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Chapter 37

Chapter 37. Plant Nutrition & Soil. M a cronutrients & M i cronutrients. 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

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Chapter 37

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  1. Chapter 37 Plant Nutrition & Soil

  2. 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

  3. Nitrogen • 80% of atmosphere • In the form of N2 • Unusable by plants • Most important macronutrient for plants • Important for plant growth and crop yield • Needed for proteins, nucleic acids, and chlorophyll • Nitrogen Fixation (N2 NH3) • Converts atmospheric nitrogen into a biologically-usable form

  4. -- Atmospheric N2 is converted into NH3 (Nitrogen fixing bacteria)  NH4  NO3 (nitrifying bacteria) which can be used by plants for incorporation into organic systems -- Ammonifying bacteria can also convert organic material into NH4 as well

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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?)

  11. Chapter 38 Angiosperm Reproduction

  12. 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

  13. 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

  14. Watch Animation • 38-01.swf

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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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