Plant Growth at Sub-Ambient Atmospheric Pressures with Control of the Partial Pressures of Constituent Gases

Home , Ambient pressure

PlantPlant GrowthGrowth atat SubSub--AmbientAmbient AtmosphericAtmospheric PressuresPressures withwith ControlControl ofof thethe PartialPartial PressuresPressures ofof ConstituentConstituent GasesGases

ChuanjiuChuanjiu He,He, RonRon LaceyLacey andand FredFred DaviesDavies

Depts. of Horticultural Sciences & Biolog. & Agr. Engineering Texas A&M University College Station, Texas PlantPlant GrowthGrowth atat SubSub--AmbientAmbient AtmosphericAtmospheric PressuresPressures

AdvantagesAdvantages ofof LowLow PressurePressure SystemSystem

ÖÖ Less structure needs to be shipped into space.

ÖÖ Less gas leakage from low pressure crop production to vacuum of Moon or near vacuum of Mars.

ÖÖ Crew could tend crops without suiting up.

ÖÖ Won’t have to ship or produce as much Nitrogen gas GasGas CompositionComposition

•• ProvidedProvided byby pressurizedpressurized NN2,, COCO2 andand OO2 cylinders.cylinders.

•Perfect Gas Law: PVPV == nRTnRT

P= pressure; V= volume; n = moles; T = temperature

Total Pressure pN2 pO2 pCO2 (kPa) (kPa) (kPa) (kPa x 10-3) 101101 8080 20.920.9 100100 5050 39.739.7 10.310.3 100100 2525 19.919.9 5.15.1 100100 ProjectProject ResearchResearch ObjectivesObjectives

1.1. ToTo characterizecharacterize plantplant growth,growth, gasgas exchangeexchange (respiration(respiration andand photosynthesis),photosynthesis), constituentconstituent gasesgases (oxygen,(oxygen, carboncarbon dioxide,dioxide, ethyleneethylene andand otherother tracetrace gases,gases, andand waterwater reclamationreclamation (transpirate)(transpirate) underunder environmentalenvironmental conditionsconditions thatthat maymay applyapply toto anan AdvancedAdvanced LifeLife SupportSupport System.System.

2.2. ToTo modelmodel thethe dynamicsdynamics ofof carboncarbon dioxidedioxide exchangeexchange inin aa closedclosed microecosystemmicroecosystem suchsuch asas anan AdvancedAdvanced LifeLife SupportSupport System.System. HistoryHistory ofof LowLow PressurePressure PlantPlant GrowthGrowth SystemsSystems atat TexasTexas A&MA&M UniversityUniversity

GenerationGeneration II –– 19871987 –– 19971997 – One low pressure & one ambient pressure chamber

– Not a closed system (CO2 measurement) – Control program not flexible – Safety and reliability issues GenerationGeneration IIII –– 19991999 –– 20022002 – One low pressure & one ambient pressure chamber – Based on upgrades from Gen I

– System not fully closed (CO2 measurement) – Flexible control program with graphic readouts HistoryHistory ofof LowLow PressurePressure PlantPlant GrowthGrowth SystemsSystems atat TexasTexas A&MA&M UniversityUniversity (con.)(con.)

GenerationGeneration IIIIII –– 20022002 –– 20052005 –– 66 semisemi--independentindependent chamberschambers » Shared mass flow controllers » GC sampling manifold –– GasGas compositioncomposition byby industrialindustrial GCGC (Rosemont(Rosemont GCX)GCX) –– ControlControl ofof totaltotal pressure,pressure, CO2,CO2, andand O2O2 partialpartial pressurespressures –– EnhancedEnhanced humidityhumidity controlcontrol –– SamplingSampling frequencyfrequency twicetwice perper hourhour A C

B D

Figure 4. (A) Six-chambered low pressure growth (LPPG) system; (B) R. Lacey & C-J He starting an experiment; lettuce at (C) early and (D) later stage of development under low pressure. LPPGLPPG GenGen IVIV ChamberChamber SchematicSchematic SensorsSensors

Maxtec MAX-250 Weak acid electrolyte oxygen sensor

Ohmic Instruments HT-761 Vaisala CARBOCAP® Analog Relative Humidity and Carbon Dioxide Module Temperature Transmitter GMM220 Sensor Calibrations

25.0 40

O2 Sensor Calibration y = 0.1025x + 3.6828 CO2 Sensor Calibration SN MJ71889108 R 2 = 0.9818 35 SN Z2110045 Chamber #1 Chamber #1 20.0 April 29, 2005 April 29, 2005

y = 0.5808x + 14.028 25 R 2 = 0.987 15.0

10.0

15 Partial O2 Pressure (kPa) CO2 Partial Pressure (Pa)

10 5.0

0.0 0 0 20 40 60 80 100 120 140 160 180 200 0 5 10 15 20 25 30 35 40 O2 Sensor Digital Number (10-bit ADC) CO2 Sensor Digital Number (10-bit)

Chamber 1 Calibration data showing linear response with partial pressure for CO2 (left) and O2 (right) transducers. 600 35 CO2 Low Pressure CO2 Ambient Pressure O2 Low Pressure O2 Ambient Pressure

