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  • Author or Editor: Jack W. Buxton x
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A controlled water table irrigation system (CWT) automatically provides water to plants. One edge of a capillary mat, on the bench surface, draws water from a trough (water table) below the bench. Each treatment trough was 30 cm long. As the distance between the water surface and the bench surface increases, the water in the growing medium decreases, the air increases; and the water potential decreases. In previous studies a constant CWT of 2 cm below the bench surface was the optimum placement for producing 15-cm pots of geranium. In this study the water table fluctuated between two distances below the bench surface. The fluctuating treatments were 2 cm to 3 cm, 2 cm to 4 cm, and 1 cm to 4 cm. The control treatment remained at a constant 2 cm below the bench surface. The fluctuating treatments were established by using two liquid level controllers connected to a switching mechanism that allowed the water table to fluctuate between the treatment settings. The rate of movement from the higher level to the lower level was determined by the rate of transpiration and evaporation occurring in individual treatments. The amount of water used for each treatment was determined by counting the number of times the solenoid turned on and multiplying this by the amount of water added to the trough. The leaf area and dry weight were the same for plants grown in 2 cm, 2 to 3 cm, and 2 to 4 cm treatments and these treatments were significantly greater than plants in the 1 to 4 cm treatment. The amount of water used by all treatments was nearly the same.

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Studies were conducted to determine if near infrared reflectance spectrophotometry (NIR) could be used to rapidly determine nonstructural carbohydrate (TNC) concentrations in marigold tissue. Marigold seedlings were grown in natural light growth chambers. Light intensity and CO2 concentration were adjusted to establish leaf samples with a wide range of the carbohydrate concentration. NIR spectra were collected on dry, ground samples using a reflectance scanning monochromator. Conventional laboratory analysis values for the same samples were correlated with spectral data. Calibration statistics were as follows: TNC; standard error of calibration (SEC)= 1.73, R2= 0.95, standard error of prediction or perfomance (SEP) = 1.64, R2= 0.95; Starch, SEC = 1.35, R2= 0.96, SEP = 1.37, R2= 0.94; Soluble Sugars, SEC = 0.26, R2= 0.91, SEP = 0.29, R2= 0.84. These results show that the NIR method can be used to rapidly determine concentrations of nonstructural carbohydrates in marigold leaf tissue and suggest the possibility for routine assessment of carbohydrate status for optimum management of environmental factors.

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The automatic subirrigation system consists of a capillary mat placed above a constant water level in a reservoir. The optimum mat height above the water level was established by slanting a flat surface so the difference in vertical height from one end of the surface to the other was 25 cm. A ground cover providing water movement but not root penetration was placed over the mat. The capillary mat extended beyond the lowest end of the slopped surface and into the reservoir, the mat at the lowest end of the slopped surface was at the same vertical height as the water in the reservoir and remained constantly saturated. Plug trays were placed at intervals of 2.5 cm in vertical height above the water level. An average of 96-100% germination was obtained with marigold, tomato, impatiens and pepper seed in trays placed 5-7.5 cm in vertical height above the water level. These seedlings continued to develop and reached transplanting stage quicker than other trays. The rate and % germination was less in trays placed on the surface nearer to the height of the water in the reservoir. Germination in trays above 12.5 cm was greatly reduced and seed that did germinate did not develop and eventually died.

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The pentose phosphate shunt (PPS) was shown to be active in roses (Rosa hybrida L.). The C6/C1 ratio indicated that possibly as much as 50% of the glucose oxidized in the rose flower is through the PPS. However, the activity of the PPS in relation to the Embden-Meyerhof-Parnas pathyway-tricarboxylic acid cycle (EMP-TCA) pathway did not change significantly throughout the cut life of the rose. There was a drop in the respiratory rate of petals throughout the cut flower life. The inner petals exhibited a consistantly higher respiratory rate than did outer petals regardless of whether the flower was kept in water or preservative.

Open Access

This study evaluated the effect of container shape and copper hydroxide on root and shoot development of marigold (Tagetes patula `Little Devil Flame') seedlings. Containers were modified in shape and volume by gluing triangular polycarbonate inserts vertically onto sides of the container. The inserts were either painted with copper or not painted. Inserts decreased container volumes (no insert = 480 cm3, two inserts = 340 cm3, and four inserts = 200 cm3). After 38 days the seedling roots were scanned for computer analysis, and leaf area and dry weights were determined. Copper effectively prevented roots from growing in contact with copper treated surfaces. Shoot dry weight and leaf area were greater with no inserts, but if inserts were treated with copper the shoot dry weight and leaf area were greater. Root dry weight was reduced 7%–10 % with two inserts and 20% with four inserts compared to no inserts. Copper treated inserts reduced the dry weight further. However, at the insert interface, root length was increased between 15%–20% by all copper treatments, with the greatest increase in the four-insert treatment.

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