Second Exam: Plants Flashcards
How do plants obtain most of their water and minerals?
From their roots via the upper soil layers
What are the basic physical properties of soil!
Texture and composition
What does soil texture describe?
The inorganic solid phase of soil
What is soil texture determined by?
The ratio of clay, silt, and sand
What does soil composition describe?
Both the inorganic and organic chemical components of soil
What are the organic components of soil also called?
Humus
What are the inorganic components of soil also called?
Mineral
What are the organic components of soil formed by?
The decomposition of living things
What do the organic components of soil do to the soil?
Organic components increase the soil’s capacity to exchange cations
Where are the inorganic components of soil typically more abundant?
Near bedrock
What do cations do in the soil?
They adhere soil particles which prevents leaching
What does cation exchange in soil do?
It enables plant uptake of cations by roots
What are 3 examples of sustainable agricultural practices?
Drip-irrigation, terraced agriculture, and crop rotation
What are the two categories of essential elements for plants?
Macro and micronutrients
What are macronutrients?
Nutrients needed in large quantities
How many essential elements are there?
17
How many essential elements are macronutrients?
9
Plants and soil microbes have a _______ relationship
Mutualistic
What do nitrifying bacteria do?
They convert stuff into NO3-
What converts stuff into NO3-?
Nitrifying bacteria
What do ammonifying bacteria and nitrogen fixation do?
They convert stuff into NH4+
What converts stuff into NH4+?
Ammonifying bacteria and nitrogen fixation
What are mycorrhizae?
Mutualistic associations of fungi and roots
What are the two types of mycorrhizae?
Ectomycorrhizae, and Arbuscular Mycorrhizae
Which type of mycorrhizae is more common?
Arbuscular mycorrhizae
What is ectomycorrhizae?
When the fungi go in between the cell walls of the root cells
What is arbuscular mycorrhizae?
When the fungi actually go inside the root cells
Describe why mycorrhizae is mutualistic
The fungi benefit because they get sugar from the roots, and the plant benefits because the fungi help it grow more roots
What are three types of plants that have nutritional adaptations that use organisms in a non-mutualistic way?
Epiphytes, parasitic plants, and carnivorous plants
What are epihphytes?
Plants that use other plants as structure
What are parasitic plants?
Plants that live on other plants and their nutrients (they steal their sugars and structure)
What are carnivorous plants?
Plants that eat bugs or rodents
Why are carnivorous plants carnivorous?
Because they adapted to live in nutrient-poor soil by getting their nutrients from animals instead of the soil
What does the root system of a plant do?
It supports the plant, and absorbs water and minerals
What is the shoot system of a plant comprised of?
Vegetative/ non-reproductive portions of the plant, such as the leaves and stems
What is the reproductive system of a plant comprised of?
Flowers and fruits
What three tissues make up the ground tissue system?
Parenchyma, collenchyma, and sclerenchyma
What do ground tissues do?
They do metabolism, storage, and support activities
Where are the ground tissues located?
In the stem
What are parenchyma cells?
They’re an undifferentiated cell that contains organelles and a primary cell well
What are collenchyma cells?
They’re similar to parenchyma cells, however, they’re differentiated and have thickened cell walls to provide support
What are sclerenchyma cells?
They have a continuous secondary cell wall and a primary cell wall, and they provide more support and strength to cells (along with xylem and phloem)
What are the two types of sclerenchyma cells?
Fibers and sclerids
What are fibers (in the stem)?
A type of sclerenchyma cell that is long and slender
What are sclerids?
A type of sclerenchyma tissue that is often spherical shaped and branched
Where is the xylem located?
At the very center of the stele, and often has two or more extensions
Which is bigger in diameter: xylem or phloem?
Xylem
What does the Xylem do, and where is this conducted?
It carries water and minerals upwards, which is conducted in tracheids and vessel elements
Describe tracheids
A part of the xylem that is long and narrow, with end walls that are perforated with pits to allow water to move from cell to cell
Where is the phloem located?
