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Biology of Plants Exam 2 > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

Leaves

A

Photosynthetic organs with a manufacturing cost

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2
Q

Leaf shape

A

A) Hight surface area for CO2 absorption (H2O loss) and light exposure, high SA:V

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3
Q

Leaf Shape

A

B) lower SA:V , less photosynthesis but better H2O conservation

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4
Q

Leaf Shape

A

C) Lowest SA:V, little SA for gas exchange best H2O conservation

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5
Q

Leaf Shapes

A

D) High SA, no self shading, must be long to achieve volume = a

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6
Q

Leaf Layer

A

-Chloroplasts are mainly located in mesophyll cells

Layer from top to bottom

  • Cuticle
  • Upper epidermis
  • Pallsiade Mesophyll Cell
  • Bundle Sheath Cell
  • Xylem
  • Phloem
  • Lower Epidermis
  • Spungy mesophyll Cells
  • Guard cell
  • Stoma
  • Cuticle
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7
Q

Leaf Fibers

A
  • made from xylem and phloem cells bundled in leaves
  • sisal and henequen come from leaves of Agave spp. *Agave sisalana *has sharp spoines that may also be used a needles, “needle and thread” plant
  • ropes made from sisal in Africa - can make heavy duty rugs/mats
  • has thorns on the side that would be used as a needle
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8
Q

Surface area to volume relationship of different leaf shapes

A

A) High SA:V = High surface area for CO2 absorption (H2O loss) and light exposure (example: standard broad leaf)

B) Lower SA:V = less photosynthesis but better H2O conservation

C) Lowest SA:V = little SA for gas exchange, best H2O conservation

D) High SA = no self-shading, must be long to achieve volume = a (Example: needle plant)

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9
Q

Chloroplast structure

A

Chloroplasts are mainly located in mesophyll cells

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10
Q

Mesophyte

A
  • Syringa vulgaris*
  • plants that live in medium conditions

Example: lilacs

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11
Q

Xerophyte

A
  • Nerium oleander* (Oleander)
  • plants that live in extremely dry conditions
  • plants of dry areas
  • multiple layers of endodermis with thick cuticle - prevents loss of water molecules
  • stomatal crypts
  • trichomes within crypts retain moisture near stomata
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12
Q

Stomatal crypts

A
  • where the stomata is sunken into the epidermis like a little cup
  • can have trichomes - prevents water loss, creates drags
  • reduce moisture loss
  • found mostly in Xerophytes
  • example: Oleander
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13
Q

Trichomes

A

DEFINNEEEEE

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14
Q

Hydrophyte

A
  • Nypmphaea* (Water lily)
  • stomata on upper surface, or lacking
  • lots of air space to conduct O2to submerged portions of plant
  • less xylem tissue
  • air spaces help move O2 to parts of submerged portions of the plant so they can get oxygen as well
  • pants that grow in wet areas, either mud or partially to wholly submerged in water*
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15
Q

Monocot - Zea mays

A
  • mesophyll does not have distinct layers
  • conspicuous bundle sheath cells (AKA Kranz antomy) - surrounding vascular bundles, a wreath-like shape
  • typical of monocots and grasses
  • monocots tend to have parallel leaf veinnation
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16
Q

xylem

A

water transport in plants

17
Q

bundle sheath and bulliform cells

A
  • bundle sheath - one or more layers of parenchyma or sclerenchyma cells that surround the vascular bundles (veins) of some plants
  • bulliform cells - open and close the “V” of a grass leaf, upon losing water cause the leaf to roll or fold up, large epidermal cells that occur in rows in grass leaves, and which are thought to play a role in leaf foldnig and unfolding
  • turgid cells open the leaf
  • folded leaf conserves water
18
Q

Cuticle

A
  • this surface blocks much of the moisture loss
19
Q

aerenchyma

A
  • tissue with large air spaces
  • present on floating and emergent leaves that have blades and stalks
  • helps in floatation as well as provides air passageways to the submerged roots for gas exchange
20
Q

Manila hemp

A
  • grown extensivey in Phillipines, where pineapple cloth is also made (for ceremonial purposes)
  • used for tectilse, cigarette filters, “Manila” envelopes, tea bags
21
Q

abscission zone

A
  • forms across the base of the leaf stalk to facilitate leaf drop
22
Q

specialized guard cells

A
  • guard cells of eudicots and many monocots are bean shaped
  • when turgid they open and close when the lose turgid
23
Q

Stomatal opening

A
  1. Zeaxanthin -pigment that is able to see blue light and activates proton pumps
  2. Active transport - protons pumped out of guard cells, forming proton gradient
  3. Facilitated diffusion - potassium ions enter guard cells through voltage-activated ion channels
  4. Solute concentration increases - chloride ions also enter guard cells through ion channels
  5. guard cells become turgid - water enters guard cells by osmosis, and stoma opens
24
Q
A
25
Q

Transpiration

A
  • the movement of water through the plant from roots, leaves, atmosphere
  • leaves play critical role in transpiration
26
Q

Leaf senescence

A
  • leaf death
  • individual leaves don’t have a very long life span
  • leaf life spans vary by species
  • in temperate species abscission is cued by shortened day length (aka cued by change in daylight)
  • starches and proteins broken down into simple sugars and amino acids that are reabsorbed by the plant
  • some essentional minerals also recovered
  • autumn in the temperate zone yields senescing leaves containing xanthophyll and carotenoid accessory pigments
27
Q

Leaf Abscission

A
  • adaptive to winter “deserts” with little water available for photosynthesis
  • leaves become a liability when they collect heavy snow causing branches and stems to snap
  • ethylene (plant hormone) promotes abscission (leaf drop)
  • protective layer of cork cells and suberin - leaf scar is made of this
  • leaf scar is created when leaf falls*
  • leaf abscission results in leaf scar
28
Q

leaf scar

A
  • protective layer of cork cells & suberin
  • created when leaf falls
29
Q

leaf modifications

A
  • water storage, Aloe
  • Epiphyte phyllotaxy (arrangement of leaves) stores rainwater (i.e. leaf cups to hold water, make pools of water to store its own water)
  • protect floral and leaf buds
  • showy
  • food storage
  • climbing tendrils (i.e. pea plant - allowed to climb)
30
Q

Phyllotaxy

A
  • arrangment of the leaves in a plant
31
Q

leaves modified for defense

A
  • spines are modified leaves (i.e. on a cacti)
  • thorns are specialized stems (i.e. Honey locust thorn)
  • prickles are extensions of epidermis or cortex (i.e. Rose prickle)
32
Q

leaves trap animals

A
  • pitcher plants
  • venus fly trap
  • sundew
33
Q

Summary points

A
  • leaves are arranged in distinct patterns on stems
  • the epidermis provides structural support and retards water loss
  • Mesophyll is the photosynthetic tissue of leaves
  • xylem and phloem are the conducting tissues of leaf veins
  • stomatal movements control transpiration
  • autumn leaf abscission is preceded by a period of senescence
  • leaf abscission is preceded by formation of an abscission zone
  • some leaves are specialized for water or food storage (i.e. pitcher plant vs. plant phyllotaxy)
  • leaves are modified for defense in some plants
  • leaves capture animal prey in some plants

Biology of Plants Exam 2 (5 decks)

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