What Research Actually Supports About Light, CO₂, Tender Growth, Water and Shelf Life
Pea shoots and pea microgreens are young seedlings of Pisum sativum harvested long before the plant reaches reproductive maturity.
They are often described as easy crops because they:
- germinate quickly
- contain large seed reserves
- elongate rapidly
- produce substantial fresh biomass
- tolerate an initial dark germination stage
But there is no scientifically established PAR, CO₂ and VPD recipe that guarantees:
tender shoots
strong stems
maximum yield
or:
long shelf life.
Direct pea-microgreen research now shows something much more interesting.
Increasing light can:
- shorten plants
- increase dry-matter percentage
- increase phenolics and flavonoids
- reduce nitrate
- increase water use
while simultaneously:
reducing fresh yield.
That means the environment producing the most compact and phytochemical-rich pea shoot is not necessarily the environment producing the most fresh biomass.
For pea shoots, the better greenhouse strategy is therefore:
measure PAR and DLI, understand the dark-to-light transition, monitor CO₂ and water demand, and define which crop-quality trait actually matters.
Quick Reference
| Variable | What It Tells You | What Pea-Shoot Research Supports |
|---|---|---|
| Darkness | Early germination environment | Direct pea studies commonly begin germination in darkness before light exposure |
| PPFD / PAR | Photosynthetic light reaching the crop now | Direct 2025 pea research tested 100–400 µmol/m²/s and found fresh yield highest at the lowest intensity |
| DLI | Total photosynthetic light accumulated through the day | Direct treatments ranged about 4.2–17.3 mol/m²/day; higher DLI increased dry matter and phytochemicals but not fresh yield |
| CO₂ | Carbon available for photosynthesis | Direct pea-shoot research found 600 and 800 ppm increased yield relative to ambient air |
| VPD | Atmospheric evaporative demand | Useful for monitoring water demand, but no validated pea-shoot stage-specific optimum exists |
| Root-zone water | Water available to the crop | Higher PPFD increased water consumption in direct pea-microgreen research |
| Spectrum | Wavelength distribution | Red, blue and combined spectra change morphology and bioactive compounds |
| Harvest timing | Developmental maturity | Pea shoots and sprouts change chemically as light exposure and crop age increase |
These are research references rather than universal crop specifications.
1. Pea Shoots, Pea Sprouts and Mature Peas Are Different Production Systems
The terms are sometimes used loosely.
A pea sprout may be grown with little or no substrate and may spend much of its development in darkness.
A pea microgreen or pea shoot is normally exposed to light and harvested after development of green shoots and leaves.
A mature pea plant develops:
- tendrils
- many true leaves
- flowers
- pods
- seeds
These stages have completely different physiological demands.
Therefore, mature-pea lighting or CO₂ data should not automatically become pea-shoot setpoints.
2. Large Seeds Change Early Pea-Shoot Physiology
Pea seeds contain substantial stored reserves.
During early germination, seedlings rely heavily on those reserves.
That allows pea shoots to develop:
- roots
- hypocotyls
- early shoots
before photosynthesis becomes the dominant carbon source.
This is why early darkness can be a normal part of pea-shoot production.
3. Direct Pea-Microgreen Research Starts With Dark Germination
A 2023 vertical-farm study used:
Pisum sativum ‘Kleine Rheinländerin’.
Seeds were soaked for:
24 hours
and then placed in a dark germination environment at approximately:
20°C.
Only after the seedlings had developed radicles longer than approximately:
6 cm
were they transferred into the illuminated production system.
This provides direct evidence that:
PAR does not need to be positive during every stage of pea-shoot production.
4. During Germination, PPFD May Legitimately Be Zero
While the crop remains in full darkness:
PPFD = 0 µmol/m²/s
can be completely appropriate.
At that point, focus on:
- seed hydration
- germination uniformity
- sanitation
- temperature
- root development
- excess moisture
- mold risk
Trying to assign a seed-stage PAR requirement during full blackout is not useful.
5. Once Shoots Enter Light, PAR Becomes Important
After dark germination, photosynthesis becomes increasingly important.
