Corn has clearly defined growth stages.
Vegetative growth is defined by how many leaves have emerged. When the ‘black layer’ forms on the seed, the maximum amount of starch is in the seed and harvest is merely a matter of waiting for the moisture content to decrease (standard weight is based on 15.5% moisture). Growth rate is based on ‘growing degree days’. If you know the temperature, you know how fast the corn will grow.
Why is this significant, as most of us are not going to grow corn in the Food Computer (it won’t fit)? The reason is phenotypic data. With corn, there are clearly defined stages of growth, and standard measurements of grain yield (but was that metric or English tons?). I do not see similar precise definitions for lettuce, and most other vegetable crops. Without such standards, comparing measurements between experiments is almost meaningless.
I am sitting beside a nice head of lettuce right now, but can I say it is ‘done’? I could have picked it several days ago, or I could let it sit for a few more days until I am in the mood for a salad. Short of tearing it apart and measuring the number of leaves (how about the ones that dried up?) and the total surface area of the leaves, how do I compare my lettuce to yours? Do we always weight it on the 31st day (but are we growing at the same temperature?)? To not have clearly defined genomic traits is like measuring temperature as ‘cold’ and ‘warm’; it is a measurement, but it is neither precise nor accurate. As we know from mathematics, when you combine numbers, the number with the least significant digits determines the precision of the outcome. Right now we have precise sensors for the Food Computer (though I find two thermometers can be off from each other by almost a degree), but we lack precise definitions for plants. It is not sufficient to say that a mature head of lettuce is ‘the size of two fists’. How ‘tight’ is the head? How ‘stiff/crisp’ are the leaves?
There is a lot to the engineering of a Food Computer and writing code for a Raspberry Pi, but these are problems with known solutions; by comparison, the ontology of phenotypic traits (at least for lettuce) is a relatively unknown problem with no clear solution at this time. These are the problems that literally wake me up in the middle of the night. Without some answers (that we can all agree upon), the Food Computer will be reduced to a very expensive toy.
What do we mean by a ‘mature head of lettuce’?