Soluble carbohydrates, concurrent photosynthesis and efficiency in regrowth following defoliation: a field study with Agropyron species.
Abstract
Agropyron desertorum and A. spicatum [Elymus spicatus] were grown with Artemisia tridentata in field experiments near Logan during 1978-81. Plants of each sp. were etiolated by covering and the apical and intercalary meristems removed. Some plants were cut to remove 85% of the photosynthetic surface before etiolation. A. desertorum consistently produced more regrowth in the absence of photosynthesis than E. spicatus, but cutting did not significantly reduce etiolated regrowth in either spp. Differences in regrowth between and within spp. were not correlated with crown non-structural carbohydrate concn., total pools or amounts utilized during regrowth. The daily contribution of C from reserves exceeded measured daily photosynthetically-fixed C for only 2.5 days following defoliation when regrowth rate was greatest. However, when apical meristems were removed and regrowth was much slower, photosynthesis during regrowth immediately outweighed stored reserves as a source of C. In both spp., apical meristem removal was followed by sharply reduced regrowth efficiency due to a delay in and reduced rate of regrowth. There was, however, no increase in respiration rate. Meristematic limitations appeared to be the dominant control on the amount of etiolated regrowth produced. These limitations may be important in determining regrowth in the light and plant grazing tolerance.