Topic 6: Plant Structures and Their Functions Flashcards
What are auxins?
A group of plant hormones that inhibit growth in plant roots and stimulate growth in shoot tips. They are involved in plant tropisms and are used in rooting powders and selective weedkillers.
What is biomass?
The total mass of organic material, measured in a specific area over a set period.
What is ethene?
A hormone that stimulates ripening in fruit.
What are gibberellins?
Plant hormones that regulate germination and flowering. They can be used commercially to control flower and fruit formation or to produce seedless fruits.
What is gravitropism?
A plant’s growth response to gravity.
What are guard cells?
Cells that surround the stomata and change shape depending on the volume of water. They control the rate of transpiration by becoming turgid or flaccid, opening or closing the stomata.
What is the inverse square law?
Light intensity is inversely proportional to the square of the distance from the light source: Light Intensity = 1/distance²
What is lignin?
A material that strengthens the walls of xylem cells.
What is a limiting factor?
A variable that limits the rate of a particular reaction.
What is the lower epidermis?
A layer of cells on the leaf’s lower surface that contains stomata and guard cells.
What is negative plant tropism?
The growth of a plant away from a stimulus.
What is the palisade mesophyll layer?
The main photosynthetic tissue in plants located below the upper epidermis. It receives the most light so contains the greatest concentration of chloroplasts.
What is phloem?
A transport tissue found in plants that is specialised to transport sugars from the leaves to the rest of the plant in both directions.
What is photosynthesis?
An endothermic reaction that takes place inside photosynthetic organisms (e.g. plants, algae) and converts light energy into chemical energy. Overall: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
What is phototropism?
A plant’s growth response to light.
What is plant tropism?
The growth response of a plant to a stimulus.
What is positive plant tropism?
The growth of a plant towards a stimulus.
What are producers?
Photosynthetic organisms (e.g. green plants or algae) at the start of the food chain that provide biomass for all living things.
What are root hair cells?
Specialised cells responsible for the uptake of water and minerals from the soil. They have long hair-like extensions known as root hairs, which provide a large surface area for absorption.
What are rooting powders?
A powder containing auxins that stimulates the growth of roots in cuttings. This enables rapid plant cloning.
What is the spongy mesophyll layer?
A type of loosely packed mesophyll tissue with air pockets which is specialised for gas exchange. It also contains some chloroplasts for photosynthesis.
What are stomata?
Small holes found on the surface of a plant that can be opened or closed by guard cells to control water loss and gas exchange.
What is translocation?
The movement of sugars (sucrose, amino acids, etc.) up and down a plant, from photosynthetic to non-photosynthetic tissues, via the phloem. Requires energy.
What is transpiration?
Water loss from plant leaves and shoots via diffusion and evaporation. The rate of transpiration is affected by light intensity, temperature and air flow.
What is the upper epidermis?
A layer of transparent cells that allows light to strike the palisade mesophyll tissue.
What is a vascular bundle?
Part of the transport system in vascular plants that consists of xylem and phloem tissue.
What is a waxy cuticle?
A waxy layer that reduces water loss from the surface of leaves.
What is xylem?
A transport tissue in plants that is specialised to transport water and dissolved minerals from the roots of the plant to the leaves.
