Transport In Plants Flashcards
What do xylem vessels transport?
Water from roots to leaves for use in photosynthesis
What are the characteristics of xylem vessels?
Long, narrow, hollow tubes that are non-living and formed from columns of elongated cells
What happens to the cells that form xylem vessels?
The contents die, cross walls breakdown, and cellulose walls thicken with lignin
How does the structure of xylem vessels facilitate water movement?
Being long, narrow, and hollow with no cross walls allows continuous water flow
What is the role of lignin in xylem vessels?
Lignin provides toughness and strength, helping to support the plant
What is the primary composition of wood?
Almost entirely composed of lignified xylem vessels
List the three mechanisms by which water moves through a flowering plant.
- Root pressure
- Transpiration
- Capillarity
What is root pressure?
A push from the roots that moves water into the xylem
How does water enter root hairs?
By osmosis
What creates root pressure?
Water entering root hairs and moving through cortex cells
Define transpiration.
The loss of water vapour from the surface of leaves
What initiates the pull in transpiration?
Water evaporating from spongy mesophyll cells
How does capillarity assist in water movement?
Xylem vessels act like capillary tubes due to their narrowness
Fill in the blank: The cohesion between water molecules and the _______ of the molecules to the xylem walls helps water movement.
adhesion
True or False: Xylem vessels are living structures.
False
What are the three processes involved in the movement of water through a plant?
- Root pressure
- Transpiration
- Capillarity
What role do palisade cells play in relation to water?
They use some of the water for photosynthesis
What is the waxy cuticle?
A protective layer on the surface of leaves that reduces water loss.
What is the function of the upper epidermis?
It provides protection and helps reduce water loss from the leaf.
What is palisade mesophyll?
A layer of cells in the leaf where most photosynthesis occurs.
What is spongy mesophyll?
A layer of loosely packed cells in the leaf that facilitates gas exchange.
What is the role of the lower epidermis?
It contains stomata for gas exchange and helps control water loss.
What is a stoma?
A small opening on the leaf surface that allows for gas exchange.
What is the transpiration stream?
The flow of water through the xylem vessels from roots to leaves.
What is root pressure?
A push from the roots that helps move water up through the xylem.
How does water enter the root hairs?
Water enters by osmosis.
What happens during transpiration?
Water vapor is lost from the leaf surface, creating a pull that draws water up the xylem.
What is capillarity in plants?
The ability of water to move through narrow xylem vessels due to cohesion and adhesion.
How do guard cells control stomata?
They become turgid to open stomata and flaccid to close them.
What occurs when guard cells are turgid?
Stomata open, resulting in rapid transpiration.
What occurs when guard cells are flaccid?
Stomata almost close, resulting in slow transpiration.
What happens to guard cells when they take in water?
Guard cells take in water by osmosis and become turgid.
What is the structure of guard cells?
Guard cells have a thick inner wall that does not stretch and a thin outer wall that stretches when the guard cells become turgid.
What occurs when guard cells lose water?
Guard cells lose water by osmosis and become flaccid, causing the stomatal pore to almost close.
What happens to stomata when water supply in soil is low?
Stomata almost close to reduce water loss by transpiration and conserve water.
What is transpiration?
Transpiration is the process of water vapor diffusing out of the stomata of plants.
How does temperature affect transpiration?
High temperatures cause rapid transpiration due to increased evaporation and diffusion, while low temperatures cause slow transpiration.
How does humidity influence transpiration?
In low humidity, transpiration is rapid due to a high concentration gradient; in high humidity, transpiration is slow due to a low concentration gradient.
What effect does wind speed have on transpiration?
In windy conditions, transpiration is rapid as water vapor is carried away; in still conditions, transpiration is slow.
How does light intensity affect transpiration?
In bright light, stomata are fully open, allowing rapid transpiration; in dim light, stomata almost close, resulting in slow transpiration.
Why is transpiration important for plants?
Transpiration draws water up for photosynthesis, keeps cells turgid, moves minerals, and cools the plant.
Free
What is one method by which plants conserve water?
Leaves have extra-thick waxy cuticles to reduce the rate of transpiration.
What is the role of water in plants?
It draws water up to leaves for use in photosynthesis and supplies plant cells with water to keep them turgid, supporting non-woody stems and leaves.
What adaptations do terrestrial plants have to conserve water?
Terrestrial plants have developed adaptations such as reducing transpiration and storing water.
How do plants reduce the rate of transpiration?
Plants reduce transpiration by having extra-thick waxy cuticles, reduced numbers of stomata, and grouping stomata in sunken pits.
What happens to stomata during high temperatures?
Stomata almost close in the daytime if temperatures are very high.
How do some plants store water?
Plants can store water by rolling leaves with stomata to the inside, having fine hairs on their surface, and shedding leaves in dry seasons.
What are some examples of plants that store water?
Examples include succulent plants like aloe and cacti, which store water in their leaves and stems.
How do plants increase the uptake of water?
Plants increase water uptake through deep tap-roots, shallow widespread root systems, and storing water in roots.
What is the function of phloem sieve tubes?
Phloem sieve tubes transport organic food, mainly sucrose and some amino acids, from leaves to all other parts of the plant.
What are sieve tube elements?
Sieve tube elements are long, narrow tubes formed from columns of elongated cells with living cytoplasm but no nucleus.
What connects the cytoplasm of adjacent sieve tube elements?
The cytoplasm of adjacent sieve tube elements is connected through small holes in the sieve plates.
What is the role of companion cells in phloem?
Companion cells contain a nucleus that controls the functioning of both the companion cell and the adjacent sieve tube element.
What are stomata in sunken pits?
Stomata located in depressions on the leaf surface, reducing water loss.
What is a rolled leaf of marram grass?
A leaf adaptation that minimizes water loss by reducing surface area exposed to air.
What are succulent stems and needle-shaped leaves of cacti?
Adaptations that store water and reduce transpiration.
What is the function of phloem sieve tubes?
Transport organic food, mainly sucrose and some amino acids, from leaves to other parts of the plant.
What are sieve tube elements?
Long, narrow cells in phloem that contain living cytoplasm but no nucleus.
What are companion cells?
Cells adjacent to sieve tube elements that contain a nucleus and control their functioning.
What is translocation?
The movement of organic food through phloem sieve tubes.
What does the pressure flow hypothesis explain?
How dissolved sugars move from a sugar source to a sugar sink through a pressure gradient.
What are sugar sources?
Parts of plants that produce or release sugars, such as photosynthesizing leaves or storage organs.
What are sugar sinks?
Parts of plants that require sugars, including stems, roots, and fruits.
How do sugars move from sugar sources to sieve tubes?
Through active transport, increasing sugar concentration in the sieve tubes.
What happens to turgor pressure in sieve tubes?
It increases due to water entering, pushing sugars through the sieve tubes.
How do sugars move from sieve tubes to sugar sinks?
By active transport, decreasing sugar concentration in the sieve tubes.
What role does osmosis play in the movement of water and sugars?
Water follows sugars by osmosis, affecting turgor pressure in sieve tubes.
What creates the pressure gradient in phloem?
The difference in pressure between sugar sources and sinks.
