1. Plant Nutrition
Chapter 37

2. Nutritional Needs Autotrophic does not mean autonomous Plants need…
sun as an energy source
inorganic compounds as raw materials
Water
CO2
minerals

3. Macronutrients
Plants require in relatively large amounts

4. Micronutrients Plants require in very small amounts
Primarily cofactors

5. Uptake of Nutrients Organism level Cellular level
What are some nutrients plants need?
Cellular level
How do they enter the plant?
What are the mechanisms that bring them into the plant?

6. 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

7. Magnesium Deficiency Symptoms Chlorosis = yellowing of leaves
What is magnesium’s function?

8. Chlorophyll
Why does magnesium
deficiency cause chlorosis?

9. Water & Mineral Uptake Water uptake Cation uptake
Plants cannot extract all water from soil, only free water
osmosis
Cation uptake is aided by H+ secretion by root cells (proton pump)
Active transport

10. The Role of Soils Plants are dependent on soil quality
Texture/structure
Relative amounts of various sizes of soil particles
Composition
Organic and inorganic components
Fertility

11. Importance of Organic Matter
Topsoil
Most important to plant growth
Rich in organic matter
Humus
Decomposing organic material formed by action of bacteria and fungi on dead organisms, feces, fallen leaves and other organic refuse
Improves soil texture
Reservoir of minerals
Organisms
Teaspoon of topsoil has ~5 billion bacteria that cohabit with various fungi, algae, and other protists, insects, earthworms, nematodes

12. Soil Health as a Global Issue
Not taking care of soil health has far-reaching, damaging consequences
1930’s Dust Bowl
Lack of soil conservation
Growing wheat
Raising cattle
Land exposed to wind erosion
Drought

13. Soil Health as a Global Issue
Soil conservation and sustainable agriculture
Maintaining healthy environment
Production of food supply
Economically viable farming industry
“A sustainable agriculture does not deplete soils or people.” Wendell Berry
Contour plowing cover crops crop rotation

14. Global Issues
Fertility
Erosion
Irrigation
Forestry destruction

15. Fertilizers “Organic” fertilizers “Chemical” fertilizers
Manure, compost, fishmeal
“Chemical” fertilizers
Commercially manufactured
N-P-K (ex )
15% nitrogen (nitrate)
10% phosphorous (phosphoric acid)
5% potassium (potash)

16. Nitrogen Uptake Nitrates Nitrogen cycle by bacteria
Plants can only take up nitrate (NO3-)
Nitrogen cycle by bacteria
Trace path!

17. Soybean Root Nodule N fixation by Rhizobium bacteria
Symbiotic relationship with legumes

18. Mycorrhizae & Plant Nutrition
Symbiotic relationship
Mycorrihizal fungus gets sugars from plant
Mycorrhizal fungus provides better absorption of water and minerals for plant

19. Parasitic Plants Tap into host vascular system
Ex: mistletoe, Indian pipe

20. Carnivorous Plants Are they really carnivores?
Ex: sundew, Venus fly trap, pitcher plant