Ch 27: Plant Form, Function, and Evolutionary History Flashcards
Desiccation
Excessive water loss; drying out.
Desiccation Tolerance
A suite of biochemical traits that allows cells to survive extreme dehydration by minimizing damage to membranes and macromolecules.
Lycophytes
A monophyletic group of spore-dispersing vascular plants that are the sister group to all other vascular plants.
Ferns and Horsetails
A monophyletic group of vascular plants in which both the gametophyte and sporophyte generations are free living and that disperse by spores.
Gymnosperms
Seed plants whose ovules are not enclosed in a carpel; gymnosperms include pine trees and other conifers, as well as cycads, gnetophytes, and ginkgo.
Angiosperms
The flowering plants; a monophyletic group of seed plants characterized by flowers, double fertilization, and fruits.
Shoots
The collective name for the leaves, stems, and reproductive organs; the major aboveground organ systems of vascular plants.
Epidermis
In mammals, the outer layer of skin, which serves as a water-resistant, protective barrier. In plants, the outermost layer of cells in leaves, young stems (lacking secondary growth), and roots. In general, the outer layer of the body.
Vascular Tissue
A plant tissue that extends from leaves to roots and allows water and nutrients to move by bulk flow.
Xylem
Vascular tissue consisting of lignified conduits that transports water and nutrients from the roots to the leaves.
Phloem
The vascular tissue that transports carbohydrates from leaves to the rest of the plant body.
Ground Tissue
In plants, all tissues other than the epidermis and vascular tissues.
Parenchyma
In plants, describes thin-walled cells that carry out a variety of functions, including photosynthesis and storage; capable of further cell division if stimulated.
Mesophyll
A leaf tissue of loosely packed photosynthetic cells.
Veins
In plants, the system of vascular conduits within the leaf; in animals, the large, low-pressure vessels that return blood to the heart.
Transpiration
The loss of water vapor from leaves.
Cuticle
In plants, a protective layer of a waxy substance secreted by epidermal cells that limits water loss; in animals, an exoskeleton that covers the bodies of invertebrates such as nematodes and arthropods.
Stomata
Pores in the epidermis of a leaf that regulate the diffusion of gases between the interior of the leaf and the atmosphere.
Guard Cells
One of two cells surrounding the central pore of a stoma.
Crassulacean acid metabolism (CAM)
A mechanism in plants that helps balance carbon dioxide gain and water loss by capturing carbon dioxide into 4-carbon organic acids at night, when transpiration rates are low, and then using it to supply the Calvin cycle during the day while stomata remain closed.
C4 Plants
A plant in which carbon dioxide is incorporated into 4-carbon organic acids in mesophyll cells that are then used to supply the Calvin cycle in bundle sheath cells; results in the suppression of photorespiration.
C3 Plants
A plant that does not use 4-carbon organic acids to supply the Calvin cycle with carbon dioxide.
Tracheids
A unicellular xylem conduit.
Vessels
A multicellular xylem conduit.
Vessel Element
An individual cell that is part of a xylem vessel for water transport in plants.
Water Potential
A parameter that combines all of the factors that influence the movement of water, such as pressure, osmosis, and gravity.
Cavitation
The abrupt replacement of liquid water in a xylem conduit by water vapor, which prevents water from being pulled through the xylem by transpiration.
Sources
In plants, a region that supplies carbohydrates to other parts of the plant.
Sinks
In plants, any portion of the plant that imports carbohydrates to fuel growth and respiration, such as a root, young leaf, or developing fruit.
Companion Cells
In angiosperms, a cell that carries out cellular functions such as protein synthesis for sieve tubes.
Phloem Sap
The sugar-rich solution that flows through both the lumen of the sieve tubes and the sieve plate pores.
Sieve Tubes
A multicellular unit composed of sieve elements that are connected end to end, through which phloem transport takes place.
Sieve Plates
In angiosperm phloem, a modified end wall with large pores that links sieve elements.
Rhizosphere
The soil layer that surrounds actively growing roots.
Root Hairs
A slender outgrowth produced by epidermal cells that greatly increases the surface area of the root.
Cortex
In a stem, the region between the epidermis and the vascular bundles, composed of parenchyma cells. In the mammalian brain, the highly folded outer layer of gray matter, about 4 mm thick, made up of densely packed neuron cell bodies and their dendrites. In the mammalian renal system, the outer layer of the kidney.
Endodermis
In plants, a layer of cells surrounding the xylem and phloem at the center of the root that controls the movement of nutrients into the xylem. Also, the inner lining of the cnidarian body.
Casparian Strip
A band of hydrophobic material that encircles each cell of the endodermis of a root, forcing water and solutes to reach the xylem by passing through the cytoplasm of endodermal cells.
Mycorrhizae
Fungi that live symbiotically among roots, enhancing nutrient uptake by the plants.
Ectomycorrhizae
One of the two main types of mycorrhizae; ectomycorrhizae produce a thick sheath of fungal cells (hyphae) that surround the root tip, as well as hyphae that grow between, but do not penetrate, cells in the interior of the root.
Endomycorrhizae
One of the two main types of mycorrhizae; endomycorrhizal hyphae penetrate into root cells, where they produce highly branched structures (arbuscules) that provide a large surface area for nutrient exchange.
Nitrogen Fixation
The process by which some Bacteria and Archaea convert nitrogen gas (N2) into ammonia (NH3), a form biologically useful to primary producers.
Root Nodule
A structure, formed by dividing root cells, in which nitrogen-fixing bacteria live.
T/F: Like bryophytes, the leaves of most angiosperms demonstrate desiccation tolerance and can survive long periods without water.
False
T/F: Tracheids are short and narrow, whereas vessel elements can be much longer and wider.
True
The forces that result in bulk flow of phloem sap originate when _____ is actively pumped into the phloem from _____ cells in the leaf, which causes _____ to enter via _____.
sugar; mesophyll; water; osmosis
T/F: Root activities supporting water transport are all passive, requiring no additional energy.
False
Vascular plants store most carbohydrate reserves as:
starch
Xylem sap and soil water differ in _____ because of _____.
solute composition; selective uptake by the endodermis
why there are abundant air spaces between mesophyll cells in leaves?
because CO2 diffusion is faster in air than in water
The structure(s) that allow gases, such as CO2, to diffuse into and out of a leaf are the:
Stomata
Photorespiration _____ O2 and _____ CO2.
consumes; releases
In vascular plants, water transport works only if:
the water column is continuous between leaves and soil.
Why may young leaves that are just emerging from the bud be considered sinks for phloem transport?
They consume more carbohydrates than they produce.
Why do plants need an endodermis in their roots?
to provide selectivity of ions entering the xylem
Vascular plants hydrate photosynthetic cells using _____, whereas bryophytes do so using _____.
soil water; surface water
How do bryophytes avoid damage to their tissues from a dry environment?
Their membranes and macromolecules are able to withstand desiccation and rehydration of the cells without damage.
Water flows from vessel to vessel through pits, which are:
primary cell walls that separated the neighboring cells as they grew.
Xylem transports _____, whereas phloem transports _____.
water; sugars
In the early 20th century, an experiment was conducted to determine how large the forces are that allow leaves to pull water from the soil. The rate at which water flowed from a reservoir into the cut tip of an actively transpiring plant was _____ the flow rate through the branch tip when it was subsequently attached to a vacuum pump.
greater than
Water is transported from the soil to the leaves in the:
xylem
