Botany Exam 2

which plants undergo true secondary growth?

woody plants, but some annuals too — has to have open vascular bundles

two lateral meristems responsible for secondary growth

vascular cambium + cork cambium

where are the two lateral meristems needed for 2 growth located?

1. vascular cambium - ring between primary xylem and phloem

2. cork cambium - outer cortex in stems, pericycle in roots

What cell types arise from the vascular cambium?

fusiform and ray initials

location of cell types arising from vascular cambium

in between vascular cambium and pith

fusiform versus ray initials? What do each give rise to?

• fusiform: oriented vertically; give rise to 2 xylem + 2 phloem

• ray: oriented horizontally; give rise to vascular rays of parenchyma

What are the three layers of the periderm? What do each do?

• cork: outside covering

• cork cambium: gives rise to periderm

• phelloderm: living parenchyma in cork cambium

What secondary tissue replaces the epidermis in stems undergoing secondary growth?

periderm

What causes annual growth rings in woody dicots?

seasonal changes in growth in vascular cambium

definition of bark?

all tissues outside vascular cambium

inner vs outer bark

• inner: living tissues like phloem and phelloderm

• outer: dead tissues like cork and phellum

hardwood (angiosperm) vs softwood (gymnosperm) wood anatomy?

• hardwood: both vessels and tracheids, rays can be multiple cells wide

• softwood: only vessels (no tracheids), resin ducts (sap), rays are 1 cell wide

early versus late wood?

• early: first half of growing season, large diameter, thin cell walls

• late: second half of season, small diameter, thick cell walls

ring porous vs diffuse porous wood

• ring porous: bigger vessels in early growth

• diffuse porous: smaller

spring bud break phenology for ring porous vs diffuse porous

ring porous leaf out later b/c they need to make new xylem bc of winter embolism

sapwood vs heartwood? function of each?

• sapwood: conducting portion of wood

  • growth

• heartwood: nonconducting

  • holds inhibitory and toxic metabolites, tyloses

tyloses

ingrowth of parenchyma into xylem, prevents spread of fungi

What is replaced by the periderm in secondary roots?

exodermis, loses epidermis

monocot “2” growth: two meristems?

primary thickening meristem (PTM) + secondary thickening meristem (STM)

monocot “2” growth: what is made by STM

new vascular and ground tissue to inside and ground tissue to outside

monocot 2 growth: adaptation

endure strong winds

intercalary meristem + adaptation

for vertical elongation across node, adapted to herbivores eating (grass)

nutrition

uptake, distribution, and utilization of nutrients

macro and micronutrients

• macro: required in large amounts

• micro: trace elements

symptoms of nutrient deficiencies

Stunted growth

Chlorosis (loss of chlorophyll)

Necrosis (tissue death)

where do deficiency symptoms show if nutrient is mobile

show in older leaves first

Leibig’s law of minimum

growth is regulated by amount scarcest nutrient (N + P for most plants)

what is a soil horizon

different layers of soil

O horizon

relatively undecomposed organic matter above A

A horizon

topsoil; most active, organic matter, organisms, humus (decay prod)

B horizon

deposition: receives leaches substances (iron oxide) from A; less weathered and bio active

C horizon

broken down + weathered rocks that from soil

what is soil texture? affects on water holding capacity?

• particle size

• field capacity (water holding after gravity) makes loamy soil best

why are most inorganic nutrients held in anionic form?

bulk flow

movement of water and nutrients down pressure gradient (high → low)

osmosis

movement of water from high to low concentration

diffusion

movement of liquid, gas, solid from high to low concentration

how is pressure gradient made in xylem? active or passive process?

• strong tension from evaporation of water from moist cell walls in leaves

how is pressure gradient made in phloem? active or passive process?

• movement of sugars in assimilate stream

• active

turgor

• positive pressure

• in sieve tube cells in phloem

tension

in xylem, negative pressure in leaves

benefits to the plant of transpirational water loss?

movement of water = movement of nutrients, also cooling

how and when does root pressure occur

• tension allows to “pull” up through stem

• at night when not transpirating

guttation

wet soil + xylem filled w/ water and pushes it out at top of veins

cohesion-tension theory of sap ascent

evaporation + diffusion of leaf cell walls (mesophyll) creates surface tension

why is cohesion important in cohesion-tension theory?

the cohesive strength of water using H-bonds keeps water column from breaking

What is the boundary layer?

still air at leaf surface that is resistant to water loss

What factors affect boundary layer thickness?

• thicker leaves = thicker boundary

• faster wind = less boundary

• leaf roughness = hold air tighter

• sunken stomata = thicker pathway in crit

How does a plant lose water from its leaves?

water vapor diffuses from areas of high pressure (leaves) to areas of low pressure (bulk air)

What are embolisms + cavitation?

air bubbles (embolisms) that can interrupt transpiration and cause cavitation

What two ways do embolisms form in xylem?

1. gases coming out of solution bc water is under tension

2. air seeding: air entering through pit membrane from other tissues

What is hydraulic lift and how and when does it occur?

• movement of water from wet to dry soil through plant

how are nutrient and water uptake in roots linked?

they happen at the same time

is nutrient uptake active or passive

active

assimilate stream

what directions can phloem sap move?

• upwards to actively growing stems

• downwards to actively growing root

• in and out of storage for both

Munch pressure flow model