2.3 Plant Tissues , Organs and Systems Flashcards
How is epidermal tissue adapted for its function ?
Epidermal tissue covers the entire plant. It has a waxy cuticle which helps reduce water loss from the leaf surface.
The upper epidermis is transparent , this allows light to pass through to the photosynthetic cells below
How is palisade mesophyll tissue adapted for its function ?
Palisade mesophyll tissue contains lots of chloroplasts which allows photosynthesis to progress at a rapid rate.
How is spongy mesophyll tissue adapted for its function ?
Spongy mesophyll tissue has lots of air spaces which allow gases (including oxygen and carbon dioxide) to diffuse in and out.
How is the xylem adapted for its function ?
• Made up of dead cells which form a continuous hollow tube - allows the movement of water and mineral ions from the roots to the leaves. ( no upper or lower margins)
• Strengthened by lignin - makes the vessel strong and waterproof.
• Has bordered pits - allow minerals to be transported to specific places.
How is the phloem adapted for its function ?
• Made up of elongated living cells.
• Cells have sieve plates that connect them together - cell sap can move through plates into other cells.
• Sieve tube cells have few organelles to allow the efficient transport of substances.
- transports dissolved sugars from the leaves to the rest of the plant
How is meristem tissue adapted for its function ?
Made up of stem cells which can differentiate into many different cell types, allowing the plant to grow.
What tissues does the leaf organ contain ?
• Epidermis
• Palisade mesophyll
• Spongy mesophyll
• Xylem
• Phloem
• Guard cells
What is the function of guard cells ?
Guard cells control the opening and closing of the stomata, according to the water content of the plant.
How are stomata adapted for their function ?
Stomata allow the control of gaseous exchange and water loss from the leaf.
• More stomata on the base of the leaf - minimises water loss as this side is cooler and shaded.
• Have guard cells which control their opening and closing.
How are root hair cells adapted for their function ?
Root hair cells allow the uptake of water and mineral ions from the soil.
• Large surface area - maximises rate of absorption.
• Contain lots of mitochondria - release energy for active transport of mineral ions.
What is translocation?
Translocation is the movement of dissolved sugars from the leaves to other parts of the plant.
What is transpiration ?
Transpiration is the evaporation of water vapour from the surface of a plant.
How does transpiration work ?
• Water evaporates from the leaf surface via the stomata.
• Water molecules cohere together - more water is pulled up the xylem in an unbroken column.
• More water is taken up from the soil - creating a continuous transpiration stream.
How does temperature affect the rate of transpiration ?
Increasing the temperature increases the rate of transpiration.
• Higher rate of evaporation and diffusion of water - therefore rate of transpiration is increased.
How does humidity affect the rate of transpiration ?
Increasing relative humidity decreases the rate of transpiration.
• High relative humidity will reduce the water vapour concentration gradient. The rate of evaporation will decrease, and so will the rate of transpiration.
