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B. Dansereau, Y. Zhang, S. Gagnon and H.L. Xu

We examined effects of single-layer glass and double-layer antifog polyethylene films on growth and flowering of stock (Matthiola incana L.) and snapdragon (Antirrhinum majalis L.) in a 3-year period. Stock produced more buds/spike with shorter but thicker stems under single-layer glass and under antifog 3-year polyethylene, and showed higher photosynthetic capacity (P c) under single-layer glass than under other covers regardless of light regimes. Similarly, growth and flowering of snapdragon were significantly better under single-layer glass than in polyethylene houses. A supplemental light of 60 μmol·m-2·s-1 accelerated flowering by 20 to 25 days, improved flower quality, and eliminated differences in plant growth and quality of snapdragon between covering treatments. The P c of stock was lower under all polyethylene covers than under single-layer glass. Among the three antifog polyethylene films, a slightly higher P c was measured for plants under antifog 3-year polyethylene. However, there was no difference among covering treatments in the net photosynthetic rate (P N) at low light level (canopy level). Supplemental lighting reduced P c of stock leaves, especially under single-layer glass, and diminished differences in P c among covering treatments. Dry mass was more influenced by larger leaf area caused by higher leaf temperature than by P N. Overall, antifog 3-year polyethylene was a good covering material when both plant quality and energy saving were considered.

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Scott Aker and William Healy

Thinning of Alstroemeria `Regina' at 0, 30, 60, or 90% did not result in induction of cyclic variation in shoot length. Thinning caused an overall decrease in stem length and final fresh weight of storage roots (SR). Number of nodes on generative shoots did not change due to thinning treatment but varied over time. Thinning by 90% reduced yield, delayed harvest and increased flower quality. In the second year, plants were rethinned and grown with supplemental HPS irradiance of either 25 or 125 μmolm-2sec-1. Weekly production diminished with increased thinning, and was amplified by increased total fluence. In a second experiment, thinning resulted in decreased shoot, rhizome and SR growth in plants sampled before and after flowering. Rhizome index increased with increased thinning, indicating a relatively smaller impact of thinning on rhizome growth compared to SR and shoot growth. The carbohydrate composition of SR tissue was unchanged by treatment. Thinning resulted in decreased SR production and decreased fresh weight per SR between thinning treatments. Change in total amount of carbohydrate reserves in the SR is therefore due to change in number & size of the SR.

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Douglas A. Hopper, Troy T. Meinke and Virginia S. Store

The computer simulation model ROSESIM is based on `Royalty' rose (Rosa hybrida L.) growth response to 15 unique treatment combinations of photosynthetic photon flux (PPF), day temperature (DT), and night temperature (NT) under constant growth chamber conditions. Environmental factors are assumed constant over an entire day, but set points may vary over the duration of the crop. Anticipated values for factors may be read from an ASCII file, allowing a variety of strategies to be modeled and compared.

A Valentine's Day crop senario compared 2 management strategies for crop development time and flower quality: [1] constant 24/17.1 DT/NT for the entire crop, or [2] 15 days warm 30/20C DT/NT to promote bud break, 10 days 20/15C DT/NT to promote stem caliper and leaf size, 10 days 25/18C DT/NT to promote bud development, and remaining time to flower 20/15C DT/NT to enhance flower size and color. PPF was increased gradually over crop time as would occur naturally for Dec. to Feb. Strategy [2] had longer stems (63 vs. 50 cm), similar stem and leaf dry weights, but less flower bud dry weight (1.0 vs. 1.6 g), while flowering 2 days earlier (41 vs. 43 days after pinch). c:\pm4\ 4

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Ria T. Leonard and Terril A. Nell

