Rate of change of composition of lettuce in response to nitrogen depletion or re‐supply

Gent, Martin P.N.

doi:10.1002/jsfa.5716

Cited by 7 publications

(7 citation statements)

References 36 publications

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“…Thus, up to 15 days of nitrate withdrawal could lower nitrate without sharply reducing total nitrogen or affecting growth and biomass of cultivated cardoon. These results are consistent with the findings of Gent (2012) who demonstrated that tissue nitrate changed more rapidly than total N over a 6-day interval of nitrogen depletion without affecting yield of hydroponic lettuce. The lowest nitrate concentration in cultivated cardoon leaves after 15 days of N-deprivation would suggest that a significant part of nitrate was assimilated in the ‘metabolic pool’ since the external

is exhausted, while little would have remained available to be stored in cell vacuoles or ‘reserve pool’ as osmotic regulator ( Santamaria et al, 1998 ).…”

Section: Discussionsupporting

confidence: 92%

“…An effective and sustainable fertigation strategy to limit nitrate waste in the environment while maintaining yield could be to terminate nitrate supply in the nutrient solution several days prior to final harvest. Nitrate withdrawal in the solution few DBH has been successfully used for lowering nitrate content in leafy vegetables with or without affecting crop productivity ( Santamaria et al, 1998 ; Gonnella et al, 2004 ; Gent, 2012 ). In fact, the results of Experiment 2 clearly demonstrated that it is possible to withdraw nitrates in the nutrient solution from 5 up to 15 DBH without any negative effects on leaf dry biomass.…”

Section: Discussionmentioning

confidence: 99%

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Changes in Biomass, Mineral Composition, and Quality of Cardoon in Response to NO3-:Cl- Ratio and Nitrate Deprivation from the Nutrient Solution

et al. 2016

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Leaf extracts of cultivated cardoon (Cynara cardunculus L. var. altilis DC) are an important source of phenols. Soilless culture represents an important and alternative tool to traditional agriculture, since it allows a precise control of plant nutrition and the maximization of yield and quality of the product. Reducing N supply, while keeping quantity as high as possible is desirable for environmental and health-related reasons, especially that N deficiency can lead to improved concentrations of secondary plant metabolites. Two greenhouse experiments were carried out in order to determine the effect of a decreasing NO3-:Cl- ratio (80:20, 60:40, 40:60, or 20:80) and nitrate deprivation (0, 5, 10, or 15 days before harvest) on biomass production, leaf chlorophyll content and fluorescence, mineral composition, and phytochemicals in leaves of cardoon ‘Bianco Avorio’ grown in a floating system. Total phenols, flavonoids and antioxidant capacity increased linearly with Cl- availability, especially when nitrate was replaced by 80% of chloride (20:80 NO3-:Cl- ratio), without having a detrimental effect on yield. Total nitrogen and nitrate concentration in leaves decreased linearly with increasing Cl- in the nutrient solution. Total phenols and antioxidant capacity recorded after 15 days of nitrate deprivation were higher by 43.1, 42.8, and 44.3% and by 70.5, 40.9, and 62.2%, at 59, 97 and 124 days after sowing, respectively compared to the control treatment. The decrease in leaf nitrate content recorded under N-deprivation occurred more rapidly than the reduction in total nitrogen. Thus, up to 15 days of nitrate withdrawal can lower nitrates without sharply reduce total nitrogen or affecting growth and biomass of cultivated cardoon. The use of N-free nutrient solution prior to harvest or the replacement of nitrates with chlorides could be adopted among growers to improve the quality of the product and enhance sustainability of crop production system.

