Inflorescence Development in Brassica Campestris L.

Abstract

Vegetative seedlings of the Ceres strain Brassica campestris L., a quantitative, long‐day plant, were induced to flower by exposure to a 16‐hr, long‐day cycle. Cytohistological and cytohistochemical changes associated with inflorescence development were examined. Developing shoot apices were classified in vegetative, transitional, and reproductive stages. The vegetative apex possessed a biseriate tunica, central zone, peripheral zone and pith‐rib meristem. The transitional stage at 48 hr was marked by an increase in size and by a stratification of the upper cell layers of the shoot apex with a concurrent decrease of apical cytohistochemical zonation. The reproductive stage was initiated at 58 hr by periclinal cell divisions in the 3rd and 4th cell layers of the flank region. Cytohistochemical zonation in the vegetative apical meristem was restored in the floral apex. An “intermediate developmental” phase was not observed between the vegetative and reproductive stage.

Bi-directional inflorescence development in Arabidopsis thaliana: Acropetal initiation of flowers and basipetal initiation of paraclades

“…In a similar anatomical study on the transition to flowering in the annual mustard Brassica campestris, Orr (1978) reported that flower primordia were initiated on the flanks of enlarged shoot apical meristems 58 h after the start of inductive photoperiods. Orr, like Miksche and Brown, did not comment on the type(s) or number of primordia produced during the 58 h between the start of inductive photoperiods and the initiation of flower primordia.…”

“…Orr, like Miksche and Brown, did not comment on the type(s) or number of primordia produced during the 58 h between the start of inductive photoperiods and the initiation of flower primordia. However, he suggested that the period was "probably representative of the prefloral phase reported for Sinapis alba" (Orr 1978). Bernier (1962) reported that 60 d-old S. alba produced leaves following the start of 16-h inductive photoperiods.…”

“…In summary, Bernier (1962) and Vaughan (1955) reported that leaf primordia are produced before flower primordia, following the photoperiodic induction of flowering in Arabidopsis and S. alba. Subsequently, Miksche and Brown (1965) and Orr (1978) implied that their results were comparable to those of Bernier (1962) and Vaughan (1955). In the three studies where photoperiodic induction treatments were used (Vaughan 1955;Bernier 1962;Orr 1978), the initiation of floral primordia was reported to occur at least 50 h after the middle of the first inductive long day, i.e., 50 h after the time at which the plants were first exposed to light for longer than 8 h. All four studies suggest that there is an interval of at least 2 d between the end of vegetative growth and the initiation of floral primordia.…”

Histological Morphology and Development of the Shoot Apical Meristem of a Rapid-flowering Desert Annual Pectis papposa Gray.

“…The prevailing one is that it does not belong to the reproductive phase, but to the transition stage in Arabidopsis (Miksch and Brown 1965), or prefloral phase in Sinapis alba (Bernier 1962), Brassica campestris (Orr 1978), etc. The other view is that the bract production is included in reproductive phase in Arabidopsis (Hempel and Feldman 1994).…”

Open and closed inflorescences: more than simple opposites

“…The presence of a CZ in the IM of Arabidopsis has been well known since the 1950s (Vaughan, 1955). As in Arabidopsis, studies performed in other members of the Brassicaceae have shown that a CZ is maintained in the IM (Vaughan, 1955;Lance-Nougarède, 1961;Hagemann, 1963;Sadik and Ozbun, 1968;Orr, 1978) (Table 1). Examples of persisting CZs in IMs from other systematic groups are also abundant (Table 1).…”