IB Biology: CH: 13 Plants

Gas exchange

Absorption of carbon dioxide and excretion of oxygen.

Waxy cuticle

Outer leaf layer preventing water loss.

Stoma

Pores for gas exchange in leaves.

Guard cells

Cells regulating stoma opening and closing.

Transpiration

Loss of water vapor from plant surfaces.

Palisade mesophyll

Upper leaf layer with chloroplast-rich cells.

Spongy mesophyll

Lower leaf layer with air spaces for gas exchange.

Xylem

Tissue transporting water in plants.

Phloem

Living cells transporting organic molecules.

Stomatal density

Number of stomata per unit area.

Transpiration pull

Tension generated by water movement in xylem.

Capillary action

Movement of water due to adhesion and cohesion.

Lignin

Compound strengthening xylem cell walls.

Dicotyledonous plant

Plant with two seed leaves.

Cambium

Tissue producing xylem and phloem cells.

Cortex

Outer layer aiding in support and storage.

Endodermis

Inner layer regulating water and nutrient uptake.

Root pressure

Pressure generated by active transport in roots.

Humidity effect

Higher humidity reduces transpiration rates.

Tension

Pulling force generated by water movement.

Air spaces

Spaces in spongy mesophyll facilitating gas exchange.

Root Pressure

Mechanism refilling xylem sap when air-filled.

Sieve Tubes

Channels for sap transport developed from cells.

Sieve Plates

Perforated structures facilitating sap flow.

Companion Cells

Support sieve tubes, facilitating transport processes.

Plasmodesmata

Cytoplasmic connections between companion and sieve cells.

Translocation

Movement of sucrose from source to sink.

Source

Tissues producing compounds via photosynthesis.

Sink

Tissues requiring substances for growth or storage.

Pressure-Flow Hypothesis

Model explaining sap movement in phloem.

Hydrostatic Pressure

Pressure from water uptake in sieve tubes.

Positive Tropism

Growth direction towards a stimulus, like light.

Negative Tropism

Growth direction away from a stimulus, like gravity.

Positive Phototropism

Shoot growth towards light source.

Phytohormones

Hormones regulating plant growth and development.

Gibberellin

Hormone promoting stem elongation and growth.

Auxin

Hormone influencing cell elongation and growth direction.

Auxin Efflux Carriers

Proteins transporting auxin across cell membranes.

Cytokinin

Hormone promoting cell division and growth.

Synergism

Interaction where auxin and cytokinin enhance growth.

Antagonism

Interaction where auxin and cytokinin inhibit each other.

Ethylene

Gas hormone that regulates fruit ripening.

Positive Feedback

Process where ripening fruit produces more ethylene.

Pollen Grain

Structure containing male gametes for fertilization.

Carpel

Female reproductive part of a flower.

Stigma

Sticky part of carpel capturing pollen.

Ovary

Part of carpel that develops into fruit.

Zygote

Fertilized egg resulting from male and female gametes.

Embryo

Developing plant from fertilized egg.

Hermaphrodite

Plant with both male and female reproductive parts.

Dioecious Plants

Plants with separate male and female flowers.

Pollination

Transfer of pollen from anther to stigma.

Self-Pollination

Pollen from the same plant fertilizes the ovule.

Self-Incompatibility

Mechanism preventing inbreeding in plants.

Seed Dispersal

Movement of seeds away from parent plant.

Germination

Process where seeds sprout and grow: needs oxygen, water, and correct temperature

Nectaries

Glands secreting nectar to attract pollinators.

Hybrid Vigor

Increased health from cross-pollination.

Wind Dispersal

Seed dispersal mechanism using wind currents.

Potometer

a device used for measuring the rate of water uptake of a plant due to photosynthesis and transpiration. Conditions to change: humidity, light intensity, temperature, wind