Exam 2 - BIO106

What are macronutrients?

Required in larger amounts

What are raw materials used to create organic molecules?

• Carbon

• Oxygen

• Hydrogen

• Nitrogen

• Phosphorus

• Sulfur

What other materials do plants need?

• Potassium

• Calcium

• Magnesium

What is carbon used for?

Backbone of organic molecules

What is nitrogen used for?

DNA/RNA, proteins, chlorophyll

What is phosphorus used for?

DNA/RNA, cell membranes, ATP

Where is carbon and oxygen obtained from?

The atmosphere

• 45% of plant’s dry mass is carbon

• Carbon comes from CO2 taken in during photosynthesis

• Enters through pores (stomata) in leaves

Where do plants get their other minerals?

The soil

• Exists as part of the soil solution in pores between soil particles

What are fertilizers?

• Enriched in nitrogen, phosphorus, and potassium

• Natural fertilizers - manure, fishmeal, compost, hair

What is soil?

A mix of organic matter and mineral particles

Mineral particles (by decreasing size)

• Rocks and pebbles

• Sand

• Silt

• Clay

Larger particles ______ at retaining water and nutrients

Not good

Smaller particles _____ and exclude oxygen

Pack too close

Where does the rich organic matter humus come from?

• Decomposing leaves

• Dead organisms

• Feces

• Organic matter produced by bacteria and fungi

Humus prevents ______ from packing together

Clay particles

• Allows air pockets for air circulation around roots

• Increases cation exchange

What life does humus house?

Bacteria, fungi, earthworms, nematodes, insects, protists, plant roots

What is a cation?

Positively charged atom

Minerals exist in soil as _____

Ions

• Positively charged ions stick to negatively charges soil particles

• To release them into soil solution, roots modify the environment to make it more acidic so minerals released from soil, into the water

Roots release ____ into water

CO2

____+_____ makes carbonic acid

CO2 + H2O = H2CO3

Carbonic acid breaks down, releasing ____

H+

H+ is changed for a _____ on soil

Positively charged ion

What is leaching?

Soil particles are negatively charged

• Bind strongly to positively charged cation in the soil solution

• Anions (negatively charged ions (NO3-)) are repelled by soil particles

Nitrogen in soil

• Atmospheric N2 diffuses into soil

• But is unusable by plants

• Must be converted into NH4+ and NO3- for plants to use

N2 gas converted to usable forms by ______

Bacteria

Ammonifying bacteria

Extract NH4+ from decaying organic matter

Nitrifying bacteria

Convert NH4+ into NO3-

Nitrogen fixing bacteria

Convert N2 gas into NH4+

Rhizobacteria

• Special group of N-fixing bacteria

• Live within nodules in the roots of legumes (beans, peas, alfalfa, clover, and lentils)

• Mutualism: bacteria release useable N, plant provides sugars and shelter

Mycorrhizal fungi symbiosis

• Fungi wrap around roots

• Increase water and nutrient absorption capabilities

• Plant supplies fungi with carbohydrates formed from photosynthesis

Ectomycorrhizae

• The mycelium forms a dense sheath over root surface

• Fungal hyphae penetrate the cortex

Endomycorrhizae

• Hyphae extend into the root and make small pockets in the cortical cells where arbuscles from

Parasitic plants (non-mutualistic associations)

Take nutrients from other plants or fungi and give nothing in return

Epiphytes (non-mutualistic associations)

Grow on other plants but don’t parasitize them

• Gather their own water and minerals mostly from the air

• Photosynthesize - don’t have to compete with forest floor species

• Orchids, some ferns, bromeliads

Carnivorous plants (non-mutualistic associations)

• Capture and digest animals

• Typically live in N-poor soils

  • Animals become major source of nitrogen

Humus consists of __________

Decomposing organic material

Topsoil __________

Is a mixture of rock fragments, living organisms, and humus

The release of CO₂ into the soil results in the formation of _____

Hydrogen ions and carbonate ions

What process is the source of the CO₂ that root hairs release into the soil?

Respiration

The binding of H⁺ ions to soil particles _____

Displaces mineral cations

Which of these ions is most likely to be leached from the soil?

Chloride ions

Acid precipitation _____

Decreases soil fertility

How do cations enter root hairs?

Diffusion

Nitrogen-fixing bacteria in the soil __________

Convert atmospheric nitrogen to ammonia

Ammonifying bacteria make ___ from ____

Ammonium; amino acids

Nitrogen-fixing bacteria make _____ from _____

Ammonia; nitrogen gas

Which statement best describes the role of soil bacteria in nitrogen cycling?

They convert unavailable nitrogen into nitrogen that is available to plants, and back again

Which of these nitrogen compounds is in the most reduced state?

NH₄⁺

Most commercial fertilizers supply nitrogen both as ammonia or ammonium and as nitrate. Yet, plants are much more efficient at taking up nitrate in their roots. What might be a benefit of adding both forms of nitrogen to the soil?

• Ammonium is eventually converted to nitrate in the soil, increasing the length of time that nitrate is available to the plants after each application of fertilizer

• Ammonium is a cation, so if it rains heavily it will remain in the soil longer than the anion nitrate, which would get washed away

The relationship between legumes and Rhizobium is __________

Mutualistic

Which of the following macronutrients plays a critical role on plant growth and crop yields?

