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  • Author or Editor: Donita L. Cartmill x
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After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic efficiency, and, in particular, to assess if low-to-moderate injury induces a compensatory increase in photosynthesis. Gas exchange and light-adapted fluorescence were measured on non-injured portions of the leaflet lamina adjacent to the injured area as well as on portions of leaflets that included leafminer injury. Results indicate that damage of the photosynthetic apparatus did not extend beyond the injured areas by leafminers. Furthermore, although a strong relationship between the proportion of leafminer injury and area-based net CO2 assimilation rate of injured leaflet tissue was found, there was no evidence that pecan leaves were able to compensate for leafminer injury by upregulating CO2 assimilation in leaflet tissue that was unaffected.

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The uptake of nitrogen (N) in nitrate or ammonium (NH4 +) form affects physiological and metabolic processes and toxicity may develop in plants receiving high concentrations of NH4 +. The objective of the present study was to delineate the response of bell pepper plants to varying proportions of NH4 + combined with increasing concentrations of potassium (K) in the nutrient solution. Bell pepper plants were tolerant to moderate proportions of NH4 + (25% or less or 50% or less); however, higher proportions resulted in growth reduction. The application of higher K concentrations in the nutrient solution did not ameliorate the growth on vegetative plant parts; however, when K was increased to 9 mm, the yield was sustained even when 50% of total N was in the NH4 + form. Decreased shoot:root ratio and harvest index indicated that biomass accumulation was affected more in the shoot than in the root and in the fruit than in the shoot, respectively. There was a lower concentration of NH4 + in the roots compared with leaves, suggesting that the higher K concentration that resulted from the increased K in the nutrient solution was associated with NH4 + translocation through the xylem. A decrease in calcium and magnesium detected in leaves suggests an antagonistic relationship with NH4 + and K in the nutrient solution, which was correlated with the acidification of the growing medium. Higher yields when K was at 9 mm may be the result of the high photosynthetic rate and stomatal conductance (g S) detected in plants fertigated with 25% of total N as NH4 + and the higher leaf water potential when the proportion of NH4 + was 50%. The biochemical composition of fruits was affected because both high NH4 + and increased K resulted in higher ethylene production, lipid peroxidation, superoxide dismutase activity, and carotenoids.

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The present study was conducted to determine the critical optimum and toxic concentrations of potassium (K) using segmented analysis and its relationship with some physiological, anatomical, and nutritional responses to increasing K in hydroponically grown Lilium sp. L. cv. Arcachon. Plants were fertigated with nutrient solutions containing K (Kext) at 0, 2.5, 5.0, 7.5, 12.5, 17.5, 22.5, and 30 mmol·L−1. Maximum flower diameter occurred when, on a dry mass basis, shoot K (Kint) ranged from 504 to 892 mmol·kg−1; however, a lower Kint was required to obtain maximum biomass accumulation and shoot length (384 and 303 mmol·kg−1, respectively). Potassium increased in all plant organs as K in the nutrient solution increased. Nitrogen increased in young leaves and magnesium (Mg) decreased as Kext increased. Concentrations of Kext from 5 to 17.5 mmol·L−1 increased the size of chlorenchyma and occlusive cells; however, metaxylem vessels were unaffected. Net photosynthetic rate was higher in young leaves, whereas water potential increased in both young and mature leaves when Kext was greater than 22.5 mmol·L−1. Critical concentrations varied according to the growth parameter. Optimum Kint ranged from 303 to 384 mmol·kg−1 for vegetative parts, whereas parameters related with flower growth ranged from 427 to 504 mmol·kg−1. Concentration of 504 mmol·kg−1 Kint was associated with optimum growth for all the parameters assessed, whereas a Kint greater than 864 mmol·kg−1 was associated with a decline in growth; thus, these concentrations were considered as the critical optimum and critical toxicity levels, respectively. The optimum and toxicity critical Kint were estimated when Kext in the nutrient solutions was 5.6 and 13.6 mmol·L−1, respectively.

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The domestication of wild orchids for commercial production is a new endeavor, which may represent a sustainable alternative to the collection/harvest from natural populations of threatened or endangered orchid species. In the present study, the growth and nutrition of vegetative plants of Laelia anceps Lindl. as affected by three components of the growing medium (peat, volcanic rock, and/or horticultural grade charcoal) and the nutrient solution concentration, measured as osmotic potential (ψS), were assessed using mixture experiments methodology. Leaf dry mass (DM) was the highest when plants were irrigated with nutrient solutions of –0.076 MPa. The lower leaf DM at lower or higher ψS was influenced by the medium because plants grown in 100% volcanic rock exhibited no effect, whereas plants grown in either 100% charcoal or 100% peat had a marked reduction. Regardless of the ψS of the nutrient solution, the highest leaf DM was observed in mixtures of two components containing charcoal and peat at high proportions. Dry mass of pseudobulbs and roots was highest in plants irrigated with solutions of –0.051 MPa, especially in mixtures with charcoal or 100% peat. Decreasing the ψS of the nutrient solution resulted in increased shoot nitrogen (N) and potassium (K) concentrations and decreased concentration of phosphorus (P), calcium (Ca), magnesium (Mg), boron (B), manganese (Mn), zinc (Zn), and copper (Cu). Increasing charcoal proportion in the growing media resulted in increased plant iron (Fe) and Cu concentration. However, increasing volcanic rock reduced plant P and K and increased Mn concentration. A higher proportion of peat was correlated with a decrease in plant Fe concentration. Leaf DM fit models on which macronutrient:micronutrient or micronutrient:micronutrient ratios were calculated, suggesting that nutrient imbalance may be responsible for a plant’s responses. The coefficients with the higher values included a micronutrient:micronutrient ratio, suggesting that an extremely fine balance in the uptake of a given micronutrient in relation to other micro- or macronutrient is of major importance for adequate growth of Laelia.

