Q57. Match the modified organs in GROUP I with their corresponding prototypic forms in GROUP II and choose the correct option.
| GROUP I | GROUP II |
|---|---|
| P. Tendrils in grape vine | 1. Modified stem |
| Q. Tendrils in garden pea | 2. Modified leaf |
| R. Spines | 3. Modified leaf Spines |
| CORRECT option | ||||
|---|---|---|---|---|
| (A) | (B) | (C) | (D) | |
| P Q R S | S1 Q2 R1 | P1 Q2 R1 S2 | P1 Q2 R1 S2 | P1 Q1 R2 S1 |
Tendrils in garden pea are modified leaves, while spines are modified leaves as well. Matching GROUP I (P: Tendrils in garden pea, Q: Tendrils in garden vine, R: Spines) with GROUP II yields the correct option (C) P-1, Q-2, R-1, where 1 is modified leaf and 2 is modified stem.
Option Analysis
Each option pairs the structures incorrectly except one, based on botanical modifications for climbing or defense.
-
(A) P-1, Q-2, R-1: Correctly matches P (garden pea tendrils as modified leaf) and R (spines as modified leaf), but Q (garden vine tendrils, like grapevine) as modified stem is accurate in some cases; however, context favors leaf for pea-specific focus.
-
(B) P-1, Q-1, R-2: Wrongly assigns R (spines) to modified stem, as spines typically derive from leaves (e.g., Opuntia).
-
(C) P-1, Q-2, R-1: Correct; P is leaf (pea upper leaflets), Q is stem (common in grapevine/cucurbits), R is leaf.
-
(D) P-1, Q-1, R-2: Incorrect, same spine error as (B).
In plant morphology, tendrils in garden pea represent classic modified leaf structures, aiding climbing via coiling around supports, while spines serve as defensive modified leaves to deter herbivores and reduce transpiration. These adaptations highlight evolutionary responses in angiosperms, key for CSIR NET life sciences preparation.
Tendrils: Leaf vs Stem Modifications
Tendrils enable weak-stemmed climbers to grasp supports through thigmotropism.
-
Garden pea (Pisum sativum): Terminal leaflets of compound leaves modify into tendrils; stipules photosynthesize.
-
Garden vine (e.g., grape, cucumber): Often stem-derived from axillary/terminal buds.
This distinction tests homology in exams.
Spines as Protective Leaf Structures
Spines minimize water loss in xerophytes and protect against grazing.
-
Examples: Entire leaves in Opuntia/cacti, leaf tips in Agave/Aloe, stipules in Acacia.
-
Not stems (thorns), which are woody and branched.
CSIR NET Exam Insights
Such matching questions assess modification origins from NCERT morphology chapters. Correct pairing reinforces: leaves for photosynthesis/climbing/defense roles when altered. Practice identifies pea tendrils as leaflets uniquely.
