Survival Strategies

Nitrogen (N)

Potassium (K+)

Magnesium (Mg+2)

Nitrogen shortage

Nitrogen fixation

Macronutrients are required in large amounts, while micronutrients are required in small amounts

Active transport

They help fix nitrogen from the air

Transpiration

From source cells to sink cells

Absorbing water and nutrients from rainwater and dust

To extract water and ions from the host plant

In bogs or other habitats with scarce nitrogen

Absorbing from the soil

Rainwater and organic debris collected in 'tanks'

To absorb water and nutrients from the soil

To facilitate the movement of water and solutes into the xylem

Transpiration pull

To regulate gas exchange between the plant and the environment

Sunlight, high CO2 concentration, and internal timing mechanism

Leaves modified into spines to decrease surface area

Plant A, since it will absorb more CO2 than plant B

Epidermal route (water flows from the epidermis directly into xylem)

Tree B

Carbon dioxide uptake is reduced by the stomata closing to prevent excessive water loss

Proteins

Bulk flow

High sugar concentration

Sink

Facilitated diffusion

Water

To transport sugars from the leaves to other parts of the plant

High in sinks

Active transport of sucrose raises the pressure at the source and lowers it at the sink

By facilitated diffusion

Leaves modified into spines decrease the surface area of the leaves, which decreases the number of stomata and therefore decreases the amount of water lost during the day.

Plant B is likely able to produce more sugars through photosynthesis when the stomata of plant A are closed while those of plant B are open.

The process is called transpiration.

The main function of the phloem is to transport the products of photosynthesis from where they are made or stored to where they are needed.

The main driving force behind the upward movement of water in the xylem is transpiration.

chlorine (Cl-), iron (Fe+2), manganese (Mn+2), boron (B), zinc (Zn+2), copper (Cu+2), nickel (Ni+2), molybdenum (Mo)

carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S), phosphorus (P)

rhizobia (with bacteria), mycorrhizae (with fungi), mutualistic symbiotic relationships with bacteria and fungi

Fungi obtain sugars and amino acids from the plant

Plants benefit from increased nutrient absorption and water uptake from the soil through the mycorrhizal fungi

The four distinct tissue layers of a root, from the outside in, are the epidermis and root hairs, the cortex, the endodermis, and the pericycle.

Root hairs greatly increase a root's absorptive surface and contain membrane proteins that bring nutrients into the cytosol of root cells.

The Casparian strip in the endodermis stops solutes from entering the xylem through cell walls and instead forces them to cross a plasma membrane into an endodermal cell.

The main driving force behind the upward movement of water in the xylem is transpiration, which is driven by the upward pull of evaporation at the stomata and the cohesive/adhesive properties of water in the xylem.

Three factors influence the opening and closing of stomata: sunlight signals guard cells to accumulate K+ and open stomata, low CO2 concentration signals guard cells to open stomata, and an internal timing mechanism (biological clock) in guard cells continues their daily rhythm of opening and closing.

Hydroponic culture studies have helped identify 17 elements essential to plant growth and reproduction, including nine macronutrients that plants require in relatively large amounts.

Ions/nutrients are moved into plant cells in the root systems through active transport, facilitated diffusion, and symplastic transport.

Symbiotic relationships with bacteria, archaea, and/or fungi aid in nutrient acquisition at the root systems through processes such as nitrogen fixation, nutrient mobilization, and nutrient transfer.

Transpiration of water occurs through a combination of physical forces such as cohesion, adhesion, and tension, which create a continuous column of water in the xylem from the roots to the stomata.

Sugars are actively transported from source cells to companion cells, and then loaded into sieve tubes in the phloem. They are then transported via pressure flow mechanism to sink cells, where they are unloaded and used for growth and metabolism.

Plants can absorb water and nutrients from rainwater, dust, and particles that collect in their tissues. Some plants have leaves that grow in rosettes to form “tanks” that collect water and organic debris. Parasitic plants obtain water and nutrients from a host plant. Carnivorous plants trap insects and other animals to absorb their nutrients.

Epiphytic bromeliads have leaves that grow in rosettes to form “tanks” that collect water and organic debris. Nutrients are absorbed through the leaves.

Haustoria are structures produced by parasitic plants. They can penetrate a host plant's vascular system to obtain water and nutrients. Most parasitic plants are photosynthetic and use haustoria to extract water and ions from the xylem of the host plant.

Carnivorous plants kill their prey and absorb the prey’s nutrients. They make their own carbohydrates via photosynthesis, using carnivory to supplement nitrogen available in the environment.

Most carnivorous plants are found in bogs or other habitats where nitrogen is scarce.

The pressure flow mechanism is the process by which sugars are transported through the phloem from sources to sinks. It involves active transport of sucrose into the phloem at the source, creating a high concentration of solute and generating pressure. The pressure then drives the flow of sugars through the phloem to the sink, where both sugar and water leave the phloem. This lowers the solute concentration at the sink and reduces the pressure. Finally, water leaves the phloem via osmosis and re-enters the xylem.

Sucrose unloading in young, growing leaves occurs by facilitated diffusion. This is because sucrose is rapidly used up in the cells of these leaves. Root cells have a large vacuole that stores sucrose, surrounded by a membrane called the tonoplast. The tonoplast contains two types of protein pumps that work to accumulate sucrose in the vacuole. As protons diffuse back out of the vacuole, a proton-sucrose antiporter moves sucrose into the vacuole against its concentration gradient.

The main driving force behind the movement of sugars through the phloem is the pressure gradient created by the pressure flow mechanism. Active transport of sucrose at the source raises the concentration of solute within the phloem, resulting in water being drawn from the xylem into the phloem tube via osmosis. This generates high pressure at the source. At the sink, both sugar and water leave the phloem tube, lowering the solute concentration and reducing the pressure. Water then leaves the phloem via osmosis and re-enters the xylem, further lowering the pressure in the phloem tube.

Sucrose is more concentrated in companion cells than in the photosynthetic cells because of active transport. Sucrose enters companion cells from source tissues by secondary active transport. Companion cells have a proton pump that uses ATP to drive the transport of protons into the source cell against their concentration gradient. Then, a symporter uses the established proton gradient to move sucrose against its concentration gradient into the companion cells, while the protons move down their concentration gradient. This active transport process results in higher concentrations of sucrose in the companion cells.

Sucrose enters companion cells from source tissues by secondary active transport. This process involves the use of ATP to drive the transport of protons into the source cell against their concentration gradient. Then, a symporter uses the established proton gradient to move sucrose against its concentration gradient into the companion cells, while the protons move down their concentration gradient. This active transport process allows sucrose to be transported into the companion cells from source tissues.