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Jong-Goo Kang and Marc W. van Iersel

To evaluate the effects of nutrient concentration and pH of the fertilizer solution on growth and nutrient uptake of salvia (Salvia splendens F. Sellow ex Roem. & Schult. `Scarlet Sage'), we grew plants with five different concentrations of Hoagland nutrient solution [0.125, 0.25, 0.5, 1.0, and 2.0× full strength; electrical conductivity (EC) of 0.4, 0.7, 1.1, 2.0, and 3.7 dS·m-1, respectively]. In a concurrent experiment, plants were subirrigated with modified Hoagland solution at 0.5× concentration and one of five solution pH values: 4.4, 5.4, 6.4, 7.2, and 8.0. Shoot and total dry weight and leaf area increased greatly with increasing nutrient solution concentrations from 0.125 to 1.0×, while leaf photosynthesis (Pn), transpiration, and stomatal conductance decreased with increasing nutrient solution concentrations. Treatment effects on growth apparently were caused by changes in carbon allocation within the plants. Shoot: root ratio and leaf area ratio increased with increasing fertilizer concentration. Plants flowered 8 days later at low concentrations of nutrient solution than at high concentrations. Shoot tissue concentrations of N, P, K, and B increased, while C, Al, Mo, and Na decreased with increasing concentration of the nutrient solution. The pH of the nutrient solution had no effect on the growth or gas exchange of the plants, while its effects on nutrient concentration in the shoot tissue generally were smaller than those of fertilizer concentration. These results indicate that 1.0 to 2.0× concentrations of Hoagland solution result in maximum growth, apparently because the plants produce leaf area more efficiently at high fertilizer concentrations.

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David R. Dreesen and Robert W. Langhans

Abbreviations: CEGR, controlled-environment growth room; HI, high irradiance levels; LAR; leaf area ratio; LI, low irradianee levels; MHI, medium-high irradiance levels; MLI, medium-low irradiance levels; MRGR, mean relative growth rate; NAR, net

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Jean-Pierre Privé and J. Alan Sullivan

Growth rates for two types of tissue-cultured plant stock for `Heritage', `Ruby', and `Redwing' red raspberry (Rubus idaeus L.) were examined. Actively growing plantlets from the greenhouse (G) were compared to cold-treated (CT) plantlets from cold storage. The greatest differences between these two occurred during the first 6 weeks after planting. At 4 weeks, CT plants for all cultivars had longer canes and internodes, sometimes twice that of G plants. Although `Heritage' had greater total plant dry weights following chilling, `Ruby' and `Redwing' had less. Chilling had no effect on `Heritage' root growth but did reduce root dry weight for `Redwing' and `Ruby'. Relative growth rate (RGR) and leaf area ratio (L-AR) were more effective variables for analyzing growth as they considered differences in initial biomass and cane number and provided a better representation of the data during the initial 6 weeks of growth. All cultivars showed a greater total plant RGR and LAR for the CT plants at 6 weeks. During the first 4 weeks, the G plants were more efficient producers of root dry matter while the CT plants were more efficient producers of cane dry matter. By 6 weeks, the G plants had partitioned a greater percentage of their assimilates into cane growth while the leaves, canes, and roots of the CT plants contributed equally to total RGR. No difference in total or individual component RGR was observed after 6 weeks.

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Marc W. van Iersel and Jong-Goo Kang

To determine the effect of fertilizer concentration on plant growth and physiology, whole-plant C exchange rates of pansies (Viola ×wittrockiana Gams.) subirrigated with one of four fertilizer concentrations were measured over 30 days. Plants were watered with fertilizer solutions with an electrical conductivity (EC) of 0.15, 1.0, 2.0, or 3.0 dS·m-1 (N at 0, 135, 290, or 440 mg·L-1, respectively). Plants watered with a fertilizer solution with an EC of 2 dS·m-1 had the highest shoot dry weight (DW), shoot to root ratio, leaf area, leaf area ratio (LAR), and cumulative C gain at the end of the experiment compared to those watered with a solution with a higher or lower EC. Shoot tissue concentrations of N, P, K, S, Ca, Fe, Na, and Zn increased linearly with increasing fertilizer concentration. A close correlation between final DW of the plants and the measured cumulative C gain (CCG) (r2 = 0.98) indicated that the C exchange rates were good indicators of plant growth. There were quadratic relationships between fertilizer EC and gross photosynthesis, net photosynthesis, and dark respiration, starting at 13, 12, and 6 days after transplanting, respectively. Although plants fertilized with a fertilizer solution with an EC of 2 dS·m-1 had the highest C exchange rates, the final differences in shoot DW and CCG among ECs of 1.0, 2.0, and 3.0 dS·m-1 were small and it appears that pansies can be grown successfully with a wide range of fertilizer concentrations. Plants with a high LAR also had higher DW, suggesting that increased growth was caused largely by increased light interception. A detrimental effect of high fertilizer concentrations was that it resulted in a decrease in root DW and a large increase in shoot to root ratio.

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Marc van Iersel

Container size can affect the growth and development of bedding plants. The effects of widely differing container sizes on growth and development of salvia (Salvia splendens F. Sellow ex Roem. & Schult.) were quantified. Plants were grown in a greenhouse in 7.3-, 55-, 166-, and 510-mL containers. Container volume affected plant growth as early as 18 days after planting. Growth was positively correlated with pot size and differences increased throughout most of the growing period. Growth of the plants in the 7.3-mL cells was reduced because of a low net assimilation rate (4.34 g·m-2·d-1), compared to the plants in the 55-, 166-, and 510-mL pots (≈5.44 g·m-2·d-1). Plants in 510-mL containers grew faster than those in 55- and 166-mL containers because of a higher leaf area ratio. Both lateral branching and leaf expansion were suppressed by root restriction and flowering was delayed. The growth rate of plants in 166-mL pots declined after the onset of flowering, and final plant size was comparable for plants in 55- and 166-mL pots. Although water deficit stress or nutrient deficiencies cannot be excluded as contributing factors, these were probably not the main reason for observed differences.

