I. Introduction A. Definition B. Evidence 1. JuliusSachs Experiment
Fig 37.2 Julius Sachs 1860’s
C. Plant Mineral Composition 1. Incorporation a. As is = Some minerals can be used as is: e.g. K+ ions for guard cell regulation b. Combined = Some minerals have to be incorporated into other compounds to be useful: e.g. Fe+ in the cytochrome complex of the light reactions c. Altered = Some mineral compounds have to be altered to be useful: NO3- must be converted to NH4+ inside the plant
d. Water i. 80–85 % of an herbaceous plant is water. ii. Water supplies most of the hydrogen and some oxygen incorporated into organic compounds by photosynthesis. iii. But > 90% of the water absorbed is lost by transpiration. iv. Water’s primary function is to serve as a solvent. v. Water also is involved in cell elongation and turgor pressure regulation
2. Dry weight a. 95% “organic” – C, H, O from air & water, assimilated by photosynthesis b. 5% inorganic minerals
II. Categories A. Essential Nutrients Nutrients that are required for a plant to grow from a seed and complete its life cycle. 1. Types: a. Macronutrients Elements required by plants in relatively large amounts. i. Categories CHOPKNS Ca Mg ii. Functions
b. Micronutrients These elements are required by plants in relatively small amounts (<0.1% dry mass). i. Categories Fe, B, Cl, Mo, Cu, Mn, Ni, & Zn ii. Functions
II. Mineral Deficiencies • A. Dependent on: • 1. the role of the nutrient in the plant 2. its mobility
B. Immobile Nutrients 1. Once they have been incorporated into plant tissue, they remain (can’t return to phloem). 2. Boron, calcium, and iron 3. Growth = normal until the mineral is depleted from soil; new growth suffers deficiency and thus youngest tissues show symptoms first.
C. Mobile Nutrients 1. can be translocated by phloem to younger (actively growing) tissue. 2. Cl, Mg, N, P, K, and S 3. When mineral is depleted, nutrients translocated to younger tissue. 4. Thus older tissues show deficiency & then die What is the adaptive value of nutrient mobility?
D. Criteria • 1. Not common in natural populations. Why? • Plants have adapted to soil components • 2. Common in crops & ornamentals. Why? • Human selection for biggest, fastest plants. Need • more nutrients than the soil provides. • Crop growth depletes the soil because no organic • matter return • 3. Deficiencies of N, P, and K are the most common. • 4. Shortages of micronutrients are less common and often soil type specific. • 5. Overdoses of some micronutrients can be toxic.
E. Symptoms 1. Chlorosis – leaves lack chlorophyll: yellow, brittle, papery. Typically lack of N or Fe. 2. Necrosis – the death of patches of tissue 3. Purpling – deficiency of N or P, causes accumulation of purple pigments 4. Stunting – lack of water, N
I. Soil Formation A. Forces II. Soil Horizons A. Names
III. Orders A. Definition B. Primary
IV. Soil Properties A. Chemistry 1. Minerals 2. Nitrogen–fixing bacteria 3. Mycorrhizal fungi 4. Water 5. Oxygen
B. Composition • 1. Chemistry – determines which minerals are • present and available, thus affecting plant community • composition • 2. Physical nature – affects porosity, texture, • density of soil, which affects #1 • 3. Soil organisms – decomposition & mineral • Return. Interact with roots to make nutrients available • Nitrogen! The only mineral that the plant can ONLY • get from reactions mediated by soil organisms.
C. Texture 1. Soil is created by weathering of solid rock by: water freeze/thaw, leaching of acids from organic matter, carbonic acid from respiration + water. 2. Topsoil is a mixture of weathered rock particles & humus (decayed organic matter). 3. Texture: sand, silt, clay Large, spaces for water & air Small, more SA for retaining water & minerals
V. Topsoil A. Characteristics 1. Bacteria, fungi, insects, protists, nematodes, & Earthworms! Create channels for air & water, secrete mucus that binds soil particles 2. Humus: reservoir of nutrients from decaying plant & animal material 3. Bacterial metabolism recycles nutrients
B. Nutrient Availability 1. Cations in soil water adhere to clay particles (negatively charged surface) 2. Anions do not bind; thus they can leach! (NO3, HPO4, SO4) 3. Cations become available for root uptake by cation exchange – H+ displaces cations on the soil particle surface 4. H+ from carbonic acid – formed from water + CO2released from root respiration 5. Humus – negatively charged & holds water & nutrients. Thus very important in the soil!!!!!
C. Soil pH • 1. Low pH (acidic) = high H+ concentration • a. More cations released • b. Too much acid – cations leach…..mineral • deficiency • 2. High pH (basic) • a. Not enough H+ for cation release….mineral • deficiency
VI. Soil conservation A. Factors Affecting 1. Natural systems: decay recycles nutrients 2. Agricultural systems: crops harvested, depleting soil of nutrients & water
3. Fertilizers: N:P:K • a. Synthetic: plant-available, inorganic ions. Faster acting. • i. Problem: • ii. leaching, acidifying the soil • b. Organic: slow release by cation exchange, • holds water, thus less leaching
B. Phytoremediation 2. Benefits: easier to harvest the plants than to remove topsoil! 1. Use of plants to extract toxic metals from soil
A. Why so important? • 1. Air is 80% Nitrogen, but….. • 2. Macronutrient that is most often limiting. • Why? Is almost always taken up as anions (NO3-) • 3. What’s it used for? • Proteins (AAs), nucleic acids, chlorophyll production
The Nitrogen Cycle N2 N2 fixation Denitrification Uptake Decomposition NO3 Nitrification Ammonification NH4 Organic N Leaching Immobilization
B. Nitrogen Cycle • 1. Steps: • a. N fixation – conversion of N2 to NH3 • b. Ammonification – conversion of NH3 or • organic N into NH4+ • c. Nitrification – conversion of NH4+ to NO3- • d. N reduction – conversion of NO3- back to • NH4+ within plant. • e. N assimilation – incorporation of NH4+into • AAs, nucleic acids, lignin, others(?) of the plant
a. Nitrogen Fixation • This process is catalyzed by the enzyme nitrogenase, • requires energy (ATP), and occurs in three ways: • i. Lightening – converts N in air to inorganic N • that falls in raindrops • ii. Non-symbiotic – certain soil bacteria • iii. Symbiotic