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This research details the influence of fertility on plant growth, photosynthesis, ethylene evolution and herbivore abundance of chrysanthemum (Dendranthema grandiflora Tzvelev `Charm') inoculated with cotton aphids (Aphis gossypii Glover). We tested five fertility levels that consisted of 0%, 5%, 10%, 20%, and 100% (375 ppm N) of recommended nitrogen levels. Aphid abundance was greatest at high fertility. Fertility affected the vertical distribution of aphids. A higher population of aphids were observed in physiologically mature and older leaves at low fertility, whereas at high fertility young leaves had 33% more aphids than older, basal leaves. Aphids depressed plant vegetative and reproductive growth, and altered carbohydrate partitioning at high fertility. Aphid-inoculated (AI) plants at high fertility had increased specific leaf area [(SLA), i.e., thinner leaves] and greater leaf area than aphid-free (NonAI) plants. Aphids caused greater ethylene production in reproductive buds and young leaves of high fertility plants, but had no effect on ethylene evolution in physiologically mature or older, basal leaves. Plant growth, leaf nitrogen (N), phosphorus (P), iron (Fe) and manganese (Mn) increased at higher fertility, as did chlorophyll and photosynthetic rates. Leaf N was highest in young and physiologically mature leaves compared to basal leaves. Aphids decreased leaf N and P. Aphids reduced photosynthesis in young leaves of high fertility plants, whereas physiologically mature and older leaves were unaffected.

Sustainable horticultural production will increasingly have to rely on economically feasible and environmentally sound solutions to problems associated with high levels of bicarbonate (HCO ^- ₃) and associated high pH in irrigation water. The ability of arbuscular mycorrhizal fungi (AMF; GlomusZAC-19) to enhance plant tolerance to HCO₃ ^- was tested on the growth, physiology and nutrient uptake of Rosamultiflora Thunb. ex J. Murr. cv. Burr (rose). Arbuscular mycorrhizal colonized and noninoculated (non-AMF) plants were treated with 0, 2.5, 5, and 10 mm HCO ^- ₃. Increasing HCO ^- ₃ concentration and associated high pH and electrical conductivity (EC) reduced plant growth, leaf elemental uptake and acid phosphatase activity (ACP), while increasing alkaline phosphatase activity (ALP). Inoculation with AMF enhanced plant tolerance to HCO ^- ₃ as indicated by greater plant growth, leaf elemental uptake (N, P, K, Ca, Fe, Zn, Al, Bo), leaf chlorophyll content, higher mycorrhizal inoculation effect (MIE), lower root iron reductase activity, and generally lower wall-bound ACP (at 2.5 mm HCO₃ ^-), and higher soluble ALP (at 10 mm HCO₃ ^-). While AMF colonization (arbuscules, vesicles, and hyphae formation) was reduced by increasing HCO ^- ₃ concentration, colonization still occurred at high HCO ^- ₃. At 2.5 mm HCO₃ ^-, AMF plant growth was comparable to plants at 0 mm HCO₃ ^-, further indicating the beneficial effect of AMF for alleviation of HCO₃ ^- stress.

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.

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 (ψ_S), 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 ψ_S 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 ψ_S 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 ψ_S 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.

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.

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 (K_ext) 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 (K_int) ranged from 504 to 892 mmol·kg⁻¹; however, a lower K_int 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 K_ext increased. Concentrations of K_ext 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 K_ext was greater than 22.5 mmol·L⁻¹. Critical concentrations varied according to the growth parameter. Optimum K_int 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 K_int was associated with optimum growth for all the parameters assessed, whereas a K_int 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 K_int were estimated when K_ext in the nutrient solutions was 5.6 and 13.6 mmol·L⁻¹, respectively.

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.

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.

In containerized crop production, subirrigation is an attractive solution to reduce excessive water runoff and nutrient loss. However, this irrigation method is mainly used for the cultivation of containerized ornamental plants, with limited research on the cultivation of vegetable species. In the present study, we assessed the feasibility of using a subirrigation system on growth, yield, and nutrient status of bell pepper plants (Capsicum annuum L.) grown in 30-cm-tall (13-L) containers by measuring the effects of flooding depth (10 and 15 cm) and duration (20 and 30 minutes) and compared with drip-fertigated plants. Subirrigated bell pepper plants exhibited a fruit number and yield comparable to those of drip-fertigated plants when the solution depth was held at 15 cm for 30 minutes. There was a substantial increase in the electrical conductivity (EC) in the medium top layers for all subirrigated plants, but this was up to 50% lower when plants were irrigated/fertigated to a 15-cm depth for 30 minutes. The higher yield of subirrigated plants flooded to a depth of 15 cm for 30 minutes was associated with a decrease in Ca concentration in the plant tissue (−16%), probably due to a dilution effect associated with the higher biomass produced by these plants. The higher nutrient use efficiency (NUE) attributed to subirrigation systems is not only due to nutrient accumulation in the growing medium, but also to a higher uptake by the plants, as compared with drip-fertigated plants, as subirrigated plants with flooding depth and duration of 15 minutes and 30 cm contained 47% higher N, 44% P, 44% K, 17% Ca, 60% Mg, and 76% S. Subirrigation of bell pepper plants is a reliable and feasible irrigation system provided flooding depth and duration are considered.