Abstract
Introduction: Spinach is a leafy vegetable which is rich source of vitamins, antioxidant compounds (e.g. flavonoids, acid ascorbic) and essential elements (e.g. Fe, and Se). Spinach is capable of accumulating large amounts of nitrogen in the form of nitrate in shoot tissues which is undesirablein the human diet. The concentration of nitrate in plants is affected by species, fertilizer use, and growing conditions. Green leafy vegetables such as spinach, generally contain higher levels of nitrate than other foods. Nitrate ofplant tissueslevels are clearly related to both form and concentration of N fertilizers applied. Nitrogen fertilizers have been known as the major factors that influence nitrate content in vegetables. Ideally, the N fertility level must be managed to produce optimum crop yield without leading to excessive accumulation of nitrate in the harvested tissues.Usinghigh amounts ofN fertilizer produced higher yield with higher nitrate inleaves but the highest amount of nitrate was accumulated in the petioles.There are several plant species that may accumulate nitrate, including the Brassica plants, green cereal grains (barley, wheat, rye and maize), sorghum and Sudan grasses, corn, beets, rape, docks, sweet clover and nightshades. The presence of nitrate in vegetables, as in water and generally in other foods, is a serious threat to man’s health. Nitrate is relatively non-toxic, but approximately 5% of all ingested nitrate is converted in saliva and the gastrointestinal tract to the more toxic nitrite. This study was aimed to investigate theeffects of nitrogen and nutrient removal on nitrate accumulation and growth characteristics of spinach (Spinacia oleraceae L.). Materials and Methods: A pot hydroponic experiment was carried out to evaluate the effect of different levels of nitrogen and nutrient removal (one week before harvest) on nitrate accumulation and growth characters. A factorial experiment based on completely randomized design was conducted with twolevels of removal (removal of nutrient one week before harvest) or not to remove and fourlevels of nitrogen (25, 50, 100 and 200 mg/l) with sixreplications. During the growing season in the greenhouse, temperature was fixed between 24-27 °C and photoperiod of 16 hours of light and 8 hours of darkness. The measured traits were root fresh and dry weight, shoot fresh and dry weight, Fv/Fm ratio, and chlorophyll index, number of leaf per plant, leaf area, nitrate and total nitrogen. Results and Discussion: The results of this experiment showed that increasingnitrogen concentration from 25 to 200 mg/l increased shoot dry weight, number of leaves and leaf area, by 22.00, 7.26, 4.79 and 14.00 fold, respectively. Nitrogen also increased Fv/Fm and chlorophyll index. Nutrient removal in a week before harvest had no significant effect on fresh and dry weight of shoots and roots, number of leaves,leaf area, chlorophyll index and Fv/Fm. Increasing concentrations of nitrogen increased nitrate and total nitrogen in petiole while removing the nutrient solution in a week before harvest significantly decreased amounts of the above-mentioned traits. Nutrient solution removal is an appropriate strategy to reduce nitrate accumulation in spinach that has no effect on yield loss. Conclusions: The results showed that increasing the concentration of nitrogen increased plant growth indicators such as shoot fresh and dry weight, root fresh and dry weight, leaf area and number of leaf per plants, so that the greatest increase was obtained from concentration of 200 mg/lit. Increasing the concentration of nitrogen enhanced nitrate and total nitrogen of petiole so that the highest concentration of nitrate and total nitrogen was observed in200 mg/lit nitrogen. Nutrient solution removal in a week before the harvest had a significant effect in reducing all traits but it decreased nitrate accumulation and total nitrogen of petiole significantly. At the end of the experiment, it was found that increasing the concentration of nitrogen increased nitrate concentrations and total nitrogen in the petioles while nutrient removal in a week before harvest reducedthe amount of leaf nitrate. Thereforethe removal ofnutrient solution is one of the strategies to reduce nitrate accumulation that had no effect on yield loss of crop. Based on the results from this research, nitrogen at a concentration of 200 mg/lit, with the removal of nutrient solution a week before harvest is recommended for growing in hydroponic culture of spinach.
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Claims 12
Claim · model-written summary
Raising nitrogen from 25 to 200 mg/l increased shoot dry weight, number of leaves and leaf area of spinach, by 22.00, 7.26, 4.79 and 14.00 fold (mapping to traits not stated).
