Biology Decisions — Species, Protocol, and a Storage Incident

2026-03-06

Between the data analysis and the autonomous agent, several biology decisions fell into place. The sensor infrastructure is running. Now we need to decide exactly what we’re growing and how.

The mint: Mentha x piperita

Spring growth is emerging in the London garden. I photographed the mint and Claude identified it from the images: Mentha x piperita — peppermint. The key features are purple-red stems and smooth, shiny leaves with a distinct peppermint scent rather than the fuzzy, rounded leaves of spearmint.

This identification matters more than it might seem. Peppermint is a sterile hybrid of watermint (M. aquatica) and spearmint (M. spicata). It cannot produce viable seeds. Every peppermint plant in every garden is a clone, spread by runners. This has two important consequences for the project:

1. TC is the natural scaling method. You literally cannot grow peppermint from seed — it’s vegetative propagation or nothing. Tissue culture isn’t an exotic technique for this species; it’s the only way to produce large numbers of genetically identical plants.

2. All explants from the garden are genetically identical. Since every runner is a clone of the same mother plant, genotype is eliminated as a variable in our experiments. Any differences in culture response are due to treatment, position, or technique — not genetics. This is a cleaner experimental setup than we’d get with most species.

Organogenesis first, not somatic embryogenesis

The March 3 research plan targeted somatic embryogenesis — reprogramming cells to form embryos. SE sounds better on paper: higher multiplication rates, publishable novelty, convergence with liquid culture automation. But after thinking it through, we’re starting with organogenesis instead.

The reasoning:

I’ve never done tissue culture before. The real risk for the first experiment isn’t a suboptimal protocol — it’s contamination. Fungi and bacteria will destroy cultures long before a wrong hormone concentration matters. Organogenesis gives faster visual feedback: you see shoots forming within 2 weeks. SE requires weeks of callus formation before anything happens, and if the culture contaminates during that time, you learn nothing about the biology.

Organogenesis is what commercial TC labs actually use day-to-day. There’s a reason for that — it’s reliable, well-documented, and forgiving. Learning to walk before running.

SE can come later. Once sterile technique is proven and we have a baseline contamination rate, we switch to SE for the temperature optimisation experiments. The skills transfer directly.

The protocol for the first attempt: nodal explants from fresh spring peppermint growth on MS medium with BAP (1-2 mg/L) for shoot induction and low NAA (0.1 mg/L) for root support. Standard textbook organogenesis. Nothing novel — deliberately.

The Syngonium Albo

A Syngonium podophyllum ‘Albo Variegatum’ arrived from eBay — the high-value species from the original research plan. These retail for £30-80 per cutting in the UK market, making them commercially interesting for TC propagation.

It’s currently acclimatising from transit stress. Not to be used for explants until it recovers and pushes new growth — stressed tissue gives worse culture initiation results and higher contamination rates. The Zhang, Chen & Henny (2006) protocol is waiting: MS + 2.5 mg/L TDZ + 0.5 mg/L NAA, petiole explants, dark incubation 5-12 weeks. But that’s Phase 2.

The PGR storage incident

The Plant Cell Technology Starter Kit arrived — a set of pre-mixed plant growth regulator solutions including BAP, IBA, and NAA. These are the hormones that tell cultured plant cells what to do: divide, elongate, form roots, form shoots.

PGRs need to be stored at 2-8°C. Ours sat on a warm radiator in the hallway for 36 hours before anyone thought to refrigerate them. Then the fridge turned out to be running at 12°C instead of the standard 4°C.

This is a known variable going into the first protocol. Most PGRs are reasonably heat-stable in solution for short periods, but prolonged warmth can cause degradation — particularly cytokinins like BAP. If the first cultures show weak hormone response (no shoot induction, slow callus formation), degraded PGRs are the first suspect before we blame the protocol itself.

This is exactly the kind of thing that makes home lab work different from institutional work. In a university, chemicals arrive into a monitored cold room. In a flat, they sit on a radiator because nobody was home when the delivery came. The important thing is documenting it honestly so we can account for it later.

Where we stand

The environment isn’t ready yet — the radiator needs to be dealt with and humidity is too low. But the biology plan is set. We know what we’re growing, how, and what could go wrong.