HORT 260 EXAM 3

container factors to consider for prop:

integrity, volume, expense, sanitation (porous), storage

types of containers

flats, plug trays, individual containers

flats

inexpensive, easily cleaned and stored, reusable (to a point)

plug trays/flats

shorten production time and reduce labor costs, less transplant shock, more expense and more space needed

individual containers

typically larger than 2.25”, similar to plug trays, more management of water required

phytochromes/ plant hormones

naturally occuring, organic, CHO based, produced endogenously

5 groups of PGR

auxin, gib, cytokinin, ethylene, abscisic acid

what is a plant growth hormone

natural or synthetic, exogenously applied. all hormones are pgrs but not all pgrs are hormones

what was the first plant hormone discovered

auxin

how is auxin transported through the plant?

basipetally

basipetally

moving from apex to base

physiological processes impacted by auxin

cellular elongation, root initiation, cambial cell activation(dicot)

what are common synthetic forms of auxin

IBA (most common),NAA

dedifferentiation

totipotency

auxin is key for what in propagations?

root initiation

auxin is synthesized where?

meristematic regions

auxin shapes what

gene expression

adventitious root primordia form where

phloem parenchyma region

what are the two phases of adventitious root formation by auxin

initiation phase, elongation phase

describe the 3 parts of the initiation phase of adventitious roots by auxin

wound response - dediff of cells at wound

proliferation of parenchyma cells-callus, formation of meristematic tissue

formation of root primordia/xylem vessels

describe the two parts of the elongation phase of adventitious root formation of auxin

root initiation- along the cambium/cortex tissue near phloem; emergence of vessel growth

root/vessel enlargement- connection to stem vessels

cut or wounded areas form what

necrotic plate/zone

why would we use auxin from a propagators perspective?

increases % root of cuttings, increases root number and quality, hastens rooting, increases uniformity

what are the commercial formulations of auxin as a PGR?

dry powder, gel, liquid

auxin powder application

easy to use, rooting often less uniform

liquid quick dip auxin

high concentrations of auxin used, more uniform

dilute solution soak

low auxin concentrations used, can be soaked in bundles

phenolic compounds

protects IAA from IAA oxidase

easy to root plants

produce all essential endogenous substances; adequate levels of auxins and cofactors; easily root on their own

moderately easy to root plants

plants in which naturally occurring cofactors are present in ample amounts but auxin is limiting

difficult to root plants

plants lack rooting cofactors and sensitivity to respond to cofactors; auxin may or may not be present. applying auxin does not help

what can be done to help form adventitious roots?

etiolation, cut back to juvenility (stooling), applying auxin

auxin is involved in the mobilization and translocation of what?

carbohydrates from young tissues

cytokinin

synthesized mainly in roots, found in tissues having considerate cell division

cytokinesis

division of cytoplasm during mitosis

why would a nurseryman use cytokinins?

to encourage shoot proliferation (morphogenesis)

recalcitrant means what

difficult to root

Gibberellin

makes plants grow excessively/abnormally

what is interesting about Gib transport?

it is not polar; moves wherever it is needed in the plant

what physiological are impacted by GA

stem/internode cell division/elongation, flower initiation and sex expression, delays senescence,

\#1 commercial use of gibberellins is

increased fruit size in seedless grapes

ethylene is synthesized

in all actively growing meristems, tissues experiencing physical stress, tissues experiencing senescence/ripening

ethylene

stimulates fruit ripening and flower initiation

ethephon

used for uniform flowering in bromeliads and bananas

what are some horticultural uses of gibberellin

promoting male flowers in cucumber, parthenocarpic fruit production (seedless fruit), overcoming seed dormancy, stimulating seed germination, overcomes cold requirement for flowering.

what physiological processes are impacted by ethylene

triple response to mechanical stress, plant decreases in longitudinal growth, fruit ripening, flower initiation, changing sex expression in flowers, degreening for citrus, aid in mechanical harvesting,

florel

formulation of ethepon. keeps them “tight”

abscisic acid

only natural,

Abscisic acid is synthesized

mostly in leaves, but also roots

what are two physiological processes are impacted by abscisic acid?

signal for plant water relations, stomatal activity, regulation of seed development preventing precocious seed germination

cutting propagation is the most important means for

clonal regeneration of many hort crops

which crops is cutting propagations important for ?

ornamentals, fruits, nuts

what is the primary regenerative process required for cutting propagation?

