temperature effects on growth & flowering in ornamentals · •negative dif means warmer night...
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Temperature Effects on Growth & Flowering in Ornamentals
Krishna Nemali, Ph.D.Purdue University
[email protected](765) 494 8179
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Why is temperature important?
Growth Differentiation
Temperature affects growth (along with light) and differentiation (solely) in plants
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68-78 °FOptimum
50-68 °FSlow
growth
< 50 °FGrowth
stops
78-85 °FExcessive growth
> 90 °FHeat
damage
Optimum temperature for several flowering plants
50
55
60
65
70
75
80
85
Tem
pe
ratu
re (
F)
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Average temperature in Indiana
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0
10
20
30
40
50
60
70
80
90
-20 10 40 70 100 130 160 190 220 250 280 310 340 370
Temperature (F)
Inside greenhouse
Outside air
Ap
ril-
May
Sep
-O
ct
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68-78 °FOptimum
50-68 °FSlow
growth
< 50 °FGrowth
stops
78-85 °FExcessive growth
> 90 °FHeat
damage
57 F 63 F 68 F 73 F 79 F
50-68 F: Low temperature controls plant growth but it comes with the cost of delayed flowering
Courtesy: Lee Ann Pramuk and Erik Runkle
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Courtesy: Lee Ann Pramuk and Erik Runkle
50-68 F: Low temperature controls plant growth but it comes with the cost of delayed flowering
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Case 1:
70 F day (12 h) /48 F night (12 h)MDT = (70 + 48)/2 = 59 F
Case 2:
65 F day (12 h) /53 F night (12 h)MDT = (65 +53)/2 = 59 F
Case 3:
70 F day (14 h) / 44 F night (10 h)MDT = [(70 x 14) + (44 x10)]/ 24 = 1416/24 = 59 F
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Flowering is affected by “mean daily temperature”
Flowering is affected by “mean daily temperature”
Erwin and Heins, 1994
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68-78 °FOptimum
50-68 °FSlow
growth
< 50 °FGrowth
stops
78-85 °FExcessive growth
> 90 °FHeat
damage
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Species Base temperature (°F)Snapdragon 36Dianthus 39Viola 39Marigold 40Petunia 40Rudbeckia 40Gazania 41Geranium 41Dahlia 42Impatiens 43Wax begonia 43Cosmos 45Salvia 45Ageratum 46Zinnia 46Blue Salvia 49Angelonia 50Celosia 50Vinca 53
< 50 F: Plant growth stops below base temperature
• Peak season for propagation is Dec-Mar when temp < 50 F
• Optimum temperature for rooting is ~70-75 F
• Common myth: Plants produce strong roots when exposed to cold temp.
• Heating required at temperature < 50 F
Finishing crops in containers: Heating is more important for cold sensitive than cold tolerant crops
Crop Delay per degree Fdecrease in temp
Orchids ~ 7 days
Petunia ~ 3 days
Impatiens ~ 2 days
Pansy ~ 1.5 days
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Air =59 F Air =70 FAir =59 F + Root = 75 F
Olberg and Lopez, 2016
Root zone heating
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Accelerate seed germination
Heat mats Cold frames
16Thermal imaging: a new and affordable tool to growers
Heat + Low light = Elongation
Erwin and Heins, 1994
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Negative DIF can be used to control stretching
• Negative DIF means warmer night and cooler day; provide negative DIF 5-7 F difference
• Usually 2-3 hours of –DIF at sun rise is sufficient
• Provide –DIF when plants are growing fast
• Effects start within 48 hr. Watch for leaf yellowing.
• French marigold, aster, tulips, hyacinths are not responsive to -DIF
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68-78 °FOptimum
50-68 °FSlow
growth
< 50 °FGrowth
stops
78-85 °FExcessive growth
> 90 °FHeat
damage
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78-83 F: Reduce fertilizer and water to control excess growth
EC = 1180 µS EC = 2240 µS
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High phosphate and high temperature = excess growth
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68-78 °FOptimum
50-68 °FSlow
growth
< 50 °FGrowth
stops
78-85 °FExcessive growth
> 90 °FHeat
damage
H.S. Wein, 2009
> 90 F: Temperature inside the high tunnel during a day in June at Ithaca, NY
95 F
77 F
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77 F 86 F 95 F 104 F Courtesy: LSU Ag Center
Effect of short duration exposure to high temperature on growth and flowering in salvia
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Which method is right? Why?
Shade cloth
Shade cloth
High tunnel High tunnel
A B
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