flower induction in the floriculture industry hrt 301 roberto g. lopez purdue university
Post on 20-Dec-2015
220 views
TRANSCRIPT
Flower Induction in Flower Induction in the Floriculture the Floriculture IndustryIndustry
HRT 301HRT 301
Roberto G. Roberto G. LopezLopez
Purdue Purdue UniversityUniversity
• Juvenility (plant size)• Photoperiod (day length)• Vernalization (cold treatment)• Hormones (Ethylene)
Outline
What plant is this? (Hint: It’s not Arabidopsis!!)
Flowering Can Be Influenced By:
• Juvenility – plant size or maturity
• Environmental signals– Cold (vernalization)– Photoperiod (day length)– Dormancy sequence
• Hormones– Ethylene
Question:Why did only the 50-cell-sized coral bells
flower in the previous example?
Answer:It’s a matter of age
or Juvenility!
Heuchera (Coral bells) flowering in Yosemite National Park
Juvenility
A young stage of plant development in which plants from seed are not capable
of flowering
Juvenility
• Juvenile period of woody plants usually lasts
many years (Table 25.1 in text)
• For most herbaceous perennials usually less
than one year.
Plant Developmental Stages
Juvenile stage
Mature stage
What is the best way for a grower to measure
juvenility?
Determine the average leaf number by:
• Counting a random group of many individuals seedlings and then calculate the average
Incomplete Vernalization of Perennials
Examples of Leaf Number Requirementsfor Flowering Herbaceous Perennials
Aquilegia Some require 15+ leaves to flower consistently
Aster alpinus Plants require at least 15 leaves to flower
consistently
Coreopsis ‘Sunray’ Juvenile phase ends with about 16 leaves
Euphorbia epithymoides Plants with six to eight leaves failed to flower
Goniolimon tatarica Plants with 10 to 14 leaves failed to flower
Heuchera sanguinea Plants require 16 leaves to flower consistently
Plant name Age Requirements
Aquilegia ‘Origami Red & White’Plants cooled for 6 weeks at 41 °F
Juvenile (Vernalized as a 128-cell plug)
6 weeks bulkingfrom 128-cell plug
Short days Long days
• Juvenility (plant size)• Photoperiod (day length)• Vernalization (cold treatment)• Dormancy sequence• Hormones (Ethylene)
Outline
What plant is this? (Hint: Sold for the holidays)
“Biological” photoperiod during the year
Definition of Flowering
• Botanical definition
• Horticultural definition
Types of Photoperiod Responses
• Day-neutral plants (DNP)
• Short-day plants (SDP)
• Long-day plants (LDP)
• Other responses
Schlumbergera (Thanksgiving cactus) is a short day plant
Types of Responses
• Facultative (Quantitative) response– Facultative SDP– Facultative LDP
• Obligate (Qualitative) response– Obligate SDP– Obligate LDP
Plants in Temperate Climates
• DNP = no response to long days
• Facultative LDP = long days accelerate (but are not required) for flowering
• Obligate LDP = long days are required for flowering
Day-Neutral Plant
Short-Day Plant
Shortdays
Pennisetum glaucum ‘Purple Baron’8 weeks forcing at 20 °C
Longdays
Longdays +HPS
• Experiments have shown that the term short-day is something of a misnomer; the cocklebur requires a sufficiently long night for flower induction.
• For example, cocklebur will flower only if exposed to darkness for at least 8.5 hours – the critical photoperiod.
• Interruption of an otherwise long night by red light (660 nm) is particularly effective and prevents flowering, unless it is followed by irradiation with far-red (730 nm) light.
Photoperiodism in Short-day Plants
Obligate Long-Day Plant
Shortdays
Stipa tenuissima10 weeks forcing at 20 °C
Longdays
Longdays +HPS
Obligate Long-Day Plant
Critical Photoperiod
• That photoperiod above or below which
induces a population of plants into flower
completely, rapidly, and uniformly.
Facultative Long-Day Plant
Intermediate-day or Short-long-day Plant
Ambiphotoperiodic Plant
Sisyrinchium tinctorium ‘Puerto Yellow’10 weeks at 20 oC under photoperiods (h):
10 12 13 14 15 16 24 4-h NI
When natural photoperiods are short, long days can be created by providing electrical lighting.
Factors that need to be considered for photoperiodic lighting include:
• the timing and duration of light delivery
• the light intensity provided
• the type of lamp used
Creating Long Days
Long-day Lighting Strategies
• Night interruption (NI)
• Predawn lighting
• Day-extension lighting
• Continuous (24 h) lighting
Simple installation of incandescent lamps for photoperiodic lighting
7:00 am 1:00 pm 7:00 pm 1:00 am 7:00 am
12 hours
12 hours
12 hours 12 hours
Flowering of Asclepias tuberosawith different long-day lighting strategies
Effect of Night Interruption Duration
10 percent lighting program (lights on for 6 minutes, off for 54 minutes) 20 percent lighting program (lights on for 6 minutes, off for 24 minutes)
• Night-break lamps can be cycled on for 6 minutes and off for 24 minutes to reduce costs and electrical load. This is termed “cyclical lighting”.