Several pulse solutions were tested for their effectiveness in preventing leaf senescence on four cut oriental lily cultivars (Lilium sp. `Acapulco', `Kissproof', `Noblesse' and `Star Gazer'). Stems were pulsed 24 hours after harvest for 1 hour, stored in boxes in the dark for 5 days at 3 °C (37.4 °F) then evaluated in postharvest conditions. A new commercial product called Chrysal BVB, a proprietary mixture manufactured by Pokon & Chrysal (Miami) containing cytokinine and gibberellic acids, was the most effective product tested. Chrysal BVB [1 mL·L–1 (0.1%)] prevented leaf chlorosis and abscission on `Acapulco' and `Noblesse' and significantly reduced it by 82% on `Star Gazer' and by 69% on `Kissproof'. Stems pulsed in Fascination, a commercial mixture containing 1.8% gibberellins (GA4+7) and 1.8% benzyladenine [5.4 mg·L–1 (ppm) each], virtually prevented leaf chlorosis on `Noblesse', reduced it by 50% or more on `Acapulco' and `Star Gazer', and significantly delayed it 8 days on `Kissproof'. A 10 μm (2 ppm) pulse in thidiazuron, a substituted phenylurea with cytokinin-like properties, delayed leaf chlorosis on `Star Gazer' but to a lesser extent compared to BVB and Fascination. Chrysal SVB, a propri-etary mixture manufactured by Pokon & Chrysal containing gibberellic acid, had no effect on reducing leaf chlorosis on `Star Gazer'. None of the pulse solutions had adverse effects on bud opening, flower quality or vase life. Maintaining stems in a bulb flower preservative significantly reduced leaf chlorosis and abscission in all cultivars when stems were not pretreated with a pulse solution or when a pulse solution was ineffective.

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C.M. Grieve, J.A. Poss and C. Amrhein

Two cultivars of Matthiola incana (L.) R. Br. (`Cheerful White' and `Frolic Carmine') were grown in greenhouse sand cultures to determine the effect of salt stress on growth, ion relations, and flower quality. Two types of irrigation waters, differing in ion composition, were prepared to simulate saline wastewaters commonly present in two inland valley locations in California. Solution ICV was typical of saline tailwaters frequently found in the Imperial and Coachella Valleys and contained Cl, Na+, SO4 2–, Mg2+, Ca2+, predominating in that order. Solution SJV was dominated by Na+ and SO4 2– and simulated saline drainage effluents often present in the San Joaquin Valley. Five treatments of each salinity type were imposed; each was replicated three times. Electrical conductivities of the irrigation waters (ECi) were 2.5, 5, 8, 11, and 14 dS·m–1. Plant heights were determined weekly. Seedlings were sampled for ion analysis 9 weeks after planting. Flowering stems were harvested when about 50% of the florets in the inflorescence were open. Total stem length, weight and diameter, numbers of florets and buds, and inflorescence length were measured at final harvest. All plants remained healthy throughout the experimental period with no visible signs of ion toxicity or deficiency. Although length of the flowering stems decreased with increasing salinity, stems were of marketable quality even at the highest salinity level. Mineral ion composition of the vegetative tissues generally reflected ion concentrations in the irrigation waters. Shoot Mg2+ and Cl were higher and shoot Na+ lower in seedlings irrigated with ICV waters than with SJV waters. Shoot P was reduced over control levels once salinity exceeded 11 dS·m–1. Both cultivars were highly selective for K+ over Na + and selectivity coefficients (SK, Na) increase about 60% as salinity increased from 2.5 to 14 dS·m–1. This study illustrates that commercially acceptable cut flowers of stock may be produced under irrigation with moderately saline wastewaters.

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G.A. Picchioni, M. Valenzuela-Vazquez and L.W. Murray

Lupinus havardii Wats. is a promising new specialty cut flower crop, but data on its greenhouse culture and management are limited. Two experiments investigated senescence-delaying activity of preharvest Ca fertilization and postharvest preconditioning with 1-MCP on L. havardii `Texas Sapphire' cut flower stems (racemes). In the first study, Ca (as CaCl2) was added to the nutrient culture solution at concentrations of 0, 2.5, 5.0, and 10.0 mm for 88 days in a greenhouse. Additional CaCl2 supply did not affect the total number of racemes produced per plant, the average number of flowers per raceme, or the retention of individual flowers on cut racemes over a 7-day vase period. However, Ca concentration in cut raceme tissues, ranging from 5.3 to 7.6 mg·g-1 dry weight, increased linearly with increasing Ca concentration in the nutrient solution, which was accompanied by a linear increase in average fresh weight retention per raceme and individual mature flowers (up to 7% above controls) during the 7-day vase period. In the second study under similar plant culture and vase conditions, 1-MCP applied at harvest resulted in an average fresh weight retention increase of 9% above controls during 7 days in the vase. Equivalent levels of desiccation in control racemes (loss in fresh weight retention) were delayed by 1.5 to 3 days in racemes with the highest Ca concentrations and those that had been preconditioned with 1-MCP. In view of the physiological significance of desiccation in cut flower quality loss, preharvest Ca fertilization and postharvest 1-MCP preconditioning may be useful techniques for delaying senescence and maintaining vase quality of cut L. havardii racemes. Chemical name used: 1-methylcyclopropene (1-MCP)

