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Catherine S.M. Ku and David R. Hershey

Geraniums (Pelargonium × hortorum L.H. Bailey `Yours Truly') were grown in a glasshouse from 15 Mar. to 9 May as single pinched plants in a growing medium with a bulk volume of 1.3 liters per 15cm diameter standard plastic pot. Plants received constant fertigation with N at 300 mg·liter-1 from 20N-4.4P-16.6K with leaching fractions (LFs) of ≈ 0, 0.1, 0.2, and 0.4. The LF is the volume of solution leached from the container divided by the volume of solution applied to the container. There were 24 irrigations during the study. Plants with LFs of 0.2 and 0.4 had 46% larger leaf area, 40% more shoot fresh mass, and 37% more shoot dry mass than plants with LFs of 0 and 0.1. By week 5, the leachate electrical conductivity (EC) at 25C for LFs of 0.1,0.2, and 0.4 had increased from ≈ 3 dS·m-1 initially to 12, 8, and 4 dS·m-1, respectively. At harvest, the EC of a saturated medium extract (ECe) was 7, 4, 3, and 2 dS·m-1 for LFs of 0, 0.1, 0.2, and 0.4, respectively. At harvest, medium EC, with LFs of 0.1, 0.2, and 0.4 was 47% 68%, and 60% less in the lower two-thirds of the pot than in the upper third. With a LF of 0, the medium EC, was `not lower in the bottom of the pot. With fertigation N at 300 mg·liter-1, minimizing the LF substantially reduced growth of container-produced geraniums. In addition to specifying LF, the number of container capacities leached per week, termed the leaching intensity (LI), should be calculated for container leaching studies. In two studies, the LFs may be the same yet the LIs can be very different.

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Matthew D. Taylor, Paul V. Nelson and Jonathan M. Frantz

The cause of sudden substrate pH decline by geranium (Pelargonium ×hortorum Bailey) is unknown. Published reports indicate that this response can be influenced in other plants by temperature and light extremes. The first of five experiments compared plants with all flowers removed to plants that were allowed to flower. Experiment 2 compared plants grown at four light levels (105, 210, 450 and 1020 μmol·m–2·s–1). Experiment 3 compared plants grown at four temperatures (14/10, 18/14, 22/18 and 26/22 °C day/night). Experiment 4 was a repeat of Experiment 1 and Experiment 5 was a factorial combining the three highest light levels and the three highest temperature levels. Plants allowed to form flowers had a final substrate pH of 5.7 compared to 6.3 for plants where flowers were removed. With increasing increments of temperature, substrate pH declined from 6.8 to 4.6 and with increasing light intensity from 6.1 to 4.8. There was no effect of flower removal in Experiment 4. Light and temperature had no consistent effects in Experiment 5 throughout 46 days after planting, with most pH values remaining in the acceptable range of 5.6–6.1. By 60 days, temperature treatments began to segregate, with pH being highest in the low-temperature treatments and lowest, down to 5.5, in the highest-temperature treatments. High temperature stimulated geranium acidification in both experiments, with the effect more severe in the first experiment. The flowering and high light effects were not duplicated in the second trial. This indicates that an additional factor is involved in expression of the light, temperature, and flowering control of acidification.

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Gary R. Bachman and Mary C. Halbrooks

The role of Fe DTPA (Diethylenetriaminepentaacetic acid) in the occurrence of a specific physiological disorder affecting the leaves of cutting geranium was investigated. Industry reports indicate that affected leaves have excessively high concentrations of Fe and sometimes Mn. Symptoms of the disorder first affect maturing leaves, and may in severe cases affect immature leaves. Symptoms progress from marginal/interveinal chlorosis and necrosis, to affect whole leaf necrosis. Rooted cuttings were grown in a soil-less peat based media, with Fe DTPA concentrations of 1, 5, 15, and 20 ppm. Iron and manganese leaf concentrations were significantly higher in symptom than in non-symptom tissue and increased as Fe DTPA treatment level increased. As Fe DTPA treatment level increased there was a significant increase in dry weight of symptom tissue and a decrease in non-symptom tissue dry weight. Plants grown in media amended with dolomite (pH> 5.8) had similar degrees of symptom occurrence compared to plants grown in unamended media (pH ≈ 5.4).

