) reviewed the evidence for this well-known “dilution effect.” Although their review has been cited over 180 times (60 times from 2000 on), few mentions of the dilution effect contain a reference, suggesting that the effect is widely regarded as common
Desmond G. Mortley, Stephanie Burrell, Conrad K. Bonsi, Walter A. Hill and Carlton E. Morris
concentration in the leaves of plants exposed to the longer light period and lower irradiance may have been the result of a “dilution” effect as evidenced by the greater storage root and foliage production among these plants. All leaf elemental concentrations
Juana C. García-Santiago, Luis A. Valdez-Aguilar, Armando Hernández-Pérez, Andrew D. Cartmill and Jesús Valenzuela-García
dilution effect associated with the higher biomass produced by these plants, as suggested by the higher total content of Ca in subirrigated plants when compared with drip-fertigated plants. Phosphorus concentration was affected in the root and in the whole
Juan Carlos Díaz-Pérez and Touria E. Eaton
.0 at 167% ETc. In 2011, CI decreased from 55.8 at 33% ETc to 53.7 at 167% ETc ( Table 1 ). Decreased CI values with increased irrigation rates were likely due to dilution effect of nutrients, since plant growth was enhanced with increased irrigation
J. Roger Harris, Patricia Knight and Jody Fanelli
Two rootball sizes as well as a nontransplanted control were randomly assigned to Acer saccharum Marsh. (sugar maple) trees in four adjacent nursery rows at Waynesboro Nurseries in Waynesboro, Va. One size (75 cm in diameter) corresponded to the American Association of Nurserymen standards. The other rootball size was 90 cm in diameter. Trees were transplanted just before bud swell or during shoot elongation. Rootball size had no effect on height, stem diameter, or twig growth, total nonstructual leaf nitrogen content (LNC), or total stem nonstructual carbohydrate (TNC). Height growth was reduced by 81%, stem diameter growth by 71%, and twig growth by 82% for trees transplanted before bud swell compared to nontransplanted trees. LNC was 25% more on transplanted trees than on nontransplanted trees, presumably due to a dilution effect. TNC was 20% higher on transplanted compared to nontransplanted trees. Growth was severely curtailed on late-transplanted trees for all characteristics measured compared to all other treatments.
Bruce Schaffer, Anthony W. Whiley, Christopher Searle and Robert J. Nissen
The effects of atmospheric CO2 enrichment and root restriction on net CO2 assimilation (A), dry mass partitioning, and leaf mineral element concentrations in `Kensington' and `Tommy Atkins' mango (Mangifera indica L.) were investigated. Trees were grown in controlled-environment glasshouse rooms at ambient CO2 concentrations of 350 or 700 μmol·mol-1. At each CO2 concentration, trees were grown in 8-L containers, which restricted root growth, or grown aeroponically in 200-L root mist chambers, which did not restrict root growth. Trees grown in 350 μmol·mol-1 CO2 were more efficient at assimilating CO2 than trees grown in 700 μmol·mol-1 CO2. However, total plant and organ dry mass was generally higher for plants grown at 700 μmol·mol-1 CO2 due to increased A as a result of a greater internal partial pressure of CO2 (Ci) in leaves of plants in the CO2 enriched environment. Root restriction reduced A resulting in decreased organ and plant dry mass. In root-restricted plants, reduced A and dry matter accumulation offset the increases in these variables resulting from atmospheric CO2 enrichment. Atmospheric CO2 enrichment and root restriction did not affect dry mass partitioning. Leaf mineral element concentrations were generally lower for trees grown at the higher ambient CO2 concentration, presumably due to a dilution effect from an increased growth rate.
J.P. Syvertsen, J.W Grosser and L.S. Lee
We grew three diploid (2X) Citrus rootstock seedlings and their autotetraploids (4X) at elevated CO2 to obtain insights into limitations on growth and net gas exchange that have been associated with tetraploidy. Well-nourished Volkamer lemon (Volk), Troyer citrange (Troy), and Cleopatra mandarin (Cleo) were grown in greenhouses at ambient or twice ambient CO2 for 3 months. We measured plant growth, water relations, mineral nutrition, and net gas exchange characteristics of leaves. Overall, tetraploid roots were thicker as 4X had lower root length: dry weight ratio or specific root length (SRL) than 2X roots. Tetraploid plants were smaller and had higher root/shoot ratios, shorter fibrous roots, and lower whole plant transpiration than 2X. Tetraploids also had lower leaf N and P concentrations on a dry weight basis. Since 4X leaves had thicker leaves (more dry weight per area) than 2X leaves, these nutrient differences disappeared when expressed on an leaf area basis. Elevated CO2 increased plant growth but decreased leaf N, P, and K apparently by a growth dilution effect. Elevated CO2 also increased fibrous root thickness, leaf thickness, and net assimilation of CO2 (ACO2) but decreased stomatal conductance and transpiration such that leaf water use efficiency increased. There was no effect of ploidy level on ACO2 but 4X Volk and Troy had lower rates of ACO2 than their diploids at elevated CO2. Hydraulic conductivity of intact root systems (measured in a pressure pot) was correlated to total plant growth but variability obscured effects of CO2 or ploidy on root conductivity. The low SRL of tetraploids were correlated with lower rates of water use and lower leaf nutrient concentrations, which may be operative in determining the growth characteristics associated with tetraploidy.
