Ch. 37 Soil & Plant Nutrition

Transcription

1 Ch. 37 Soil & Plant Nutrition Feb 10 4:02 PM 1

2 Essential Question: How do nutrients affect plant growth? Feb 10 4:03 PM 2

3 Needed for plants to grow: a. Mineral nutrients: inorganic ions found in soil that plants use for growth ex. nitrogen in form of nitrate b. water 80 90% of plant gives hydrogen and some oxygen to plant most is lost in transpiration functions: 1. solvent 2. volume for cell elongation 3. keeps cell turgid c. carbon dioxide from air organic substance that makes up most of dry matter is carbohydrates most abundant elements are C, H, O Feb 10 4:05 PM 3

4 Essential elements (nutrient) chemical that is required by plant to complete life cycle and reproduce researchers use Hydroponics to study the effect of chemicals on plants Feb 10 4:16 PM 4

5 macronutrients elements that plants require in large amounts ex. carbon, oxygen, hydrogen, nitrogen, potassium, Calcium, magnesium,phosphorus, sulfur makes up major organic compounds Ex. magnesium is component in chlorophyll, activates enzymes deficiencies usually occur with phosphorus, potassium, nitrogen Micronutrients elements that plants require in small amounts ex. chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum make cofactors non protein helpers in enzyme reactions Ex. iron for cytochromes in ETC molybdenum for nitrate reduction to make nitrate ions Feb 10 4:18 PM 5

6 Feb 12 9:26 AM 6

7 dependent on function: 1. deficiency in magnesium causes chlorosis (yellowing of leaves) 2. deficiency in iron also causes chlorosis involved in chlorophyll synthesis Magnesium deficiency in tomato plant Feb 10 4:26 PM 7

8 dependent on mobility in plant if nutrient moves easily, deficiency shows up in older tissue first young tissue gets first dibs on nutrients Ex. magnesium shows chlorosis in older leaves first if nutrient is immobile, shows up in younger tissue first Ex. iron (slow) yellowing young leaves Feb 12 9:27 AM 8

9 most common deficiencies: nitrogen phosphorus potassium to diagnose deficiencies analyze plant and soil Can use hydroponics to get optimal nutrition and regulation disadvantage expensive nitrogen is the most limiting to plant growth. Feb 10 4:33 PM 9

10 Nitrogen Fixation atmosphere = 78% nitrogen but not in useable plant form useable form is nitrate, so atmospheric nitrogen has to be converted to ammonium and then to nitrate (comes from decay of humus by bacteria) Feb 11 12:07 PM 10

11 bacteria for nitrogen fixation are either found in soil or plant root nodules (symbiosis) nitrifying bacteria produce nitrate by oxidizing ammonium root nodules Feb 11 12:12 PM 11

12 Role of bacteria in symbiotic nitrogen fixation happens in legume family (peas, beans, alfalfa, peanuts, clover) root nodules contain nitrogen fixing Rhizobium bacteria Rhizobium form bacteroids Feb 11 10:21 PM 12

13 Rhizobium uses atmospheric nitrogen and change it to ammonium used by plant symbiosis provides right amount of fertilizer without farmer having to fertilize saves $ each legume is associated with a specific Rhizobium strain mutualistic relationship: plant gets nitrogen from bacteria bacteria get carbohydrates and organic compounds from plant Feb 11 10:26 PM 13

14 1. plant secretes flavenoids that certain strains of Rhizobium detect and absorb 2. activates a gene regulating protein in bacterium and which on genes (nod) to make nodule 3. Nod factors from bacteria signal root to let Rhizobium enter and form the nodule Feb 12 9:53 AM 14

15 "Super" varieties of plants have more protein than normal disadvantage high demand for nitrogen so need high fertilizer use consumes lots of energy (fossil fuels) poor countries need high protein crops, but not able to afford them Feb 11 12:17 PM 15

16 crop rotation Feb 12 9:53 AM 16

17 Mycorrhizae associations between fungi and roots (mutualistic) fungus gets supply of sugar plant gets increased surface area for water and mineral uptake, growth factors from fungus which help lengthen the roots and antibiotics to prevent pathogens scientists believe this relationship helped plants evolve to become land plants Feb 11 10:35 PM 17

