Plant Physiology II: Transport, Gas Exchange, Soil, and Nutrition

Flashcards covering plant gas exchange, nutrient requirements, soil composition, and specialized nutritional adaptations based on lecture notes.

Stomata

Small pores on plant surfaces that allow for gas exchange, specifically letting $ext{CO}_2$ diffuse into the leaf and $ext{O}_2$ and $ext{H}_2 ext{O}$ diffuse out.

Guard cells

Cells that control the opening of the stomatal pore by swelling (plump) when hydrated to open the pore or flattening when dry to close it.

Macronutrients

Essential nutrients that make up $96$ percent of the plant, including Carbon ($C$), Hydrogen ($H$), Oxygen ($O$), Nitrogen ($N$), Phosphorus ($P$), Potassium ($K$), Calcium ($Ca$), Magnesium ($Mg$), and Sulfur ($S$).

Micronutrients

Essential nutrients required in smaller amounts, including Iron ($Fe$), Manganese ($Mn$), Boron ($B$), Molybdenum ($Mo$), Copper ($Cu$), Zinc ($Zn$), Chlorine ($Cl$), Nickel ($Ni$), Cobalt ($Co$), Sodium ($Na$), and Silicon ($Si$).

Transpiration

The loss of water from the plant through evaporation at the leaf surface, which acts as the main driver of water movement in the xylem.

Cohesion-tension theory

The theory explaining sap ascent where water is pulled up by negative pressure from transpiration and held together by the adhesion of water to xylem walls and the cohesion of water molecules to each other.

Water potential ($ext{Ψ}_{total}$)

A measure that determines the direction of water movement; water moves into cells when it is higher outside than inside.

Turgor pressure ($ext{Ψ}_p$)

Pressure exerted by water against the cell wall that keeps the plant erect, resulting when water potential is higher outside the plant cells than inside.

Pedosphere

The Earth's body of soil, which serves as a medium for growth, water storage/purification, atmosphere modifier, and habitat.

Humus

The organic material of soil, composed of microorganisms (dead and alive) and dead animals and plants in varying stages of decay.

Sand

Soil particles that are $0.1$ to $2 ext{ mm}$ in diameter.

Silt

Soil particles between $0.002$ and $0.1 ext{ mm}$ in diameter.

Clay

The smallest soil particles, measuring less than $0.002 ext{ mm}$ in diameter.

Loams

Soils containing a mixture of sand, silt, and humus with no dominant particle size; considered the ideal blend for growing plants.

O horizon

The top layer of the soil profile featuring freshly decomposing organic matter (humus) at the surface and decomposed vegetation at the base.

A horizon

The beginning of true mineral soil, consisting of a mixture of organic material and inorganic products of weathering.

B horizon

A dense layer of soil consisting of an accumulation of mostly fine material that has moved downward.

C horizon

The soil base or parent material, including both organic and inorganic material broken down to form soil.

Biological Nitrogen Fixation (BNF)

The conversion of atmospheric nitrogen ($N_2$) into ammonia ($ext{NH}_3$) by prokaryotes, represented by the equation: $N_2 + 16 ext{ ATP} + 8 ext{ e}^- + 8 ext{ H}^+ ightarrow 2 ext{NH}_3 + 16 ext{ ADP} + 16 ext{ Pi} + H_2$.

Rhizobia

Root-loving bacteria, such as ‘Bradyrhyzobium japonicum’, that infect the nodules of legume roots to facilitate nitrogen fixation.

Mycorrhizae

Symbiotic associations between fungi and plant roots where the fungi facilitate mineral uptake and potentially obtain up to $20$ percent of the plant's total carbon.

Autotrophic plants

Plants that can make their own food from inorganic raw materials, such as $ext{CO}_2$ and $ext{H}_2 ext{O}$, through photosynthesis.

Parasitic plants

Plants that depend on a host for nutrients and water by penetrating the host's vascular tissue; examples include mistletoe and dodder.

Saprophyte

A plant lacking chlorophyll that obtains food from dead matter using enzymes, often relying on fungi to digest the material.

Epiphyte

A plant that grows on other plants for physical support but is not dependent on the host for nutrition.

Insectivorous plants

Photosynthetic plants found in nitrogen-poor environments (like bogs) that extract minerals and energy by trapping and digesting insects.