Download basic horticulture – notes

BASIC HORTICULTURE – NOTES
WEEK #3
ROOTS
HANDBACK LAB SHEETS and ASSIGNMENTS
 ASSIGNMENT on Artificial Classification due TODAY Go over ambiguity of Sunset Book & Artificial Classification
 Go over microscope, magnification, dissecting micro.
REVIEW FOR EXAM #1 – END OF LECTURE TODAY
ROOTS
ORGANS – have ONE or MORE FUNCTIONS and composed of
SEVERAL TISSUES
 Roots, stems, leaves and flowers (fruit and seeds)
Start with ROOTS because of their SIMPLICITY (Quote #4)
FUNCTIONS OF ROOTS
 ANCHORAGE
 ABSORBING and CONDUCTING water and nutrients
 FOOD STORAGE
o Especially important to PERENNIALS
ALL ROOTS do these three things, but SOME ROOTS also
can reproduce by ROOT CUTTINGS
Example: Blackberries, Canada Thistle, Lilacs
(Form ADVENTITIOUS BUDS on roots that send out
shoots)
CLASSIFICATION OF ROOTS
 Based on ORIGINATION (or WHERE they originate)
o PRIMARY – first seedling root or RADICLE
o SECONDARY – branches off of the primary or
secondary roots to form LATERALS
o ADVENTITIOUS – arise from OTHER PLANT
PARTS, but NOT ROOTS
Example: stem cuttings rely on production of
adventitious roots to produce new plant
(Show rooted cuttings)
 Based on ROOT SYSTEM
o TAPROOT – primary root is DOMINANT
Example: Carrots, dandelions, conifers
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DEEP, non-branching roots
Good ANCHORING
Can be ENLARGED for STORAGE
DIFFICULT to TRANSPLANT – easily
damaged
o FIBROUS – primary and secondary roots
DEVELOP EQUALLY
Examples: Sod, Rhododendrons
 SHALLOWER, SPREADING roots
 Good EROSION CONTROL - large surface
area to capture water and soil
 EASY to TRANSPLANT
 ALL ADVENTITIOUS root systems are
FIBROUS
o FASCICLED – or TUBEROUS root system
 Fibrous root system used to STORE FOOD
Examples: Dahlia, Sweet potato
ROOT STRUCTURE – ANATOMY (show overhead / handout)
ROOT TIPS are the last inch of roots
 ROOT CAP
o PROTECTS young growing tip
o Mucilaginous cells LUBRICATE root tip as grows,
cells break and slough off
 QUIESCENT ZONE
o REPLACEMENT cells for root cap
 MERISTEMATIC REGION – Apical Meristem
o Divides both ways
o Cells appear SQUARE
 ELONGATION REGION
o Elongation PUSHES root into soil
o No differentiation
 MATURATION REGION
o DIFFERENTIATION taking place
o Formation of SPECIALIZED tissues
 XYLEM, PHLOEM, EPIDERMIS, CORTEX
 ROOT HAIRS
 2-3 weeks lifespan
 constantly replaced
 mature roots lose root hairs
 90% of water uptake done here
 Some plants only grow root hairs if
when needed
Example: plants growing in marshy
areas or saturated soils
 Some plants don’t have root hairs
o Use young roots to absorb water
only
o Mycorrhorizal associations
Example: Blueberries, Pines, Conifers
 TRANSPLANTING SUCCESS
 PRESERVE root tips and hairs
 Get largest ROOT BALL possible
 WATER WELL to offset root loss and
aid recovery
 Move SPRING / FALL before roots
actively growing – Temps low,
humidity high - less stress
 ROOT PRUNING allows secondary
roots to grow before transplanting
ANATOMY of a MATURE ROOT (Show overhead)
EPIDERMIS
 PROTECTS internal tissues
 Produces ROOT HAIRS near tip
 LACKS SUBERIN to promote water absorption
CORTEX
 FOOD STORAGE - parenchyma cells with starch
grains
 Water movement occurs in INTERCELLULAR spaces
VASCULAR CYLINDER
 ENDODERMIS
o ONE CELL thick layer
o CASPARIAN STRIP - boundary between cortex
and vascular cylinder
 Like a RUBBER BAND around each cell of
the endodermis that is soaked in SUBERIN
 FORCES WATER, etc. THROUGH the
CYTOPLASMIC MEMBRANE –semipermeable
 Acts as a FILTER – WATER moves
EASILY, other substances must be
ACTIVELY TRANSPORTED across
 PERICYCLE
o Gives rise to SECONDARY roots
o MERISTEMATIC tissue
o Interior location aids in PROTECTION of
emerging root
