To determine if Poa pratensis strains of different origins would respond differently to a series of temperatures, ‘Merion,’ ‘0217,’ and ‘Newport’ cultivars were grown in controlled environment growth chambers at four different temperature regimes.Top growth, density, and total available carbohydrates in stem bases were determined after 8 weeks in the growth chambers. Plants were clipped to 4 cm at weekly intervals during the treatment period.A differential response to temperature among the three strains was demonstrated. Merion and 0217 had the highest density at the higher temperatures and Newport had the highest density at the lower temperature regimes. The 0217 strain had significantly greater density at all temperatures than did Merion or Newport. All strains accumulated more carbohydrate reserves at the lower temperatures, but Newport had signficantly lower reserves at all temperatures than did Merion or 0217. Only Merion had a significantly greater carbohydrate reserve at the lowest temperature compared to the next warmer regime. Clipping yields were greater at the warm temperatures compared to the cool temperatures for all strains.
Significant differences were observed for salinity tolerance among creeping bentgrass varieties grown in solution cultures. Top growth of all varieties decreased with increased salinity. In terms of relative yields of clippings, ‘Arlington,’ ‘Seaside,’ ‘Pennlu,’ and ‘Old Orchard’ were most tolerant; ‘Congressional’ and ‘Cohansey‘ were intermediate; and ‘Penncross’ was least tolerant. Seaside had the highest survival rating under extreme saline conditions and the best recovery when removed from the salt treatments. Congressional had the lowest survival rating at the high salt levels. There was evidence of variation for salt tolerance among individual plants within the Seaside variety.
Cynodon dactylon (L.) Pers., ‘Coastal,’ and Poa pratensis L., ‘Newport,’ were grown in four different temperature regimes to study the effect of temperature upon the accumulation of carbohydrate.Plants were harvested at two‐week periods for 8 weeks and the stem bases were analyzed for alcohol soluble sugars, fructosan, and starch.The highest concentration of carbohydrate occurred at the coolest temperature for both Kentucky bluegrass and Coastal bermudagrass. Carbohydrate accumulation generally increased as a function of time. Alcohol soluble sugar levels were approximately equal for both species at each temperature regime with the exception of a high amount in bluegrass grown at the coolest temperature.
Kentucky bluegrass (Poa pratensis L., is used for turf in many areas where soil and air temperatures are high for long periods. Using controlled temperature water baths and growth chambers, Kentucky bluegrass ‘Merion’ plants were grown at various soil and air temperatures and at three clipping heights to determine the interaction effects of temperature and defoliation on growth. Defoliation reduced dry weight of tops, number of innovations, root length and percent of nonstructural carbohydrates at all soil and air temperatures. Although a soil temperature of 18 C produced the most root and top growth in unclipped plants, this superiority was completely negated by defoliation. A soil temperature of 27 C resulted in reduced root growth compared to that at 18 C. Defoliation intensified the unfavorable effect of the high soil temperature. Nonstructural carbohydrate levels were lowest at the soil temperature (18 C), that produced the highest vegetative growth in unclipped plants. Differences in nonstructural carbohydrates among the soil temperature treatments were greatly reduced by defoliation. In the growth chambers where soil and air temperatures were in equilibrium results were in general consistant with those where soil temperatures were regulated separately by means of the water baths. Highest number of innovations was obtained at 10 C regardless of defoliation treatment. Highest dry matter production of tops was obtained at 21 C on unclipped plants while all plants became dormant at 32 C and made no measurable growth.
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.
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