ATHCOR1 mRNA and Chlide to Chl ratio during flower development. A, ATHCOR1 mRNA during wild-type flower development (stages 1–6) showing higher levels of transcripts (arrowhead) at the stage of buds, compared with ubiquitin (UBQ). B, Northern blot of ATHCOR1 in flower buds of wild-type (wt), coi1 mutant, sense (wtS, coi1S), and antisense (wtA) plants showing high expression of the sense (wtS1, coi1S2) and antisense (wtA1) mRNA relative to normal wild type. Lower levels of sense messages are observed in wtS4, wtA1, and coi1 plants, as compared with the major approximately 1.3-kb ATHCOR1 transcript (arrowhead). C, The ratio of Chlide a+b to Chl a+b in young (stages 1 and 2) and developed flowers (stage 5) of wild-type, coi1, sense, and antisense plants, indicating increased Chlase activities in mature flowers relative to buds, in all plants examined, excepted in coi1, where the difference between the means were not statistically significant. Values are the mean of five independent measurements plus the sd.