STEM ANATOMY OF THREE SPECIES OF GENUS Hylocereus (Berger) Britton & Rose (CACTACEAE) IN MÉXICO

Abstract

The stem anatomy of three species of Hylocereus (H. ocamponis, H. purpusii, H. undatus) distributed in México was studied to evaluate the variation among species and the relationship of wood with distribution (latitude, longitude, elevation) and climate (temperature and rainfall) variables. Dermal, fundamental, and vascular tissues were analyzed on 50 samples from 10 populations. The primary tissues were embedded in paraffin while secondary tissues were sec-tioned with sliding microtome without embedding. Differences among populations or species were asserted by analysis of variance and by a mean comparison test (Tukey, 0.05). Wood variables plus three distribution and three climate variables were included in a principal component analysis to identify those variables which explained the higher percentage of variance. The results showed that the three species of Hylocereus have vessel elements with simple perforation plates, pseudoscalariform intervascular pits, libriform fibers, scanty paratracheal parenchyma, and heterogenous rays; this wood is considered mesomorphic and distinctive of Cactoideae subfamily. There were differences (P ≤ 0.05) among species for vessels element length, fiber length, and ray size. Principal component analysis showed that wood characters related to water movement had the highest contribution to explain variance, suggesting a trade-off between water movement efficiency and mechanical support.