BISC 121 - Plant Biology III - Midterm 3
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133 Terms
What do plants, like multicellular animals, have?
Organs composed of different tissues, which are in turn composed of cells.
What are the three basic organs that evolved in plants?
Roots, stems, and leaves.
How are the three basic organs organized in plants?
Into a root system and a shoot system.
What are the functions of roots?
Anchoring the plant, absorbing minerals and water, and often storing organic nutrients (e.g. think carrots, radishes…).
What is the main photosynthetic organ of most vascular plants?
The leaf.
What have some plant species evolved in terms of leaves?
Modified leaves that serve various functions.
What are examples of modified leaves?
Tendrils, spines, and bracts.
Where are apical meristems located?
At the tips of roots and in the buds of shoots.
What do apical meristems do?
Elongate shoots and roots, a process called primary growth.
What does primary growth produce?
The primary plant body, the parts of the root and shoot systems produced by apical meristems.
Where does secondary growth occur?
In stems and roots of woody plants but rarely in leaves.
What does the secondary plant body consist of?
The tissues produced by the vascular cambium and cork cambium.
What are the three developmental processes that produce the plant body?
Growth, morphogenesis, and cellular differentiation.
How do growth, morphogenesis, and cellular differentiation act?
In concert to transform the fertilized egg into a plant.
What adaptations were key steps in the evolution of vascular plants?
Adaptations for acquiring resources.
What is the function of shoots in vascular plants?
To capture light.
What is the function of roots in vascular plants?
To acquire water and nutrients.
On what three scales does transport in vascular plants occur?
Transport of water and solutes by individual cells, short-distance transport of substances from cell to cell at the levels of tissues and organs, and long-distance transport within xylem and phloem at the level of the whole plant.
Through what part of the plant do water and mineral salts from the soil enter?
Through the epidermis of roots.
To where do water and mineral salts ultimately flow?
To the shoot system.
Through what do water and minerals ascend from roots to shoots?
Through the xylem.
What do plants lose an enormous amount of water through?
Transpiration, the loss of water vapor from leaves and other aerial parts of the plant.
What must replace the transpired water?
Water transported up from the roots.
What regulates the rate of transpiration?
Stomata.
What characteristics of leaves increase photosynthesis and water loss?
Broad surface areas and high surface-to-volume ratios.
How can stomata control water loss?
They can be opened and closed.
What is translocation?
The transport of organic nutrients in a plant – generally from sources to sinks.
Through what structure is transport from the stem to roots carried out?
Through the phloem.
What is soil described as in Concept 37.1?
A living, complex ecosystem and a finite resource.
Why is rich soil essential?
It is essential for agriculture.
What can easily deplete rich soil?
Agricultural practices that lead to erosion, compaction, contamination, alteration of microbiota, and/or loss of nutrients.
Why are soil problems major global issues?
Many farms are rapidly depleting soil that was generated and accumulated over eons by grazing animals, periodic floods, etc.—processes that have virtually stopped.
Can quality soil be regenerated by chemical fertilizers or monocultures alone?
No, quality soil cannot be regenerated by addition of chemical fertilizers alone nor by growth of typical agricultural monocultures.
What effect do pesticides often have on soil organisms?
They often kill or inhibit beneficial soil organisms that create and maintain soil quality.
What is the goal of sustainable agricultural practices?
To maintain soil quality while permitting high long-term yield.
From where do plants derive most of their organic mass?
From the CO₂ of air.
On what do plants also depend besides CO₂?
Soil nutrients such as water and minerals.
What are the nutrients plants depend on?
Minerals, H₂O, and O₂.
What are macronutrients?
Essential nutrients required by plants in large amounts (there are also important micronutrients).
Which mineral often has the greatest effect on plant growth?
Nitrogen.
Why do plants require nitrogen?
As a component of proteins, nucleic acids, chlorophyll, and other important organic molecules.
What are the two types of mutualistic relationships plants have with other organisms?
Symbiotic nitrogen fixation (involving roots and bacteria) and mycorrhizae (involving roots and fungi).
What kinds of organisms are critical to plant nutrition besides bacteria?
Soil Archaea.
Who carries out the fixation of atmospheric nitrogen (N₂)?
Certain bacteria and archaea in soil and in special symbioses.
What other critical aspects of the nitrogen cycle are there?
Nitrification and denitrification.
Who dominates the first step of nitrification in many places?
Archaea (based on studies from 2004 to today).
What are nodules?
Swellings along roots of legumes composed of plant cells “infected” by nitrogen-fixing Rhizobium bacteria.
What form do Rhizobium bacteria assume inside root nodules?
Bacteroids, which are contained within vesicles formed by the root cell.
What do Rhizobium bacteria obtain from the plant?
Sugar.
What do Rhizobium bacteria supply the plant with?
Fixed nitrogen.
What are mycorrhizae?
Symbiotic structures consisting of plant roots united with fungal hyphae.
What must be considered when treating fungal pests on crops?
That fungi form mutualistic mycorrhizae with plant roots and are important for absorption of water and minerals.
What types of relationships does plant nutrition often involve?
Relationships with other organisms.