Lecture 8 Flashcards
Shoot Apical Meristem function
Site for formation of lateral organs (leaves, flowers), replenishes cells
SAM regions (2)
Tunica (2 surface layers that contribute to the epidermis and ground tissue)
- anticlinal division
Corpus (make internal stem tissues)
- anticlinal and periclinal division
SAM zones (3)
Central Zone (large cells/vacuole, slow division, self-renewal cells)
Peripheral Zone (small cells/vacuole, high division, contain cells incorporated into epidermal/peripheral tissues, lateral organs)
Rib Zone (intermediate cells, incorporated into central stem tissue)
SAM cell types (2)
Initials (replace themselves)
Derivatives (differentiate)
SAM ans RAM beginning forming in what embryogenic stage?
Late heart stage
What is stm?
Shootmeristemless
A mutation in Arabidopsis plants that cause them to lack SAM and cotyledon formation during the first heart stage
Where do leaves arise from? What is the function of this structure? What dictates it’s positioning?
Leaf primordia
Protects the apical meristem from drying out
Positioning determined by local zones where plant hormone auxin accumulates
What are axial buds? What do they contain and when are they activated?
Arise from axial cells (in armpit of leaf primordia)
Contain many metabolic organelles that remain dormant unless needed (ex. When attacked/injured)
Leaf parts: simple leaf (3)
Blade (photosynthetic tissue)
Petiole (transport tissue)
Auxiliary bud (becomes lateral shoot)
Leaf parts: compound leaves (2)
Dissected (little leaflets to break up airflow and prevent lead from over-heating/absorption)
Rachis (provides flexibility and displays photosynthetic tissue)
Root Apical Meristem Function
Acts as a reserve for pluripotent cells ready when needed (aren’t particularly actively dividing, only activated when needed)
Root cap
Protects Apical Meristem as Root pushes through soil (as cells are constantly being knocked off as they slide through)
What is hbt?
Hobbit
Mutation in root Apical Meristem that cause Arabidopsis to lack proper root formation
Caused by improper development of suspensor cells causing improper development of hypophysis
Quiescent cent and columella don’t form at all
Root Function (6)
Water uptake
Anchor/support shoot
Stores resources
Mineral nutrient acquisition
Sense environment (nutrient/water availability)
Mutual w fungi/soul bacteria to gather resources
Basic root dicot structure (7)
Epidermis (skin)
Cortex (stores nutrients/carbs)
Endodermis (filters water entering xylem)
Pericycle (where lateral roots/vascular cambium originate)
Phloem (in pace bw xylem poles)
Xylem (in center of vascular cylinder)
Root hairs (single cell outgrowths)
Paths of water flow in root (2)
Symplastic route (across cells) Apoplastic route (along cell walls)
Symplastic route is favoured bc water can be filtered of dangerous content by the plasmalemma while the apoplastic route lacks a means of filtration
Casparin strip Function
A hydrophobic band that blocks water flow in a particular area
Functions to control flow of ions (move apoplastic ions into the symplast)
Older roots have Suberin all over causing loss of absorptive ability but prevention of leakage into dry soils
What is root pressure?
When water from the cortex flows into the vascular cylinder (stele) carrying ions/organic acids causing a reduction in water potential in the stele so water flows in, pressurizing the stele
Function of root pressure (3)
Remove embolisms (repair cavitated xylem)
Move ions/sugars up the plant when transpiration is difficult (but is not a means of moving water lost by transpiration)
Titration (forcing out of water/xs ions)
What is a hydathode and what functions does it perform (2)?
Collections of cells that direct a pressured xylem stream out of the leaf through the parenchyma cells to exit the pore (form guttation drops)
Functions:
Prevent flooding of intracellular spaces into the extracellular spaces
Reabsorb valuable nutrients from guttation stream
What is the rhizosphere? How does it alter it’s chemical environment (4)?
Root region where plant alters its chemical environment to increase nutrient mobility and favour growth of beneficial bacteria/fungi
Secrete: Protons (decrease pH) Chelators (mobilize ions) Carbs (support microbial growth) Enzymes (break down organic matter)
Monocot Root Structure
Ring of vascular tissue (lacks vascular cylinder)
Surrounds pith of parenchyma cells
Types of root (3)
Tap roots (has a central root, common in eudicots, adapted to deep soils)
Fibrous roots (lack central root, common in monocots, found in surface layers)
Cluster/Proteoid roots (have high density lateral roots, common in roots found in poor nutrient soils)
How do lateral roots form?
In phosphorus deficient soils the pericycle cells become meristematic and form lateral root tips that rupture out of the epidermis and form lateral roots
Lateral root Function
Increase SA for nutrients and mobilize P
Adventitious root Function
Aerial root Function
Adventitious: roots from non-root tissue that help prop plants up
Aerial: roots above ground that are used for support/anchoring
What’s so special about Mangrove roots?
They have adapted to flooding and high salinity conditions
Specialty roots (4)
Cable/Prop roots (anchor plant)
Pneumataphors (shoot upward and form air channels to absorb/transport air; are photosynthetic)
Feeder roots (embedded, absorb nutrients)
Embryonic roots (form fruit while still attached to parents and allow fruit to grow until they reach the seawater)
Define mycorrhizae
Mutual relationship between fungus (provide mineral nutrients and protection) and the root (provide carbohydrates)
Types of mycorrhizae (2)
Ectonycorrhizae (ECM) (doesn’t penetrate into root but forms a Hartig net)
Endomycorrhizae (AM)/Vascular Arbascular Mycorrhizae (VAM) (fungus penetrates into root and forms hautoria while stored in vesicles)
Advantages of mycorrhizae (4)
Cheaper than roots
Fungus are good decomposing organic matter
Fungi can mobilize recalcitrant ions
Fungi can suppress pathogens
Essential Macronutrients in plants (6)
N, P, K, Ça, Mg, S
Essential Micronutrients in plants (7)
Fe, Cl, B, Mn, Zn, Cu, Mo
Nutrient availability according to pH
Low pH (acidic): - Fe/Mn/Al abundant - Ca/K deficient High pH (basic): - Ca abundant - K/Cu/Zn deficient Neutral pH: - K abundant
What is the golden angle? What is it associated to?
137.5°
The angle of optimal leaf placement for light absorbance and maximum packing density
Associated w golden ratio (1.618)
