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Mayuko Otsubo and Mari Iwaya-Inoue

Florets of cut gladiolus (Gladiolus ×grandiflora hort. cv. Fujinoyuki) spikes kept at 25 °C under 14 h light/10 h dark condition showed severe wilting 4 days after flower opening. Treatment with 0.1 m trehalose prolonged vase-life 2 days, whereas inhibitors and other sugars had no effect. The upper florets also opened properly in trehalose-treated spikes, but not in cycloheximide-treated ones. After 4 days, the first florets of trehalose-treated spikes maintained water content more effectively than did controls or spikes treated with other sugars. The parenchyma adjacent to vascular bundles in the petals of trehalose-treated spikes maintained viability for 4 days. These results suggest that trehalose preserves cell viability in gladiolus spikes, thereby enhancing water uptake into petal tissues.

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Leon H. Allen Jr., Mary P. Brakke, and James W. Jones

A water flow model was developed which uses irradiance, leaf-to-air vapor concentration difference, and soil water potential to establish stomatal conductance. Water flow to the roots was computed using a linear approximation of radial flow through the soil toward the axis of the roots across concentric shells. Root length density and soil rooting volume within four separate layers or compartments were included in the model. The simulation was executed in small time step iterations. A small increment of transpiration was translated to a water content deficit at the root and then sequentially through the concentric shells to simulate water uptake and change of soil water potential. The change in soil water potential was used to increment changes in stomatal conductance and transpiration. The output of the model simulated the pattern of diurnal stomatal behavior observed in other types of experiments, as well as the total soil water extraction patterns of young potted citrus trees.

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Caroline H. Pearson-Mims and Virginia I. Lohr

Cut `Samantha' roses (Rosa hybrida L.) were placed in deionized water or a 20-mm Ca(NO3)2 pulsing solution for 72 hours. Flowers then were held in preservative solutions containing 0 or 4 mg fluoride/liter. Fresh weight gain, solution uptake, degree of flower opening, and flower longevity were reduced in the presence of fluoride in the holding solution. Visual symptoms of injury and reduced flower quality also were noted in treatments with fluoride. Pulsing improved fresh weight gain and degree of opening of flowers held in solutions containing fluoride. Pulsing also delayed the onset of visual symptoms of fluoride injury. Water uptake for flowers that were pulsed and exposed to fluoride was not different from uptake for flowers exposed to fluoride alone. Flower longevity for roses in all treatments was increased by using the calcium nitrate pulse, but pulsed flowers in fluoride did not survive as long as the control flowers.

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Theo J. Blom and Brian D. Piott

Low volume drip (2 l/h) was compared with 2 subirrigation ('trough' and `ebb and flo') systems for production of poinsettias and chrysanthemums in 15 cm diameter (1.6 l) `azalea' pots. Irrigation frequency as well as fertilizer rates were the same for all systems. The drip system received 280 ml per watering.

Two plantings of poinsettias (fall) as well as two plantings of chrysanthemums (spring and summer) showed no differences in plant growth between the drip and the subirrigation systems. Water uptake by the medium was similar for all irrigation systems, but water and fertilizer application was 70% higher for the drip system. Nutrients, measured at 4 depths within the pot at monthly intervals, increased with time and was markedly more concentrated in the top layer, regardless of the irrigation system.

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Mayuko Otsubo and Mari Iwaya-Inoue

Florets of cut gladiolus (Gladiolus ×grandiflora hort. cv. Fujinoyuki) spikes kept at 25 °C under 14 h light/10 h dark condition showed severe wilting 4 days after flower opening. Treatment with 0.1 m trehalose prolonged vase-life 2 days, whereas inhibitors and other sugars had no effect. The upper florets also opened properly in trehalose-treated spikes, but not in cycloheximide-treated ones. After 4 days, the first florets of trehalose-treated spikes maintained water content more effectively than did controls or spikes treated with other sugars. The parenchyma adjacent to vascular bundles in the petals of trehalose-treated spikes maintained viability for 4 days. These results suggest that trehalose preserves cell viability in gladiolus spikes, thereby enhancing water uptake into petal tissues.

