Spine micromorphology of normal and hyperhydric Mammillaria gracilis Pfeiff. (Cactaceae) shoots

Abstract

Artificial conditions of tissue culture affect growth and physiology of crassulacean acid metabolism plants which often results in formation of hyperhydric shoots. In in vitro conditions Mammillaria gracilis Pfeiff. (Cactaceae) growth switches from organized to unorganized way, producing a habituated organogenic callus which simultaneously regenerates morphologically normal as well as altered hyperhydric shoots. In this study, influence of tissue culture conditions on morphology of cactus spines of normal and hyperhydric shoots was investigated. Spines of pot-grown Mammillaria plants and of in vitro regenerated shoots were examined with stereo microscope and scanning electron microscope. The pot-grown plants had 16-17 spines per areole. In vitro grown normal shoots, even though they kept typical shoot morphology, had lower number of spines (11-12) and altered spine morphology. This difference was even more pronounced in spine number (six to seven) and morphology of the hyperhydric shoots. Scanning electron microscopy analysis revealed remarkable differences in micromorphology of spine surface between pot-grown and in vitro grown shoots. Spines of in vitro grown normal shoots showed numerous long trichomes, which were more elongated on spines of the hyperhydric shoots; the corresponding structures on spine surface of pot-grown plants were noticed only as small protrusions. Scanning electron microscopy morphometric studies showed that the spines of pot-grown plants were significantly longer compared to the spines of shoots grown in tissue culture. Moreover, transverse section shape varies from elliptical in pot-grown plants to circular in normal and hyperhydric shoots grown in vitro. Cluster and correspondence analyses performed on the scanning electron microscope obtained results suggest great variability among spines of pot-grown plants. Spines of in vitro grown normal and hyperhydric shoots showed low level of morphological variation among themselves despite the significant difference in shoot morphology.

Spines and ribs of Pilosocereus arrabidae (Lem.) Byles & G.D. Rowley and allies (Cactaceae): Ecologic or genetic traits?

“…This is another case that can be attributed to watering under home cultivation. The only apparently discordant data are those from Peharec et al (2010), where the "hyperhydric" stems of Mammillaria gracilis Pfeiff. presented shorter spines when compared to pot grown plants.…”

“…All rights reserved. Schmalzel et al, 2004;Peharec et al, 2010) and ecological interactions (Pérez-Harguindeguy et al, 2013). Nobel (1983), Loik (2008), and Drezner (2011) found that the spine coverage directly affects the downward solar radiation on the stem.…”

The plant size and the spine characteristics of the first generation progeny obtained through the cross-pollination of different genotypes of Cactaceae

“…For ornamental cacti, as are the species described here, the presence of spines is a positive element for their decorative traits. Peharec et al (2010) evaluated the spines of pot-grown Mammillaria plants and in vitro-regenerated shoots and found that the pot-grown plants had 16-17 spines per areole, whereas the in vitro-grown shoots were normal but displayed a lower number of spines (11-12). Parra et al (2010) argued that genetic diversity should be conserved and should be promoted by artificial selection, which, despite the high levels of gene flow, moderate the genetic structure between wild and managed populations.…”

Anatomical and morphological spine variation in Gymnocalycium kieslingii subsp. castaneum (Cactaceae)

“…Although a large variation of spine traits within single species has been described ( Peharec et al 2010 ), there is no extant report describing spine variation within an areole. Since the spines grow from the same lateral bud, low variation of anatomical and morphological parameters would be expected.…”

“…Although, there is evidence that spine development is influenced by genetic ( Mihalte and Sestras 2012 ) and environmental conditions as water availability or solar radiation can modified spine growth (e.g. Peharec et al 2010 , Menezes et al 2015 ). Nevertheless, to the best of our knowledge, there is no prior study analyzing spine and fiber structure variation within areoles, individuals or populations, with the exception of variation in spine number and length (e.g.…”