Measure PPFD at:
actual shoot height.
Do not rely only on:
- lamp wattage
- fixture distance
- visual brightness
Pea shoots can grow rapidly upward, changing their distance from the light source within only a few days.
6. Direct 2025 Research Tested 100–400 PPFD
One of the strongest modern pea-microgreen experiments used:
‘Dwarf Grey Sugar’ pea
and compared four PPFD treatments:
100
200
300
and:
400 µmol/m²/s
with a:
12-hour photoperiod.
The corresponding DLIs were approximately:
4.2
8.6
13.0
and:
17.3 mol/m²/day.
This gives us unusually good direct pea-specific light-response data.
7. Fresh Yield Was Highest at the Lowest PPFD
The pea fresh yields were approximately:
100 PPFD → 3.24 kg/m²
200 PPFD → 2.94 kg/m²
300 PPFD → 2.74 kg/m²
400 PPFD → 2.72 kg/m²
So increasing PPFD from:
100 → 400 µmol/m²/s
did not increase fresh yield.
Fresh yield actually declined by approximately:
16%.
This directly contradicts the simple assumption:
higher PAR = more pea-shoot yield.
8. Individual Shoot Fresh Weight Also Declined
Mean shoot fresh weight was approximately:
431 mg/shoot at 100 PPFD
versus:
363 mg/shoot at 400 PPFD.
Again:
higher intensity did not produce heavier fresh shoots.
This is particularly important for a crop sold primarily by fresh mass.
9. Higher Light Made Pea Shoots Shorter
Plant height declined strongly as light intensity increased:
100 PPFD → 17.60 cm
200 PPFD → 16.21 cm
300 PPFD → 12.80 cm
400 PPFD → 12.34 cm
Therefore, stronger light produced a much more compact crop.
This is a real morphological effect.
But:
shorter does not automatically mean better.
10. Commercial Stem Length Matters
Pea shoots are often harvested and sold with visible stems.
A longer, tender shoot may be commercially desirable because it can provide:
- easier harvesting
- greater fresh volume
- attractive presentation
A highly compact crop may have different advantages.
Therefore:
maximum compactness
and:
maximum fresh yield
are not the same production target.
11. Higher PPFD Increased Dry-Matter Percentage
Although fresh yield decreased, dry-matter percentage increased:
100 PPFD → 8.33%
200 PPFD → 9.12%
300 PPFD → 9.68%
400 PPFD → 10.21%.
This is a crucial tradeoff.
Higher-light plants contained:
less water relative to total mass
and:
more dry matter per unit of fresh tissue.
12. But Total Dry Biomass Barely Changed
Dry biomass per square meter remained approximately:
265–277 g/m²
across the four light treatments.
So much of the apparent fresh-yield difference was related to:
- shoot morphology
- water content
- tissue composition
rather than a dramatic change in total accumulated dry matter.
That is a much more nuanced biological explanation than:
“more PAR makes stronger shoots.”
13. Higher Light Increased Water Consumption
Pea water consumption increased from approximately:
27.26 L/m² at 100 PPFD
to:
31.50 L/m² at 400 PPFD.
That is an increase of roughly:
16%.
This provides direct evidence that stronger lighting changes the crop’s water demand.
Therefore:
light and plant-water management must be interpreted together.
14. Water-Use Efficiency Declined at the Highest Light
Dry-matter water-use efficiency was approximately:
10.03 g DW/L at 100 PPFD
but only:
8.82 g DW/L at 400 PPFD.
So the highest light required more water without providing a corresponding gain in dry biomass.
This matters for:
- production cost
- irrigation design
- sustainability
Again:
maximum light is not automatically maximum resource efficiency.
15. Higher Light Strongly Increased Phytochemicals
The same experiment measured:
- phenolics
- flavonoids
- antioxidant activity
- chlorophyll
- carotenoids
And here the result moved in the opposite direction from fresh yield.
Total phenolics increased approximately:
12.04 → 19.08 mg GA/g DW
from 100 to 400 PPFD.
Total flavonoids increased approximately:
1.58 → 4.30 mg CE/g DW.
