C. Plant Mineral Compositi on 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: NO 3 - must be converted to NH 4 + 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
a. 95% “organic” – C, H, O from air & water, assimilated by photosynthesis b. 5% inorganic minerals 2. Dry weight
Nutrients that are required for a plant to grow from a seed and complete its life cycle. 1. Types: a. Macronutrients A. Essential Nutrients Elements required by plants in relatively large amounts. CHOPKNS Ca Mg ii. Functions i. Categories II. Categories
Information taken from Table 37.1 CategoryForm AvailableUses CarbonCO 2 Organic compounds HydrogenH20H20Organic compounds OxygenCO 2 (air), O 2 (soil)Organic compounds PhosphorusH 2 PO 4 -, HPO 4 2- Nucleic acids, phospholipids, ATP PotassiumK+K+ Water balance (stomata), protein synthesis NitrogenNH 4 +, NO 3 - Proteins, nucleic acids, hormones, chlorophyll SulfurSO 4 2- Proteins CalciumCa 2+ Cell walls & membranes, enzyme activation MagnesiumMg 2+ Chlorophyll, enzyme activation
b. Micronutrients These elements are required by plants in relatively small amounts (<0.1% dry mass). Fe, B, Cl, Mo, Cu, Mn, Ni, & Zn ii. Functions i. Categories
CategoryForm AvailableUses ChlorineCl - Required for photosystem II to split water and water balance IronFe 3+ or Fe 2+ Component of cytochromes and enzyme activation ManganeseMn 2+ A.A. formation, enzyme activation, and split water in PS II BoronH 2 BO 3- Cofactor in chlorophyll synthesis, involved in carbohydrate transport and nucleic acid synthesis, and role in cell wall function ZincZn 2+ Cofactor in chlorophyll synthesis and enzyme activation CopperCu + or Cu 2+ Involved with re-dox and lignin biosynthesis enzymes NickelNi 2+ Cofactor in nitrogen metabolism enzymes MolybdenumMoO 4 2- Essential for mutualistic relationship with nitrogen fixing bacteria and cofactor for nitrogen reducing enzymes Information taken from Table 37.1
A. Dependent on: 1. the role of the nutrient in the plant 2. its mobility III. Mineral Deficiencies
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
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.
Large, spaces for water & air Small, more SA for retaining water & minerals 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
V. Topsoil 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 A. Characteristics
B. Nutrient Availability 1. Cations in soil water adhere to clay particles (negatively charged surface) 2. Anions do not bind; thus they can leach! (NO 3, HPO 4, SO 4 ) 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 + CO 2 released 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
1. Use of plants to extract toxic metals from soil 2. Benefits: easier to harvest the plants than to remove topsoil! B. Phytoremediation
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 (NO 3 - ) 3. What’s it used for? Proteins (AAs), nucleic acids, chlorophyll production VII. NITROGEN
The Nitrogen Cycle Organic N NH 4 NO 3 Decomposition N2N2 Ammonification Nitrification Immobilization Uptake Leaching Denitrification N 2 fixation
B. Nitrogen Cycle 1. Steps: a. N fixation – conversion of N 2 to NH 3 b. Ammonification – conversion of NH 3 or organic N into NH 4 + c. Nitrification – conversion of NH 4 + to NO 3 - d. N reduction – conversion of NO 3 - back to NH 4 + within plant. e. N assimilation – incorporation of NH 4 + into AAs, nucleic acids, lignin, others(?) of the plant
Fig 37.9 All steps within the soil are mediated by bacteria!!!!
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 with Legumes Legumes: peas, beans, alfalfa The legume/bacteria interaction results in the formation of nodules on roots Plant – gets ample inorganic N source Bacteria – gets ample carbon source
iii. Fixation in Non-legumes Here in the NW: alder Azolla (a fern) contains a symbiotic N fixing cyanobacteria useful in rice paddies. Plants with symbiotic N fixers tend to be first colonizers. Why? b. Ammonification i. conversion of NH 3 or organic N into NH 4 +
i. Unfortunately NH 4 + is a highly desirable resource for free–living bacteria, oxidizing it to NO 3 -. ii. Consequently the predominant form of N available to roots is NO 3 -. c. Nitrification d. Nitrate Reduction i. NO 3 - must be reduced back to NH 4 + in order to be incorporated into organics. ii. This process is energetically expensive but required.
i. The actual incorporation of NH 4 + into organic molecules in the plant body. ii. This process is similar to that of an electron transport chain. iii. Reduced N passes through a series of carriers that function repeatedly but in the long run are unchanged. iv. Usually occurs within the roots. e. Nitrogen Assimilation
2. Loses a. Leaching – loss of NO 3 - by soil water movement b. Denitrification – conversion of NO 3 - back to N 2 c. ???
a. Parasitic plants i. Extract nutrients from other plants Ex. Mistletoes on Douglas Fir & Ponderosa pine Ex. Indian pipe – parasite on trees via mycorrhizae C. Nutritional Adaptations
b. Carnivorous plants i. Digest animals & insects – why? Grow in soils lacking an essential nutrient ii. Motor cells! iii. Trap insects & secrete digestive juices Ex. Venus flytrap, pitcher plant, Darlingtonia
c. Mycorrhizal relationships i. Fungus & plant roots ii. Fungus gets carbos iii. Plants get greater SA for water & phosphorus uptake iv. Almost all plant species! v. 2 types: Ectomycorrhizae – hyphae form dense sheath over root; extend into cortex & out into soil. Thickened roots of woody plants Endomycorrhize – microscopic, more common.