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S. Jiménez and M.T. Lao

The plant quality in function of the ratio nitrate:ammonium has been studied. The experiment was carried out in a recicling system in a Buried Solar Greenhouse. Dieffenbachia amoena `Tropic Snow' was cultivated in expanded clay substrate. The parameters considered to evaluate the quality have been plant height, leaf area index (LAI), leaf area ratio (LAR), leaf weight ratio (LWR), biomass, shoot to root ratio, number of buds, number of leaves, leaf length and width, leaf color, variegation, and ornamental visual quality evaluated by a group of experts and consumers. The rehearsed NO3-:NH4 + ratios has been 100:0, 50:50, and 0:100. The amoniacal form improves the following productive parameters: plant height, LAI, biomass, number of leaves, number of buds and color of the leaf, as well as the visual quality as much for experts as for consumers.

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M.M. Gaye and A.R. Maurer

Abbreviations: LAR, leaf area ratio; LWR, leaf weight ratio; SLA, specific leaf area. Contribution no. 403 from Agriculture Canada, Research Station, Agassiz, B.C. V0M 1A0. We thank F. Seywerd and M. Henderson for technical assistance, and M

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D. Michael Glenn

This study examined the interaction between a reflective particle film and water use efficiency (WUE) response of irrigated and non-irrigated apple trees (Malus ×domestica) over a wide range of environmental conditions. The objectives were to measure isotopic discrimination (Δ13C and δ18O), specific gas exchange, and WUE response of ‘Empire’ apple treated with a reflective particle film (PF), with and without supplemental irrigation, compared with an untreated control, with and without supplemental irrigation, over a range of leaf area indices (LAI), seasonal evapotranspiration (ETo), and vapor pressure deficits (VPD) to determine the mechanisms of action affecting WUE in apple. Short-term whole canopy gas exchange studies and isotope discrimination analysis were used to test the hypothesis that WUE was modified by the use of a PF. In whole canopy gas exchange studies, carbon assimilation (A) and transpiration tended to increase, and WUE and canopy conductance tended to decrease, with VPD within each LAI class from 2 to 6. For VPD > 1 kPa, the PF irrigated treatment consistently had the greatest WUE and other treatments were intermediate for LAI of 2 to 4. The PF irrigated and non-irrigated treatments had greater WUE than the control irrigated and non-irrigated treatments for VPD ≤ 2 kPa and there were no treatment effects for VPD > 2 kPa in the LAI range of 4 to 6. The PF non-irrigated was equivalent to the control non-irrigated treatment at VPD of 1 to 3 kPa, but was significantly lower at VPD of 3 to 4 kPa. PF irrigated and non-irrigated treatments had the greatest carbon isotope discrimination (Δ13C), the control non-irrigated treatment had the lowest Δ13C, and the control-irrigated treatment was intermediate. Oxygen isotope enrichment (δ18O) was positively correlated with the mean growing season VPD and mean growing season evapotranspiration. Δ13C was significantly and positively correlated with δ18O. Seasonal WUE was negatively correlated with Δ13C and there was an interaction with LAI. The seasonal water use of apple is better evaluated with stable isotope discrimination integrating seasonal variation rather that the use of whole canopy gas exchange measurements that measure WUE for brief periods of time. Δ13C was an accurate measurement of apple WUE and indicated that the PF irrigated treatment had the greatest Δ13C and so the lowest WUE compared with the control non-irrigated treatment at LAI from 4 to 6. The reduced WUE of the PF irrigated treatment compared with the control non-irrigated treatment is likely due to increased g S from lower canopy temperature and increased canopy photosynthetically active radiation diffusion that drove increased A. δ18O was an indicator of seasonal water use over six growing seasons due to its high correlation with ETo. In ‘Empire’ apple, A can be increased with PF and irrigation treatments, but at the cost of decreased WUE.

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Ariana P. Torres and Roberto G. Lopez

directly correlated with biomass allocation to leaves. Leaf area ratio (LAR) was calculated as total leaf area divided by total dry weight, representing the amount of biomass located in a certain leaf area ( Lambers et al., 2008 ). Relative leaf chlorophyll

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Dean E. Knavel and Robert L. Houtz

Plants of Main Dwarf, a short-internode mutant of the normal-internode `Mainstream' muskmelon (Cucumis melo L.), have shorter internodes, fewer nodes, less total vine length, less total dry weight, smaller leaves, increased chlorophyll concentrations, increased specific leaf dry weight, and increased ribulose-1, 5-bisphosphate carboxylase/oxygenase (EC, rubisco) activity per unit leaf area than `Mainstream' plants. Main Dwarf plants produce an equal number of fruit as `Mainstream' plants but are only half their size. Many of the plant and fruit characteristics for F1(Main Dwarf × `Mainstream') are similar to those of `Mainstream', except for greater leaf chlorophyll and rubisco activity per unit leaf area. The F1 (`Mainstream' × Main Dwarf) produced fewer and lower weight fruit than its reciprocal, F1 (Main Dwarf × `Mainstream').