Antioxidant activity increased approximately:
29.26 → 52.42 µmol Trolox/g DW.
16. Therefore Higher PPFD Created a Yield–Quality Tradeoff
This is one of the strongest findings for the AquaHorti article.
At:
100 PPFD
pea shoots produced the greatest:
fresh yield
and:
shoot height.
At:
400 PPFD
they produced greater:
- dry-matter percentage
- phenolics
- flavonoids
- antioxidant capacity
but less fresh yield.
Therefore:
the “best” light depends on what the grower is optimizing.
17. Higher Light Also Reduced Nitrate
Pea nitrate concentration declined as PPFD increased.
Approximate nitrate at:
100 PPFD = 640 mg/kg FW
and the highest-light crop had substantially lower nitrate.
Nitrogen and potassium concentrations also declined with increasing intensity.
Meanwhile, some minerals such as:
- calcium
- sulfur
- manganese
were lower at 100 PPFD than under stronger lighting.
Again:
nutritional response is multidimensional.
18. This Means “Tender” Cannot Be Defined by One PPFD
The lower-light plants were:
- taller
- heavier on a fresh-weight basis
- higher in water content
while higher-light plants were:
- shorter
- higher in dry-matter percentage
- richer in several measured phytochemicals
But the study did not directly measure:
- sensory tenderness
- stem-fiber resistance
- chewing force
Therefore, it would be incorrect to write:
“100 PPFD produces tender stems”
or:
“400 PPFD produces tough stems.”
Those are stronger claims than the data support.
19. PAR Is Not a Stem-Strength Meter
PAR tells you how many photosynthetic photons reach the crop.
It does not directly measure:
- fiber
- lignin
- tissue toughness
- succulence
- fracture force
If stem texture matters commercially, measure it separately.
Do not infer it automatically from PPFD.
20. Pea-Shoot Light Response Is Also Affected by Spectrum
A 2026 study grew pea microgreens under:
- blue
- red
- blue + red
- cool white
- darkness
at approximately:
145 µmol/m²/s
for:
16 hours/day.
That corresponds to approximately:
8.35 mol/m²/day.
Different spectra produced substantially different morphological and biochemical responses.
21. Blue Light Produced the Highest Fresh Weight in 2026 Microgreens
In that experiment, pea microgreens under:
blue light
produced the highest fresh weight among the illuminated treatments at approximately:
0.291 g per measured plant/sample unit.
Other spectra changed:
- pigments
- polyphenols
- antioxidant activity
differently.
Therefore:
PPFD alone cannot explain pea-shoot quality.
22. Pea Sprouts and Pea Microgreens Respond Differently to the Same Spectrum
The 2026 experiment compared both:
sprouts
and:
microgreens.
The highest growth response did not occur under exactly the same spectrum for both developmental forms.
This matters because:
a recommendation for sprouts cannot automatically be copied to pea shoots.
Developmental stage changes the light response.
23. Direct Pea-Sprout Research Also Shows Red/Blue Ratio Matters
A 2024 study examined pea sprouts under different:
- red/blue ratios
- light intensities
- photoperiods
The experimental range included approximately:
9–90 µmol/m²/s
and:
4–20 hours/day.
Red light and a:
red ratio around 4:1
promoted favorable morphological development under the tested conditions.
But quality traits responded differently.
24. Maximum Dry Matter and Maximum Flavonoids Were Not the Same Treatment
The 2024 study mathematically modeled:
- total flavonoid concentration
- total flavonoid yield
- dry matter mass
and found that each had a different optimal combination of:
- red/blue ratio
- intensity
- photoperiod
The authors also reported a tradeoff:
increasing dry-matter mass by:
1 mg
was associated with approximately:
0.78 mg less total flavonoid concentration
within their model.
Again:
maximum yield and maximum phytochemical concentration are different objectives.
25. Very Long Photoperiods Also Change Pea Metabolism
A 2026 metabolomics experiment compared pea sprouts under:
8 h
16 h
and:
24 h
photoperiods.
Researchers measured approximately:
100 metabolites and phytohormones.