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Mana Libran and David J. Williams

Leca clay pebbles were characterized and tested as a possible growing-medium for use in floriculture production systems that recycle irrigation water. Leca clay pebbles are light porous particles made by heating clay. X-ray diffraction tests indicate that high manufacturing temperatures (1100C) result in final particles composed primarily of quartz. Water-holding capacity was determined by pressure plate apparatus at eight pressures. Leca particles that were 4 to 8 mm retained more water than particles sized 12 to 18 mm. The bulk density of the particles were 0.43 and 0.37 g/cc for the 48-mm and the 12- to 18-mm particles, respectively. The pH of the leca particles was 7.77. The cation exchange capacity of the leca particles was relatively low compared to a standard soilless growing medium of 1 pine bark: 1 peat: 1 perlite (by volume). Leca particles have a CEC of o.82 me/100 g Ca and 6.36 me/100 g K, where the CEC of the previously mentioned soilless.medium was 24.21 me/100g Ca and 30.08 me/100 g K. Leca clay pebbles were tested as growing medium for the production of geraniums (Pelargonium hortorum) stock plants.

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Susan Parent

The most appropriate time for VAM inoculation has been assumed to be the early stages of plant growth, and this study aimed to investigate the impact of VAM inoculation at the seedling and at the 10-week geranium plant stage. Seeds were planted in propagation plug trays (200) filled with four different seed-germinating substrates: half were inoculated with Glomus intraradices while the other half were noninoculated controls. Two types of media received inoculum or not (control); they consisted of sphagnum peat with perlite in one case and vermiculite in the other. After 10 weeks growth, the root systems were checked for colonization, and height, weight, and leaf number were registered. The subsequent growth was carried out in 4-inch azalea pots with the appropriate medium. The pre-in-oculated plants were transferred in Mycori-Mix, and the controls were transferred in Pro-Mix. All plants received mild liquid fertilization at each irrigation time (20N–2P–20K). The number of cuttings and flowers were monitored 6 weeks after beginning of pot growth. The pots were displayed in a complete factorial block with six replicates per treatment, and 10 plants were used for each experimental unit. Significant differences did occur between plants initiated in the different germinating substrates; when pre-inoculated, 12.5 cuttings and 7 flowers were recorded in comparison to 9.8 and 3.9, respectively, for controls. These results reflect the importance of introducing VAM at the earliest growth stage.

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N.S. Khoury, E.J. Holcomb, J.W. White and M. Rand

Excessive electroconductivity measurements have been observed in the surface layer of subirrigated substrates. A hydrophilic gel and rockwool were used as pot mulches in order to reduce the surface layer salt buildup by absorbing the salts and/or reducing evaporation.

Six treatments of `Crimson Fire' and `Victoria' CVI geraniums were grown in 11 cm. pots. Treatments were: Trt 1 - top irrigation, N source 20-10-20; trt 2 - subirrigation, N source 20-10-20; trt 3 - subirrigation, N source in equal portions of 20-10-20 and CRF, gel mulch; trt 4 - subirrigation, N source CRF, gel mulch; trt 5 - subirrigation, N source in equal portions of 20-10-20 and CRF, wool mulch; trt 6 - subirrigation, all N source CRF, wool mulch.

Pots were divided into 3 equal volume portions. Electroconductivity, as a measure of soluble salt (SS) level, was taken. All treatments had increasing SS levels with increasing pot height. Trt 2 had surface layer salt levels significantly higher than trt 1. `Victoria' trts 3,4,5 and 6 surface layers had significantly lower SS levels than trt 1 surface layers. `Crimson Fire' trt 4's surface layer had significantly lower SS levels than the surface layer of trt 1. Trts 4 and 6 bottom layers of both cultivars had significantly lower SS levels than all other treatments.

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Michael Compton and Timothy Zauche

