Something to keep in mind,
From the article:
“This was a proof-of-concept study, and I’m satisfied because the data were very beautiful and clearly demonstrate that this approach works,” says Nakamichi.
Ran in to this,
http://www.ncbi.nlm.nih.gov/pubmed/27012548
Linked to a subscription service http://pcp.oxfordjournals.org/content/57/5/1085.long
First submitted for publication in January 2014 and accepted in March 2016. Have not found anything on the results, data or outcomes that was not behind a paywall... their "free to read abstracts" are about as informative as the overly simplified article above. However, they do point to why there is more biomass which is left out of the article...
From the abstract:
Concomitant analyses of relative growth rate, flowering time and photosynthetic activity suggested that increased biomass of PRR5-VP plants is mostly due to late flowering, rather than to alterations in photosynthetic activity or growth rate.
Now, I also found this paper form way back in 2009... at least one shared author Nakamichi in it,
Bioinformatics approaches have indicated that the set of up-regulated genes in d975 and the set of cold-responsive genes have signifi cant overlap. We found that d975 is more tolerant to cold, high salinity and drought stresses than the wild type. In addition, dehydration-responsive element B1/C-repeat-binding factor ( DREB1/CBF ), which is expressed around mid-day, is more highly expressed in d975 .
So they have known about the stress tolerance factors involving those genes for a while also the earlier paper briefly does look at the type of impact the mutation/disruption have on flowering cycle.