1. Chapter 37.
Plant Nutrition

2. Nutritional needs Autotrophic does not mean autonomous plants need…
sun as an energy source
inorganic compounds as raw materials
water (H2O)
CO2
minerals

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

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

5. Micronutrients Plants require in very small amounts
primarily cofactors

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. Take 2 fertilizer pellets & call me in the morning
Magnesium deficiency
Symptoms
chlorosis = yellowing of leaves
what is magnesium’s function?

8. Chlorophyll Why does magnesium deficiency cause chlorosis?
The chlorosis shows up in older leaves first, because plant moves Mg to newer leaves. Why?

9. Water & mineral uptake Water uptake Cation uptake
plants cannot extract all water from soil, only free water
osmosis
Cation uptake
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 & inorganic chemical components
fertility

11. Importance of organic matter
So don’t rake your lawn or bag your leaves
Importance of 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

12. Soil health as a global issue
Not taking care of soil health has far-reaching, damaging consequences
1920’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 & 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

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

17. What will the plant use N for?
Nitrogen uptake
Nitrates
plants can only take up nitrate (NO3-)
Nitrogen cycle by bacteria
trace path of nitrogen fixation!
root
What will the plant use N for?

18. Soybean root nodules N fixation by Rhizobium bacteria
symbiotic relationship with bean family (legumes)

19. Increasing soil fertility
Plow it under?
Why would you that?
Increasing soil fertility
Cover crops
growing a field of plants just to plow them under
usually a legume crop
taking care of soil’s health
puts nitrogen back in soil
erosion control, too

20. Some plant oddities…

21. Parasitic plants tap into host plant vascular system Indian pipe
Mistletoe

22. Plants of peat bogs High acid environment
most minerals & nutrients bound up & are not available to plants
must find alternative sources of nutrients

23. Carnivorous plants Are they really carnivores? Sundew Venus fly trap
Pitcher plant
Are they really carnivores?

24. Pitcher plant