3.2 Specialisation and organisation of plant cells Flashcards
What is meristematic tissue of a plant?
Meristematic tissues are made of cells that can undergo cell division and continue to divide for life of the plant. Found in tips of roots and sheets and is responsible for increase in length of plant stems and roots.
What is dermal tissue of a plant?
Dermal tissue protects plants and minimises water loss. E.g epidermal tissue made of flattened cells forms the outer layer of stems and leaves.
Transpiration can only occur given?
Loss of water will occur provided a concentration gradient exists between the water content of the leaf (high) and in the air outside the leaf (low).
Why are plants forced to go through such a wasteful process of water loss?
Plants have to go through such a wasteful process because leaves are the site of photosynthesis and in order to make sugars CO2 is required which is captured from the atmosphere . The entry point of CO2 to a leaf is via open stomata. For every CO2 molecule approx 400 Water molecules leave which means if if we stop transpiration we are stopping photosynthesis as CO2 can’t be captured however when stomata are left open plant falls risk of dehydration.
What happens to the two guard cells of the stomata when photosynthesis is occurring?
In sunlight when photosynthesis is occurring the guard cells take up water and swell , resulting in the opening of the stomata .
What happens to the two guard cells of the stomata in the dark?
In dusk, when there is no sunlight , so photosynthesis can’t occur and thus co2 is not needed , when CO2 not needed the guard cells shrink and lose water the stomata close and H20 loss is prevented.
What is the function of the stomata and where are they located?
They are the site of CO2 uptake and loss of water and they are located in the lower epidermis of leaves.
What is adhesion?
The attraction of water molecules to some surfaces.
E.g meniscus
What is cohesion?
The attraction of water molecules to other water molecules?
What happens if water column in one set of xylem tubes break?
The water is replaced by air and that set of tubes become useless for any further water transport.
What is the root system of plants and what is to responsible for?
The root system is the below-ground system of plants which anchors the plant in the soil.
It is responsible for the absorption and conduction of water minearals and the excess storage of sugars ( starch)
What is the shoot system and what is its main function?
The shoot systems the above ground system of plants.
It is the site of photosynthesis and the site of reproductive organs.
Describe the arrangement of the major types of permanent tissue in a vascular plant?
Dermal forms the epidermis layer.
Ground forms the majority of the internal tissue that encloses more bundles of vascular tissue.
Describe how the absorption of water takes place in plants?
The absorption and uptake of liquid water takes place through root hairs. Water enters the root hairs from the soil solution via osmosis.
What are some differences between tracheas and vessels?
Similarities:
Both tracheids and vessels are part of the xylem tissue
Both tracheids and vessels are elongated cells that have lignified walls, which provide strength and support to the plant.
Both tracheids and vessels are dead at maturity.
Both responsible for conduction of water.
Differences:
Tracheids are long and thin cells with tapered ends. They are found in all vascular plants. - Tracheids have pits, which are areas where the lignified walls are thin and allow for the lateral movement of water.
Vessels are wider and shorter cells that are found only in flowery plants.. have perforations at their ends, which allow for more efficient water movement. Vessels do not have pits like tracheids do.