• Cyclical night-break lighting is mainly used for short-day plants, and is sometimes effective for long-day plants.
• Continuous night-break lighting is usually applied to long-day plants as “insurance” for a strong response.
Night Interruption Lighting
Cyclic Lighting
Beamflicker Incandescent lamps
High-Pressure Sodium Lamps on Moving Boom
Effect of Night Interruption Intensity
• Plants must have attained the “capacity to flower” to be induced to flower (juvenility)
• Newly mature leaves are most capable of being induced to flower
• In most species, repeated favorable photoperiods (cycles) are required for flowering
• In most species, once a plant has initiated flowers, they continue to develop to anthesis even when under an unfavorable photoperiod
Photoperiodism Generalities
• Photoperiod is measured in the leaf, then some signal is transmitted to the shoot apex and acts upon the meristem
• “Florigen”
- A graft-transmissable compound
- Moves through the phloem
- Generated in the leaf of one species that can be grafted onto another species and initiate flowering.
Photoperiodism Generalities
• Juvenility (plant size)• Photoperiod (day length)• Vernalization (cold treatment)• Hormones (Ethylene)
Outline
What plant is this?
Vernalization
• Response categories
• Effective cooling temperatures
• Duration of cold treatment required
• Facilities to provide cold treatment
Easter Lily (Lilium longiflorum) has a vernalization requirement
Cold Treatment (Vernalization)
• Cold treatment beneficial or required– Facultative (quantitative) cold response– Obligate (qualitative) cold response
Effective Temperatures
• Range from 28 to 55 °F (-2.5 to 12 °C)
• 41°F (5 °C) is recommended
• Temperatures below freezing can be used, but
avoid temperatures below 28°F (-2°C)
Duration
• Varies by species
• In some instances, as little as 2 to 3 weeks is long enough to provide beneficial effects of cold.
• Generally 6 to 10 weeks of cold is adequate for most perennial species tested
Delivering Cold Treatment
• Cool seedlings or cuttings in the plug tray.
• Pot in finish container, grow for several weeks under short days (in the fall), and then cool plants.– Species with a juvenile phase
Delivering Cold Treatment
• In a cooler
• In a greenhouse
• Under a thermal blanket outdoors
• Purchase plugs that have been cooled
Delivering Cold Treatment
Delivering Cold Treatment
Delivering Cold Treatment
Delivering Cold Treatment
Vernalization
• Vernalization (for 6 weeks or more) improves flowering in many ways: more plants flower, flower count increases, and time to flower decreases. Thus, cold treatment is highly recommended.
Veronica spicata ‘Red Fox’6 weeks at 68 °F
2 weeks vernalization
28 32 37 41 46 50 55 59 64 68 Control
Vernalization Temperature (°F)
Veronica spicata ‘Red Fox’6 weeks at 68 °F
4 weeks vernalization
28 32 37 41 46 50 55 59 64 68 Control
Vernalization Temperature (°F)
Veronica spicata ‘Red Fox’6 weeks at 68 °F
6 weeks vernalization
28 32 37 41 46 50 55 59 64 68 Control
Vernalization Temperature (°F)
Veronica spicata ‘Red Fox’6 weeks at 68 °F
8 weeks vernalization
28 32 37 41 46 50 55 59 64 68 Control
Vernalization Temperature (°F)
Achillea ‘Moonshine’6 Weeks Vernalization
6 Weeks Forcing at 20°C
28 32 37 41 46 50 55 59 64 68
Vernalization Temperature (°F)
Campanula ‘Birch Hybrid’
-2.5 0 2.5 5 7.5 10 12.5 15 17.5 20W
eeks
of
cool
ing
12
9
7
3
5
Temperature (ºC)
Miltoniopsis Augres ‘Trinity’
52 °F 57 °F 63 °F 68 °F 73 °F
9-h photoperiod
8 weeks at 73 °F with 9-h pre-vernalization photoperiodsFollowed by 8 weeks at:
46 °F
0 70 100 40 10 0
Plants were subsequently forced at 68 to 73 oF under 16-h
photoperiods
Phalaenopsis Miva Smartissimo × Canberra ‘450’12-h Photoperiod
20 Weeks Forcing at: (°F)
57 68 63 73 79
Visible Inflorescence Percentage
Flowering Percentage0 10 100 100 10
100 100 100 100 10
84
0
0
• Juvenility (plant size)• Photoperiod (day length)• Vernalization (cold treatment)• Hormones (Ethylene)
Outline
What plant is this? (Hint: It’s an epiphyte)
Hormones
Bromeliads flowering in Iguazu Falls National Park, Brazil
Information and photos presented in this lecture were generated by Researchers at Michigan State and Purdue Universities.
Acknowledgments