Controlled environment studies have shown temperature to be one of the most important factors controlling nonstructural carbohydrate levels and density of Kentucky bluegrass (Poa pratensis L.) turf. Little information is available showing similar responses to temperature on a seasonal basis in the field. The objective of this experiment was to determine how nonstructural carbohydrate levels and density of Kentucky bluegrass turf differ among climatic areas and from season to season within an area. Total nonstructural carbohydrates (TNC) and innovation development were studied in five Kentucky bluegrass cultivars grown in the field in three distinct climate areas of California. These are a maritime climate of coastal southern California, a southern California interior valley thermal belt, and a temperate mountain valley. The respective soils of these areas are San Emigdio sandy loam classified as coarse‐loamy, mixed (calcareous), thermic Typic Xerofluvents; Arlington fine sandy loam classified as coarse‐loamy, mixed, thermic Haplic Durixeralf; and Havala sandy loam classified as fine‐loamy, mixed, thermic Typic Argixerolls. Results showed that changes in TNC levels and numbers of innovations followed seasonal patterns which were closely associated with the prevailing temperatures of each specific location. Consistently high summer temperatures reduced TNC stores but moderate temperatures did not affect them. Brief periods of exceptionally high temperature also reduced TNC levels. Accumulation of TNC occurred at each location at the time when temperatures were well below optimum for growth at that location. In the cold winter location, TNC levels decreased during the winter months. Flushes of growth occurring in spring depleted TNC. Density, the number of innovations per unit area, decreased throughout the summer at the high temperature location but increased through the cool winter. In the location of moderate summer and winter temperatures the number of innovations remained high and showed less seasonal fluctuation. Temperature, rather than day length, appeared to be the primary factor affecting innovation development.
Synopsis The growth of Puccinellia distans, Seaside bentgrass, Alta fescue, Kentucky bluegrass, and common bermudagrass as influenced by exchangeable sodium percentage in soils was studied using both untreated and VAMA treated soils. Puccinellia distans and Seaside bentgrass exhibited good tolerance and only moderate reduction in growth at ESP values of 26 to 28. The other grasses were reduced in growth by about one‐third to one‐half in this range but showed only slight reduction in growth at ESP values of 11 or 12.
Five cool-season turfgrass mixtures were grown under iwo culling heights and two nitrogen levels. Turfs were sampled for population density each spring and fall for a three-year period, using the core-sampling method. Densities of all declined steadily throughout the period in all treatments. With one exception, populations of any one species were at the same low level at the end of the study, regardless of the treatment.
Because siduron is absorbed by roots and transported by the transpiration stream, its phytotoxicity might be affected by environmental factors that influence transpiration. To test this, bermudagrass (Cynodon dactylon L. ‘Santa Ana’) and Kentucky blue‐grass (Poa pratensis L. ‘Merion’) were grown in controlled‐environment chambers at various temperatures and light intensities and treated with 1 and 5 ppm siduron. Untreated plants were also included. Bermudagrass was susceptible to 1 and 5 ppm siduron concentrations at all temperatures and light intensities. Shoot growth was reduced more than root growth. When air temperature was 30/20 C (day/night) the toxicity of the herbicides was greater than at a lower air temperature (22/15 C). Low light intensity decreased the toxicity of siduron to bermudagrass. Bluegrass was tolerant at all concentrations and all temperature and light treatments. Root temperature did not affect toxicity of the herbicide but maximum growth of bermudagrass was at 20 C and Kentucky blue‐grass at 15 C root temeprature. At 10 C, growth of both species was distinctly reduced. Differential rates of absorption are not the basis for selectivity.
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