Plant Nutrition

Question 1

How did plant ancestors absorb nutrients?

Answer 1

absorbed nutrients directly from their aquatic environment

Question 2

What did the move to plants result in?

Answer 2

over time as plants moved onto land, competition for resources resulted in taller plants, with broader leaves (more SA) for more light absorption

Question 3

What were the challenges associated with the adaptations that evolved when moving to land?

Answer 3

More SA for light also means more SA for water loss
Larger plants also need larger roots for anchorage (lots of energy is spent making the root system, super tall means greater distance to transport nutirents )
Greater distance to transport nutrients between the root and shoot systems

Question 4

What evolved that allowed the challenges of coming to land be overcome?

Answer 4

Evolution of vascular tissues move this all possible
Xylem -> transports water and nutrients from roots to shoots
Phloem -> transports photosynthates from source to sink

Question 5

What varies greatly amongst land plants?

Answer 5

Shoot architecture (i.e. morphology) varies greatly amongst land plants

Question 6

What examples of shoot architecture that vary in plants?

Answer 6

Stem length and widths -> allows plants to grow tall
Branching pattern -> allows better light harvesting
Limitations in architecture due to finite energy to devote to shoot growth

Question 7

leaves

Answer 7

Various adaptations for specific habitats, preventing water loss and maximizing photosynthesis
Most large, leafed plants are tropical, smaller leafed plants are temperate, and very small, leafed plants occur in harsh habitats

Question 8

Phyllotaxy

Answer 8

is the arrangement of leaves on a plant

Determined and genetically controlled by the SAM

Question 9

What is the function of the stem?

Answer 9

support leaves and act as conduits for water and nutrient transport

Question 10

One leaf per node

Answer 10

alternate, spiral

Question 11

Two leaves per node

Answer 11

opposite

Question 12

Multiple leaves per node

Answer 12

whorled

Question 13

What affects the productivity of plants?

Answer 13

Total leaf area affects the productivity of each plant

Question 14

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Answer 14

Leaves can shade other leaves on the same plant, reducing photosynthetic capacity (ie. They respire more than photosynthesise!)
Plants can self-prune leaves(and branches!)to optimizing leaf area index

Question 15

leaf area index

Answer 15

the ratio of the total upper leaf surface of a single plant or an entire crop divided by the surface area of the land on which the plant or crop grows

Question 16

What can affect photosynthetic capacity explain

Answer 16

Leaf orientation
In low light -> horizontal leaves are best
In high light -> vertical leaves prevent water loss and burning

Question 17

Describe the photosynthesis – water loss compromise

Answer 17

Broad leaves absorb more light, have more stomata

• Stomata open to exchange gas, but there is water loss!

Question 18

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Answer 18

Roots maximize morphology and growth to absorb nutrients
Won’t branch in areas of low N availability
Branches more in areas of high nutrient loads, makes more proteins to take up more nitrogen
Associate with mycorrhizae to increase surface area of more nutrient uptake

Question 19

What are the two main “compartments” of plant systems?

Answer 19

the apoplast and the symplast

Question 20

Apoplast

Answer 20

everything external to the plasma (inside) membrane (including cell walls and internal spaces of dead tracheids and vessels)

Question 21

Symplast

Answer 21

consists of the cytosol, plasmodesmata, and cytoplasmic interconnections

Question 22

What are the 3 main transport “routes” ?

Answer 22

Apoplastic->water and solutes move along the cell walls and extracellular spaces (like water through a sponge)
Symplastic -> water and solutes move through the cytosol (requires substances to cross a plasma membrane once, when they first enter the plant. After entering one cell, substances can move from cell to cell via plasmodesmata)
Transmembrane->water and solutes move out of one cell, across the cell walls, and into the next cell

Question 23

What do plant cells and other cells have in common in terms of transport?

Answer 23

Both active and passive transport mechanisms occur in plants, and plant cell membranes are equipped with the same general types of pumps and transport proteins (channel proteins, carrier proteins, and cotransporters) that function in other cells

Question 24

Compare the use of H+ and Na+ in animal and plant cells

Answer 24

Uses H+ for membrane potentials resulting from proton pumps (primary active transport)
• Animals used Na+

H+ is also co-transported in plants (ex. sugar in phloem cells) (secondary active transport)
• Animals co-transport Na+

Have gated ion channels (produces electrical signals similar to action potentials in animals)
• K+ ions for the opening/closing of guard cells

Question 25

Describe cotransport in plants

Answer 25

, plant cells use the energy in the H+ gradient and membrane potential to drive the active transport of many different solutes

cotransport with H+ is responsible for absorption of neutral solutes, such as the sugar sucrose, by phloem cells and other plant cells. An H+/ sucrose cotransporter couples movement of sucrose against its concentration gradient with movement of H+ down its electrochemical gradient (Figure 36.6b). Cotransport with H+ also facilitates movement of ions, as in the uptake of nitrate (NO3−) by root cells