Plants need light, water, carbon dioxide, oxygen and minerals to conduct photosynthesis. Aquatic plants have minerals and water all around them, but land plants have to obtain these substances from the ground. When plants evolved to live on land, several changes occurred that allowed them to survive. Most adaptations of land plants have to do with obtaining, retaining and using water and minerals.
A waxy cuticle covers the leaves and stem of land plants to minimize the rate of water evaporation, allowing the plants to retain more water. Unlike water plants, land plants are exposed to air, which could cause the plants to dry out except when relative humidity is 100 percent. A waxy cuticle keeps the water inside the plants so that they can survive prolonged exposure to air.
Waxy cuticle prevents air from diffusing into and out of land plants, so they have to adapt to allow cellular respiration and photosynthesis. Land plants have small openings on the underside of leaves. They open and close depending on the environmental and physiological conditions. Stomata open to let oxygen and carbon dioxide in and out of the plants and they close to minimize water loss.
Aquatic plants can absorb dissolved gases and minerals from the water they live in. On land, plants can only get water and minerals from the ground, so they need to remain close to the ground. However, plants also need to grow taller to get more sunlight and block sunlight from competing plants. To grow tall, plants need a system to transport water and nutrients from the soil up to the rest of the body. Plants developed vascular cells known as xylem and phloem to move water and nutrients.
Plants need rigidity and structure to allow them to support their own weight as they grow taller. They developed lignin to bind cellulose together to form the woody tissue that provides structural support for growth.
Land plants don't have plentiful water and minerals floating around them like aquatic plants do. They had to develop true roots to allow them to absorb water and minerals from the soil to survive. Roots also anchor the plants to the soil so they have consistent supply of water and minerals.
The reproductive cells of primitive water plants have to swim through water for fertilization to occur. To reproduce, land plants develop pollen that wind, insects and animals can disperse so the pollen can fertilize female plants of the same species. Plants then develop embryos in seeds that animals or wind disperse. Some plants have fruits that animals eat and defecate or seeds with hooks that can attach to animal fur and fall elsewhere. These seeds then grow as new plants.