Between xylem arms
What does the phloem do, and what specifically does this?
The phloem’s sieve tube elements move dissolved sucrose down from the leaves and to the rest of the plant
Where is the vascular cambium located?
Inbetween the xylem and phloem
What is the vascular cambium designed to do?
It makes roots wider
What does the epidermis do in above ground plant organs?
It’s involved with gas exchange
What does the epidermis do in below ground plant organs?
It’s involved with water and ion uptake
What does the epidermis do in all parts of the plant?
It protects soft tissues and controls interactions with the plant’s surroundings
What does primary growth increase?
The length of the plant
What does secondary growth increase?
The width of the plant
Where does primary growth occur?
At the apical meristems, which are at the root’s tips, as well as the shoots and within the buds of stems
What types of plants does secondary growth occur in?
Woody plants
What type of plants does primary growth occur in?
All plants
What does secondary growth do?
It adds wood and bark
Where does secondary growth occur?
At the lateral meristems at the vascular cambium and cork cambium
What’s the difference between apical and lateral meristems?
The apical meristem is involved with primary growth, and the lateral meristem is involved with secondary growth
What are taproot systems?
Root systems with one main root formed from the radicle, with many lateral roots branching out from the taproot
What type of root system gives access to deeper resources faster?
Taproot system
What type of plants is the taproot system characteristic of?
Dicots, eudicots, and gymnosperms
What are fibrous root systems?
Root systems that consist of many main roots of similar size arising from the stem, with lateral roots branching off of these roots
What type of plants is the fibrous root system characteristic of?
Oak trees and monocots
Monocots are most likely to have ________ root systems
Fibrous
What is a radicle?
A seedling’s embryonic root
What is the difference between a primary eudicot root and a monocot root?
Monocots have a central pith, and eudicots have an x shaped center
What is the pith of a root?
Nonliving old tissue that makes up the “meat”
What is the difference between apoplastic and symplastic movement?
Apoplastic movement is movement through interconnected cell wall spaces in the cortex, and symplastic movement is through cells’ and their cytoplasm
What is the structure of roots with secondary growth?
Woody eudicots lay down concentric rings as they get wider because of dead tissues like phloem getting pushed out, old xylem gets pushed into the dense center, and bark doesn’t exist on roots because they need to absorb nutrients
What are two examples of mutualistic relationships between roots and other organisms?
Roots and nitrogen fixing bacteria, and roots and mycorrhizae (fungi)
What are three types of roots that are modified to perform uncommon functions?
Modified starch-storing roots, aerial roots, and humadiphor roots
What is an example of a modified starch-storing root?
Potatoes
What do aerial roots do?
They absorb gas water in humid areas above ground
What are humadiphor roots? What are 2 examples?
Roots that grow out of the ground and up. Examples include mangroves and possibly cyprus trees
What’s the difference between simple and compound leaves?
Simple leaves only have one leaf, compound leaves have multiple
What are the three types of leaf arrangements?
Alternating, opposite, or whorled
What are the two types of leaf veins structures?
Parallel and netted
What are the types of netted veins?
Palmately, denate, or pinnately netted
What are the types of parallel veins?
Longitudinally and pinnately
What’s the difference between leaf anatomy of eudicots and monocots?
Eudicots have more stomata on the lower surface, monocots have evenly distributed stomata
How does blue light relate to stomata?
Blue light can cause stomata to open
What are the reasons why guard cells would close the stomata?
It’s night, there’s a high concentration of CO2 in the guard cells, or the guard cells are dehydrated
When the guard cell holds the stomata open, what are its conditions?
It’s turgid and has a low concentration of CO2
Define turgid
Having lots of water
What does transpiration do to plants?
It dehydrates them and causes them to need more water and close their stomata at night
What’s the difference between transpiration and guttation?
