Plant Nutrition & Soil

Chapter 37

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

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

-- 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

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?)

Angiosperm Reproduction

Chapter 38

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

Watch Animation

38-01.swf

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

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