The three photoperiods produced clearly different metabolic profiles.
26. Longer Light Periods Were Not Metabolically Free
Compared with the short-day treatment, long or continuous light increased:
- sugars
- several stress-related hormones
Short-day treatment increased several amino acids.
Notably, the 16-hour treatment increased:
abscisic acid
and strongly increased:
salicylic acid
relative to the short-day treatment.
The researchers interpreted this as evidence of photoperiod-related metabolic stress.
Therefore:
longer lighting is not simply free additional photosynthesis.
27. DLI Is Useful — But One Universal Pea-Shoot DLI Is Not
Current direct pea research includes successful conditions around:
4–17 mol/m²/day
depending on:
- cultivar
- photoperiod
- production goal
- spectrum
The strongest 2025 intensity experiment shows clearly that:
17.3 DLI did not maximize fresh yield.
Therefore, AquaHorti should not publish:
“pea shoots require 18–22 DLI.”
That would misrepresent current evidence.
28. A Practical Pea-Shoot Light Reference
For commercial pea microgreens, roughly:
100–300 µmol/m²/s
and:
about 4–13 mol/m²/day
are well represented in recent direct experimental work.
But this should be treated as:
a research comparison region
not:
a universal optimum.
If the goal is:
maximum fresh yield
lower intensity may perform very well.
If the goal is:
compactness or phytochemical enrichment
higher intensity may be useful.
29. Light Uniformity Matters — But Not Quite the Way We Might Expect
A 2023 vertical-farm study specifically examined:
light uniformity
in pea microgreens.
Researchers created:
- one relatively uniform lighting area
- two nonuniform lighting areas
while maintaining similar average PPFD values.
They harvested plants after:
12 days of light treatment.
30. Average Tray Yield Did Not Differ Significantly With Uniformity
Interestingly, trays receiving the same average PPFD but different spatial uniformity did not show significant differences in overall crop yield.
However, individual plants told a different story.
31. Local PPFD Explained About 31% of Individual Fresh-Weight Variation
When researchers compared individual plants, local differences in PPFD explained approximately:
31% of fresh-weight variation.
The remaining variation was associated with:
- germination
- biological variability
- microenvironmental factors
This is an important measurement lesson.
Average PPFD can hide plant-to-plant differences.
32. Therefore Measure Multiple Positions
For pea shoots, check:
- tray center
- corners
- rack edges
- representative plant positions
One center measurement is not enough to describe the entire crop.
This is especially important when trying to diagnose uneven harvest height or fresh weight.
33. CO₂ Has Direct Pea-Shoot Evidence
Unlike several other microgreen crops, pea shoots have direct crop-specific CO₂ research.
A study of baby pea shoots compared:
- ambient air
- approximately 600 ppm CO₂
- approximately 800 ppm CO₂
in semi-controlled growth chambers.
The researchers also evaluated microbial inoculants.
34. 600 and 800 ppm Increased Pea-Shoot Yield
Compared with ambient air:
600 ppm CO₂ increased yield by approximately 9.4%.
800 ppm increased yield by approximately 20%.
This provides direct evidence that pea shoots can respond positively to moderate CO₂ enrichment.
35. 800 ppm Also Changed Nutritional Production
At approximately:
800 ppm CO₂
the study reported increases per production area in:
- crude protein
- lipid
- energy
relative to ambient conditions.
But the experiment also included microbial inoculation treatments, and some of the strongest responses occurred when elevated CO₂ was combined with those inoculants.
36. Does This Make 800 ppm the Pea-Shoot CO₂ Optimum?
No.
The experiment compared:
- ambient
- 600
- 800 ppm
and showed a positive response.
It did not test enough concentrations or economic conditions to establish:
800 ppm as the universal commercial optimum.
A correct AquaHorti statement is:
600–800 ppm has direct pea-shoot research support as an enrichment range that increased yield in one controlled experiment.
Not:
pea shoots require 800 ppm.
37. CO₂ Conditions Also Vary Naturally in Enclosed Farms
The 2023 vertical-farm pea experiment did not inject CO₂.
