Abstract
ABSTRACT Leaf chlorophyll content is closely related to leaf nitrogen (N) content, so it is reasonable to assume that NH4–N:NO3–N ratio in the nutrient solution used to grow tomatoes (Lycopersicon esculentum Mill.) hydroponically may affect leaf greenness, and consequently chlorophyll meter (SPAD) readings. It has also been shown that increasing nutrient solution strength (NSS) increases tomato productivity, but there are no reports regarding how NSS affects SPAD readings under greenhouse conditions. Genotype may also influence SPAD readings, and standardization for cultivar and sampling time may be needed. The objective of this study was to characterize SPAD readings for five tomato cultivars, and SPAD reading response to a combination of two nutrient solutions strength (NSS) (1X and 4X Steiner solution strength daily applied 18 days after transplanting at 7 p.m.) and two concentrations of NH4–N in solution (0 and 25%) in order to evaluate the potential of SPAD readings as a tomato yield predictor in greenhouse production systems. The SPAD readings were not uniform across tomato varieties tested, being consistently higher for “Max” and lower for the other varieties. Initially, SPAD readings for tomato varieties used in this study were low at the vegetative stage, and increased up to 40 days after transplant (DAT), but subsequently decreased at 49 DAT, or the fruit set of the first and second clusters. After this time, SPAD readings showed no variation. Chlorophyll meter readings for Max were higher in the top plant layers, but decreased in the top plant layer of the other tomato varieties. The SPAD readings were higher for plants supplied with 25% NH4–N than those without NH4–N in solution, but the use of a nighttime nutrient solution did not affect SPAD readings. None of the possible interactions among tomato variety, NH4–N:NO3–N ratio, and NSS were consistently significant. SAPD readings may be useful in monitoring low or high supply of N in greenhouse grown tomato plants.
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Claims 11
Claim · model-written summary
SPAD readings differed across tomato varieties, with Max consistently higher.
- Taxon
- tomato
Solanum lycopersicumt0 - Material
- Maxe0
- Outcome
- SPAD readingse0
- Direction
- highere0
- Comparator
- the other varietiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The SPAD readings were not uniform across tomato varieties tested, being consistently higher for “Max” and lower for the other varieties”
t0“TOMATO”
Claim · model-written summary
SPAD readings were lower for tomato varieties other than Max.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- the other varietiese0
- Outcome
- SPAD readingse0
- Direction
- lowere0
- Comparator
- Maxe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The SPAD readings were not uniform across tomato varieties tested, being consistently higher for “Max” and lower for the other varieties”
t0“TOMATO”
Claim · model-written summary
SPAD readings rose from the vegetative stage through 40 days after transplant.
- Taxon
- tomatoSolanum lycopersicume0
- Organ / stage
- vegetative stagee0
- Outcome
- SPAD readingse0
- Direction
- increasede0
- Value
- 40 days after transplant (DAT)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD readings for tomato varieties used in this study were low at the vegetative stage, and increased up to 40 days after transplant (DAT)”
Claim · model-written summary
SPAD readings declined at 49 days after transplant or first and second cluster fruit set.
- Taxon
- tomatoSolanum lycopersicumt0
- Organ / stage
- fruit set of the first and second clusterse0
- Outcome
- SPAD readingse1
- Direction
- decreasede0
- Value
- 49 DATe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“subsequently decreased at 49 DAT, or the fruit set of the first and second clusters”
t0“TOMATO”
e1“SPAD readings for tomato varieties used in this study were low at the vegetative stage, and increased up to 40 days after transplant (DAT)”
Claim · model-written summary
After fruit set, SPAD readings did not vary.
- Taxon
- tomatoSolanum lycopersicumt0
- Outcome
- SPAD readingse0
- Direction
- no variatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After this time, SPAD readings showed no variation”
t0“TOMATO”
Claim · model-written summary
Max had higher chlorophyll meter readings in the top plant layers.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- Maxe0
- Organ / stage
- top plant layerse0
- Outcome
- Chlorophyll meter readingse0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chlorophyll meter readings for Max were higher in the top plant layers”
t0“TOMATO”
Claim · model-written summary
Other tomato varieties had decreased chlorophyll meter readings in the top plant layer.
- Taxon
- tomatoSolanum lycopersicumt0
- Material
- the other tomato varietiese0
- Organ / stage
- top plant layere0
- Outcome
- Chlorophyll meter readingse1
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decreased in the top plant layer of the other tomato varieties”
t0“TOMATO”
e1“Chlorophyll meter readings for Max were higher in the top plant layers”
Claim · model-written summary
Plants supplied with 25% NH4–N had higher SPAD readings than plants without NH4–N.
- Taxon
- tomatoSolanum lycopersicumt0
- Treatment
- 25% NH4–Ne0
- Outcome
- SPAD readingse0
- Direction
- highere0
- Comparator
- those without NH4–N in solutione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The SPAD readings were higher for plants supplied with 25% NH4–N than those without NH4–N in solution”
t0“TOMATO”
Claim · model-written summary
Nighttime nutrient solution did not affect SPAD readings.
- Taxon
- tomatoSolanum lycopersicumt0
- Treatment
- nighttime nutrient solutione0
- Outcome
- SPAD readingse0
- Direction
- did not affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the use of a nighttime nutrient solution did not affect SPAD readings”
t0“TOMATO”
Claim · model-written summary
Interactions among cultivar, nitrogen ratio and nutrient solution strength were not consistently significant for SPAD readings.
- Taxon
- tomatoSolanum lycopersicume0
- Outcome
- interactions among tomato variety, NH4–N:NO3–N ratio, and NSSe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“None of the possible interactions among tomato variety, NH4–N:NO3–N ratio, and NSS were consistently significant”
Claim · model-written summary
The authors suggest SPAD readings may help monitor low or high nitrogen supply in greenhouse tomatoes.
- Taxon
- tomatoSolanum lycopersicume0
- Outcome
- monitoring low or high supply of Ne0
- Setting
- greenhousee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SAPD readings may be useful in monitoring low or high supply of N in greenhouse grown tomato plants”
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