Chapter 37 Plant Nutrition & Soil

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

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

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

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

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

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

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?)

Chapter 38 Angiosperm Reproduction

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

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

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

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

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

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