18 two types of mycorrhizae: 1. ectomycorrhizae mycelium forms mass over surface of root and grow into root apoplast (extracellular space) usually don't form root hairs ex. pines, spruce, oak, walnut, willow, beech 2. endomycorrihizae no dense mass, hyphae extend inwards form arbuscles (branched invaginations of hyphae) found in 90% of plants ex. corn, wheat, legumes arbuslces fungal sheath ectomycorrihizae endomycorrihizae 2. endomycorrhizae fine hyphae from soil into root cells and grow tube that invaginates a root cell arbuscles branched structures for nutrient transfer found in 85% of plant species Feb 11 10:45 PM 18

19 Other relationships in plants epiphytes plants that live on other plants, but get their own nutrients usually through their leaves, not roots ex. orchids, staghorn ferns staghorn fern in Florida Feb 11 10:52 PM 19

20 Parasitic plants live on a host and absorb sugars and minerals ex. mistletoe, dodder, Indian pipe Indian Pipe Feb 12 9:56 AM 20

21 Carnivorous plants photosynthetic plants, but get some nitrogen and minerals by killing insects and digesting them. Usually live in acid bogs ex. Venus Fly trap, Pitcher plant, sundews Feb 12 9:56 AM 21

22 Soil's texture and composition will change depending on where they are found, so nutrients will change too. texture = particle size (sand, silt, clay) composition = organic and inorganic chemical components soil is formed by rock weathering (freezing, acids, mechanical fracturing topsoil mixture of particles from rock, living organisms, and humus (remains of partially decayed organic matter) humus prevents clay from packing together, builds crumbly soil for aeration has minerals when microorganisms breakdown organic material Feb 10 4:37 PM 22

23 soil is arranged in horizons (layers) A horizon = topsoil, richest and most important for plant growth loam made of equal amounts of sand, silt and clay clay for large surface area sand provide air spaces (oxygen for cellular respiration) not enough air = suffocation by water, mold attack on roots Feb 10 4:43 PM 23

24 Topsoil includes organisms (5 billion bacteria, worms, insects, algae, fungi) earthworms add air to soil, add mucus to hold particles together bacteria use nitrogen fixation, alter mineral composition roots prevent erosion Roots take in a soil solution made of water and dissolved minerals (ions) some particles are bound tightly to soil due to charge anions: nitrate, phosphate, and sulfate are not bound tightly easily released from soil leached from soil during rainstorms cations: potassium, Calcium and magnesium are bound to soil particles Feb 10 4:48 PM 24

25 Cation exchange Hydrogen ions made by secretion of root hairs and cellular respiration replace cations attached to soil, so they can then be absorbed by root Feb 10 5:15 PM 25

26 Soil Conservation and Sustainable Agriculture soil mismanagement Ex. "dustbowl" in 1930' s in U.S. caused by overgrazing of cattle, wheat crops instead of grasses, drought left topsoil exposed Feb 11 11:38 AM 26

27 agriculture depletes nutrients in soil use fertilizers to replace lost nutrients farmers also need to irrigate crops Soil conservation goals: irrigate properly fertilize properly prevent erosion Feb 12 9:31 AM 27

28 Fertilizers three ingredients: nitrogen (as ammonium or nitrate), phosphorus (as phosphoric acid), potassium (potash) N P K ratio ex organic fertilizers= manure, fishmeal, compost excess minerals not taken up by roots are leached away, can pollute water Feb 11 11:44 AM 28

29 soil ph influences uptake of minerals at certain ph's some minerals absorbed, others not if acidic can add calcium carbonate or calcium hydroxide if alkaline add sulfate in tropical areas, soil is acidic, aluminum dissolves and is toxic to roots plants can secrete organic ions to bind with Al and make it harmless Apr 2 8:49 AM 29

30 Irrigation diversion of water from rivers is major issue irrigation in arid areas, makes soil salty infertile types of irrigation: overhead drip furrow Feb 11 11:52 AM 30

31 Erosion movement of soil from one place to another two main causes: water and wind to prevent erosion: 1. windbreaks planting trees surrounding the fields to prevent wind erosion 2. contouring pattern 3. terracing Feb 11 11:57 AM 31

32 sustainable agriculture long term productive farming practices that are environmentally safe Soil reclamation reclaiming soil that has been contaminated with heavy metals or organic pollutants for soil 1. can remove contaminated soil and store in landfill 2. phytoremediation use of plants to extract soil pollutants and concentrating them into plant tissue and then disposed ex. alpine pennycress collects zinc in shoots (300x most plants) Feb 11 12:01 PM 32

33 Apr 2 8:51 AM 33