Plants Flashcards

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1
Q

Plants

A

● Multicelled, eukaryotic, photosynthetic autotrophs

● Their cell walls are mad of cellulose, and their surplus carbohydrate is stored as starch

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2
Q

Sporopollenin

A

● A tough polymer, is resistant to almost all kinds of environmental damage and protects plants in a harsh terrestrial environment
- Found in the walls of spores and pollen

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3
Q

Gametangia

A

● A protective jacket of cells that gametes and zygotes form within some plants
● Prevents them from drying out

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4
Q

Cutin

A

● The waxy coating on the leaves

● Helps prevents water loss

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5
Q

Stomates

A

● Open to exchange gases

● Close to minimize water loss

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6
Q

Mycorrhizae

A

● A symbiotic fungus that lives on some roots

● Increases hte amount of water hte plant absobrs

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7
Q

Lignin

A

● Embedded in xylem and other plant cells

● Provides support

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8
Q

Leaf

A

● Organized to maximize sugar production while minimizing water loss
● Epidermid is covered by a waxy cuticel made of cutin to minimize water loss
- Guard cells control the opening of the stomates
● Inner part consists of palisade and spongy mesophyll
- Vascular bunders/veins are located here

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9
Q

Guard cells

A

● Modified epidermal cells that contain chloroplasts
● Photosynthetic
● Control the opening of the stomates

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10
Q

Palisade mesophyll cells

A

● Photosynthesis

● Pakced tightly

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11
Q

Spongy mesophyll cells

A

● Photosynthesis

● Packed loosely to allow for diffusion of gases into and out of these cells

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12
Q

Vascular bundles/veins

A

● Loaed int he mesophyll cells
● Carry water and nutrients from the soil to the leaves
● Carry sugar, the product of photosynthessi, from the leaves to the rest of the plant

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13
Q

Bundle sheath cells

A

● Specialized mesophyll cells
● Surround the veins and separate them from the rest of mesophyll
● Involved in special C4 photosynthesis

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14
Q

Stomatal crypts

A

● Some platns have stomates nestled in these
● THey further minimize exposure of the stomate to air
● This reduced water loss even more

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15
Q

Osmosis

A

● The diffusion of water across a membrane
● The direction in which water idffuses in determined by water potential
● Responsibled for short-distance transport of water

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16
Q

Water potential

A

● Free water, water not bound to solutes, diffuses from regions of higher water potential to lower water potential

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17
Q

Aquaporins

A

● Speical transport proteins that facilitate the rapid osmosis of water across emmbranes
● THe opening and closing of these selective channels affect the rate at which water flow, not its direction

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18
Q

Bulk flow

A

● The movement of liquid in response to pressure gradient
● Always occur from higher to lower pressure
● Independent of slolute concentration
● Occur within vascular tissue (phloem and xylem)

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19
Q

Phloem

A

● Transports sugars produced by photosyntehssis from leaves to all parts of a plantf or immediate use or storage

20
Q

Xylem

A

● Transports fluid, water and minerals from the soil, rises in a platn against gravity but requires no energy
● The fluid can be pushed up by root pressure or pulled by transpirational pull

21
Q

Root pressure

A

● Results from water flowing into the stele from the soil as a result of the high mineral content in the root cells
● It push xylem sap upward only a few yard
● Known as guttation

22
Q

Transpirational pull

A

● Evaporation of water from leaves
● Causes negative pressure (tension) to develop int eh xylem tissue from the roots to the leaves
● The cohesion of water due to strong attraction between water molecules makes it possible to pull a column of water from above within the xylem
● The absorption of usnlight drives this

23
Q

Transpirational pull-cohesion tension theory

A

● States that for each molecule of water that evaporates from a leaf by transpiration, another molecule of water is drawn in at the root to replace it

24
Q

Plant hormones

A

● Help coordinate growth, development, and responses to environemntal stimuli
● Produced in very small quantities, but they have a profound effect ont eh plant because the hormone signal is amplified

25
Q

Signal transduction pathway

A

● amplify the hormonal signal and connect it to specific cell responses

26
Q

Tropism

A

● Growht of a plant toward or away from a stimulus

● Examples are thigmotropism (touch), geotropism or gravitropism (gravity) and phototropism (light)

27
Q

Positive tropism

A

● A growth of a plant toward a stimulus

28
Q

Negative tropism

A

● A growth of a plant away from a stimulus

29
Q

Phototrpism

A

● Result from an unequal distribution of one category of plant hormones called auxins htat accumulate on teh side of the plant away from the light
● Cells ont he shady side of the plant enlarge and the stem bends toward the light

30
Q

Auxin

A

● Cause primary growth (in length)

31
Q

Geotropism

A

● Results from an interaction of auxins and statoliths

32
Q

Statoliths

A

● Specialized plastids containing dense starch grains

33
Q

Photoperiod

A

● The environmental stimulus a plant uses to dtect the time of year
● THe relative lengths of day and night

34
Q

Circadian rhythm

A

● Biological clock set to a 24-hour day

35
Q

Photoperiodism

A

● Physiological response to the photoperiod

- Such as flowering

36
Q

Long-day plants

A

● Plants that flower only when the light period is longer than a certain number of hours
● Plants respond to the legnth of darkness not the length of light

37
Q

Short-day plants

A

● Plants that flower only when the light period is shorter than a certain number of hours
● Plants respond to the legnth of darkness not the length of light

38
Q

Day-neutral plants

A

● Plants that flower regardless of the length of day

39
Q

Phytochrome

A

● Photoreceptor pigment responsible for keeping track of the length of day and night
● Two forms Pr and Pfr

40
Q

Pr/red-light absorbing

A

● A form of phytochrome
● Phytochromee is synthesized in the Pr form
● It is in Pr form in dark

41
Q

Pfr/Infrared light absorbing

A

● A form of phytochrome

● Phytochrome is converted to Pfr when exposed to light

42
Q

What are the strategies that enabled plants to move to land?

A

● Cell walls made of cellulose lend support to the plant whose cells, unsupported bby a watery environemtn, must mainttain their own shape
● Roots and root hairs absorb water and nutrients from the soil
● Transport tissue, xylem and phloem, can move fluid great distances
- Also enables plants to grow tall
● Stomates
● Cutin
● Gametangia
● Sporopollenin
● Seeds and pollen are a meanas of dispersing offspring with protective coat that prevents dessication
● Mycorrhizae
● Lignin

43
Q

What happens when water is introduced to guard cells and why?

A

● Cellulose microfibrils are oriented in such a direction that when the guard cells absorb water by osmosis and become turgid, they curve like hot dogs, causingt he stomate to open
● Wehn guard cells lose water and become flaccid, the stomate clses

44
Q

What controls short-distance movement of substances into and out of cells?

A

Selective permeability of plasma membranes

45
Q

What are the factors that affect the rate of transpiration?

A

● High humidity slows down transpiration, while low humidity speeds it up
● Wind can reduce humidity near the stomates adn thereby increase transpiration
● Increased light intensity will increase photosynthesis and thereby increase the amount of water vapor to be transpired and increase the rate of transpiration
● Closing sotmates stops transpiration

46
Q

How does plant keep track of time?

A

● The conversion from one from of phytochrome to another

● Plant is able to sense the concentrations of the two phytochromes and respond accordingly