Chapter 5: Plant tissues, organs and organ systems Flashcards
What is the epidermis?
The outermost layer of cells of a plant. These cells have less chloroplasts, allowing more light to travel through them to the palisade mesophyll, which is directly under the epidermis
What are the functions of the epidermis?
Regulating gas exchange, preventing water loss, water and mineral uptake
What is the palisade mesophyll?
Tissue found below the epidermis. Cells in this layer are tightly packed, have a regular shape, and contain a large number of chloroplasts. This layer is the main site of photosynthesis
What is the spongy mesophyll?
Tissue found below the palisade mesophyll layer, near the bottom of the leaf. The cells in this layer are more spherical and have gaps between them, making them appear spongy. This layer contains large numbers of stomata
What are stomata?
Small pores found on the underside of a leaf that allow water vapour and gas to escape. Stomata have guard cells around them which control their size and the amount of gas leaving the plant
What is meristem tissue?
Tissue where stem cells are produced, which is found in shoot tips and root tips
What are roots?
Plant organs found below the soil. They are white due to the fact that they do not need to photosynthesise, so contain no chlorophyll. They absorb water by osmosis and minerals by active transport from the soil. They also anchor the plant to the ground. In some plants, they store glucose produced during photosynthesis
What are shoots?
Stem, leaves and buds all form a shoot. The tip of a shoot has meristem tissue
Describe the plant transpiration system
Water enters root hair cells by osmosis. It travels by osmosis through the cells of the root and into the xylem cells. It travels through the root and stem in long continuous columns of xylem cells. Eventually the xylem branches out to form veins that carry the water to the leaves. This water evaporates out of the spongy mesophyll cells and enters the leaf air spaces as vapour. It then diffuses out of the leaf through the stomata
What is the purpose of transpiration?
The constant evaporation of water from the leaves sucks up more water from the soil through the plant in a long, unbroken transpiration stream. Transpiration provides water to cells to keep them turgid and for photosynthesis. It also transports minerals to the leaves
What factors affect the rate of transpiration?
High rates of transpiration are achieved when:
There is more wind (air outside constantly being replaced)
There is a high temperature (more evaporation of water)
The air is less humid (steeper gradient)
The light intensity is high (more photosynthesis so water is used up more rapidly)
What happens during translocation?
Phloem tubes transport dissolved sugars made in the leaves to the rest of the plant
