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Mechanisms of absorption and movement of water and nutrients in plants.
Transport in plants refers to the mechanisms by which plants absorb and move water and nutrients from the soil to their leaves, stems, and roots. This process is crucial for plant growth, development, and survival. Understanding transport in plants helps us appreciate the complexity of plant biology.
Water absorption in plants occurs through the root hairs, which are specialized cells that increase the surface area for water uptake. The process is driven by osmosis, where water molecules move from an area of high concentration to an area of low concentration. In the roots, water enters the plant through the apoplast, a pathway outside the cell membrane, and then moves into the symplast, the internal compartment of the cell. This movement of water is facilitated by aquaporin proteins, which form channels across the cell membrane.
The xylem transport system is responsible for moving water and minerals from the roots to the leaves of a plant. It consists of tracheids, vessels, and xylem parenchyma cells. Water and minerals are absorbed by the root hairs and then transported upward through the xylem tissue via transpiration-driven flow. The cohesion-tension theory proposes that the water column in the xylem is maintained by hydrogen bonding between water molecules, allowing for the upward movement of water against gravity.
The phloem transport system is responsible for moving sugars and other organic compounds produced during photosynthesis from the leaves to the rest of the plant. It consists of sieve cells, companion cells, and phloem parenchyma cells. The movement of these compounds occurs through a process called mass flow, where the pressure-flow theory proposes that the movement of solutes creates a pressure gradient that drives the transport of sugars and other organic compounds.
Transpiration is the process by which plants release water vapor into the air through their leaves. It occurs through small openings called stomata, which are found on the surface of the leaf. The rate of transpiration is influenced by factors such as temperature, humidity, and light intensity. Transpiration plays a crucial role in the xylem transport system, as it creates a negative pressure that drives the upward movement of water from the roots to the leaves.
Osmosis is the process by which water molecules move through a selectively permeable membrane from an area of high concentration to an area of low concentration. In plants, osmosis plays a crucial role in maintaining water balance by regulating the movement of water into and out of cells. The turgor pressure generated by osmosis helps maintain the plant's structure and supports its growth.
The evolution of transport mechanisms in plants has been driven by selective pressures to optimize water and nutrient uptake, as well as to minimize water loss. The development of complex vascular tissues such as xylem and phloem allowed plants to colonize a wider range of environments and adapt to changing conditions.
What is the primary function of transpiration in plants?
What is the process by which plants absorb water molecules?
Which type of vascular tissue is responsible for transporting sugars and amino acids throughout the plant?
What is the term for the movement of water molecules from an area of high concentration to an area of low concentration?
What is the primary function of the phloem in plants?
What is the term for the process by which plants release water vapor into the air?
Which of the following is NOT a function of xylem in plants?
What is the term for the movement of solutes that drives the transport of sugars and other organic compounds in plants?
What is the term for the process by which water enters the plant through the root hairs?
What is the term for the type of vascular tissue responsible for transporting water and minerals from roots to leaves?
Discuss the importance of understanding transport mechanisms in plants. How do these mechanisms impact agriculture and our daily lives? (20 marks)
Describe the evolutionary pressures that drove the development of complex vascular tissues in plants. How do these tissues enable plants to colonize a wider range of environments and adapt to changing conditions? (20 marks)