If the plants are in a bed that can be reached/weeded from both sides, so you don't need to walk on it, you can plant them all at 45cm spacing.
If you are planting on a big area, plants can still all be equidistant at 45Cm, , but after a few rows, you'll need a pathwidth left bare to walk along before the next row of the same or a different vegetable. Otherwise I find I'm treading on something to weed, or water, if that makes sense?
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