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Jocelyn L. Catley and Ian R. Brooking

Flowering responses of Heliconia psittacorum L.f. × H. spathocircinata Aristeguieta `Golden Torch' to temperature and photosynthetic photon flux (PPF) were determined in controlled-environment conditions using a 2 × 2 factorial combination of temperature (32C day/20C night and 24C day/20C night) and PPF (475 and 710 μmol·m–2·s–1). Temperature had no significant effect on new shoot production, with an average of 9.3 shoots per plant being produced over the 248 days of treatment. More shoots, however, were produced at the higher PPF level (10.1 compared with 8.3 shoots). The proportion of shoots that initiated flowers (85%) was similar in all treatments. The duration from shoot until inflorescence emergence was significantly less at 32C day/20C night than at 24C day/20C night (140 and 146 days, respectively) and was unaffected by PPF. This duration also was significantly affected by the interacting effects of order of shoot appearance and the number of leaves subtending the inflorescence. The second shoots to emerge had the shortest duration from shoot emergence to inflorescence emergence. The number of leaves subtending the inflorescence increased at the higher temperature and decreased as shoot order increased but was unaffected by PPF. Temperature and PPF levels influenced total leaf area at flowering, with highest areas being achieved in the high temperature–low PPF combination. Acceptable flower quality with at least two, opened, well-formed, well-colored bracts was obtained in all treatments, although flower stems were taller and thicker at 32C day/20C night and these dimensions increased further with increasing order of shoot appearance. Stem diameters tended to be thinner at the lower PPF level. Overall, temperature was more dominant than light in influencing production and quality of flowers, but developmental factors associated with the order of shoot appearance also played a significant role. Flower production of `Golden Torch' should be feasible in temperature-controlled glasshouses in temperate regions where mean air temperatures can be maintained at ≈20C.

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Susan S. Han

The effects of the duration of cold storage, as well as the concentration, timing, and means of application of a solution containing 25 mg·L-1 each of benzyladenine (BA) and gibberellins (GA4+7) on the postharvest quality of cut Asiatic and Oriental lilies (Lilium sp.) were evaluated. Depending on the cultivar, lower leaves began to turn yellow between 1 and 2 weeks after placing non-cold-stored stems in a 20 °C room illuminated 12 h·d-1 with 8 μmol·m-2·s-1 from cool-white fluorescent lamps. Leaf yellowing continued to progress upward until the end of the vase life. Cold storage (3.3 °C) worsened the leaf disorder, particularly, on the Oriental lily `Stargazer'. The longer the duration of cold storage, the earlier the development of leaf yellowing and the higher the percentage of leaves that were chlorotic. In addition, cold storage induced bud blasting, inhibited flowers from fully opening, and reduced the longevity and fresh weight of open flowers and the vase life of cut stems. Spraying leaves with a solution containing 25 mg·L-1 each of BA and GA4+7 significantly reduced cold-storage-induced leaf yellowing, bud blasting, and vase life of three of the four cultivars tested. The development of leaf yellowing declined with increasing concentration of BA+GA4+7. The susceptibility of `Stargazer' to cold-storage-induced leaf yellowing and bud blasting can be counteracted by a concentration of growth regulators higher than that which was effective for the other cultivars. Timing of the BA+GA4+7 application was not critical, as there were no differences in leaf yellowing or bud development when the solution was sprayed before or after the cold storage. Addition of BA+GA4+7 (0.5 or 2.5 mg·L-1 of each) to the preservative solution or a pulsed treatment in solutions containing 25 mg·L-1 each of BA and GA4+7 for 4 hours prevented leaf yellowing, but increased bud blasting. For practical applications, growth regulators can be sprayed prior to or after cold storage in order to improve the postharvest leaf and flower quality of cut lilies.

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and maintained at 2-inch depths. The addition of herbicide (trifluralin + isoxaben) had little to no impact on weeding frequency or time when plots were mulched. Tuff Particle Size Improves Lily Flower Quality Limited information is available about the

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Yun-wen Wang, Bruce L. Dunn, Daryl B. Arnall and Pei-sheng Mao

geranium and their relationship with flower quality traits. The objective of this study was to see if NDVI and SPAD values could be used to monitor the nutrient status in potted geraniums. Materials and Methods Plant materials and growth conditions. On 2