SB6 Plant Structure, Photosynthesis, and Transport

Vocabulary practice flashcards covering plant biology topics, including photosynthesis, leaf structure adaptations, transport in xylem and phloem, transpiration, translocation, and environmental adaptations.

Photosynthesis

The endothermic chemical process by which plants use light energy trapped by chlorophyll to convert carbon dioxide and water into glucose and oxygen ($6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$).

Chloroplasts

Green disc-shaped organelles found inside plant cells where photosynthesis occurs.

Chlorophyll

A green pigment contained within chloroplasts that traps light energy transferred from the Sun.

Starch

An insoluble polymer into which plant cells convert glucose in order to store energy.

Sucrose

A soluble disaccharide carbohydrate converted from glucose that is transported through the phloem to other parts of the plant.

Cellulose

A complex carbohydrate polymer synthesized from glucose that plants use to build and strengthen cell walls.

Waxy Cuticle

A waterproof outer layer covering the leaf epidermis that prevents water loss and stops the entry of disease-causing microorganisms.

Palisade Cells

Specialized cells located near the upper surface of a leaf that are tightly packed with chloroplasts to absorb maximum light and carry out the most photosynthesis.

Spongy Mesophyll Layer

A layer of loosely arranged leaf cells containing air spaces that provide a large surface area for rapid gas diffusion to and from photosynthetic cells.

Stomata

Microscopic pores found predominantly on the lower epidermis of a leaf that permit carbon dioxide to enter and oxygen and water vapour to exit by diffusion.

Guard Cells

Specialized pairs of cells flanking each stoma that swell with water to become rigid and open the pore in the light, or shrink to close it and conserve water.

Limiting Factor

An environmental variable present in shortest supply that restricts the rate of a physiological process, such as photosynthesis, from increasing further.

Denaturation (Photosynthetic Enzymes)

The structural deformation of an enzyme's active site occurring at high temperatures (above $40\,^\circ\text{C}$), which prevents the substrate from binding and rapidly decreases the rate of photosynthesis.

Variegated Leaf

A leaf that contains white or pale areas lacking chlorophyll alongside green areas containing chlorophyll, used to prove chlorophyll is essential for starch synthesis.

Hydrogencarbonate Indicator

A pH indicator solution that detects changes in carbon dioxide levels, appearing yellow/orange at pH $7.6$ when $\text{CO}_2$ concentration is high and purple at pH $9.2$ when $\text{CO}_2$ is removed by photosynthesis.

Gas Syringe

A calibrated piece of laboratory equipment used to collect and accurately quantify the volume of oxygen gas produced by aquatic plants during photosynthesis rate experiments.

Inverse Square Law

The mathematical relationship stating that light intensity ($I_{\text{new}}$) is inversely proportional to the square of the distance ($d_{\text{new}}^2$) from the light source: $I_{\text{new}} = \frac{I_{\text{orig}} \times d_{\text{orig}}^2}{d_{\text{new}}^2}$.

Root Hair Cells

Specialized epidermal root cells possessing long, thin extensions that increase surface area and minimize diffusion distance for the absorption of water and mineral ions.

Active Transport (in Roots)

The energy-consuming process that moves mineral ions across the cell membrane from a low concentration in soil water into a higher concentration inside root hair cells.

Nitrates

Mineral ions absorbed from the soil by root hair cells that are necessary for plant cells to synthesize amino acids and proteins.

Phosphates

Mineral ions absorbed by plants from soil that provide essential components needed to construct DNA and other nucleic acids.

Magnesium

An inorganic mineral ion absorbed by roots that is required as a vital component for synthesizing the green photosynthetic pigment chlorophyll.

Xylem

Vascular tissue composed of hollow, non-living cell tubes with cell walls reinforced by lignin, responsible for transporting water and dissolved minerals one way upwards from roots to leaves.

Lignin

A woody, waterproof chemical polymer deposited into xylem cell walls that provides structural rigidity and prevents the tubes from collapsing.

Phloem

Vascular tissue composed of living sieve tube elements with perforated end walls that transport sucrose, amino acids, and other organic nutrients bidirectionally around the plant.

Sieve Plate

The perforated end wall separating individual phloem sieve tube cells that allows cytoplasm and dissolved solutes to flow directly from one cell to the next.

Companion Cells

Specialized nucleated cells adjacent to phloem sieve tube elements, packed with mitochondria to generate energy for actively loading and unloading sucrose.

Transpiration

The process involving water movement through a plant from the roots, up the stem, and its eventual evaporation from aerial parts, particularly through leaf stomata.

Transpiration Stream

The continuous, unbroken column of water pulled upward through xylem vessels due to the negative pressure created as water evaporates from leaves.

Potometer

A laboratory apparatus consisting of a capillary tube, water reservoir, and air bubble, used to estimate transpiration rate by measuring the rate of water uptake by a plant shoot.

Translocation

The active transport of organic solutes, especially sucrose, through phloem sieve tubes from photosynthetic source cells to storage or growth sinks via the pressure flow mechanism.

Rolled Leaf

A xerophytic leaf adaptation where the leaf rolls inward to trap moist, humid air around sunken stomata and hairs, reducing the concentration gradient and minimizing water loss.

Stimulus

Any detectable change in an organism's external or internal environment—such as light, water, or gravity—that evokes a specific functional response.