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Fisun G. Çelikel and Michael S. Reid

The respiration of flowers of stock [Matthiola incana (L.) R. Br.] had a Q10 of 6.9 between 0 and 10 °C. Simulated transport for 5 days resulted in marked reduction in the vase life of flowers transported at 10 °C and above. Flower opening, water uptake, and vase life of the flowers increased somewhat in a vase solution containing 50 ppm NaOCl, and considerably in a commercial preservative containing glucose and a bactericide. Exposure to exogenous ethylene resulted in rapid desiccation and abscission of the petals, effects that were prevented by pretreatment with 1-methylcyclopropene (1-MCP). Even in the absence of exogenous ethylene, the life of the flowers was significantly increased by inhibiting ethylene action using pretreatment with silver thiosulfate (STS) or 1-MCP. STS was more effective than 1-MCP in maintaining flower quality.

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Carlos A. Parera and Daniel J. Cantliffe

Generally, sweet corn cultivars (Zea mays L.) carrying the shrunken-2 (sh2) gene have lower germination and seedling vigor than normal or sugary (su) cultivars. Seeds of sh2 `How Sweet It Is' (HSII) and `Crisp N'Sweet 711' (CNS-711) were imbibed for 6 hours. Rapid water uptake, higher seed leakage, and fungal infection were found in HSII, the lower germinating cultivar. Imbibition rate and leakage conductivity were reduced in both cultivars during the first 5 hours at 5C as compared with 25C. Sodium hypochlorite was an effective seed disinfectant. When the seeds were primed with sodium hypochlorite via solid matrix priming (SMP), germination under stressful conditions (soilcold test) was significantly improved in both cultivars. Primed seeds had significantly lower imbibitional rates and leakage conductivity than nonprimed seeds. The superior germination measured in primed and disinfected seeds was possibly due to the lower imbibitional rate and reduced seed fungal infection.

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R. H. Stamps, T. A. Nell, and D. J. Cantliffe

Abstract

Leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] was grown in controlled environment chambers set for day/night temperatures of 35/24C (high temperature regime, HTR) or 24/13C (low temperature regime, LTR). Fronds were harvested for vase life studies at 1100 and 1800 HR and held in holding rooms in deionized water. Plants were then moved to a greenhouse environment (16–25C) and, after 1 week, an additional set of fronds were harvested. Water uptake of harvested fronds declined exponentially and was generally lower for HTR fronds. HTR fronds had, for the most part, reduced vase life compared to LTR fronds. Most (81%) of the HTR fronds exhibited desiccation symptoms, whereas none of the LTR fronds did. These differences did not appear to be related to preharvest diffusive resistance or water potential differences.

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R. M. Taylor, L. B. Fenn, and C. A. Pety

Abstract

Several different split-root techniques, both horizontal zonation (1, 3, 6) and vertical zonation (2, 4, 7, 8), have been employed to study plant growth and water and nutrient uptake from differentially salinized root zones. High salinity level in one portion of the root zone may not affect overall plant performance if other portions of the root zone are relatively salt free (1, 3, 8). With uniform salinization, sodium chloride concentrations up to −0.8 MPa did not affect the 15N absorption rate in cotton, but osmotic pressures of −1.2 MPa substantially reduced it. However, water uptake and plant growth were affected to a greater extent than was 15N absorption (5).

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Jose M. Montano and William M. Proebsting

Abstract

Cut coastal Douglas-fir trees (1.0 to 1.5 m) were allowed to dry to various water potentials in a greenhouse. About one-half of the tree population, dried to a water potential (ψ) of −3.5 MPa, lost significant quantities of needles but were otherwise comparable to undried trees. Drying to −4.0 MPa or below resulted in significantly reduced water uptake after rehydration and irreversible damage. Changes in percentage of moisture content and stomatal conductance generally paralleled ψ but were less useful indices of the damage threshold. Bark wrinkling and percentage of broken needles were useful morphological indices of the damage threshold. Subjective ratings of quality were less reliable indices of the damage threshold. Water potential was an appropriate single measurement of Christmas tree water status and a suitable index of the damage threshold.