Microgravity Hydroponics: Root Growth & Nutrient Diffusion

Environment

Gravity level 1.00 g

Nutrient diffusion D 1.0×

Simulation speed 1.0×

Live Readouts

Tip deviation from vertical

0.0°

Nutrient conc. at root zone

100%

Total root length

0 mm

How it works

Two independent gravity-dependent effects are modelled at once, both documented in real spaceflight plant-growth chambers (NASA Veggie / Advanced Plant Habitat):

1. Gravitropism. A root's growth direction is a weighted sum of the gravity vector and a persistent random-walk / circumnutation term:

dir = normalize( g·(0,-1,0) + (1-g)·wander + circumnutation )

At g = 1 the downward term dominates and roots grow straight down. As g → 0 the gravitropic cue vanishes and roots "wave" and "skew" — a real, photographed phenomenon on the ISS — since phototropism/thigmotropism/circumnutation are all that remain.

2. Diffusion-limited nutrient transport. Concentration C in the growth medium obeys the 2-D diffusion equation with a root sink and a convective mixing term:

∂C/∂t = D∇²C − k·ρ_root·C + m·(C_bulk − C)

D is molecular diffusivity, ρ_root is local root density (the sink), and m is a mixing rate that stands in for buoyancy-driven natural convection. On Earth, uptake-driven density gradients rise and sink, continuously replenishing the root surface (m scales with g). In microgravity there is no buoyancy, so m ≈ 0 and a depletion halo grows around every root, exactly why real orbital hydroponic systems (Veggie, APH) add forced airflow across the root zone — the "Forced-flow mixing" toggle reproduces that engineering fix by adding a constant m independent of g.

Gravity level — sets both the gravitropic weight and the natural-convection mixing rate.
Diffusion D — molecular mobility of the nutrient ion; larger ions (e.g. phosphate) diffuse slower than small ones (e.g. nitrate).
Forced-flow mixing — the real countermeasure engineers use to keep 0g roots fed.

Root tissue Nutrient-rich medium Depleted zone

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