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- sieve elements and
- companion cells.
Sieve elements are so-named because their end walls are perforated. This allows cytoplasmic connections between vertically-stacked cells. The result is a sieve tube that conducts the products of photosynthesis --- sugars and amino acids --- from the place where they are manufactured (a "source"), e.g leaves, to the places ("sinks") where they are consumed or stored; such as
- roots
- growing tips of stems and leaves
- flowers
- fruits, tubers, corms, etc.
Sieve elements have no nucleus and only a sparse collection of other organelles. They depend on the adjacent companion cells for many functions.
Companion cells move sugars and amino acids into and out of the sieve elements. In "source" tissue, such as a leaf, the companion cells use transmembrane proteins to take up --- by active transport --- sugars and amino acids from the cells manufacturing them. Water follows by osmosis. These materials then move into adjacent sieve elements by diffusion through plasmodesmata. The pressure created by osmosis drives the flow of materials through the sieve tubes.
In "sink" tissue, the sugars and amino acids leave the sieve tubes by diffusion through plasmodesmata connecting the sieve elements to the cells of their destination. Again, water follows by osmosis where it may
- leave the plant by transpiration or
- increase the volume of the cells or
- move into the xylem for recycling through the plant.
What else can I help you with?
What are four basic types of wave interactions?
deflection
Why do birds and mammals have four chambered heart?
Simple answer-The four chambered heart increases the efficiency of delivery of oxygenated blood to tissues by preventing mixing with deoxygenated blood
What four types of persitication?
There is no such thing as persitication
What is the scientific definition of tissue culture?
There are four main types of tissues in animals; epithelial, nervous, muscular, and connective.
What are the 4 main types of contamination?
There are four main categories of contamination. The four main types are water, dilute acids, dilute bases, and organic solvents.
What are the four basic types of tissues?
Two are the transport and the protective Epidermal, connective, storage, and support.
What four types of tissue found in the stomach?
There are four types of tissue that are found in the stomach. These tissues are epithelial, connective, muscle, and nervous tissues.
What are the four basic types of blood?
The four basic blood types are A, B, AB, and O.
How many tissues are found in the stomach?
There are four types
Types of monocotyledon plants?
four types
What are the four types of tissues?
Epithelia, Connective, Muscular and Nervous
What are not one of the four basic types of wave interactions?
One of the four basic types of wave interactions is diffraction, but reflection, refraction, and interference are.
How do the 4 basic tissue types support a healthy human body?
The four basic tissue types (epithelial, connective, muscle, and nervous) work together to support a healthy human body. Epithelial tissues form protective barriers and facilitate absorption and secretion, connective tissues provide structure and support to organs and tissues, muscle tissues enable movement and organ function, and nervous tissues transmit electrical signals for communication and coordination within the body. Together, these tissues maintain the overall structure, function, and homeostasis of the human body.
What is the meaning of tissues?
Tissue that can be pumped full of fluid to change its size, shape and turgidity.
Mention four types of ornamental plants?
Four types of ornamental plants might include grasses, ornamental trees like crepe myrtle, flowering plants, and fruiting plants.
What are the four plants types?
Nonvascular plants Ferns Gymnosperms Flowering Plants
What are the basic types of tissue in the body?
The four basic types of tissues in the body are epithelial, connective, muscle, and nervous tissue. Epithelial tissue covers and protects body surfaces, connective tissue supports and binds body parts together, muscle tissue allows for movement, and nervous tissue carries electrical impulses for communication.