Transpiration is with water and usually happens because of open stomata in the leaves, guttation is the exhumation of xylem sap on leaves
What is guttation?
The exudation of xylem sap on leaves
What are four examples of modified leaves?
Lily pads have modified leaves to float in a watery environment, pine needles have a reduced surface area for cold temperatures, onions are leaves with storage for starches due to lack of nutrients in soil, and cacti have needle leaves so they don’t get eaten by dehydrated animals
What are trichomes?
Leaves with stingy hairs so people don’t eat them (ex: stinging nettle)
Soil particles are _____ charged
Negatively
80-90% of a plant’s fresh mass is _____
water
4% of a plant’s dry mass is __________
inorganic substances from soil
96% of a plant’s dry mass is _____
from CO2 assimilated during photosynthesis
What three factors contribute to plant growth?
Soil, air, and water
What are the most common plant nutrient deficiencies?
Nitrogen, potassium, and phosphorus
What is nitrogen fixation?
The conversion from N2 to NH3, which is then converted to NH4+
Describe the conversion to NO3
Nitrifying bacteria oxidize NH3 to nitrite (NO2–) then nitrite to nitrate (NO3–), but some nitrogen is lost to the atmosphere when denitrifying bacteria convert NO3– to N2
What are nodules?
Bumps in a plant’s roots where it’s “infected” with rhizobium bacteria
What are rhizobium bacteria?
Nitrogen-fixing bacteria that provide plants (legumes) with a source of fixed nitrogen
What are bacteroids? Where are they?
A form of rhizobium bacteria which is contained within vesicles formed by the root cell
What makes the relationship between rhizobium and plant roots mutualistic?
The plant obtains fixed nitrogen from Rhizobium, and Rhizobium obtains sugar and an anaerobic environment
What does crop rotation take advantage of?
The symbiotic relationship between legumes and nitrogen-fixing bacteria
What do root cap cells secrete and why?
They secrete lubricating polysaccharides to reduce friction
Besides secreting, what else do root cap cells do?
Protect the apical meristem
What are root hairs?
Short-lived tubular extensions located just behind the growing root tip
What is development of roots and root hairs controlled by?
Two regulatory genes that code for transcription factors
What’s the order of the sections present in the cross-section of roots from outside to inside?
Root hairs, epidermis, exodermis, cortex, endodermis, pericycle, phloem, xylum
What is the cortex of a root made of?
Parenchyma cells
What type of cells are in the exodermis of a root?
Sclerenchyma cells
Where is the Casperian Strip located?
In the endodermis of roots
What is the endodermis?
The innermost layer of the cortex
What is the Casperian Strip?
A water-impermeable strip of waxy material that forces water and solutes to cross the plasma membranes of endodermal cells instead of slipping between the cells.
Why does the Casperian Strip have to do the job it does?
To ensure that only materials required by the root pass through the endodermis, while toxic substances and pathogens are generally exclude
What is the pericycle in roots?
Nonvascular tissue separating the endodermis from the phloem
What do root hairs do?
Increase the surface area of the root, which helps with absorption
What comprises the majority of the root?
The cortex
How many layers of epidermal cells cover roots?
One
What does most water that enters the root do?
It moves along the cell walls made of cellulose
What is the primary function of the root cortex?
Starch storage
What does the endodermis do?
It regulates the movement of water and minerals that enter the xylem
Each endodermal cell has what?
A casperian strip on its radial and transverse walls
What is the waterproof material in casparian strips made out of?
Suberin
What two pathways does water follow in the root?
Symplast pathways and apoplast pathways
The symplast pathway consists of what?
Living cells interconnected by plasmodesmada
To reach the vascular tissues of the xylem, water must pass through what?
The plasma membranes of endodermal cells
What is the stele?
The center of a eudicot’s primary root
What does vascular cambium produce?
Xylum
Where does photosynthesis take place in leaves?
Palisade mesophyll
