Entity

Time filter

Source Type

New Haven, CT, United States

Gent M.P.N.,CT Agricultural Experiment Station
Acta Horticulturae | Year: 2011

The diurnal variation of nitrate and sugars may vary with plant size and the ability to take up, synthesize, and use metabolites. Three sequential plantings of Bibb lettuce germinated at 2-week intervals were grown in hydroponics to provide plants differing in size. These plants were sampled at 3-hour intervals from 600 to 2100 hours on 14 August 2007. Samples were frozen and freeze dried, and dried tissue was extracted and analyzed for soluble sugars and nitrate using LC chromatography. There was a greater increase during the day in dry/fresh weight ratio for small compared to large plants. On a fresh weight basis, tissue nitrate of small plants was only half that for larger plants. It did not vary with time. Soluble sugars were similar for all plant sizes early in the day, but increased two-fold more in the light for small compared to large plants. To model this behavior, plants were simulated as a 'big-cell' with simplified metabolic reactions and transport processes sensitive to internal metabolite concentrations. Photosynthesis and nitrate reductase were affected by irradiance and leaf area index. Amino acid, protein, and structure synthesis depended on concentrations of ammonium and sugars. Use of nitrate in leaves was affected both by nitrate reductase and availability of sugars. Sugars were produced by photosynthesis and consumed by respiration and processes related to growth. The strengths and weaknesses of this model are discussed. Source


Gent M.P.N.,CT Agricultural Experiment Station | Elmer W.H.,CT Agricultural Experiment Station | McAvoy R.J.,University of Connecticut
Acta Horticulturae | Year: 2012

Sub-irrigation for production of potted ornamental plants combats the waste of water and fertilizer inherent to traditional overhead watering systems used in greenhouses. Because current ebb and flow watering systems for flooded floors operate slowly, the root medium takes up water to near saturation during each irrigation event. We used a system that delivered and removed water rapidly, to restrict the water provided to the plants. We examined several parameters that vary between this partial saturation ebb and flow watering on a flooded floor compared to full saturation watering. Plants took up 20 to 30% less water and fertilizer. Biomass until flower development and bloom, and stem height, were reduced by 10 to 20% under partial saturation. This watering method did not affect flower development, or plant composition. Volumetric water content was the only parameter of the root medium that was affected by location on the flooded floor. Source


Gent M.P.N.,CT Agricultural Experiment Station | Elmer W.,CT Agricultural Experiment Station | McAvoy R.,University of Connecticut
Acta Horticulturae | Year: 2011

Sub-irrigation for production of potted ornamental plants combats the waste of water and fertilizer in traditional overhead watering systems used in greenhouses. However, current ebb and flow watering systems for flooded floors operate slowly. The root medium takes up water to near saturation during each watering cycle. There is no ability to restrict the water provided to the plants. We have examined a system to rapidly deliver and remove water. Less water is absorbed by the root medium and little if any water drains out of the pots. This improves plant quality and prevents spread of disease. We examined several parameters that vary between this partial saturation ebb and flow watering on a flooded floor compared to full saturation watering. Plants took up 20 to 30% less water and fertilizer. Biomass until flower development and bloom, and stem height, were also reduced by 10 to 20% under partial saturation. In one experiment with Poinsettia, inoculation of some plants with Pythium resulted in wilting of 20 of 240 non-inoculated plants grown under full saturation. No plants were affected under partial saturation. Postharvest quality of leaves and flowers in a controlled environment were similar under the two watering regimes. Source

Discover hidden collaborations