J.M. Smagula, W. Litten and S. Dunham
In the acid podzol soils of Maine where most lowbush blueberries are grown, low availability of boron tends to keep foliar B concentration below the 24 ppm standard. To compare efficacy of soil and foliar boron application methods, 1.5 × 7.6-m treatment plots in a commer-cial lowbush blueberry field received soil-applied borate at 0, 1.1, 2.2, or 3.3 kg·ha-1 B with or without additional DAP (89 kg·ha-1 P) and ZnSO4 (3.3 kg·ha-1 Zn) or foliar-applied Solubor at 0, 0.24, 0.49, or 0.74 kg·ha-1 B with or without the additional DAP and Zn. These 16 treatments were replicated eight times in a randomized complete-block design. Leaf B concentrations were raised by all soil-applied borate treatments and by the 0.49 and 0.74 kg·ha-1 B foliar Solubor treatments, compared to the controls. When borate at 2.2 or 3.3 kg·ha-1 B was combined with DAP plus Zn a lower leaf B concentration was observed compared to B alone, possibly due to a dilution effect caused by an increase in DAP-induced growth. Leaf P deficiency (<0.125% P) was corrected when DAP and Zn were included in the fertilizer treatment. The greatest potential yield (flower buds/stem and flower bud density) was measured in treatment plots receiving a combination of DAP plus Zn and either borate at 2.2 kg·ha-1 B or Solubor at 0.74 kg·ha-1 B. With no additional treatments applied in 1999, leaf B concentrations were slightly higher in soil-treated and foliar-treated plots than in controls suggesting a small carryover from 1997-applied boron. Carryover may vary with rainfall.
J.P. Syvertsen, L.S. Lee and J.W Grosser
Diploid (2x) and autotetraploid (4x) Citrus L. rootstock cultivars were grown at elevated CO2 to obtain insights into limitations on growth and net gas exchange that have been associated with tetraploidy. Well-nourished 2x and 4x seedlings of `Volkamer' lemon (Volk, C. volkameriana Ten & Pasq.), `Troyer' citrange [Troy, C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.] and `Cleopatra' mandarin (Cleo, C. reticulata Blanco.), were grown in greenhouses at either ambient or twice ambient CO2 for 4 months. Plant growth, water relations, mineral nutrition, and net gas exchange characteristics of leaves were measured. Most 4x plants were smaller and had lower rates of whole plant transpiration but shorter fibrous roots than 2x plants. Fibrous roots of 4x were thicker than 2x roots as indicated by a lower specific root length (SRL) in 4x than in 2x roots. Root hydraulic conductivity was correlated to total plant growth but there were no effects of CO2 or ploidy on root conductivity. Tetraploid leaves had lower N concentrations than 2x leaves when expressed on a dry weight basis but these differences disappeared when N concentration was expressed on an leaf area basis because 4x leaves had more leaf dry weight per area (LDW/a) than 2x leaves. Plant growth was greater and SRL was lower at elevated CO2 than at ambient CO2. LDW concentrations of N, P, and K were lower at elevated CO2 than at ambient apparently due to a growth dilution effect. LDW/a, net CO2 assimilation (ACO2), and leaf water use efficiency were greater at elevated CO2 than at ambient. Overall, there was no effect of ploidy on ACO2 but 4x Volk and Troy had lower rates of ACO2 than their 2x at elevated CO2. Net gas exchange of tetraploid leaves was less responsive to elevated CO2 than 2x leaves. The low SRL of tetraploids was correlated with low whole plant transpiration rates and low leaf area-based N concentrations, which may be operative in determining the growth characteristics associated with tetraploidy.
Philip J. White, John E. Bradshaw, M. Finlay, B. Dale, Gavin Ramsay, John P. Hammond and Martin R. Broadley
hypothesized that increasing yields has resulted in decreased concentrations of mineral elements in produce because of a “dilution effect” caused by plant growth rates exceeding the ability of plants to acquire these elements ( Jarrell and Beverly, 1981 ) that