adventitious root formation

what are the two types of adventitious root formation

preformed (latent) root initials, and wound induced rooting

preformed (latent) root initials

develop naturally on stem and are dormant

wound induced rooting

develop only after cutting is made in response to wounding

what is stage 1 of wound induced rooting

dedifferentiation: ability of previously developed cells to initiate cell divisions and form new meristems

what is stage 2 of wound induced rooting

formation of root initials: from certain cells near vascular bundles, or vascular tissue which have become meristematic by dediff

what is stage 3 of wound induced rooting

root primordia: subsequent development of organized root initials

what is stage 4 of wound induced rooting

growth and emergence of root primordia outward through outer stem tissue plus formation of vasc tissue b/w root prim and existing vasc tissue of cutting

what is the location of adventitious root formation in herbaceous plants?

originate outside and between vascular bundles

what is the location of adventitious root formation in woody perennials

originate from cambium or young phloem

preformed 1 degree meristems

cells still meristematic (rare)

wound induced 2 degree meristems

dedifferentiated cells

limiting factor of leaf cuttings are

the formation of adventitious BUDS (not roots)

do root cuttings develop roots or shoots first?

shoots

what is the best candidate for root cuttings?

suckers

how can you propagate a thornless blackberry and why?

stem cuttings; because the adven. shoots will form from the L1 tissue

what is the general process for stem cuttings

sanitized sharp shears, keep cuttings hydrated, trim to standard size, treat with pgr, stick cutting to the proper depth, keep cuttings hydrated with mist

what should you remember when sticking stem cuttings?

to keep leaves off substrate

what are the stem cutting types?

hardwood, softwood, semi hardwood, herbaceous/tropical

what is a basal cut and why do we do it

cut at an angle; can affect adven. root formation,

nodal cut

about 1/8” below bottom node; prevents fungal rot, ensures bud is below substrate surface

internodal cut

about 1/4” below bottom node; does not ensure bud below substrate surface, does not reduce fungal growth

deciduous hardwood stem cutting

dormant season, mature, firm stem- late fall to early winter; 4-30” in length, basal cuts right above nodes, 2 to 3” in substrate, tops can be waxed to prevent rot

why should stem cuttings have two nodes and 1/4”-1 in in diameter?

carbohydrates

what are the three systems for planting deciduous stem cuttings?

direct fall planting, initiating roots with bottom heat, direct spring planting

direct fall planting

areas with mild winters, cuttings made and lined out in fall, auxin applied to base, dug after full growing s

initiating roots with bottom heat

areas with mild winters, recalcitrant species, cuttings made fall or winter, auxin applied to base, cuttings bundled and placed in substrate, tops exposed to ambient temp, protect from additional moisture, line out prior to spring bud break

direct spring planting

easy to root species, cutting material gathered in dormant season, wrap in moist material, store at 35-40 degrees F until spring, cuttings made to proper length and lined out with no mist, make sure wood does not bud during storage

what are the three types of conifer stem cuttings?

straight, heel, mallet

what is the difference between mature and old?

mature- reproduce

heel cutting

small portion of older \n wood attached; not from last \n flush of growth

new shoots from root cuttings form at

proximal end (crown)

mallet

small section of entire stem of older wood attached; not from last flush

softwood cuttings

cutting taken in spring during flush of growth, tissue is still soft, flexible but breaks when bent, intermittent mist is key, usually quicker and easier to get roots, 70-80 degrees f, rooted in 2-5 weeks

process for softwood cuttings

take cuttings early in the morning,3-5” long, basal cut, remove lower leaves, treat with auxin, be careful with high pgr conc, medial better than terminal cuttings,

herbaceous cuttings

typically produce no woody tissue (lignification), 3-5” long, but can vary, cut basal end, keep foliage off substrate, don’t allow to wilt, auxin not required but can be applied, mist is key

terminal cutting

contains a terminal bud

medial cutting

no terminal bud

single eye medial cut

alt leafed plant

double eye medial cut

opp leafed plant

split node medial cuttiing

splitting of the node of an opp leafed plant

chimera

plant with two or more genetically dissimilar tissue growing side by side

in a chimera, outer layers

maintain integrity because they divide anticlinally

anticlinal vs perclinal

anticlinal forms a sheet of cells one layer thick, periclinal division results in girth

what are the three types of chimeras?

mericlinal, sectorial, periclinal

mericlinal

genetically different tissue is found in part of a single meristem layer