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What were some of the problems encountered by plants as they made the transition from sea to land?
-dehydration
-transportation
-desiccation
-ventilation
-gravity
-fertilization
How did early land plants overcome dehydration during the transition from sea to land?
developed waxy cuticle to prevent water loss through evaporation
How did early land plants overcome transportation issues during transition from sea to land?
-development of vascular system (xylem/phloem)
-root system
How did early land plants overcome desiccation during transition from sea to land?
development of tolerance to survive periods of dryness by entering dormant state
How did early land plants overcome ventilation issues during transition from sea to land?
development of stomata to facilitate gas exchange allowing CO2 to enter for PS and O2 to exit
How did early land plants overcome gravity issues during transition from sea to land?
-development of lignin to provide structural support, growth upright
How did early land plants overcome fertilization issues during transition from sea to land?
pollen/seeds developed so plants could reproduce without water
What 3 groups of plants are considered bryophytes?
-mosses
-liverworts
-hornworts
What value (economically, etc.) do early land plants have?
-moss: peat
-liverworts: prevent erosion, form soil
-hornworts: research
-lycopods: cosmetics, pill coating
-ferns: food, ornamentals
-horsetails: scrubbing sponge
What is plant awareness disparity?
The tendency of people to overlook or undervalue plants in their environment
What solutions/efforts have been made to help PAD?
-integrating early plant edu. for young people
-focus on the value of plants themselves & not just what they provide humans
-understand plant/pollinator interactions
When/where did Ag in the Fertile Crescent begin?
13-11,000 ya in the Middle East
What is meant by the Green Revolution?
Lead by Norman Borlaug: a project that combined dwarf, disease resistant plants & fertilizers to try to feed the masses in developing worlds
What developments in Ag have the potential for helping solve the problem of world hunger?
-irrigation in the Near East & Mexico
-fertilizer manufactured
-breeding hybrids
-efficient machinery
-Green Revolution
What is the Urban Heat Island Effect?
Areas that have higher energy costs, air pollution, & heat related illnesses due to natural landcover being replaced with pavement & buildings that retain heat
How do we reduce the UHIE?
-plant trees, grasses in barren areas, right of ways, under solar panel, etc.
-plant native, drought tolerant plants
-plants that encourage shade
-fun green improve. projects
-green roofs
What attributes of a neighborhood or city impact the level of tree cover? (Burghardt et al. 2022)
-poles
-underground utilities
-soil compaction
-accessibility to water
-cost
-perception
-diversity
What are ecosystem services?
a benefit that wildlife or ecosystems provide to people
What are provisioning services?
benefit that can be extracted
(i.e. food, oil, timber)
What are regulating services?
benefit from a process
(i.e. pollination, water, purification, erosion)
What are cultural services?
non-material benefit, source of cultural, social, recreational benefit
What are supporting services?
benefits that allow for continuation of other services
(i.e. nutrient cycling, water cycle, etc)
What are examples of plants that contribute to provisioning services?
-blueberries, wheat, rice for food
-oak/pine for firewood
-aloe vera for medicine
What are examples of plants that contribute to regulating services?
-trees absorb CO2
-willows stabilize soil, prevent erosion
-sunflowers attract pollinators for reproduction
What are examples of plants that contribute to cultural services?
-cherry blossoms are celebrated in Japan
-maple trees signify fall in north America
-native herbs important to medicine, spiritual
What are examples of plants that contribute to supporting services?
-legumes fix nitrogen (symbiotic relationship)
-prairie grasses stabilize soil
-coral reefs provide habitat for marine life, supports biodiversity
What are plastids?
-flexible, responsive to environment, adaptable
-reproduce by dividing in half
-2 membranes, thylakoids, stroma
What are the various types of plastids?
-chloroplasts
-chromoplasts
-leucoplasts
What roles do chloroplasts play in the cell?
-contain chlorophyll (green), carotenoids (yellow, orange)
-photosynthesis
-starch storage
What roles do chromoplasts play in the cell?
-carotenoids (yellow, orange)
-seed dispersal
-pollinator attracting insects, animals
What roles do leucoplasts play in the cell?
-no pigment
-storage
How do primary cell walls differ from secondary cell walls?
-primary wall is formed first on the outside of the protoplast
-secondary wall is formed second on the inner surface of the primary wall
What is the function of the primary cell wall?
-maintain cell shape
-control rate & direction of growth
-resists internal turgor pressure of cell
-wound healing, regen
What is the function of the secondary cell wall?
-deposited after cell stops growing
-part of specializationW
What is the function of the middle lamella?
-binds neighboring cells
-coordinated growth & development
What is the cell cycle?
-series of events that cells go through as they grow and divide
-consists of G1, S, G2, M phases
What key events occur in the G1 phase of the cell cycle?
-prep for DNA replication
-nucleus moves to center of cell via cytoplasmic strands
-cytoplasmic strands fuse to phragmosome
-longest phase
What key events occur in the S phase of the cell cycle?
-DNA replicated
What key events occur in the G2 phase of the cell cycle?
-check all is replicated
-preprophase band forms around nucleus
-chromosomes start condensing & replicate
What key events occur in the M phase of the cell cycle?