Anaerobic digestion-derived biosolids (ADB) has the potential to become a complete or partial substitute for sphagnum peat in the greenhouse and nursery industry. Bedding plant production being one of the largest segments of the floriculture industry may possess the greatest application for this new organic addendum to soilless media. An experiment was conducted in which geraniums (Pelargonium ×hortorum `Red Elite') were grown in potting mixes formulated with vermiculite and perlite plus various concentrations and combination of anaerobic digestion-derived biosolids (ADB) and sphagnum peat to determine if ADB could be used as a partial or complete replacement for sphagnum peat in soilless horticultural growing media. Plants were grown during June and July 2003–05 in the greenhouse at 75 ± 5 °F and normal light and photoperiod. Plant growth was assessed by measuring the dry weight of stem tissue. Plants were harvested when at least 50% of the total number of plants produced at least one inflorescence. Floriferousness was measured by counting the number of visible inflorescences per plant. Dry weight of plants grown in media containing ADB was greater than those grown in media containing sphagnum peat as the sole organic addendum. Plants grown in media containing ADB were also more floriferous. This study demonstrates that ADB has great potential for use as an organic addendum to horticultural growing media as a partial or complete replacement for sphagnum peat. Use of anaerobic digester-derived biosolids in horticultural growing media is a protected intellectual property and available for license through the WiSys Technology Foundation.

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Ritika Gupta, S. Banerjee, G.R. Mallavarapu, S. Sharma, S.P.S. Khanuja, A.K. Shasany and Sushil Kumar

An efficient protocol has been established for generating somaclones in the Indian rose-scented geranium Pelargonium graveolens cv. Bipuli, which yields Reunion Island-type essential oil. Murashige and Skoog's (MS) medium supplemented with 4.5 mg·L-1 BA and 1.0 mg·L-1 NAA was found optimal for induction of callus from leaf explants. Callus regenerated shoots when transferred to MS medium with 2.5 mg·L-1 BA and 0.1 mg·L-1 NAA. The regeneration percentage as well as number of shoots per cm2 of callus was greatly improved by addition of ADS at a concentration of 3.0 mg·L-1. Regenerated shoots rooted within 20 days following transfer to half-strength MS medium with 0.1 mg·L-1 NAA. Plantlets were acclimatized under glasshouse conditions with 80% to 85% survival. Randomly selected 30 individual calliclones were subjected to field trial with wild-type parent in randomized block design, replicated three times with 90% survival for two successive years. Characterization of these calliclones for essential oil yield and quality traits demonstrated induction of variability in all the characteristics examined in negative and positive directions in comparison with the wild-type parent. This screening led to the identification of somaclone B22, which out-yielded the wild-type parent as well as the rest of the somaclones. The quality of the essential oil of B22 was similar to that of the parent. Chemical names used: N 6-benzyladenine (BA); naphthalene acetic acid (NAA); adenine di-sulphate (ADS).

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R.M. Madakadze, J.E. Krochko and T. Senaratna

Storage proteins in zygotic and somatic embryos of `Scarlet Orbit Improved', zonal geranium (Pelargonium hortorum L.H. Bail.) were identified and characterized using gel electrophoresis. The major seed storage proteins in zygotic embryos were an 11S globulin and two low molecular weight (LMW1-2) proteins. The 11S globulin consisted of four distinct subunits (53-74 ku), with each subunit being composed of an acidic polypeptide (A1-A4; 28-44 ku) linked via disulphide bonds to a basic polypeptide (B1-B4; 20-25 ku) and was named pelargin. The LMW (15.5 and 12,5 ku) albumins were not linked with disulphide bonds. Mature somatic embryos contained 80% of the proteins in zygotic embryos. Although protein profiles were more distinct in mature somatic embryos compared to nonmature, none of the zygotic embryo storage protein was present in the somatic embryos, indicating lack of complete maturity of somatic embryos. This study identified zygotic embryo proteins and demonstrated that maturation of somatic embryos improves protein content and types of proteins.

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Catherine S. M. Ku and David R. Hershey

Single-pinched `Yours Truly' geranium (Pelargonium × hortorum) were greenhouse grown in 15-cm diameter pots. They received constant liquid fertigation with a modified Hoagland solution #1 at 0.25, 0.5, 1.0, and 1.5 strength. The 1.0 strength Hoagland solution contained 210 mg/L NO3-N and 31 mg/L P. Leaching fractions (LFs) were 0, 0.2 and 0.4. The total P applied via fertigation ranged from 33 mg at 0 LF and 0.25x Hoagland to 407 mg at 0.4 LF and 1.5x Hoagland. The leachate P concentration ranged from <5 mg/L to -60 mg/L. The P concentration in the recently matured leaves was in the acceptable range for all treatments. We were able to recover 90 to 99% of the applied P by analyzing the shoots, soilless medium, and leachate. Only 4% of the recovered P was in the leachate for plants receiving 0.5x Hoagland and a 0.2 LF. However, these plants were equal in yield to plants receiving higher fertigation rates and higher LFs.