Abstract
Short height and high yield per unit energy in controlled environments are essential to the success of a food production system for spaceflight. Temperature and light quality can be manipulated in controlled environments to reduce plant height and increase yield. Although the effects of temperature on height and yield are well studied at ambient CO2, temperature effects at elevated CO2 with a hydroponic root zone are not well characterized. We studied soybean yield and height under two lamp types over a broad range of temperatures. Temperature had little effect on yield or height, but lamp type had a significant effect on canopy height. This first study highlighted the importance of understanding spectral quality in controlling plant growth, especially canopy height. Numerous studies have compared lamp types and suggested that profound differences in leaf area, canopy height, yield, and total dry mass responses were due to blue light differences. Unfortunately, the most energy-efficient light sources have the least blue light. We have a poor understanding of the specific morphological and histological effects of blue light on leaves and stems. Three species, soybeans, wheat, and lettuce, were grown at five blue light fractions (0, 2, 6, 12, and 26%) and two light levels (200 and 500 μmol m-2 s-1). Phytochrome photoequilibria were constant among treatments. Blue light responses were species dependent. Wheat leaf area, dry mass, and stem length were insensitive to blue light fraction. Increasing blue light to 26% decreased soybean stem length, but leaf area was greatest at 6% blue. Lettuce leaf area, stem length, and dry mass were highly sensitive to blue light fraction between 0% and 6% under high pressure sodium lamps, but were insensitive between 6% and 26% under metal halide lamps. These results may be complicated by sensitivity to other wavelengths . The decrease in soybean stem length with increasing blue light was caused by an inhibition of cell division, while the decrease in leaf area was caused primarily by a decrease in cell expansion. Increased lettuce leaf area with increasing blue light fraction was caused by both cell division and expansion. This research indicates that lamps high in blue photons are not only energetically wasteful, but do not benefit, and in some cases reduce, plant growth. However, some blue light is necessary for controlling plant height in soybean and even required for proper growth and development in lettuce.
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Claims 13
Claim · model-written summary
Temperature had little effect on soybean yield and height.
- Taxon
- soybean
Glycine maxt0 - Treatment
- Temperaturee0
- Outcome
- yield or heighte0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Temperature had little effect on yield or height”
t0“soybean yield and height”
Claim · model-written summary
Lamp type significantly affected soybean canopy height.
- Taxon
- soybeanGlycine maxt0
- Treatment
- lamp typee0
- Outcome
- canopy heighte0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lamp type had a significant effect on canopy height”
t0“soybean yield and height”
Claim · model-written summary
Wheat leaf area, dry mass, and stem length did not respond to blue light fraction.
- Taxon
- Wheat
Triticum aestivume0 - Treatment
- blue light fractione0
- Outcome
- leaf area, dry mass, and stem lengthe0
- Direction
- insensitivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Wheat leaf area, dry mass, and stem length were insensitive to blue light fraction.”
Claim · model-written summary
Increasing blue light to 26% decreased soybean stem length.
- Taxon
- soybeanGlycine maxe0
- Treatment
- blue light to 26%e0
- Outcome
- stem lengthe0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increasing blue light to 26% decreased soybean stem length”
Claim · model-written summary
Soybean leaf area was greatest at 6% blue light.
- Taxon
- soybeanGlycine maxt0
- Treatment
- 6% bluee0
- Outcome
- leaf areae0
- Direction
- greateste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf area was greatest at 6% blue”
t0“decreased soybean stem length”
Claim · model-written summary
Lettuce leaf area, stem length, and dry mass responded strongly between 0% and 6% blue light under high pressure sodium lamps.
- Taxon
- Lettuce
Lactuca sativae0 - Treatment
- blue light fraction between 0% and 6%e0
- Outcome
- leaf area, stem length, and dry masse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce leaf area, stem length, and dry mass were highly sensitive to blue light fraction between 0% and 6% under high pressure sodium lamps”
Claim · model-written summary
Lettuce leaf area, stem length, and dry mass were insensitive between 6% and 26% blue light under metal halide lamps.
- Taxon
- LettuceLactuca sativae0
- Treatment
- between 6% and 26% under metal halide lampse0
- Outcome
- leaf area, stem length, and dry masse0
- Direction
- insensitivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce leaf area, stem length, and dry mass were highly sensitive to blue light fraction between 0% and 6% under high pressure sodium lamps, but were insensitive between 6% and 26% under metal halide lamps.”
Claim · model-written summary
Inhibited cell division explained reduced soybean stem length under increasing blue light.
- Taxon
- soybeanGlycine maxe0
- Treatment
- increasing blue lighte0
- Outcome
- decrease in soybean stem lengthe0
- Qualifier
- inhibition of cell divisione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease in soybean stem length with increasing blue light was caused by an inhibition of cell division”
Claim · model-written summary
Reduced cell expansion primarily explained lower soybean leaf area.
- Taxon
- soybeanGlycine maxt0
- Outcome
- decrease in leaf areae0
- Qualifier
- decrease in cell expansione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the decrease in leaf area was caused primarily by a decrease in cell expansion”
t0“decrease in soybean stem length”
Claim · model-written summary
Cell division and expansion explained greater lettuce leaf area as blue light increased.
- Taxon
- lettuceLactuca sativae0
- Treatment
- increasing blue light fractione0
- Outcome
- Increased lettuce leaf areae0
- Qualifier
- cell division and expansione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increased lettuce leaf area with increasing blue light fraction was caused by both cell division and expansion”
Claim · model-written summary
The authors conclude that blue-rich lamps can reduce plant growth.
- Taxon
- soybeans, wheat, and lettuceGlycine maxLactuca sativaTriticum aestivumt0
- Outcome
- reduce, plant growthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lamps high in blue photons are not only energetically wasteful, but do not benefit, and in some cases reduce, plant growth”
t0“soybeans, wheat, and lettuce”
Claim · model-written summary
Some blue light is necessary to control soybean height.
- Taxon
- soybeanGlycine maxe0
- Outcome
- controlling plant heighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“some blue light is necessary for controlling plant height in soybean”
Claim · model-written summary
Some blue light is required for proper lettuce growth and development.
- Taxon
- lettuceLactuca sativae0
- Outcome
- proper growth and developmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“even required for proper growth and development in lettuce”
The same questions in other papers
halide · growth · Lactuca sativa (garden lettuce)Positive and negative results
1 in the opposite direction
- positive
light · growth · Glycine max (soybean)Positive and negative results
46 papers in the same direction as this paper · 33 in the opposite direction · 1 reporting no difference from an alternative
- no effect
- negative
- no effect
77 papers more in this group
See all 81 papers →light · growth · Triticum aestivum (wheat)Positive and negative results
38 papers in the same direction as this paper · 46 in the opposite direction
- positive
- positive
- positive
81 papers more in this group
See all 85 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.