-nuclear division (mitosis)
-cell division (cytokinesis)
-phragmoplast forms afterwards
What is cytokinesis?
division of cytoplasm where:
-vesicles are trapped by phragmoplast
-fusing of vesicles to told wall
-new cell plate reaches old wall & vesicles fuse to form plasma membrane
What role does the phragmosome play during cytokinesis?
-divide the vacuole and centralize the nucleus
What role does the phragmoplast play during cytokinesis?
-guides, traps vesicles for fusion & development into new cell wall
What role does the cell plate play during cytokinesis?
-divides the cell into 2 daughter cells
-vesicles fuse within plate forming plasma membrane
What 3 features of plant cells distinguish them from animal cells?
-cell wall
-plastids
-large central vacuole
Once regarded as depositories for waste products in plant cells, Vacuoles are now known to play what roles?
-cell growth
-remove toxins from cytoplasm
-signaling & attraction
-physical defense
-degrading other organelles
-hold cell sap
What is the preprophase band? What role does it play in plant cell division?
-made of microtubules & forms around nucleus
-precursor for where cell plate joins the cell wall
What is the difference between plasmodesma & desmotubule?
-plasmodema are channels that connect plant cells
-desmotubules are components within the channels that contribute to structure and selective transport
What is water potential & what value does the concept have for plant physiologist?
-stored energy of water, capacity to do work
-gives insight to water movement, nutrient uptake, stress responses, & growth regulation
What is osmotic potential?
the potential for water molecules to move from one area to another due to osmosis
What is pressure potential?
(turgor potential) the physical pressure exerted by water within plant cells
What is turgor pressure?
-hydrostatic pressure in plant cells
-result of osmosis and/or uptake of water
What are the 2 types of tracheary elements?
-tracheids
-vessel elements
How do tracheids & vessel elements differ?
-tracheids do not have perforations, and VEs do
-tracheids are not efficient water conductors, while VEs are due to their width
-tracheids are secure, while VEs are vulnerable to embolism
What is transpiration and why is it dubbed an "unavoidable evil"?
-loss of water by plants via stomata
-leads to water loss, but is vital for nutrient transport, and is inevitable
How does the cohesion-tension theory account for the movement of water to the top of tall trees?
water flows from high to low potential, creating a transpirational pull of water in through the xylem
What is the difference between sources vs. sinks?
-sources are exporters of solutes
-sinks are importers that cannot meet nutritional needs
What is an example of a source & a sink for sucrose in a plant?
-source: leaves, produce sugars through PS
-sink: roots, require sugars for growth
How does the osmotically generated pressure-flow mechanism account for the movement of sugars from source to sink?
high pressure at the source and low pressure at the sink drives the movement of phloem sap from source to sink
What are the two types of sieve elements & how do they differ?
-sieve tube cells
-sieve elements
What is a meristem, and what is its composition?
plant stem cells capable of differentiating into specialized cell types such as apical, lateral, and intercalary
develop into various tissues & organs in plant
What are the three tissue systems of the plant body?
-dermal tissue
-ground tissue
-vascular tissue
What does the dermal tissue system consist of?
-epidermis
-periderm
How do parenchyma, collenchyma, and sclerenchyma cells differ from one another?
-P are living cells made of cellulose with large vacuoles
-C are living cells with thick walls made of cellulose & pectin, elongated
-S are dead at maturity, thick, lignified walls that are highly specialized & rigid
What does the vascular tissue system consist of?
-xylem
-phloem
What does the ground tissue system consist of?
-parenchyma
-collenchyma
-sclerenchyma
What are the functions of the collenchyma?
mechanical support and flexibility in growing regions (stems, leaves), withstand against stressors
What are the functions of the sclerenchyma?
structural support, protection (found in bark, hard stems)
What are the functions of the parenchyma?
photosynthesis, storage, secretion, gas exchange (found in leaves, stems, roots)
What are the principal conducting cells in the xylem?
tracheary elements:
-tracheids
-vessel elements
What are characteristics of the xylem?
-transports water/minerals from roots to rest of plant
-moving upward
-structural support
What are the principle conducting cells in the phloem?
-sieve tube elements: facilitate flow of nutrients, no nucleus
-companion cells: loading/unloading of sugars in sieve tubes
What are characteristics of the phloem?
-transports sugars, amino acids, lipids, proteins
-movement up & down
What is the mesophyll?
ground tissue between upper and lower epidermis
composed of parenchyma cells
main site of photosynthesis in green plants
What are annuals?
lifecycle completed in single growing season
What are biennials?
2 growing seasons to complete lifecycle
What are perennials?
vegetative structures live year after year
How does secondary growth affect the primary body of the stem?
increases thickness of the stem to grow stronger & taller, forms bark, and enhances transport
What tissues are produced by the cork cambium, and what is the function of the periderm?
produces periderm which provides protection, insulation, gas exchange, and wound healing
What is bark, and how does its composition change during the life of a woody plant?
-outermost layer of stems/roots in woody plants
-periderm replaces epidermis through growth
-outer bark thickens through maturity, dead layers of cork & phloem accumulate
If a nail were driven into a tree at a height of five feet from ground level, and the tree increased in height by, on average, two feet per year, approximately how high above ground level would the nail be 10 years later?
5 ft
trunk grows in height from tips of branches not base
trunk does not elongate, it thickens due to secondary growth
