Plant Nutrition Chapter 37

Uptake of nutrients happens in roots and leaves. Roots, through mycorrhizae and root hairs, absorb water and minerals from soil. Essential nutrient required for plant to grow from seed and complete life cycle. Macronutrients needed in large numbers; micronutrients are not.

Texture, pH, composition of soil determines types of plants that grow in area. Soil may be acidic or basic because of minerals that absorb in soil.

Soil made of topsoil - mixture of rock, living organisms, and humus (residue of partially decayed organic material) Can be washed away by water, robbing soil of important nutrients.

Plants cannot use nitrogen in form of N 2. Bacteria, nitrogen-fixing bacteria, convert N 2 to NH 3 (ammonia), via nitrogen fixation.

Roots also form symbioses with organisms; relationships that are helpful to both species. Legume’s roots have swellings called nodules - plant cells that contain nitrogen-fixing bacteria.

Crop rotation increases amount of nitrogen in soil. Farmers do this so nitrogen-rich plants (legumes) can add nitrogen to different soil areas.

Mycorrhizae - modified roots, made of symbiotic relationships between fungi and roots. Fungus increases surface area for water uptake, secretes growth factors that stimulate roots to grow and branch, and produces antibiotics. Mycorrhizae - hyphae - help increase surface area; also invade cells by digesting cell wall.

Some plants - parasites - will not photosynthesize. Tap into other plants that do. Epiphytes (orchids) - not parasitic; grow on other plants. Some plants evolved modified leaves that trap insects.