Cytokinins inhibit epiphyllous plantlet development on leaves of Bryophyllum (Kalanchoe) marnierianum

Abstract

When leaves of Bryophyllum marnierianum are detached from the plant, plantlets develop from primordia located at their margins. Leaves excised with a piece of stem attached do not produce plantlets. Severing the major leaf veins overcomes the inhibitory effect of the attached stem, indicating that the control agent is transmitted through the vascular system. A possible mechanism is that an inhibitory substance, possibly a known plant hormone, transported from the stem to the leaf, suppresses plantlet development. A number of hormones were tested for their ability to inhibit plantlet primordium development in whole isolated leaves. Auxins had no effect, indicating that apical dominance is not involved. The cytokinins zeatin, kinetin, and benzylaminopurine (BAP) strongly inhibited plantlet development, suggesting that they may be the or a factor involved in maintenance of plantlet primordium dormancy when the leaf is attached to the plant. This hypothesis was strongly supported by the finding that treatment of leaves attached to stems with a cytokinin antagonist (purine riboside) released the primordia from inhibition. In contrast to whole leaves, plantlet primordium development on leaf explants incubated on Murashige Skoog medium containing 3% sucrose was strongly stimulated by cytokinins. A possible explanation of these observations is that in whole leaves the cytokinin signal is transduced into an inhibitory signal whereas in the isolated primordium cytokinin has a direct stimulatory effect. The inhibitory cytokinin pathway must be dominant as long as the leaf is attached to the plant. A model is proposed which could explain these findings. This study points to a novel role of cytokinins in the maintenance of foliar plantlet primordium dormancy.

Analysis of gene expression in Kalanchoe daigremontiana leaves during plantlet formation under drought stress

“…(Catarino, 1965) reported that cytokinin activated bud development in K. pinnata (Bryophyllum calcynum). In contrast, cytokinin was found to play a central role in the suppression of plantlet primordium development in the leaf (Kulka, 2006). Our study complements the results of Kulka in that the expression of the SAHH gene (contig 32) under drought stress (with plantlets) was more than threefold greater than in the control (no plantlets).…”

Hormonal control of root development on epiphyllous plantlets of Bryophyllum (Kalanchoe) marnierianum: role of auxin and ethylene

“…The formation of miniature plants on the leaves of Bryophyllum species has intrigued biologists since Goethe (1820) . In some species such as B. daigremontianum , plantlets develop spontaneously on leaves attached to the plant ( Henson and Wareing, 1977 ) whereas in other species such as B. calycinum ( Goethe, 1820 ), B. fedschenkoi , and B. marnierianum ( Kulka, 2006 ), plantlets develop only when the leaves are detached from the plant. The latter type of species is convenient for studying the regulation of plantlet formation as the development can be induced at any time by leaf excision.…”

“…Although some papers, when taken together, hinted at an answer to this question ( Loeb, 1915 ; Henson and Wareing, 1977 ; Yazgan and Vardar, 1977 ), no definitive solution was reached. In this laboratory, a related species, B. marnierianum , was used to study the question of plantlet primordium dormancy further ( Kulka, 2006 ). The experiments indicated that cytokinins originating in the plant stem maintain plantlet dormancy.…”

Antidiabetic potential of ethanol leaf extract of Bryophyllum pinnatum on alloxan-induced diabetic rats and their haematological profiles

“…Bryophyllum pinnatum is an incessant medicinal plant that grows in the wild and used as a traditional medicinal as well as ornamental plant in tropical America and Africa, India, Australia, and China. The genus belongs to the family of Crassulaceae and is cultivated as ornamental house plant on rocks or in the garden (Kulka, 2006). The present herb under study is routinely called an air plant, Canterbury bell, cathedral bell, life plant and resurrection plant.…”