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Plant Nutrition & Soil Chapter 37
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Macronutrients & Micronutrients Essential nutrients – Nutrients that must be consumed, plants cannot make these nutrients Macronutrients – Needed in large amounts Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorous, Sulfur, Potassium, Calcium, & Magnesium Micronutrients – Needed only in small amounts Iron, Manganese, Zinc, & Copper
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Nitrogen 80% of atmosphere In the form of N 2 Unusable by plants Most important macronutrient for plants Important for plant growth and crop yield Needed for proteins, nucleic acids, and chlorophyll Nitrogen Fixation (N 2 NH 3 ) Converts atmospheric nitrogen into a biologically- usable form
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-- Atmospheric N 2 is converted into NH 3 (Nitrogen fixing bacteria) NH 4 NO 3 (nitrifying bacteria) which can be used by plants for incorporation into organic systems -- Ammonifying bacteria can also convert organic material into NH 4 as well
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Rhizo - Rhizosphere – soil layer bound to the plant’s roots Rhizobacteria – soil bacteria Some rhizobacteria are called plant-growth-promoting rhizobacteria (PGPR) Wanna guess what they do? They promote plant growth by: Producing chemicals that stimulate growth Produce antibiotics to protect roots from infection Absorb toxic metals or make nutrients available for plants
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Rhizobacteria (Page 2) Plant benefits were discussed on prior slide Bacterial benefits since 20% of photosynthetic products go to the bacteria Hence, bacteria benefit from a healthy plant (roots) in the rhizosphere
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Rhizobium Bacteria Bacteria that fix atmospheric nitrogen + supply it as ammonium Legumes have a ready source of nitrogen Symbioses with Rhizobium (Root living) bacteria Peas, soybeans, peanuts, and alfalfa Nodules – swellings in the roots infected by rhizobium bacteria Bacteroids – bacteria in vesicles in root cells in the nodules
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Mutualistic Relationship? Rhizobium bacteria provide nitrogen in a usable form Used to make amino acids for plant growth Plant provides photosynthetic products to the nodules via the vascular system
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Mycorrhizae Mutualistic relationship between plant roots and fungus Two types Ectomycorrhizae Mycelium forms a dense sheath over the root surface Hyphae extend from the root to the soil = increase surface area for absorption of water & minerals Hyphae do NOT penetrate root cells
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Mycorrhizae (Page 2) Endomycorrizae Also called arbuscular mycorrhizae (That’s a mouthful!) Most common type (85% of associations) Look like regular roots No dense mantle covering root surface Hyphae penetrate the cortex (Which tissue type?)
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Angiosperm Reproduction Chapter 38
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Angiosperm Reproduction Angiosperms have 3 unique features: Flowers, Fruits, & Double Fertilization Microsporangia Pollen sacs in the anther Diploid cells = meiosis male gametophyte (pollen) Pollen has 2 haploid nuclei Tube nucleus – 1 sperm develops into a pollen tube Generative nucleus – divides into 2 sperm cells which remain inside the pollen tube
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Ovary Ovules form with a diploid cell Soon 4 haploid megapsores form Eventually get 8 haploid nuclei, but only 3 are most important 1 haploid nucleus = egg Will combine with sperm nucleus to form the zygote 2 other nuclei are called polar nuclei Polar nuclei will fuse with sperm nucleus to make 3n endosperm
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Watch Animation 38-01.swf
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Pollination Pollen lands on stigma Pollen tube made from pollen grain Pollen tube grows down into the ovary When pollen tube reaches ovule, double fertilization occurs
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Double Fertilization Double fertilization is the union of 2 sperm cells forming zygote & endosperm Unique to angiosperms 1 sperm fertilizes the egg zygote Zygote develops into the embryo sporophyte Other sperm combines with both polar nuclei = 3n nucleus This 3n tissue endosperm Endosperm – food storing tissue in the seed
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After double fertilization Ovule develops into a seed Ovary develops into fruit which encloses the seed Fruit protects the enclosed seed Fruit aids in dispersal by wind or animales Seed coat – protects embryo & its food supply Radicle – embryonic root Epicotyl – shoot tip with pair of miniature leaves
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Seed As the seed matures, It goes dormant Low metabolic rate, growth and development are suspended Seed resumes growth given suitable environmental conditions for germination
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Asexual Reproduction in Plants Asexual reproduction in plants is called vegetative reproduction Fragmentation Type of vegetative reproductive When a part of the parent plant is separated and then generates into a new plant, genetically identical to parent plant Self-fertilization is another means of asexual reproduction
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