Assertion & Reason Test: Plant Kingdom - NEET MCQ

Cycads are known for their specialized coralloid roots, which harbor symbiotic cyanobacteria capable of nitrogen fixation. This symbiotic relationship allows cycads to thrive in nitrogen-poor soils, as the cyanobacteria convert atmospheric nitrogen into a form that the plants can use. This mutualistic interaction is crucial for the nutrient uptake of cycads, making the reason a correct explanation for the assertion.

The defining characteristic of gymnosperms is that their seeds are not enclosed by an ovary, which is why they are referred to as having "naked seeds." This contrasts with angiosperms, where the seeds are enclosed within a fruit. The lack of an ovary in gymnosperms means that the ovules and subsequently the seeds are exposed, directly on the surface of reproductive structures like cones. This trait is a key evolutionary adaptation of gymnosperms, making the reason a correct explanation for the assertion.

Mosses, being non-vascular plants, do not have a true vascular system like xylem and phloem found in higher plants for transporting water and nutrients. Instead, they absorb water and nutrients directly through their leaves, which is a characteristic adaptation to their environment. This direct absorption is facilitated by the mosses' small size and the moist habitats in which they typically live.

It's true that algae contribute significantly to global photosynthesis, thanks in part to their abundance in aquatic environments, where they play a key role in carbon fixation. While algae do possess a diverse array of photosynthetic pigments allowing them to efficiently capture light energy, the primary reason for their substantial contribution to Earth's photosynthesis is their vast numbers and widespread distribution, especially in the oceans. Therefore, while both statements are true, the reason given is not the direct explanation for the assertion.