Plant Nutrition

Nutritional needs Autotrophic plants need… sun as an energy source inorganic compounds as raw materials water (H2O) CO2 minerals

Macronutrients Plants require these nutrients in relatively large amounts C, O, H, N, P, K, Ca, Mg, S

For what & from where? C macromolecule synthesis CO2 O H macromolecule synthesis & proton pumps H2O N protein & nucleic acid synthesis soil P nucleic acids, ATP, phospholipids K stomate control, water balance Ca cell wall & membrane structure, regulation Mg chlorophyll S proteins, enzymes

Micronutrients Plants require in very small amounts Cl, Fe, Mn, Bo, Zi, Ni, Mb primarily cofactors for enzyme function

Nutrient deficiencies Lack of essential nutrients exhibit specific symptoms dependent on function of nutrient dependent on solubility of nutrient Mineral deficiency symptoms depend not only on the role of the nutrient but also on its mobility within the plant. If a nutrient moves about freely, symptoms will show up first in older organs because young, growing tissues have more “drawing power” for nutrients in short supply. For example, magnesium is relatively mobile and is shunted preferentially to young leaves. Therefore, a plant starved for magnesium will show signs of chlorosis first in its older leaves. The mechanism for preferential routing is the source–to–sink translocation in phloem as minerals move along with the sugars to the growing tissues. In contrast, a deficiency of a mineral that is relatively immobile will affect young parts of the plant first. Older tissues may have adequate amounts, which they are able to retain during periods of short supply. For example, iron does not move freely within a plant, and an iron deficiency will cause yellowing of young leaves before any effect on older leaves is visible. Deficiencies of nitrogen, phosphorus, and potassium are most common. Shortages of micronutrients are less common and tend to occur in certain geographic regions because of differences in soil composition. The symptoms of a mineral deficiency are often distinctive enough for a plant physiologist or farmer to diagnose its cause

Magnesium deficiency Symptoms chlorosis = yellowing of leaves Why? What is magnesium’s function?

The role of soils Plants are dependent on soil quality texture / structure relative amounts of various sizes of soil particles composition organic & inorganic chemical components fertility

organic matter Topsoil most important to plant growth rich in organic matter humus decomposing organic material breakdown of dead organisms, feces, fallen leaves & other organic refuse by bacteria & fungi improves soil texture reservoir of minerals organisms 1 tsp. of topsoil has ~5 billion bacteria living with fungi, algae, protists, insects, earthworms, nematodes

Fertilizers “Organic” fertilizers “Chemical” fertilizers manure, compost, fishmeal “Chemical” fertilizers commercially manufactured N-P-K (ex. 15-10-5) 15% nitrogen 10% phosphorus 5% potassium