K. daigremontiana as a Model Plant for the Study of Auxin Effects in Plant Morphology

Abstract

A large number of studies have been conducted in order to understand the mechanisms by which shoots, plantlets and vegetative propagules are produced. According to the first studies reported by Yarbrough [2, 3], in the fern species Camptosorus rhizophyllus (which has two different kinds of leaves), shoots are produced at the tip of long acuminate leaves, while in the species Tolmiea menziesii shoots are originated in a notch near the junction of the petiole and the leaf blade; in both cases, the shoots are produced from meristematic tissue and once they are mature are naturally detached from the leaf and fall to the ground originating a new plant. Also, in the orchid Malaxis paludosa, cells at the tip of mature leaves have an intense meristematic activity which originates embryo-like structures that once the mature leaf is wilted the small shoot detaches originating a new plantlet [4]. This phenomenon has been widely studied in plants of the Crassulaceae family, mainly in the genus Kalanchoe. According to the capacity to asexually produce such plants, species of this genus have been classified in four categories: a) plants which do not produce plantlets (K. marmorata, K. rhombopilosa, K. tomentosa and K. thyrsiflora), b) plants that spontaneously produce plantlets (K. daigremontiana), c) plants that produce plantlets by the action of an environmental stress (K. pinnata, K. fedstchenkoi, K. strepthantha, K prolifera and K. crenata) and d) plants that produce spontaneously plantlets by the action of stress and/or (K.