9.1 - Transport systems in dicotyledonous plants Flashcards
Why do multicellular plants need transport systems?
Plants need transport systems to move substances such as water, glucose, oxygen, mineral ions, nutrients, and hormones between leaves, stems, and roots.
How do the pressures in plant transport systems compare to other systems?
The pressure in the phloem, one of the main transport tissues in plants, is around 2,000 kPa, which is much higher than the 16 kPa pressure in human arteries but lower than the 4,000 kPa pressure in steam turbines of power stations.
How does the pressure in plant transport systems remain contained?
The high pressures in plants are confined to much smaller spaces than those in human arteries or steam turbines, allowing efficient transport without structural damage.
What are the three main reasons plants need transport systems?
1) Metabolic demands
2) Large size
3) Small surface area to volume ratio (SA:V).
How do metabolic demands create a need for transport systems in plants?
Some parts of the plant, like underground roots, cannot photosynthesize, so they rely on transport systems to receive glucose and oxygen. Waste products also need to be removed.
What role do mineral ions play in plant metabolism?
Mineral ions absorbed by roots are transported to all cells to help produce proteins necessary for enzyme function and cell structure.
Why do hormones need to be transported in plants?
Hormones made in one part of the plant must be transported to other areas where they regulate growth and development.
How does plant size affect the need for transport systems?
Many plants, especially perennial plants, grow to large sizes and need efficient transport systems to move substances between roots, stems, and leaves.
What are some of the tallest plant species in the world?
The Coastal Redwood and Giant Redwood in the USA (up to 115m tall) and the Mountain Ash in Australia (114m tall).
How does the surface area to volume ratio (SA:V) affect transport in plants?
Although leaves have a large SA:V ratio for gas exchange, the overall plant structure (including stems, trunks, and roots) has a relatively small SA:V ratio, limiting diffusion efficiency.
Why can’t plants rely on diffusion alone to transport substances?
Due to their large size and small SA:V ratio, diffusion alone is too slow to supply all cells with nutrients and remove waste effectively.
Where are the vascular bundles located in the stem of a young herbaceous plant?
The vascular bundles are arranged around the edge of the stem to provide strength and support.
What tissues are found in the vascular bundle of a plant stem?
The vascular bundle contains xylem, phloem, and parenchyma (packing and supporting tissue).
What is the function of parenchyma in the plant stem?
Parenchyma acts as packing and supporting tissue, helping maintain the plant’s structure.
How are the vascular bundles arranged in the root of a young herbaceous plant?
They are centralized in the middle of the root to help withstand the tugging forces caused by wind and movement.
What are the key tissues found in a plant root cross-section?
Epidermis, exodermis, endodermis, cortex, xylem, and phloem.
What is the function of the endodermis in a plant root?
The endodermis regulates water and mineral uptake into the xylem via the Casparian strip.
What role do root hairs play in plant roots?
Root hairs increase surface area for efficient water and mineral absorption from the soil.
What is the main vascular structure in a dicot leaf?
The midrib, which contains the vascular bundle (xylem and phloem) and provides support.
How is the vascular bundle arranged in a dicot leaf?
Xylem is positioned on top, and phloem is positioned below within the vascular bundle.
What is the function of the palisade mesophyll in the leaf?
It is the main photosynthetic tissue, containing many chloroplasts for maximizing light absorption.
Why does a leaf need small branching veins?
Small veins help in transporting water, sugars, and nutrients while also providing structural support.
What are dicotyledonous plants (dicots)?
Dicots are plants that produce seeds with two cotyledons, which act as food stores for the developing embryo and form the first leaves during germination.
What are the two main types of dicotyledonous plants?
1) Herbaceous dicots – soft tissues, short life cycles.
2) Woody (arborescent) dicots – hard lignified tissues, long life cycles (some lasting hundreds of years).
What type of dicot plants are studied in this topic?
Herbaceous dicots, which have vascular bundles running through their stems, roots, and leaves.
What is the vascular system in dicots?
A network of transport vessels that run through the stem, roots, and leaves to move substances efficiently.
What are the two main transport vessels in dicot plants?
1) Xylem – transports water and minerals.
2) Phloem – transports organic substances like sugars (sucrose).
How are xylem and phloem arranged in herbaceous dicots?
They are arranged together in vascular bundles, found in the stems, roots, and leaves.
How is the vascular tissue arranged in the stem of a dicot?
Vascular bundles are positioned around the edge to provide strength and support.
How is the vascular tissue arranged in the roots of a dicot?
Vascular bundles are in the center, helping the plant withstand pulling forces from wind and movement.
How is the vascular tissue arranged in the leaves of a dicot?
The midrib contains the main vascular bundle, with branching veins that help in transport and structural support.