CO₂ naturally varied approximately between:
400 and 600 ppm.
The lowest concentrations occurred during the:
light period
when photosynthesis consumed CO₂.
The highest occurred near the end of the dark period.
This is a very useful real-world finding.
38. CO₂ Can Drop While PAR Is High
This suggests a practical monitoring strategy.
Track:
PAR and CO₂ on the same timeline.
A pattern such as:
lights turn on → PAR rises → CO₂ declines
may reveal a real change in the crop environment.
That is more informative than assuming the room always remains at outdoor ambient CO₂.
39. Temporary CO₂ Spikes Can Also Mislead Measurements
In the same experiment, human presence temporarily raised CO₂ to approximately:
1200 ppm.
That is a useful reminder when collecting data in indoor farms.
A single manual reading may reflect:
- workers entering the room
- doors opening
- ventilation changes
rather than the normal crop environment.
Continuous logging provides much stronger evidence.
40. What About VPD?
This is where AquaHorti should stay conservative.
Current pea-shoot research reports temperature and humidity conditions, but there is not a sufficiently strong body of pea-microgreen research establishing a universal:
- germination VPD
- vegetative VPD
- pre-harvest VPD
optimum.
Therefore, old precise VPD stage tables should be removed.
41. Experimental Humidity Is Not an Optimum VPD
For example, the 2023 vertical-farm pea experiment maintained approximately:
20 ± 2°C
and:
75 ± 5% RH.
Another 2024 pea-microgreen experiment maintained approximately:
50–60% RH
with:
21/17°C day/night temperature.
Both successfully grew peas.
But these different environments do not prove that either VPD is universally optimal.
They simply describe the experimental systems.
42. General Microgreen Guidance Also Uses a Broad Humidity Range
Virginia Tech’s 2026 controlled-environment microgreen guide notes that common microgreen humidity levels are roughly:
50–70% RH.
That is useful operational context.
It should still not be converted into a pea-specific VPD optimum.
The stronger role for VPD is:
understanding atmospheric water demand.
43. Why VPD Matters Even Without a Target
As:
- temperature rises
- humidity falls
VPD generally rises.
That can increase:
- transpiration
- water use
- tray drying
Direct pea research already shows that:
higher PPFD increases water consumption.
Therefore, PPFD and VPD should be interpreted together when diagnosing water demand.
44. High VPD Does Not Automatically Mean Tough Pea Shoots
VPD does not directly measure:
- fiber
- stem breaking force
- tenderness
- succulence
A crop may experience high atmospheric demand while still receiving sufficient root-zone water.
Another crop may experience moderate VPD but become stressed because the tray dries.
Therefore:
VPD cannot be used as a pea-shoot tenderness meter.
45. Root-Zone Water Must Be Considered Separately
Pea seedlings need consistent access to water during rapid shoot expansion.
Monitor:
- tray weight
- substrate moisture
- irrigation frequency
- root health
If higher light is used, expect water demand to increase.
The 2025 direct pea experiment gives us quantitative evidence for this relationship.
46. Very High Humidity Is Not Automatically Better
Pea shoots have dense canopies.
Very humid conditions can reduce evaporative demand.
But they can also encourage:
- persistent leaf wetness
- slow canopy drying
- microbial problems
So the production target should not be:
lowest possible VPD.
It should be:
stable hydration with adequate airflow and sanitation.
47. Pea Shoots Have Direct Postharvest Spectrum Research
A 2025 Scientia Horticulturae study grew pea shoots under:
- red
- blue
- red + blue
- white light
- darkness/control conditions
at approximately:
81 µmol/m²/s
for:
16 h/day.
After harvest, shoots were stored at:
5°C
and:
85% RH
for up to:
10 days.
48. Red + Blue Pre-Harvest Light Improved Retention of Several Phytonutrients
Pea shoots grown under combined:
red + blue light
retained several nutritional compounds better during storage.
At different storage points, the treatment helped preserve:
- ascorbic acid
- leucine
- phenylalanine
- lysine
- lutein
- zeaxanthin
- β-carotene
- phenolic compounds
- antioxidant activity
better than several comparison treatments.
