Abstract
Winterkill is recurrently observed on annual bluegrass ( Poa annua L.) golf greens in northern climates. Although annual bluegrass susceptibility to freezing temperatures has been pointed out as a major factor responsible for winter damages, little information exists on freezing tolerance and cold hardening of green‐type annual bluegrass. This study was conducted to assess freezing tolerance and carbohydrate changes occurring during cold acclimation of green‐type annual bluegrass ecotypes cold hardened under both environmentally controlled and simulated winter conditions in an unheated greenhouse. The 50% killing temperatures (LT 50 ), levels of fructans, and mono and disaccharides were determined during cold acclimation in three annual bluegrass ecotypes originating from Western Pennsylvania (OK), Coastal Maryland (CO) and Central Québec (CR). The ecotypes differed significantly with regard to their freezing tolerance (LT 50 ranking: OK < CO < CR) and maintained their relative ranking under both environmentally controlled and simulated‐natural winter conditions. Maximum freezing tolerance was observed after exposure to nonlethal subfreezing temperatures and annual bluegrass achieved high levels of freezing tolerance with LT 50 of −31.2°C for OK, −24.6°C for CO, and −22.8°C for CR. High molecular weight fructans (DP>6) were the most abundant carbohydrates found in plants cold‐acclimated under low, nonfreezing temperature with levels up to 170 mg g −1 dry weight as compared with 60 to 70 mg g −1 dry weight in nonacclimated plants. Sucrose levels in crowns of annual bluegrass markedly increased at temperatures below freezing and maximum sucrose concentration coincided with maximum freezing tolerance of annual bluegrass. However, variations in fructan and sucrose levels were not related to differential freezing tolerance among the three annual bluegrass ecotypes tested.
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Claims 11
Claim · model-written summary
The three annual bluegrass ecotypes differed significantly in freezing tolerance (LT50 ranking OK < CO < CR).
Poa annuaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“The ecotypes differed significantly with regard to their freezing tolerance (LT 50 ranking: OK < CO < CR)”
Claim · model-written summary
The relative freezing tolerance ranking of the ecotypes was maintained under both environmentally controlled and simulated winter conditions.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“maintained their relative ranking under both environmentally controlled”
Claim · model-written summary
Maximum freezing tolerance was observed after exposure to nonlethal subfreezing temperatures.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“Maximum freezing tolerance was observed after exposure to nonlethal subfreezing temperatures”
Claim · model-written summary
Ecotype OK reached an LT50 of -31.2°C.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“annual bluegrass achieved high levels of freezing tolerance with LT 50 of −31.2°C for OK, −24.6°C for CO, and −22.8°C for CR”
Claim · model-written summary
Ecotype CO reached an LT50 of -24.6°C.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“annual bluegrass achieved high levels of freezing tolerance with LT 50 of −31.2°C for OK, −24.6°C for CO, and −22.8°C for CR”
Claim · model-written summary
Ecotype CR reached an LT50 of -22.8°C.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“annual bluegrass achieved high levels of freezing tolerance with LT 50 of −31.2°C for OK, −24.6°C for CO, and −22.8°C for CR”
Claim · model-written summary
High molecular weight fructans (DP>6) were the most abundant carbohydrates in annual bluegrass cold-acclimated under low, nonfreezing temperature.
- Treatment
- under low, nonfreezing temperaturee2
- Outcome
- High molecular weight fructans (DP>6) were the most abundant carbohydratese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“High molecular weight fructans (DP>6) were the most abundant carbohydrates”
e2“under low, nonfreezing temperature”
Claim · model-written summary
Fructan levels reached up to 170 mg g-1 dry weight in cold-acclimated plants compared with 60 to 70 mg g-1 dry weight in nonacclimated plants.
- Treatment
- under low, nonfreezing temperaturee2
- Outcome
- High molecular weight fructanse1
- Direction
- higherinferrede3
- Value
- up to 170 mg g −1 dry weighte3
- Qualifier
- 60 to 70 mg g −1 dry weighte3
- Comparator
- nonacclimated plantse3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“High molecular weight fructans (DP>6)”
e2“under low, nonfreezing temperature”
e3“with levels up to 170 mg g −1 dry weight as compared with 60 to 70 mg g −1 dry weight in nonacclimated plants”
Claim · model-written summary
Sucrose levels in crowns of annual bluegrass markedly increased at temperatures below freezing.
- Organ / stage
- crownse1
- Treatment
- temperatures below freezinge1
- Outcome
- Sucrose levelse1
- Direction
- markedly increasede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“Sucrose levels in crowns of annual bluegrass markedly increased at temperatures below freezing”
Claim · model-written summary
Maximum sucrose concentration coincided with maximum freezing tolerance of annual bluegrass.
- Outcome
- maximum sucrose concentration coincided with maximum freezing tolerancee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“maximum sucrose concentration coincided with maximum freezing tolerance”
Claim · model-written summary
Variations in fructan and sucrose levels were not related to differential freezing tolerance among the three annual bluegrass ecotypes.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Poa annua L.”
e1“variations in fructan and sucrose levels were not related to differential freezing tolerance among the three annual bluegrass ecotypes tested”