Nitrogen

The bulk of a plant's dry weight is derived from

CO2

Which of the following elements is required for the stability of cell walls?

Calcium

For an element to be considered a macronutrient, __________

It must be required in relatively large amounts

You are weeding your garden when you accidentally expose some roots of your pea plants. You notice swellings (root nodules) on the roots, and there is a reddish tinge to the ones you accidentally damaged. Most likely your pea plants

Are benefiting from a mutualistic bacterium

Fungal hyphae form a covering over roots. These hyphae create a large surface area that helps to do which of the following?

Aid in absorbing water and minerals

What are epiphytes?

Plants that grow on other plants but do not obtain nutrients from their hosts

Nitrogen fixation is a process that

Converts nitrogen gas into ammonia

Which of the following plant structures shares the most common features and functions with a fungal hyphae?

Root hairs

Mycorrhizae are __________

Mutualistic associations between plant roots and fungi

Root system:

• Anchor plant (support)

• Bring in nutrients and water

• Can store carbohydrates

Shoot system:

• Stems are structural (upright) and transport nutrients and water

• Leaves change gases with air and do photosynthesis

What are taproots?

Penetrates soil deeply with lateral roots branching off

• Supports tall plants (prevents toppling)

• Absorption occurs in lateral roots

What are fibrous roots?

Multiple slender roots emerge from stem

• Form underground mat of interwoven branching roots

• Prevents grazers from uprooting plant

• Anchors topsoil

Absorption

• Occurs primarily at root tips

• Root hairs - thin extensions of individual cells

What is stems main function?

Elongate and orient the shoot to maximize:

1. Photosynthesis - positioning leaves toward the sun above neighboring plants

2. Reproduction - Facilitating dispersal of pollen and fruit

What is stems structure?

• Nodes - points where leaves emerge

• Internodes - segments between nodes

• Apical bud - growing shoot tip

• Axillary bud - Place where a branch can from

What are leaves main function?

Photosynthesis

• Capture light

• Exchange gas with atmosphere

• Take part in water uptake

What does a leaf consist of?

• Flattened blade

• The petiole, a stalk which joins the leaf to a node of the stem

What is dermal tissue?

Outer layer

• Protect plant

What is ground tissue?

Middle layer

• Bulk of the plant

• Carries out most functions

What is vascular tissue?

Central layer

• “Circulatory system”

• Tubes distribute water and nutrients through body

Waxy cuticle in dermal tissue

Reduces water loss

Epidermis in dermal tissue

Single layer of tightly packed cells

Periderm in dermal tissue

As plants grow thicker they gain an extra protective layer

What is xylem?

Tubes that transport water and minerals upward from roots into the shoots

What is the structure of xylem?

• Dead tubular cells stacked end to end

  • Dead cells form long pipes (vessels) - have perforations between the cells for water flow

• The initial cell walls have lignin in them (strong and rigid)

What are vessel elements in xylem cells?

• Wider, shorter with larger openings

• Aligned end to end forming continuous tube

• Have perforation plates for flow from cell to cell

What are tracheids in xylem cells?

• Long, tapered

• Water flows cell to cell laterally via pits

What does phloem do?

Moves organic nutrients (sugars) from where they are made (or stores) to where needed

What are sieve-tube element cells in phloem?

• Living cells connect end to end forming a tube

• Lack most organelles (including nucleus and ribosomes)

• Connect end to end via sieve plates

What are companion cells in phloem?

Supply proteins etc. to sieve-tube element cells

What is ground tissue?

Anything that is NOT dermal or vascular

• Fills in between/around dermal tissue and vascular tissue

• Includes various cells specialized for functions such as storage, photosynthesis, and support

What is pith in ground tissue?

Internal to vascular tissue of roots and stems

What is cortex in ground tissue?

External to vascular tissue of roots and stems

Root hairs are important to a plant because they __________

Increase the surface area for absorption

Which of the following is correctly matched with its tissue system?

Cortex ... ground tissue system

Mycorrhizal associations are symbiotic interactions between __________ and __________

Root systems … soil fungi

Root hairs, which absorb the water and minerals in the majority of plants, are the extensions of root

Epidermal cells

Xylem, a vascular tissue, performs which of the following functions?

Transport of water and minerals

Plant roots, stems, and leaves are all composed of what tissue types?

Dermal, vascular, and ground

Adventitious roots in monocots are very helpful in coastal ecosystems to reduce

Soil erosion

An association between the roots of a terrestrial plant with soil fungus is referred to as

Symbiosis

Storage roots, stems, and leaves are some of the evolutionary adaptations of plants. Which of the following are listed in the order of modified root, stem, and leaf?

Rhizome, stolon, tendril

What does indeterminate growth mean?

Grow continually throughout life

What is primary growth?

Elongation

What is secondary growth?

Increase in width

How do herbaceous plants grow?

Plants restricted to primary growth (don’t growth wide)

How do woody plants grow?

Primarily and secondary

What are meristems?

Zone of dividing cells (stem cells)