How the Disocactus perianth grows

Two species and two stages

Rosas-Reinhold and colleagues studied Disocactus speciosus and D. eichlamii. Buds of the former came from wild plants in the Pedregal de San Ángel reserve, Mexico, and those of the latter from the UNAM Botanical Garden collection. This sampling provided material for comparing organs of different final sizes. [Rosas-Reinhold et al. 2026, pp.1021–1024]

Early buds of both species measured 1 cm. Buds sampled before anthesis reached 10 cm in D. speciosus and 5 cm in D. eichlamii. Outer and inner tepals were compared. Their cells were examined in sections and by scanning electron microscopy. [Rosas-Reinhold et al. 2026, pp.1022–1025]

Cell division and expansion

In a 1 cm bud, floral organs were already clearly differentiated. Tepal cells were similar in size in the two species at this stage. Subsequent development revealed differences in the duration of proliferation and expansion. In D. speciosus, the cell growth phase lasted longer. [Rosas-Reinhold et al. 2026, pp.1025–1029]

The size of a whole tepal depends on cell number, cell size and arrangement. The authors analysed these properties separately. Prolonged proliferation and expansion in D. speciosus were associated with a larger final organ size. This relationship was established for the studied species and developmental stages. [Rosas-Reinhold et al. 2026, pp.1027–1033]

The developing flower transcriptome

RNA sequencing enabled gene activity to be compared between bud stages. A transcriptome comprises RNA reads present in the tissue at sampling. It indicates which cellular programmes were active at a particular place and time. Comparison with microscopy linked those programmes to actual tepal structure. [Rosas-Reinhold et al. 2026, pp.1024–1032]

Candidates associated with growth included homologues of BIG BROTHER, BIG PETALp and NAC100. Two BIG BROTHER copies in D. speciosus showed different directions of expression change between stages. The authors identified them as components requiring further functional investigation. [Rosas-Reinhold et al. 2026, pp.1029–1033]

From anatomy to mechanism

Expression differences identify associations between gene activity and organ growth. Establishing the role of an individual gene requires experiments that alter its activity and examine the effect in tissue. The 2026 study provides this research direction by jointly analysing morphology, cells and RNA. [Rosas-Reinhold et al. 2026, pp.1031–1033]