**Assertion (A):** The Casparian strip ensures that all water and ions entering the xylem must pass through the endodermal cytoplasm. **Reason (R):** The Casparian strip is a band of cellulose in the anticlinal walls of endodermal cells that blocks lateral diffusion.

**Assertion (A):** Guttation occurs more commonly at night when transpiration is low. **Reason (R):** At night, root pressure continues to build up in xylem because stomata are closed and transpiration pull is absent, forcing water out through hydathodes.

**Assertion (A):** Nitrogen deficiency symptoms first appear in older leaves. **Reason (R):** Nitrogen is a mobile element that is translocated from older leaves to young growing tissues when supply is limited.

**Assertion (A):** The apoplast pathway is faster than the symplast pathway. **Reason (R):** In the apoplast pathway, water does not need to cross any plasma membranes, allowing unimpeded flow through cell walls.

**Assertion (A):** Adding solutes to pure water always decreases its water potential. **Reason (R):** Solute potential (Ψs) is always negative, and it lowers the overall water potential.