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Tadashi Higaki, Joanne S. Imamura, and Robert E. Paull

The optimum fertilizer levels of N, P, and K for flower production of field-grown Anthurium andraeanum Andre in Hawaii were determined. Applications were at 0, 224, and 448 kg·ha-1·year-1 with all combinations of each nutrient level. Optimum flower production was achieved at 312N-448P-375K kg·ha-l·year-1. Increased N and K application resulted in a linear increase in flower size. Flower stem length also increased with increasing N, P, and K rates. Maximum flower yield occurred when leaf-tissue levels were 1.87% N, 0.17% P, and 2.07% K. Flower stem length and flower size were at their maximum with leaf N at 1.59% and 1.67% and K at 2.20% and 1.86%, respectively. No relationship was observed between leaf percent P, flower size, or stem length. A range of leaf-tissue levels associated with optimum anthurium flower production was determined for Ca, Mg, B, Mn, Fe, Zn, Cu, and Mo).

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Melinda McVey McCluskey, Ellen T. Paparozzi, and Susan L. Cuppett

Previous research on leaf lettuce has shown that altering the N:S ratio has an effect on plant color and N and S content. It appears that nitrogen rates can be decreased if known rates of sulfur are applied. The next step was to determine what effect altering the N:S ratio in lettuce had on consumer acceptance of the product.

`Grand Rapids' lettuce was grown hydroponically at six rates of S (0, 7.5, 15, 30, 60, 120 ppm) and four rates of N (30, 60, 120, 240 ppm). Sensory evaluation was performed on 20 of 24 treatments. The sensory panel was composed of 12 panelists who used the nonstructured hedonic scale to evaluate each lettuce treatment on appearance, color, texture, flavor, bitter flavor, and overall acceptability.

Results from the sensory evaluation indicate that differences in color, appearance, and bitter flavor were detected between treatments by the panel. Lettuce plants that received higher amounts of N in relation to S were considered less bitter in flavor and, over all, more acceptable than plants which received higher amounts of S in relation to N. These results indicate that altering the N:S ratio will affect consumer acceptance of leaf lettuce.

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Oswaldo A. Rubio, Patrick H. Brown, and Steven A. Weinbaum

Leaf N concentrations (% dry wt) appear relatively insensitive to high levels of applied fertilizer N (Weinbaum et al, HortTechnology 1992). This insensitivity may be attributable to growth dilation, lack of additional tree N uptake, a finite capacity of leaves to accumulate additional N or our inhability to resolve a limited increment. Our objective was to asses the relative accumulation of mobile forms of N (NO3, NH4 and amino acids) relative to a total N over a range of fertilizer N application rates in 3 year old, field-grown “Fantasia” nectarine trees. Between 0 and 136 Kg N/Ha/Yr we observed a linear relationship between N supply and all N fractions. Above 136 Kg N/Ha/Yr leaf concentrations of amino acids and total N remined constant, but NO3 and NH4 accumulation continued. These results suggest that leaf concentration of NO3 and NH4 are more sensitive indicators of soil N availability and tree N uptake than was total leaf N concentration.

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Mikal Saltveit, Youngjun Choi, and Francisco Tomás-Barberán

A wound signal originates at the site of injury in lettuce [Lactucasativa (L.)] leaf tissue and propagates into adjacent tissue where it induces a number of physiological responses that include increased phenolic metabolism with the de novo synthesis of phenylalanine ammonia lyase (PAL, EC 4.3.1.5), the synthesis and accumulation of soluble phenolic compounds (e.g., chlorogenic acid), and subsequent tissue browning. Exposing excised mid-rib leaf tissue to vapors (20 μmol·g-1 FW) or aqueous solutions (100 mm) of n-alcohols inhibited this wound-induced tissue browning by 40% and 60%, respectively. Effectiveness of the alcohol increased linearly from ethanol to the seven-carbon heptanol, and then was lost for the longer n-alcohols 1-octanol and 1-nonanol. The 2- and 3-isomers of the effective alcohols did not significantly reduce wound-induced phenolic accumulation at optimal 1-alcohol concentrations, but significant reductions did occur at much higher concentrations (100 μmol·g-1 FW) of the 2-, and 3-isomers. The active n-alcohols were maximally effective when applied during the first 2 h after excision, and were ineffective if applied 12 h after excision. Phospholipase D (PLD) and its product phosphatidic acid (PA) are thought to initiate the oxylipin pathway that culminates in the production of jasmonic acid, and PLD is specifically inhibited by 1-butanol, but not by 2- or 3-butanol. These results suggest that PLD, PA, and the oxylipin pathway may be involved in producing the wound signal responsible for increased wound-induced PAL activity, phenolic accumulation, and browning in fresh-cut lettuce leaf tissue.

