphologically considered a modified shoot. Reason (R): In a flower, the shoot apical meristem transforms into a floral meristem, where internodes do not elongate and the axis gets condensed.
A flower is indeed a modified shoot because its developmental pathway involves the transition of the shoot apical meristem into a floral meristem, where internodal elongation is suppressed, resulting in a condensed axis bearing modified floral leaves (sepals, petals, etc.) at successive nodes.
Question 130 of 300
📘 CLASS XI
Statement I: The arrangement of flowers on the floral axis is termed as phyllotaxy. Statement II: Inflorescences are classified into major types based on whether the main floral axis terminates in a flower or continues to grow. Select the correct option:
Statement I is incorrect because the arrangement of flowers on the floral axis is termed inflorescence (phyllotaxy is the arrangement of leaves on a stem). Statement II is correct; the classification into racemose and cymose is based on whether the apex of the floral axis continues growing or terminates in a flower.