49. Some Benefits Persisted for About 4–6 Days
The strongest differences in several:
- amino acids
- carotenoids
- antioxidants
were particularly evident through roughly:
4–6 days
of refrigerated storage.
By later storage points, nutritional differences among treatments declined.
This is a much stronger basis for discussing pre-harvest light and shelf life than assigning a single pre-harvest VPD.
50. But Light Does Not Replace Refrigeration
The pea shoots in this experiment were stored at:
5°C.
Postharvest temperature remained a major part of the preservation system.
Therefore, even if production light improves certain phytonutrients:
good refrigeration is still essential.
51. Pea-Sprout Shelf Life Has Also Been Studied Directly
Separate pea-sprout research has examined:
- refrigerated storage temperature
- changing storage temperature
- indirect sunlight exposure after cooling
The results show that postharvest handling can strongly influence:
- freshness
- appearance
- bioactive compounds
- microbial quality
Again:
shelf life is not determined by one pre-harvest VPD number.
52. Harvest Timing Changes the Product
Recent pea studies harvest at different ages depending on the production system.
Examples include:
- approximately 7 days for sprouts
- approximately 10–14 days for shoots or microgreens
- 12 days after transfer to light in some vertical-farm systems
As the crop ages:
- stem length changes
- tendrils develop
- leaves expand
- dry matter changes
- texture changes
- metabolite composition changes
Therefore, harvest age must be recorded when comparing “tenderness.”
53. Older Pea Shoots Are Not Automatically a Lighting Problem
If one crop has tougher stems than another, ask first:
- Was it harvested later?
- Was the cultivar different?
- Did water availability differ?
- Was temperature different?
- Did the shoot contain more dry matter?
Do not automatically blame:
- PPFD
- VPD
- CO₂
without controlling the other variables.
54. A Practical Greenhouse Production Workflow
Step 1 — Dark Germination
Focus on:
- soaking
- germination uniformity
- temperature
- moisture
- sanitation
PAR may legitimately be zero.
Step 2 — Move to Light
Once shoots are ready for green development, expose the crop to light.
Measure PPFD at actual canopy height.
Step 3 — Measure Several Tray Locations
Check:
- center
- corners
- rack edges
- uneven growth zones
Local PPFD can influence individual fresh weight.
Step 4 — Record DLI
When sunlight or lighting changes across the day, log PAR continuously.
Step 5 — Define the Production Goal
Are you optimizing for:
- maximum fresh yield?
- compact shoots?
- higher dry matter?
- higher phenolics?
- lower nitrate?
- energy efficiency?
Different PPFDs may favor different outcomes.
Step 6 — Track CO₂
Compare CO₂ with light periods.
Pay attention to:
- photosynthetic drawdown
- worker-induced spikes
- ventilation events
Step 7 — Track Temperature and Humidity
Use them to understand atmospheric water demand and VPD.
Step 8 — Track Water Use
Higher PPFD can increase water consumption substantially.
Step 9 — Record Crop Measurements
Measure:
- fresh yield
- shoot height
- individual shoot weight
- dry matter
- harvest age
If tenderness matters commercially, evaluate texture directly.
55. Practical Research-Based Reference Points
Germination
Dark germination is strongly represented in direct pea-shoot research.
Do not assign a PAR requirement to a fully covered crop.
PPFD
The strongest recent pea-microgreen light-intensity study directly tested:
100–400 µmol/m²/s.
Fresh yield was greatest at:
100 PPFD
while higher PPFD produced:
- shorter shoots
- higher dry-matter percentage
- greater phytochemical concentrations
Therefore:
100–300 PPFD is a useful direct research range for comparison
but there is no universal optimum.
DLI
At a 12-hour photoperiod, the same study tested approximately:
4.2–17.3 mol/m²/day.
Higher DLI did not maximize fresh yield.
For pea shoots, DLI should therefore be matched to:
production goal
rather than treated as a single required threshold.
CO₂
Direct pea-shoot research found:
600 ppm → about +9.4% yield
and:
800 ppm → about +20% yield
compared with ambient air.
