plant tissues Flashcards
(9 cards)
Why do multicellular plants need transport systems? (3)
Plants need to transport water minerals and sugars and return waste to the environment
They have a small surface area to volume ratio and a high metabolic rate
So direct diffusion would be too slow to meet their metabolic needs
What are the functions of xylem and phloem in plants? (2)
Xylem Transports water and mineral ions upward from roots to leaves
Phloem Transports sugars in solution both upwards and downwards throughout the plant
What is the structure and function of xylem in the roots? (2)
Xylem is arranged in an X-shape in the centre surrounded by phloem
This arrangement provides structural support for the root as it pushes through soil
How is the xylem structured in stems? (2)
Xylem is found on the inside of vascular bundles
Which are arranged in a ring around the stem with phloem on the outside and separated by cambium
How are xylem and phloem arranged in leaves? (2)
Xylem and phloem form a network of veins that support the leaves
With xylem on top and phloem on the bottom
What is the structure of xylem vessels? (3)
Xylem vessels are long tube-like structures made from dead cells with no end walls
Forming an uninterrupted tube for water transport
The walls are thickened with lignin which strengthens waterproofs and allows flexibility
What are pits in xylem vessels and what is their function? (2)
Pits are areas in the xylem walls with no lignin
Allowing water and ions to move in and out of the vessels
What is the structure of phloem vessels? (2)
Phloem is composed of sieve tube elements and companion cells
Sieve tube elements have no nucleus and few organelles and they are connected end-to-end with sieve plates
Allowing solutes to pass through
What is the function of companion cells in the phloem? (2)
Companion cells have a dense cytoplasm large nucleus and many mitochondria
They provide energy for active transport and other functions of the sieve tube elements
