VERBENA FLOWER RED COPY SPACE SERIES

The changes in primordia identity and, most likely, their relative size between the two stages of growth is evidently insufficient for a change in phyllotactic pattern quality. In the model plant Arabidopsis thaliana, the vegetative phyllotaxis of the leaves assembled into a rosette is spiral shaped, mirroring that of the cauline leaves and cryptic bracts on the inflorescence axis in the next phase of growth (Kang et al. What is then required for a change in phyllotaxis if not a new identity of the organ primordium? An intuitive guess is that it should be an appropriate change in its size relative to that of the shoot apical meristem (SAM). The last two cases indicate that the genetic mechanism specifying primordia distribution acts independently from that responsible for their identity. Petalody in Magnolia stellata shows that additional petals are not laid out in whorls but in spirals (Wróblewska et al. Moreover, the phyllotaxis of the newly initiated leaf-like organs in reverted flowers of Impatiens balsamina does not return to the spiral mode, which is typical for this plant’s vegetative growth phase, but remains floral, i.e., whorled (Battey and Lyndon 1990). However, phyllotactic transitions may occur even when organ identity does not change, as in the vegetative shoots of Abies balsamea and in the gynoecia of Magnolia (Zagórska-Marek 1985, 1994). The Magnolia flower has its perianth elements in trimerous whorls, but the stamens and carpels are spirally arranged. The bijugate phyllotaxis of the Torreya shoot becomes decussate within the domain of cataphylls formed at the end of each growing season (Banasiak and Zagórska-Marek 2006). The converse situation is exemplified by all Calycanthaceae (Staedler et al.

While vegetative phyllotaxis is often spiral, floral phyllotaxis is mostly whorled. Opposite cotyledons may be followed by spirally arranged foliage leaves. Transformations of phyllotaxis are often associated with a new phase of development, during which the identities of organs change. However, over the years, quite a large body of empirical evidence has accumulated, indicating that phyllotactic diversity, especially among spiral patterns, is more complex than originally thought, and all patterns may transform developmentally, one into another (Zagórska-Marek 1985, 1994). The best known and most common are whorled or spiral phyllotactic patterns, and among the latter, the main Fibonacci pattern prevails. 2011 Zagórska-Marek 1985 for review see Gola and Banasiak 2016). 2018), clubmosses (Gola 1996 Yin and Meicenheimer 2016), and seed plants (Yin et al. Interesting examples of this universal phenomenon have been found among brown algae (Peaucelle and Couder 2016), leafy bryophytes (Zagórska-Marek et al. The regular distribution of lateral organs in plant axial systems, called phyllotaxis, has intrigued scientists for a long time. Common verbena emerges from this research as a plant that may become a new model suitable for further studies on the causes of phyllotactic transitions. The results of this study highlight the complex relationships between various systems that have to coordinate their growth and differentiation in the developing plant shoot. This raises the question of the role of the vascular system in determining primordia initiation sites, and possibly challenges the autonomy of the apex. The most important finding is that the changes in the primary vascular system, associated with phyllotactic transitions, precede those taking place at the apical meristem. Data from the experiments in silico, confronted with empirical observations, suggest that secondary transitions might be triggered by the cumulative effect of fluctuations in the continuously decreasing bract primordia size. The latter are no longer associated with the change in lateral organ identity, and the sequence of phyllotactic patterns is puzzling from a theoretical point of view.

VERBENA FLOWER RED COPY SPACE SERIES

It has been found that in common verbena ( Verbena officinalis L.), a perennial, cosmopolitan plant, phyllotaxis differs not only between growth phases in primary transitions but also along the indeterminate inflorescence axis in a series of multiple secondary transitions. The plants studied so far, such as Magnolia, Torreya or Abies, are not suitable for experimental work, and the most popular model plant, Arabidopsis thaliana, does not show sufficient phyllotactic variability. Phyllotactic diversity and developmental transitions between phyllotactic patterns are not fully understood.

Verbena flower red copy space