The measurement of the cell yield in liquid cultures confirmed what observed in the spot assay analysis (Fig. 3C).
I bumped into this sentence today, and that «what observed» feels like it’s missing a was, i.e. it should be «what was observed». I could even explain it as an italianism, seen as the sentence would translate to «[…] hanno confermato quanto osservato […]», where quanto is a relative pronoun and hence translates to what, and osservato is the past participle of osservare=observe, hence translates to observed, stitch the two together et voilà, «what observed». I am not a native and have no detailed grammatical rule to support this claim though, which is why I am asking:
Is this acceptable or is it ungrammatical, as my gut feeling suggests? Could you pinpoint why it is ungrammatical, if it is?
“…confirmed what was observed in the spot assay analysis.” puts the relative clause in passive voice, meaning that the measurement confirmed the observations in the spot analysis.
“…confirmed what observed in the spot assay analysis.” puts the relative clause in active voice, meaning that the measurement confirmed what was doing the observing in the spot assay analysis.
Context strongly suggests that the former is the meaning you’re looking for, in which case “what was observed” is correct.