Q.18 Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R):
Assertion (A): Gnetum is closer to angiosperms than gymnosperms.
Reason (R): There is complete elimination of archegonia in the female gametophyte of Gnetum.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Both (A) and (R) are true and (R) is the correct explanation of (A)
(2) Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
(3) (A) is true but (R) is false
(4) (A) is false but (R) is true
Both Assertion (A) and Reason (R) are true, but (R) is not the complete or primary explanation of (A). Gnetum exhibits angiosperm-like features (e.g., vessels, reticulate venation, tetrasporic embryo sac), making it morphologically closer to angiosperms than typical gymnosperms like Cycas/Pinus, though molecular data disputes strict phylogeny. Archegonia are indeed completely absent in Gnetum’s female gametophyte, like angiosperms, but vessel elements and other traits better explain the affinity. The correct answer is option (2).
Option Explanation
-
(1) Both true, (R) correct explanation: Incorrect; while both hold, (R) is one factor among many (vessels primary), not the sole explainer.
-
(2) Both true, (R) NOT correct explanation: Correct; affinities stem from multiple advanced traits; archegonial loss supports but doesn’t fully justify (A).
-
(3) (A) true, (R) false: Incorrect; (R) verified true—archegonia absent in Gnetum.
-
(4) (A) false, (R) true: Incorrect; (A) true morphologically (botany exams emphasize this) despite molecular views placing Gnetum sister to conifers.
Gnetum closer to angiosperms archegonia elimination captures a key botanical debate, where Gnetum’s lack of archegonia in female gametophyte mirrors angiosperms, unlike archegonia-bearing Cycas/Pinus. Yet, broader affinities include xylem vessels, dicot-like embryos, and enclosed ovules.
Morphological Affinities
-
No archegonia: Free nuclei function as eggs post-fertilization.
-
Vessels in xylem: Advanced conduction, absent in other gymnosperms.
-
Tetrasporic embryo sac, reticulate venation, two cotyledons.
Molecularly, Gnetum clusters with conifers, but exam contexts stress morphology.
Assertion-Reason Insights
| Statement |
Status |
Explanation |
| (A) Closer to angiosperms |
True (morphological) |
Multiple shared traits |
| (R) Archegonia elimination |
True |
But not sole reason (vessels key) |
Vital for competitive exams; Gnetum bridges gymnosperm-angiosperm evolution.
