Seed morphology and variation in the genus Pachycereus (Cactaceae)

Abstract

Seeds of 13 Pachycereus species and two Stenocereus species that have been suggested as closely related were examined with the scanning electron microscope. Quantitative features were evaluated using multivariate analysis in order to identify characters that distinguish them. Several species groups were recognized on the basis of 16 qualitative characters. All species studied are keeled. Stenocereus aragonii and S. eichlamii share with most Pachycereus species large size, glossy appearance, and a flat relief on periclinal cells in the lateral region. Pachycereus gatesii and P. schottii are unique in having the smallest seeds and a deeply impressed hilum-micropylar region. P. hollianus does not exhibit micro-relief on periclinal walls in the lateral region, and P. fulviceps has no expanded testa border. Multivariate analysis showed that four characters, length, breadth, hilum-micropylar region length, and angle, made the greatest contribution to distinguishing among species groups. More than 80% of P. fulviceps, P. hollianus, P. tepamo, P. weberi, and S. eichlamii seeds could be classified correctly using four seed features and the percentage was even higher using just two or three features for P. gatesii, P. grandis, P. militaris, P. pringlei, and P. schottii. Testa appearance, testa cell-pattern, and position relative to the rim of the hilum-micropylar region were found to be potentially informative and should be combined with other sources of data in future phylogenetic analyses.

Germinação in vitro e desenvolvimento pós-seminal de plântulas de Pilosocereus aurisetus (Werderm.) Byles & G.D. Rowley (Cactaceae)

“…Na região mais angulada da semente, localiza-se o hilo e, em algumas sementes, a polpa funicular mucilaginosa pode estar presente. Essas informações são importantes, pois características como coloração do tegumento, forma e cor do hilo possibilitam a diferenciação de espécies de cactáceas, mesmo quando pertencentes a um mesmo gênero (Arias & Terrazas, 2004).…”

Tissue culture of ornamental cacti

“…The construction of a dam near Zimapan, México, caused the Several factors must be taken into account for seed germination to occur, such as the color, form, size, age, temperature, salinity, light, water potential, acidity, weight and origin of the seeds (Rojas-Aréchiga et al, 1997; Arias and Terrazas, 2004;Orozco-Segovia et al, 2007;Jiménez-Aguilar and Flores, 2010). For germination of cactus seeds, humidity and temperature are the most important factors.…”

Effects of Pollen Load and Donor Diversity on Seed and Fruit Mass in the Columnar Cactus, Pachycereus schottii (Cactaceae)

“…Flowers are hermaphroditic, containing -100 anthers, one pistil, and an inferior ovary with 200-400 ovules (Holland and Chamberlain 2007). Fruits contain hundreds of seeds, the smallest in size of the Pachycereus genus (Arias and Terrazas 2004), more than 95% of which germinate on moistened filter paper (Holland and Fleming 1999). At sunset, flowers open and anthers dehisce; flowers close <12 h later, often before sunrise, thereby excluding diurnal copoUinators (Holland and Fleming 2002).…”