Unit 5 Flashcards
What are the 3 main types of plant tissue and where are they found?
The 3 main types are dermal, vascular, and ground tissues, which are all found in all plant organs (roots, stems, and leaves).
Describe the dermal tissues.
Dermal tissues consist of the epidermis, cuticle to prevent water loss from the epidermis, and specialized epidermal cells called guard cells that facilitate gas exchange in shoots.
Describe vascular tissue.
Vascular tissue facilitates the transport of materials through the plant and provides mechanical support. There are two types of vascular tissue: xylem and phloem.
Describe ground tissue.
Tissues that are neither dermal nor vascular are the ground tissue system. Ground tissue includes cells specialized for storage, photosynthesis, support, and transport. There are three main types of cells in ground tissue - parenchyma, collenchyma, and sclerenchyma.
What are roots?
A root is an organ that anchors the plant, absorbs minerals and water, and stores carbohydrates. The primary root emerges first and branches to form lateral roots, which improve anchorage and water absorption
In most plants, absorption of water and minerals occurs primarily near the tips of roots. Root hairs, finger-like extensions of epidermal cells, form near the root tip and increase the absorptive surface of the root.
What are stems?
A stem is a plant organ consisting of an alternating system of nodes, the points at which leaves are attached
internodes, the stem segments between nodes. The growing shoot tip, or apical bud, causes the elongation of a young shoot. An axillary bud is a structure that has the potential to form a lateral branch, thorn, or flower. The primary function of the stem is to elongate and orient the shoot to maximize photosynthesis.
What are leaves?
The leaf is the main photosynthetic organ of most vascular plants. Leaves intercept light, exchange gases, dissipate heat, and defend the plant from herbivores and pathogens. Leaves generally consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem
Put the components of the pressure flow theory of phloem transport in order.
- Companion cells load sugar from a sugar source to sieve tube through active transport. This increases the solute concentration in the sieve tube.
- Water moves by osmosis from the xylem into adjacent phloem and creates high pressure.
- High pressure near sources drives phloem sap through sieve tubes toward areas of low pressure.
- Companion cells unload sugar from phloem into sink cells (could be fruit, which uses active transport, or growing cells, which uses passive transport). This increases the osmotic potential of the sieve tube.
- Water moves by osmosis from phloem to xylem or other adjacent tissues and creates low pressure.
Describe the order of water and nutrients going through xylem.
- Most water and mineral absorption occurs near root tips, where root hairs are located and the epidermis is permeable to water. After soil solution enters the roots, the extensive surface area of cortical cell membranes enhances uptake of water and selected minerals
Active transport enables essential minerals to accumulate at much higher concentrations in roots compared to the surrounding soil. - The endodermis is the innermost layer of cells in the root cortex that surrounds the vascular cylinder and is the last checkpoint for selective passage of minerals from the cortex into the vascular tissue.
- The negative pressure in the top of the plant (leaves) drives the movement of water and solute up the xylem tissues.
What is Bulk flow?
Water and solutes move through xylem vessels and sieve tubes by bulk flow, the movement of a fluid driven by pressure. In phloem, for example, hydrostatic pressure generated at one end of a sieve tube forces sap to the opposite end of the tube. In xylem, it is actually tension (negative pressure) that drives long-distance transport. Transpiration, the evaporation of water from a leaf, reduces pressure in the leaf xylem.
This creates a tension that pulls xylem sap upward from the roots.
Bulk flow is driven by a water potential difference at opposite ends of xylem tissue. Bulk flow is driven by transpiration and does not require energy from the plant. Bulk flow is driven by differences in pressure potential, not solute potential.
Explain the Cohesion-Tension Theory and the role of water potential in plant water transport
According to the cohesion-tension hypothesis, transpiration and water cohesion pull water from shoots to roots. Xylem sap is normally under negative pressure, or tension. Water vapor in the air spaces of a leaf diffuses down its water potential gradient and exits the leaf via stomata. As water evaporates, the air-water interface retreats into the mesophyll cell walls. The surface tension of water at the air-water interface creates a negative pressure potential. Negative pressure potential lowers water potential. Water molecules are pulled from more hydrated areas of the leaf by the negative pressure potential created at the air-water interface. The cohesion of water molecules transfers the pulling forces to the water in the xylem.
What is the difference between an open and closed circulatory system?
In insects, other arthropods, and some mollusks, circulatory fluid called hemolymph bathes the organs directly in an open circulatory system. In a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid. Annelids, cephalopods, and vertebrates have closed circulatory systems
What is a circulatory system composed of?
A circulatory fluid, a set of interconnecting vessels, and a muscular pump, the heart
Describe the organization of the circulatory system in vertebrates.
The three main types of blood vessels are arteries, veins, and capillaries (blood flow is one way in these vessels). Arteries branch into arterioles and carry blood away from the heart to capillaries. Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid. Venules converge into veins and return blood from capillaries to the heart. Arteries and veins are distinguished by the direction of blood flow, not by O2 content. Vertebrate hearts contain two or more chambers. Blood enters through an atria and is pumped out through ventricles.
Describe single circulation.
In single circulation, blood travels and returns to its starting point in a single loop. First oxygen poor blood leaves the ventricle to the gills, where oxygen is diffused into the blood. The oxygen rich blood moves through the body capillaries. The oxygen poor blood moves through the veins back to the atria. Single circulation is found in sharks, rays, and bony fish that all have 2 chambers.
