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Title: SOIL MOISTURE POTENTIAL AFFECTS PHYLLOCHRON IN COOL-SEASON GRASSES

Author
item Bartholomew, Paul
item Williams, Robert

Submitted to: American Society of Agronomy Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2004
Publication Date: 6/27/2004
Citation: Bartholomew, P.W., Williams, R.D. 2004. Soil moisture potential affects phyllochron in cool-season grasses [abstract]. Southern Section of the American Society of Agronomy Branch Meeting. Paper No. s-bartholomew204960-poster. 2004 CDROM.

Interpretive Summary: Abstract Only

Technical Abstract: Cumulative leaf appearance in cool-season grasses is closely linked to accumulated temperature, which may therefore serve as an indicator of the onset of growth in spring. Earlier work has shown that the interval between the appearance of successive leaves (phyllochron) is influenced by the frequency of exposure to below-freezing temperature. The effect on the phyllochron of moisture stress and its interaction with cold exposure is not well defined. Experiments were undertaken in controlled environment to examine the effect of soil moisture contents of 10, 20 or 30% on the phyllochron of Italian ryegrass and tall fescue seedlings that were exposed to air temperatures of -5°C for 11h on two or four successive nights, or maintained at a constant 0°C overnight temperature. The mean phyllochron increased from 102 Growing Degree Days (GDD) per leaf, with no exposure to below-freezing temperature, to 117 GDD per leaf, with four exposures to -5°C. Decrease in soil moisture content from 30 to 20% increased phyllochron from a mean of 83 GDD per leaf to 95 GDD per leaf, and further decrease in soil moisture to 10% increased phyllochron to 148 GDD per leaf, (P<0.001). There was no significant (P>0.05) interaction between cold exposure and moisture potential in their effects on phyllochron. If accumulated temperature values are used to predict the stage of development in cool-season grasses during early growth in the spring, allowance needs to be made for the frequency of seedling exposure to below-freezing temperatures and to moisture stress.