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Byoung Ryong Jeong, Chi Won Lee, and Larry S. Daley

A non-destructive in vivo spectroscopic method for leaf chlorophyll (Chl) measurement was developed. Spectroscopic analyses of intact leaves of ageratum, petunia and salvia showed strong correlations between leaf light absorption at 723 nm and Chl-a contents. NH4 + increased Chl contents in both ageratum and petunia whereas NO3 - increased Chl contents in salvia. Plants fed with NH4 + + NO3 - also contained higher Chl. Chl-a/-b ratio in salvia was lowered by NO3 -. Ageratum, petunia and salvia grown with either NH4 +, NO3 -, or NH4 + + NO3 - were also examined for their light absorption characteristics. Light absorption at 705 nm by ageratum and petunia leaves was increased by NH4 + treatment. NH4 + is believed to have changed the structure of photosystem I in both ageratum and petunia but not in salvia. This result explain reasons for salvia's sensitivity to NH4 + fed as a sole N source.

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Byoung Ryong Jeong, Chi Won Lee, and Larry S. Daley

A non-destructive in vivo spectroscopic method for leaf chlorophyll (Chl) measurement was developed. Spectroscopic analyses of intact leaves of ageratum, petunia and salvia showed strong correlations between leaf light absorption at 723 nm and Chl-a contents. NH4 + increased Chl contents in both ageratum and petunia whereas NO3 - increased Chl contents in salvia. Plants fed with NH4 + + NO3 - also contained higher Chl. Chl-a/-b ratio in salvia was lowered by NO3 -. Ageratum, petunia and salvia grown with either NH4 +, NO3 -, or NH4 + + NO3 - were also examined for their light absorption characteristics. Light absorption at 705 nm by ageratum and petunia leaves was increased by NH4 + treatment. NH4 + is believed to have changed the structure of photosystem I in both ageratum and petunia but not in salvia. This result explain reasons for salvia's sensitivity to NH4 + fed as a sole N source.

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John A. Biernbaum, William Argo, and Janet Pumford

Unlike vegetable and fruit crops, where petiole analysis has been used for many years, root media analysis is the primary method of checking fertility status of container-grown flowering greenhouse crops. With the emphasis on lower constant water-soluble fertilizer rates to prevent nutrient runoff, petiole analysis may be a better indicator of N and K status. During Fall 1993, samples were collected from 10 flowering pot plant species subirrigated with either 50, 100, or 200 mg·liter–1 N and K concentrations. During Spring 1995, samples were collected from major bedding plant species and Easter lilies. Sap was extracted using a hydraulic press and nitrate and potassium were measured with the Cardy flat electrode ion meters. Sampling methods and protocols will be presented with results of sampling technique experiments. Floriculture plant nutrition researchers were contacted to identify other research in progress, potential applications, and possible concerns with using this technique. Further research needed will be identified.

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Richard J. Heerema, Dawn VanLeeuwen, Rolston St. Hilaire, Vince P. Gutschick, and Bethany Cook

in leaf N concentration and leaf area-based N content ( Diver et al., 1984 ; Heerema et al., 2009 ; Klein et al., 1991 ), which suggests that growing fruit and seeds can draw on N remobilized from nearby leaves to help meet N demands, especially

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Yung-Liang Peng, Fang-Yin Liu, Rong-Show Shen, and Yu-Sen Chang

plant growth and influences plant quality, by affecting leaf weight, leaf area, leaf chlorophyll content, and plant size ( Bar-Tal et al., 2001 ; Wang et al., 2012 ). N deficiency is commonly caused by inadequate fertilization regimes in which N supply

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Yiwei Jiang, Yaoshen Li, Gang Nie, and Huifen Liu

, especially under N-limiting conditions. Although nitrogen use and metabolic changes in response to low or high N have been reported in perennial ryegrass ( Foito et al., 2013 ; Liu and Hull, 2006 ; Rasmussen et al., 2008 ; Roche et al., 2016 ), leaf and