o ALIGNS VASCULAR SYSTEM of emerging
root with existing root
 XYLEM
o 3-5 spokes or arms
o Conducts WATER and NUTRIENTS
 PHLOEM
o Tissue lies between spokes of xylem
o FOOD conducting tissue
 VASCULAR CAMBIUM
o Single layer between xylem and phloem
o DICOTS - lateral or secondary MERISTEM
 Allows growth in width or girth
o MONOCOTS – no vascular cambium
 Have pith in center of stele
 Xylem and phloem occur in clumps between
pith and pericycle
 GROWTH in width due to CORTEX
DIVIDING
SPECIALIZED ROOTS and ASSOCIATIONS
Most specialized roots are ADVENTITIOUS ROOTS –
develop from other plant parts not from roots
TYPES
 PROP ROOTS – added support
Example: corn, tropical plants
 CLIMBERS – climbing trees, walls
Example: Ivy
 PNEUMATOPHORES – roots grow from stem into air
to provide anchoring and aeration in swampy soils
Example: Bald Cypress
 EPIPHYTES – grow above ground on trees without soil
o hang on trees by roots
o absorb moisture from air
o some photosynthesize
Example: orchids, bromeliads, mosses, lichens, licorice
fern (Show Cecile’s orchid)
 CONTRACTILE ROOTS
o Contract or expand to pull bulb into soil for
correct depth
Example: lily, freesia bulbs
 PARASITIC ROOTS - called haustoria
o Penetrate host for water and sometimes nutrients
Example: Mistletoe, Dodder
 SUCKERS - roots that have adventitious buds that
form new plants
Example: Blackberries, raspberries, oaks
Some species roots will form natural connections or
GRAFTS with the roots of other species, to share
carbohydrates and hormones
MYCORRHIZAL ASSOCIATIONS
Probably 95 % of all plants have formed mycorrhizal
associations
MUTUALISTIC or Symbiotic relationship between a plants
roots and a fungus (“fungus root”)
 ROOTS and FUNGAL FILAMENTS combine together
in the root zone
 MYCORRHIZAE HELP ABSORB NUTRIENTS &
WATER for plants
 PLANTS PROVIDE SUGARS to fungus
 BOTH BENEFIT and would perform poorly on their
own
Example: Salal story (Ericaceae family)
MICROBIAL ASSOCIATIONS
Some plants (legumes and cycads) form associations with
NITROGEN FIXING BACTERIA
 Bacteria reside in the root nodules
 BACTERIA GET FOOD from plant
 PLANTS GET EXTRA NITROGEN to grow better
ABSORPTION and CONDUCTION of WATER and MINERALS
ACTIVELY GROWING PLANTS absorb an amount of
water equal to their weight daily
ROOT HAIRS absorb 90% of water the plant needs from
young root tips
Water is a SOLVENT for minerals and gasses in the soil
ROOT PHYSIOLOGY - WATER CONDUCTION
 ROOT PRESSURE
o Caused by OSMOSIS (see overhead)
 Chemical process
 Water seeks to EQUALIZE
CONCENTRATION in cells of root
compared to pores in soil
o Root hairs absorbs water into cell vacuole till
TURGID then pumps out excess into cortex cells
and intercellular spaces
o ENDODERMIS with CASPARIAN STRIP forces
all water to go through cell membrane before
entering xylem
o Allows endodermis to be SELECTIVE
 CAPILLARY ACTION
o Chemical property of water due to the POSITIVE
& NEGATIVE CHARGES on the WATER
MOLECULE
 COHESION – attraction of two ALIKE
substances to each other
Example: Bead, or drop of water
 ADHESION attraction of two DIFFERENT
substances to each other
Example: Meniscus of water to glass tube
o When the DIAMETER of a TUBE is small
enough, WATER WILL RISE AGAINST the
FORCE of GRAVITY
Example: Capillary tube with water, or like
XYLEM cells (very small capillary tubes)
 TRANSPIRATIONAL PULL
o STOMATA in leaves LEAK out water vapor,
called DIFFUSION process (similar to osmosis)
o Cells in return REPLACES WATER
o Xylem in turn leaks water to cells
o Continuous loss of water PULLS water up
through plant
o 95 % of water absorbed by roots lost through
transpiration
o EVAPORATION cools leaves – RELEASES 540
cal. of HEAT to change liquid water to vapor