Growth, photosynthesis and assimilate partitioning in Lolium temulentum exposed to chilling temperatures

Vegetative plants of Lolium temulentum L, grown at 20°C with an 8 h photoperiod were transferred to either 5 or 2°C (8 h photoperiod) at 4th leaf maturity. Measurement of dry weight gain indicated a marked decline in relative growth rate below 5°C, with growth being reduced as much between 5 and 2°C as between 20 and 5°C. This reduction was not associated with increased mortality and was reversible if plants were returned to 20°C. Tissue explants from cold‐treated plants retained the ability to extend if returned to 20°C Rates of extension in explants were less temperature sensitive than the relative growth rates observed in intact plants. Measurements of photosynthetic capacity, and of the patterns of accumulation of reserve carbohydrate in plants exposed to different temperatures, suggested that the inhibition of growth caused by chilling is not caused by an inability of the plants to fix sufficient carbon.