30 500

25 400

300 O2 (kPa) O2 CO2 (Pa) CO2 15

200 10

100 5

0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 :0 : :0 : :0 : :0 : :0 : :0 : :0 : :0 : :0 0 2 0 2 0 2 0 2 0 2 0 2 0 2 0 2 0 1 1 1 1 1 1 1 1 5 5 5 5 5 5 5 5 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 / 0 / 0 / 0 / 0 / 0 / 0 / 0 / 0 / 6 / 7 / 8 / 9 / 0 / 1 / 2 / 3 / 4 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 / 1 / 1 / 1 / 1 / 2 / 2 / 2 / 2 / 5 / 5 / 5 / 5 / 5 / 5 / 5 / 5 / 5 5 5 5 5 5 5 5 5 Time Partial pressure of CO2 (left axis) and O2 (right axis) during a seven day test of lettuce in the Gen IV LPPG. During the light period (8:00 am to 8:00 pm) the level of CO2 was controlled to 100 Pa, while during the dark period (8:00 pm to 8:00 am) the level was allowed to rise with plant respiration. O2 was controlled to a minimum of 6 kPa and 21 kPa for Chambers 1 and 2, respectively. O2 was allowed to rise with photosynthesis during the light period. Data were taken at one minute intervals. Chamber 1 was at a total pressure of 25 kPa and chamber 2 was at a total pressure of 101 kPa. CurrentCurrent PlantPlant BiologyBiology ResearchResearch ObjectivesObjectives

•• CharacterizeCharacterize thethe influenceinfluence ofof hypobarichypobaric conditionsconditions onon optimaloptimal plantplant growthgrowth ofof lettucelettuce ((LactucaLactuca sativasativa).).

•• CharacterizeCharacterize influenceinfluence ofof hypobarichypobaric conditionsconditions onon plantplant gasgas exchangeexchange andand ethyleneethylene evolutionevolution.. (He, Davies, Lacey, 2003)

101 kPa 101 kPa

50 kPa 101 kPa • Low pressure had no significant effects on net photosynthesis, stomatal conductance, and germination rate of lettuce and wheat.

• In Lettuce, low O2 (6.2%) significantly reduced ethylene production under low or ambient pressure. In Wheat, ethylene was reduced by low pressure but

not significantly by low O2 (6.2%) at ambient pressure. • Accumulation of ethylene in chambers had significant effect on lettuce and wheat growth. • Lettuce was more sensitive to ethylene than wheat. No Tip Burn Low pressure: 50 kPa; Low light: 300 µmol

100 Pa CO2 Day 6

Tip Burn Ambient: 101 kPa; Low light: 300 µmol

100 Pa CO2 Day 6 Figure E5. CO2 draw-down at 8:10 (10 minutes after lights on) of ambient (101 kPa) and low (50 kPa) lettuce plants.

5-12

500 101 Kpa 400 y = -2.3991x + 464.53 R2 = 0.9982 (Pa) 300 2

CO 200 50 kPa y = -1.3482x + 300.12 100 2 R = 0.9988 0 0 20 40 60 80 100 120 140 160

Time (min) Figure E6. Dark respiration over a 12-h dark cycle at ambient (101 kPa) and low (50 kPa) total pressure of lettuce plants.

May 12

600 101 Kpa 500 y = 0.5212x + 123.66 400 R2 = 0.9945 (Pa)

2 300

CO 200 50 Kpa y = 0.285x + 123 100 R2 = 0.9923 0 0 60 120 180 240 300 360 420 480 540 600 660 720 780 Time (min) Ratio of Net CO2 assimilation / Respiration 10 0 2 4 6 8

-652 6-2 5-23 5-16 6 Kpa O2 101 Kpa 25 Kpa

21 Kpa O2 Date 12 Kpa O2

21 Kpa O2

12 Kpa O2

21 Kpa O2 Figure E7. Lettuce plants at day 0 @ 25 and 101 Kpa.

D0 25 Kpa D0 101 Kpa

D0 25 Kpa D0 101 Kpa Figure E8. Lettuce plants at day 7 @ 25 and 101 Kpa.

D7 25 Kpa D7 101 Kpa

D7 25 Kpa D7 101 Kpa 2500 101 kPa High Light: 600 µmol; CO2: 600 Pa

2000 50 kPa 1500

1000 ) ) 1 1 - - 500

2500 Low Light: 300 µmol CO2: 100 Pa nmol moL nmol moL 101 kPa ( ( 2000

1500 50 kPa

1000

500 Ethylene Concentration in Chambers Ethylene Concentration Ethylene Concentration in Chambers Ethylene Concentration 0 1 3 6 Duration of Treatment (days) SummarySummary ofof LowLow PressurePressure (LPPG)(LPPG) SystemsSystems

ÖÖ Lettuce can be grown under low pressure (LP).

ÖPhotosynthesis and stomatal conductance not adversely affected by LP. ÖÖ Dark respiration and ethylene levels are much higher under ambient than low total pressure with lettuce production.

ÖDARK RESPIRATION (at(at night)night) lowerlower underunder LPSLPS == greatergreater plantplant yield.yield.

ÖÖ Tendency for tip burn under ambient pressure. FutureFuture ResearchResearch

•• Characterizing growth & development of lettuce under low pressure

[LP] (25 kPa) with variable partial pressures of CO2 and O2.

• Characterizing CO2 assimilation and dark respiration at low pressure with variable partial pressures of CO2 and O2.

•Characterizing ethylene biosynthesis at low pressure.

•ACC synthase and ACC oxidase activities at low pressure, and

variable partial pressures of CO2 and O2. AcknowledgementAcknowledgement

•NASA- NNJ04HF53G  Plant Growth at Sub-Ambient Atmospheric Pressures with Control of the Partial Pressures of Constituent Gases

•NASA-TAMU Low Pressure Environment Homepage http://aggie-horticulture.tamu.edu/faculty/davies/research/nasa.html

•Real Time View of the Low Pressure Plant Growth System at TAMU http://baen.tamu.edu/users/rel/LPPG/