Honors Bio - Plants

Turgor Pressure

The pressure exerted by water inside the cell against the cell wall; maintains plant rigidity and structure.

Xylem

Vascular tissue that transports water and minerals UPWARDS from roots to leaves.

Phloem

Vascular tissue that transports sugar (food) bidirectionally (up and down) to the rest of the plant.

Stomata

Pores on the leaf surface that allow gas exchange (CO2 in, O2 out) and water loss (transpiration).

Guard Cells

Specialized cells flanking the stoma; they swell (open) to release water/gas when water is abundant and become flaccid (close) to conserve water when dry.

Transpiration

The evaporation of water vapor from plant leaves; this process pulls water up from the roots.

Chloroplast

The organelle where photosynthesis occurs; contains the pigment chlorophyll.

Thylakoid

Disc-like structures inside the chloroplast containing chlorophyll; the site of Light Dependent Reactions.

Stroma (Chloroplast)

The fluid-filled space inside the chloroplast surrounding the thylakoids; the site of Light Independent Reactions (Dark Reactions).

Light Dependent Reaction

The first phase of photosynthesis occurring in the thylakoid; sunlight splits H2O molecules to create ATP and releases Oxygen.

Light Independent Reaction (Calvin Cycle)

The second phase of photosynthesis occurring in the stroma; uses ATP and CO2 to produce Glucose (sugar).

Photosynthesis Equation

6CO2 + 6H2O + Sunlight → C6H12O6 + 6O2

Cellular Respiration Equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Auxins

Plant hormones found in shoot/root tips that promote growth and elongation; responsible for bending plants toward light.

Phototropism

A plant's growth response to light; caused by auxins accumulating on the shaded side, making the plant bend toward the light.

Gravitropism

A plant's growth response to gravity; roots grow down, stems grow up.

Thigmotropism

A plant's growth response to touch (e.g., vines wrapping around an object).

Annuals vs. Perennials

Annuals complete their life cycle in one year; Perennials live for many years.

Cellulose

A complex carbohydrate that makes up the rigid cell walls of plants.