MYRTILLOCACTUS GEOMETRIZANS (Mart. ex. Pfeiff.) Console (Cactaceae) STOMATA: VARIATION ALONG ITS DISTRIBUTION RANGE

Abstract

Stomatal size and density variation were evaluated in 20 populations of Myrtillocactus geometrizans, (Mart. ex. Pfeiff.) Console, in order to learn if the position of the segment in the branch and the geographic distribution modify type, density, and size of the stomata. Forty-nine samples were collected in the states of San Luis Potosí, Guanajuato, Querétaro, Hidalgo, Puebla, and Oaxaca. Epidermal segments 1.8 cm in diameter were removed from the apical and middle portion of the branch, in which stomata/mm² and their length were quantified. The results showed that parallelocytic stomata occurred in all the populations, and without and differences for stomatal size between the apical and middle position of the branch (P > 0.41), but only for density (P < 0.0001). A non significant correlation was detected between both positions (P > 0.27). This behavior could be related to the development of the other epidermal cells. Significant differences were detected in stomatal density and stomatal size among populations (P ≤ 0.05), having 18 stomata/mm² in San Pedro Jocotipac and 30 stomata/mm² in Santa Maria del Río, while Barranca de Tolimán had 33.97 μm and Paradero Villele 45.57 μm. Although there was an altitudinal difference of 1300 m, no effect for neither stomata character was detected (P > 0.07 and 0.90). The stomatal density and size were associated positively with latitude (P < 0.0001).