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is exhausted, while little would have remained available to be stored in cell vacuoles or ‘reserve pool’ as osmotic regulator ( Santamaria et al, 1998 ).…”

Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Changes in Biomass, Mineral Composition, and Quality of Cardoon in Response to NO3-:Cl- Ratio and Nitrate Deprivation from the Nutrient Solution

et al. 2016

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“…The leaf blade to whole shoot dry weight ratio also varied with plant size, but the change resulting from irradiance was small. The composition of the leaf blade differs from that in the petiole (Gent, 2012a(Gent, , 2012b. However, changes in the weight ratio of these two plant parts is not likely the primary cause of changes in whole shoot composition with irradiance.…”

Section: Resultsmentioning

confidence: 98%

“…Total nitrogen and elemental composition were determined as described previously (Gent, 2012a). Nitrate, amino acids, soluble sugars, and organic acids were extracted and analyzed using liquid chromatography as described previously (Gent, 2012b). The 12 plantings were combined for analysis of variance (ANOVA) with hydroponic systems in two greenhouses used as replicate plots within each planting.…”

Section: Methodsmentioning

confidence: 99%

Effect of Daily Light Integral on Composition of Hydroponic Lettuce

Gent

2014

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The concentrations of metabolites in plants are affected by sunlight integral and other factors such as plant size, water content, and time of day. Tissue composition was measured for various sizes of hydroponic lettuce (Lactuca sativa L.) grown under seasonal variation in sunlight in a greenhouse and harvested in the morning or afternoon. Daily sunlight integral varied from 4 to 14 mol·m−2·day−1 photosynthetically active irradiance, and plant size varied from 2 to 260 g fresh weight (FW)/plant in this study. Much of the variation in tissue composition on a FW basis could be explained by the increase in dry matter content with irradiance normalized per unit area. Except for nitrate, metabolite concentrations on a FW basis increased with irradiance, and the changes resulting from irradiance were greater when harvested in the afternoon than in the morning. Nitrate concentration decreased with normalized irradiance, and the trend was the same whether measured in morning or afternoon. Malic acid increased with irradiance but not enough to counter the decrease in nitrate on a charge equivalence basis. Irradiance normalized per unit leaf area explained many effects of light and plant size on dry matter content and soluble metabolite concentrations. Lettuce for human consumption is best harvested in the afternoon after growth under high light, when it has the least nitrate and more of other nutrients.

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“…Total nitrogen and elemental composition were determined from dried samples hydrolyzed in sulfuric acid and hydrogen peroxide as described previously (Gent, 2012a). Nitrate, phosphate, malic and oxalic acids, amino acids (except proline), and soluble sugars were extracted and analyzed using liquid chromatography as described previously (Gent, 2012b). The five plantings in 2009 were combined for analysis of metabolite concentrations, with the two or four hydroponic systems used as replicate plots within each planting to determine the effects of irradiance, temperature, and time of day.…”

Section: Methodsmentioning

confidence: 99%

Effect of Irradiance and Temperature on Composition of Spinach

Gent¹

2016

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The composition of spinach (Spinacea oleracea L.) was studied in response to daily light integral (DLI) and diurnal variation in a greenhouse. Values for plantings with different irradiance were compared using normalized daily light integral (NDLI), which was DLI divided by leaf area index. The dry mass as a ratio of fresh mass increased with NDLI as it increased from 3 to 27 mol·m−2·d−1. Reduced nitrogen (N) changed with time of day under high but not under low NDLI. Nitrate and amino acids were affected by temperature more than NDLI. Starch increased with NDLI to 27 mol·m−2·d−1 in morning or afternoon. However, sugars decreased with temperature more than with NDLI, due to a decrease in petioles up to 20 °C. Oxalic acid increased with NDLI or temperature. Over a diurnal cycle, starch had minimum value at 0800 hr and maximum at 1800 hr in all parts. The sugars, sucrose, glucose, and fructose, had a binary response with high values in the day and low values in the night. Oxalic acid increased at the end of the day. Other metabolites had no response to time of day. The growth of spinach may be slow in fall compared with summer due to the effect of low temperature on metabolism of sugars and nitrate.

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Rate of change of composition of lettuce in response to nitrogen depletion or re‐supply

Cited by 7 publications

References 36 publications

Changes in Biomass, Mineral Composition, and Quality of Cardoon in Response to NO3-:Cl- Ratio and Nitrate Deprivation from the Nutrient Solution

Changes in Biomass, Mineral Composition, and Quality of Cardoon in Response to NO3-:Cl- Ratio and Nitrate Deprivation from the Nutrient Solution

Effect of Daily Light Integral on Composition of Hydroponic Lettuce

Effect of Irradiance and Temperature on Composition of Spinach

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