- Taxon
- Spinach
Spinacia oleraceat0 - Treatment
- nitrogen concentration from 25 to 200 mg/le0
- Outcome
- shoot dry weight, number of leaves and leaf areae0
- Direction
- increasede0
- Value
- 22.00, 7.26, 4.79 and 14.00 folde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e0“The results of this experiment showed that increasingnitrogen concentration from 25 to 200 mg/l increased shoot dry weight, number of leaves and leaf area, by 22.00, 7.26, 4.79 and 14.00 fold, respectively”
Claim · model-written summary
Nitrogen increased Fv/Fm and chlorophyll index of spinach.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Nitrogene1
- Outcome
- Fv/Fm and chlorophyll indexe1
- Direction
- increasede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e1“Nitrogen also increased Fv/Fm and chlorophyll index”
Claim · model-written summary
Nutrient removal one week before harvest had no significant effect on fresh and dry weight of shoots and roots of spinach.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Nutrient removal in a week before harveste2
- Outcome
- fresh and dry weight of shoots and rootse2
- Direction
- no significant effecte2
- Comparator
- not to removee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e2“Nutrient removal in a week before harvest had no significant effect on fresh and dry weight of shoots and roots, number of leaves,leaf area, chlorophyll index and Fv/Fm”
e3“with twolevels of removal (removal of nutrient one week before harvest) or not to remove”
Claim · model-written summary
Nutrient removal one week before harvest had no significant effect on number of leaves and leaf area of spinach.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Nutrient removal in a week before harveste2
- Outcome
- number of leaves, leaf areae2
- Direction
- no significant effecte2
- Comparator
- not to removee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e2“Nutrient removal in a week before harvest had no significant effect on fresh and dry weight of shoots and roots, number of leaves,leaf area, chlorophyll index and Fv/Fm”
e3“with twolevels of removal (removal of nutrient one week before harvest) or not to remove”
Claim · model-written summary
Nutrient removal one week before harvest had no significant effect on chlorophyll index and Fv/Fm of spinach.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Nutrient removal in a week before harveste2
- Outcome
- chlorophyll index and Fv/Fme2
- Direction
- no significant effecte2
- Comparator
- not to removee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e2“Nutrient removal in a week before harvest had no significant effect on fresh and dry weight of shoots and roots, number of leaves,leaf area, chlorophyll index and Fv/Fm”
e3“with twolevels of removal (removal of nutrient one week before harvest) or not to remove”
Claim · model-written summary
Increasing nitrogen concentration increased nitrate and total nitrogen in spinach petioles.
- Taxon
- SpinachSpinacia oleraceat0
- Organ / stage
- petiolee4
- Treatment
- Increasing concentrations of nitrogene4
- Outcome
- nitrate and total nitrogene4
- Direction
- increasede4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e4“Increasing concentrations of nitrogen increased nitrate and total nitrogen in petiole while removing the nutrient solution in a week before harvest significantly decreased amounts of the above-mentioned traits”
Claim · model-written summary
Nutrient solution removal one week before harvest significantly decreased nitrate accumulation and total nitrogen in spinach petioles.
- Taxon
- SpinachSpinacia oleraceat0
- Organ / stage
- petiolee5
- Treatment
- Nutrient solution removal in a week before the harveste5
- Outcome
- nitrate accumulation and total nitrogen of petiolee5
- Direction
- decreasede5
- Comparator
- not to removee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e5“Nutrient solution removal in a week before the harvest had a significant effect in reducing all traits but it decreased nitrate accumulation and total nitrogen of petiole significantly”
e3“with twolevels of removal (removal of nutrient one week before harvest) or not to remove”
Claim · model-written summary
Nutrient solution removal one week before harvest significantly reduced all traits of spinach.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- Nutrient solution removal in a week before the harveste5
- Outcome
- all traitse5
- Direction
- reducinge5
- Comparator
- not to removee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e5“Nutrient solution removal in a week before the harvest had a significant effect in reducing all traits but it decreased nitrate accumulation and total nitrogen of petiole significantly”
e3“with twolevels of removal (removal of nutrient one week before harvest) or not to remove”
Claim · model-written summary
The authors recommend nutrient solution removal as an appropriate strategy to reduce nitrate accumulation in spinach.
- Taxon
- spinachSpinacia oleraceae6
- Treatment
- Nutrient solution removale6
- Outcome
- nitrate accumulatione6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e6“Nutrient solution removal is an appropriate strategy to reduce nitrate accumulation in spinach that has no effect on yield loss”
Claim · model-written summary
Nutrient solution removal one week before harvest had no effect on spinach yield loss.
- Taxon
- spinachSpinacia oleraceae6
- Treatment
- Nutrient solution removale6
- Outcome
- yield losse6
- Direction
- no effecte6
- Comparator
- not to removee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e6“Nutrient solution removal is an appropriate strategy to reduce nitrate accumulation in spinach that has no effect on yield loss”
e3“with twolevels of removal (removal of nutrient one week before harvest) or not to remove”
Claim · model-written summary
The authors recommend 200 mg/l nitrogen with nutrient solution removal one week before harvest for hydroponic spinach.
- Taxon
- spinachSpinacia oleraceae7
- Treatment
- nitrogen at a concentration of 200 mg/lite7
- Outcome
- growing in hydroponic culturee7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e7“nitrogen at a concentration of 200 mg/lit, with the removal of nutrient solution a week before harvest is recommended for growing in hydroponic culture of spinach”
Claim · model-written summary
Nutrient removal one week before harvest reduced leaf nitrate in spinach.
- Taxon
- SpinachSpinacia oleraceat0
- Treatment
- nutrient removal in a week before harveste7
- Outcome
- amount of leaf nitratee7
- Direction
- reducede7
- Comparator
- not to removee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Effects of Nitrogen and Nutrient Removal on Nitrate Accumulation and Growth Characteristics of Spinach (Spinacia oleraceae L.)”
e7“while nutrient removal in a week before harvest reducedthe amount of leaf nitrate”
e3“with twolevels of removal (removal of nutrient one week before harvest) or not to remove”
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