Abstract
Abstract Leaf chlorophyll content is closely related to leaf nitrogen (N) content, so it is reasonable to assume that ammonium‐N (NH4‐N): nitrate‐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 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 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.
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Claims 9
Claim · model-written summary
SPAD readings differed among tomato varieties and were consistently highest for Max.
- Taxon
- Tomato
Solanum lycopersicumt0 - Material
- ‘Max’e0
- Outcome
- SPAD readingse0
- Direction
- highere0
- Comparator
- the other varietiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Tomato leaf”
e0“The SPAD readings were not uniform across tomato varieties tested, being consistently higher for ‘Max’ and lower for the other varieties”
Claim · model-written summary
SPAD readings rose through 40 DAT from low vegetative stage readings.
- Taxon
- TomatoSolanum lycopersicumt0
- Organ / stage
- vegetative stagee0
- Outcome
- SPAD readingse0
- Direction
- increasede0
- Qualifier
- up to 40 DATe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Tomato leaf”
e0“SPAD readings for tomato varieties used in this study were low at the vegetative stage, and increased up to 40 DAT”
Claim · model-written summary
SPAD readings decreased at 49 DAT during first and second cluster fruit set.
- Taxon
- TomatoSolanum lycopersicumt0
- Organ / stage
- fruit set of the first and second clusterse0
- Direction
- decreasede0
- Qualifier
- 49 DATe0
Not reportedOutcome
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Tomato leaf”
e0“subsequently decreased at 49 DAT, or the fruit set of the first and second clusters”
Claim · model-written summary
SPAD readings showed no variation after 49 DAT.
- Taxon
- TomatoSolanum lycopersicumt0
- Outcome
- SPAD readingse0
- Direction
- no variatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Tomato leaf”
e0“After this time, SPAD readings showed no variation”
Claim · model-written summary
Max had higher readings in the top plant layers.
- Taxon
- TomatoSolanum lycopersicumt0
- Material
- ‘Max’e0
- 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
t0“Tomato leaf”
e0“Chlorophyll meter readings for ‘Max’ were higher in the top plant layers”
Claim · model-written summary
Other tomato varieties had lower 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
t0“Tomato leaf”
e0“but decreased in the top plant layer of the other tomato varieties”
e1“Chlorophyll meter readings for ‘Max’ were higher in the top plant layers”
Claim · model-written summary
Plants given 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
- without NH4‐N in solutione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Tomato leaf”
e0“The SPAD readings were higher for plants supplied with 25% NH4‐N than those without NH4‐N in solution”
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
t0“Tomato leaf”
e0“the use of a nighttime nutrient solution did not affect SPAD readings”
Claim · model-written summary
Interactions among variety, nitrogen form ratio and solution strength were not consistently significant for SPAD readings.
- Taxon
- TomatoSolanum lycopersicumt0
- 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
t0“Tomato leaf”
e0“None of the possible interactions among tomato variety, NH4‐N: NO3‐N ratio, and NSS were consistently significant”
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