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Crop Science Abstract -

Effects of Gibberellic Acid on the CO2 Exchange Rates of Bermudagrass and St. Augustinegrass when Exposed to Chilling Temperatures1


This article in CS

  1. Vol. 23 No. 3, p. 514-517
    Received: June 17, 1981

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  1. K. J. Karnok and
  2. J. B. Beard2



This study was conducted to determine if a relationship exists between chilling injury and carbon dioxide exchange rate (CER) of two warm-season turfgrasses, and also to see how the relationship is influenced by exogenously applied gibberellic acid (GA3). The CER ‘Ormond’ (chill tolerant) and ‘Pee Dee’ (chill sensitlve) bermudagrass [Cynodon dactylon (L.) Pers] and ‘Floratam’ (chill tolerant) and ‘Texas Common’ (chill sensitive) St. Augustlnegrass [Stenotaphrum secundatum (Walt.) Kuntze] were monitored continuously for 14 days chilling temperatures (day/nlght, 7/5 C, respectively). Ormond, Pee Dee, Texas Common, and Floratam showed reductions of 54, 68, 79, and 84% respectively, in daytime CER during the initial chilling photoperiod. Both bermudagrass cultivars showed a significant increase and Floratam a significant decrease in daytime CER 10 hours after GA3 application. Texas Common did not respond. After 2 weeks of chilling stress, Ormond exhibited a significantly higher percentage of the prechill daytime carbon dioxide exchange rate (PCER) than Pee Dee, Texas Common, and Floratam. Ormond and Pee Dee treated with GA3 had significantly higher daytime PCER than nontreated Ormond and Pee Dee, as well as treated and nontreated Texas Common and Floratam. All treatments showed a rapid and continual reducton in nighttime CER with increased chilling exposure.

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