Seed germination and root growth

Who it is for

• Space agency plant and life-support programmes (for example ISRO, NASA, ESA crop and bioregenerative life-support teams)
• University plant biology labs studying gravitropism, phototropism and root growth
• Seed and agri-biotech companies screening varieties or reporter lines for space farming
• Nutrition and food researchers looking at sprouts as fresh food for crews
• Student and early-career research teams needing a short, automated plant flight

What earlier flights found

How LELP-1 runs it

Sample. Dry seeds of Arabidopsis thaliana (for example Col-0 and WS, or a GFP reporter line), about 20 seeds per plate. A large-seed crop such as cowpea or moong can replace one plate. Container. Four sealed square seed plates (about 100 mm, nutrient gel or germination membrane) with gas-permeable covers. They are held upright in a fixed orientation in the large-bay cassette frame. Each plate is plumbed to the bay fluidics for hydration and fixation. Launch. Dry, dormant seeds (not hydrated), dark, bay at 18-22 C. Light and gas. White LEDs 16 h on / 8 h off (the photoperiod CROPS used). From day 4, one-sided blue LED light on half the plates for the phototropism test. Dim green or IR light only for imaging in the dark period. No CO2 supply: the bay is sealed with launch air (CROPS started at 20.9% O2 and 400-600 ppm CO2), and O2/CO2 are logged. Seedling biomass at this stage is small.

1. day -2

   Ground: load dry seeds on plates, seal bay, integrate. Split the same seed lot into a ground control and an unflown dry-seed archive.

2. day 0

   After orbit checkout: image dry plates, bring bay to 22 C, and hydrate each plate with dilute nutrient solution from the fluidics reservoir. Start white LED 16 h / 8 h and time-lapse imaging every 6 h.

3. day 2

   Score germination (radicle emergence) from images. Add water only if sensors show plates drying.

4. day 4

   Switch two plates to one-sided blue light (phototropism test). Two plates stay on white light. Keep the robotic arm idle during this window if possible.

5. day 6

   Fluorescence imaging of reporter-line plates (if flown) and final morphology image set.

6. day 7

   Fix in flight: flood two plates with RNA-stabilising fixative (RNAlater-type, for gene expression) and two with an aldehyde fixative (for microscopy). Image after fixation, then set bay to 4 C.

7. day 8

   Hold at 4 C with lights off until re-entry (any day up to day 14). Hand to the customer's courier on the recovery ship.

The payload module, in CAD

Every item in the module sheet, drawn and packed into the large bay deck by deck. The back face mates with the bay: blind-mate connector, and a cold wall against the bay's thermoelectric block. The front face carries Dexter-L's grapple fixture, and the fluid lines run down a channel just behind it. What you load before launch is marked blue in the configurator's payload guide.

CAD generated by cad/build_modules.py (CadQuery, OpenCascade kernel) from the catalog's module items: concept geometry, not a released design. Standard parts keep their real formats; the rest are sized from their catalog mass. The front panel and grapple fixture are left off in the 3-D view and are in the STEP.

• Each camera sees one column of two plates from 116 mm: about 99 degrees of diagonal field, so the 'macro' optics have to be wide-angle; a third and fourth camera, or a longer module, would ease it.
• Reagent volumes the catalog does not state are split evenly from 75 % of the reservoir item's mass.
• Fluid pack: 3 reagent bags in 3 layers (79 x 119 x 69 mm), every port on a front edge.
• The catalog gives 1.61 kg for structure and containment; as an aluminium box that is a 0.76 mm skin on 0.48 kg of posts and shelves.
• The grapple fixture stands 26 mm proud of the front panel, into the bay opening; everything else is inside the bay envelope.

Ground control

An identical flight-spare module on the ground, loaded from the same seed lot on the same day. It runs the same hydration, light, imaging and fixation timeline at 1 g with plates held vertical, and replays the logged flight temperature, humidity and light record about 1-2 days behind the flight. An unflown dry-seed archive kept at matched temperature separates storage and launch effects from germination effects. A clinostat or random positioning machine run can be added as a simulated-microgravity reference, but it does not replace flight.

Coming home

Samples are fixed in orbit, so they do not need to be alive at return. Keep fixed plates at 4 C from fixation (day 7) to the lab. 336 h covers the time from fixation to re-entry on day 14, plus courier time. This limit is our estimate; check it against the fixative maker's storage data. Live seedlings returned unfixed would no longer reflect the microgravity state after landing.

Limits of this flight

• 2-14 days covers germination and early seedlings only (up to about the two-leaf stage in crops like cowpea). No flowering, seed-to-seed cycles or crop yield studies.
• No in-flight 1 g centrifuge, unlike the EMCS on the ISS. Flight and ground differences therefore mix microgravity with launch, radiation and hardware effects.
• No -80 C freezer for return. Samples are chemically fixed at 4 C, which suits RNA and microscopy but limits some assays (for example, metabolites or enzyme activity may need frozen tissue).
• Fixing in flight is not proven for this layout. In microgravity, fixative may not cover gel-grown seedlings evenly. Fixative delivery must be tested on the ground and in a flight-like setup first.
• No crew: plates cannot be swapped, re-wet by hand, or rescued if seeds fail to hydrate. Water behaves differently in microgravity and can bead or bubble.
• Sealed bay air with no CO2 supply limits plant number and growth stage. Larger seedlings or many seeds would change O2/CO2 levels.
• In flight, imaging covers whole plates only. Detailed cell-level root data comes only after return.
• A 550 km sun-synchronous orbit has a different radiation environment from the ISS. Log the dose and compare it before pooling results with ISS data.
• Any live material after landing has sensed gravity again during the 1-2 day trip. Only samples fixed in flight reflect the microgravity state.