This makes 600–800 ppm a useful crop-specific research reference.
It is not a universal commercial optimum.
VPD
There is no sufficiently validated pea-shoot stage-specific VPD target.
Use VPD to understand atmospheric water demand and relate it to:
- PPFD
- irrigation
- temperature
- crop response.
56. A Better Way to Think About Pea-Shoot Measurements
Instead of asking:
What PPFD makes pea shoots tender?
ask:
Am I optimizing fresh yield, height, dry matter or nutritional quality?
Instead of:
What VPD makes stronger stems?
ask:
How strong is atmospheric water demand, and is the root zone supplying enough water?
Instead of:
What DLI gives the highest yield?
ask:
Are additional daily photons increasing fresh biomass, or mainly changing dry matter and phytochemicals?
Instead of:
What CO₂ concentration should pea shoots have?
ask:
Does CO₂ fall during active photosynthesis, and does enrichment improve yield enough to justify the cost?
Those questions are much more consistent with current pea-shoot research.
Final Takeaway
Greenhouse pea shoots do not have one scientifically established PAR, CO₂ and VPD recipe for tender growth, strong stems or maximum yield.
But pea shoots now have unusually strong crop-specific lighting evidence.
A 2025 greenhouse experiment directly compared:
100, 200, 300 and 400 µmol/m²/s
at a 12-hour photoperiod.
Fresh yield actually declined from:
3.24 kg/m² at 100 PPFD
to:
2.72 kg/m² at 400 PPFD.
Plant height declined from:
17.60 cm
to:
12.34 cm.
At the same time, dry-matter percentage increased from:
8.33%
to:
10.21%.
And total phenolics, flavonoids and antioxidant activity increased strongly with light intensity.
That means:
maximum fresh yield and maximum phytochemical concentration are not the same lighting goal.
Higher PPFD also increased water consumption from approximately:
27.26 to 31.50 L/m²
while water-use efficiency declined at the highest light treatment.
Direct pea research also shows that local PPFD matters.
A 2023 vertical-farm experiment found local light differences explained approximately:
31% of individual plant fresh-weight variation
even though overall tray yield did not differ significantly between lighting distributions with similar average PPFD.
CO₂ has direct pea-shoot evidence as well.
Compared with ambient air:
600 ppm increased yield by approximately 9.4%
and:
800 ppm increased yield by approximately 20%
in one controlled pea-shoot experiment.
But that does not establish 800 ppm as a universal optimum.
For VPD, current pea-shoot research does not justify one rigid stage-specific kPa table.
The better greenhouse strategy is therefore:
Use darkness appropriately during germination.
Measure PPFD at actual shoot height.
Use DLI to understand total daily light.
Monitor multiple tray positions.
Track CO₂ during light periods.
Measure temperature, humidity and VPD together.
Track root-zone water and actual water use.
Then compare those measurements with the production trait that actually matters:
fresh yield, shoot height, dry matter, nutritional quality, texture or shelf life.
That provides a much stronger basis for greenhouse pea-shoot production than unsupported PAR / CO₂ / VPD stage recipes.
References
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LED Spectral Light Combination During Production Preserves the Phytonutritional Composition of Green Pea Shoots (Pisum sativum L.) at Postharvest Storage. Scientia Horticulturae, 2025.
The Shelf Life and Quality of Green Pea (Pisum sativum) Sprouts During Storage at Different Refrigerated Temperatures and Durations of Indirect-Sunlight Exposure. Postharvest Biology and Technology, 2024.
Virginia Cooperative Extension. Introduction to Microgreen Production in Indoor Vertical Farms and Greenhouses. 2026.
Related AquaHorti Tools
For instantaneous PAR / PPFD measurements and checking tray-to-tray light distribution, see AquaHorti AH-Quantuv.
For recording changing greenhouse PAR throughout the day and measuring DLI, see AquaHorti AH-PARDLI.
For greenhouse monitoring where PAR, DLI, CO₂, temperature, humidity and VPD need to be reviewed together over time, see AquaHorti AH-200.