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Anthurium is native to habitats characterized by low nutrient supply; however, when cultivated, it demands a complete fertilization program. The objective of the present study was to determine the effect of varying proportions of anions [nitrate (NO3 ), phosphate (H2PO4 ), and sulphate (SO4 2−)] in the nutrient solution on the growth and nutrient status of container-grown anthurium. The effect of the anion proportion was modeled using mixture analysis. Plant growth increased when fertigated with solutions containing an anion proportion of 0.78:0.12:0.10, 0.20:0.12:0.68, and 0.80:0.02:0.18. The contour plots showed that optimum response may be achieved in two areas, an area with high NO3 proportion (0.50–0.80) and an area with high SO4 , provided H2PO4 was high (0.09–0.12 for H2PO4 and 0.55–0.70 for SO4 2−). The counter plots indicate that high SO4 2− proportions combined with low NO3 and H2PO4 were detrimental and that optimum growth depends not only on nitrogen (N) concentration, as it may be attained at either high or low NO3 . Nitrogen and sulfur (S) concentration was higher in plants fertigated with high NO3 (0.55–0.80) and SO4 2− (0.40–0.70) solutions. Shoot P was higher when plants were fertigated with solutions of low (as long as NO3 was at proportion of 0.50 and SO4 2− at 0.35) or high H2PO4 proportions (as long as SO4 2− proportion was at 0.35). At low concentration of S in the shoot, increasing S resulted in increasing shoot N; however, further S increments in the shoot were associated with a decrease in N. Plants fertigated with the highest proportion of H2PO4 resulted in the lowest S concentrations despite some solutions contained high SO4 2−, suggesting that H2PO4 counteracted the uptake of SO4 2−. Nitrogen and S were predominantly diverted to the roots in control plants; however, when plants were fed with both high SO4 2− and high H2PO4 solutions, even more S was allocated to the roots, which explains the increased shoot growth due to the lower S concentrations. In conclusion, the increased growth of anthurium was attained at either high or low NO3 proportion and it is able to cope with high SO4 2− by avoiding the transport of S to the shoot, decreasing SO4 2− intake, maintaining a favorable internal N/S and S/P proportion, and increasing P tissue concentration.

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Planting depth during container production may influence plant growth, establishment, and subsequent landscape value. A lack of knowledge about the effects of common transplanting practices may lead to suboptimal performance of planted landscape trees. Planting depth, i.e., location of the root collar relative to soil grade, is of particular concern for posttransplant tree growth both when transplanted to larger containers during production and after transplanting into the landscape. It is unknown whether negative effects of poor planting practices are compounded during the production phases and affect subsequent landscape establishment. This study investigated effects of planting depth during two successive phases of container production (10.8 L and 36.6 L) and eventual landscape establishment using lacebark elm (Ulmus parvifolia Jacq.). Tree growth was greater when planted at grade during the initial container (10.8 L) production phase and was reduced when planted 5 cm below grade. In the second container production phase (36.6 L), trees planted above grade had reduced growth compared with trees planted at grade or below grade. For landscape establishment, transplanting at grade to slightly below or above grade produced trees with greater height on average when compared with planting below grade or substantially above grade, whereas there was no effect on trunk diameter. Correlations between initial growth and final growth in the field suggested that substantial deviations of the original root to shoot transition from at-grade planting was more of a factor in initial establishment of lacebark elm than the up-canning practices associated with planting depth during container production.

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Tree transplanting practices influence plant survival, establishment, and subsequent landscape value. However, transplanting practices vary substantially within the horticultural industry. Of particular importance is the location of the root collar relative to soil grade at transplant. The objective of this study was to determine the effects of factorial combinations of planting depths, root collar at grade or 7.6 cm either above or below grade, and soil amendments on container-grown (11 L) Quercus virginiana Mill. Soil treatments included a tilled native soil (heavy clay loam, Zack Series, Zack-urban land complex, fine, montmorillonitic, thermic, udic paleustalfs), native soils amended with 7.6 cm of coarse blasting sand or peat that were then tilled to a depth of 23 cm, or raised beds containing 20 cm of sandy loam soil (Silawa fine sandy loam, siliceous, thermic, ultic haplustalfs). A significant (P ≤ 0.05) block by soil amendment interaction occurred for photosynthetic activity. Incorporation of peat significantly decreased the bulk density of the native soil. Planting depth had no significant effect on photosynthetic activity or stem xylem water potential at 3 months after transplant. Soil water potentials did not statistically differ among treatments.

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