Developmental Reaction Norms for Water Stressed Seedlings of Succulent Cacti

Succulent cacti are remarkable plants with capabilities to withstand long periods of drought. However, their adult success is contingent on the early seedling stages, when plants are highly susceptible to the environment. To better understand their early coping strategies in a challenging environment, two developmental aspects (anatomy and morphology) in Polaskia chichipe and Echinocactus platyacanthus were studied in the context of developmental reaction norms under drought conditions. The morphology was evaluated using landmark based morphometrics and Principal Component Analysis, which gave three main trends of the variation in each species. The anatomy was quantified as number and area of xylem vessels. The quantitative relationship between morphology and anatomy in early stages of development, as a response to drought was revealed in these two species. Qualitatively, collapsible cells and collapsible parenchyma tissue were observed in seedlings of both species, more often in those subjected to water stress. These tissues were located inside the epidermis, resembling a web of collapsible-cell groups surrounding turgid cells, vascular bundles, and spanned across the pith. Occasionally the groups formed a continuum stretching from the epidermis towards the vasculature. Integrating the morphology and the anatomy in a developmental context as a response to environmental conditions provides a better understanding of the organism's dynamics, adaptation, and plasticity

Morpho-anatomy of species in Tribe Pachycereeae seedlings. Until when are they seedlings? [Morfo-anatomóa de plántulas en especies de pachycereeae: ZapotitlánHasta cuZapotitlánndo son plántulas?]

Morpho-anatomy of species in Tribe Pachycereeae seedlings is described and compared with the aim to find differences between the initial growth and establishment stages and to determine the point in time of the change from seedling to young plant. The morpho-anatomical traits were observed from sampling more than 500 seedlings of six species belonging to five genera of this tribe. Seedlings were collected weekly the first three-months after germination and afterwards they were collected monthly to complete 24-months of growth. Statistical differences (P < 0.05) were observed for seedling height, root length, and stem width and height between the species at different ages. A delay in stem and root development was found in Escontria chiotilla and Myrtillocactus geometrizans, species with the smallest seeds. Moreover, the studied species share dermal, fundamental, and vascular tissue traits, however the protein bodies distinguish Pachycereus grandis and the prismatic crystals in epidermis-hypodermis characterize species of Neobuxbaumia. At the onset of vascular cambium, only vessel elements and wide band tracheids become differentiated, whereas fibers appeared in some species after they had one-year of age. We concluded that disappearance of cotyledons, differentiation of ribs, establishment of vascular cambium, a greater accumulation wood, and differentiation of medullary bundles allow us to determine the limits between the seedling stage and the young plant stage

Morpho-anatomy of species in Tribe Pachycereeae seedlings. Until when are they seedlings? [Morfo-anatomía de plántulas en especies de pachycereeae: ¿Hasta cuándo son plántulas?]

Morpho-anatomy of species in Tribe Pachycereeae seedlings is described and compared with the aim to find differences between the initial growth and establishment stages and to determine the point in time of the change from seedling to young plant. The morpho-anatomical traits were observed from sampling more than 500 seedlings of six species belonging to five genera of this tribe. Seedlings were collected weekly the first three-months after germination and afterwards they were collected monthly to complete 24-months of growth. Statistical differences (P < 0.05) were observed for seedling height, root length, and stem width and height between the species at different ages. A delay in stem and root development was found in Escontria chiotilla and Myrtillocactus geometrizans, species with the smallest seeds. Moreover, the studied species share dermal, fundamental, and vascular tissue traits, however the protein bodies distinguish Pachycereus grandis and the prismatic crystals in epidermis-hypodermis characterize species of Neobuxbaumia. At the onset of vascular cambium, only vessel elements and wide band tracheids become differentiated, whereas fibers appeared in some species after they had one-year of age. We concluded that disappearance of cotyledons, differentiation of ribs, establishment of vascular cambium, a greater accumulation wood, and differentiation of medullary bundles allow us to determine the limits between the seedling stage and the young plant stage

Morphological seed traits and germination of six species of Pachycereeae (Cactaceae)

Morphological seed traits and germination responses of freshly matured seeds of six species of Pachycereeae: Escontria chiotilla, Myrtillocactus geometrizans, Neobuxbaumia mezcalaensis, N. multiareolata, Pachycereus grandis, and Stenocereus queretaroensis were studied at room temperature in laboratory conditions with the hypothesis that seed size affects germination. Seeds are different in shape and testa structure. Both, number of seeds per fruit and seed traits (length, width, width/length ratio, and mass) showed statistically significant differences. The highest correlation coefficients corresponded to seed length and width, length and mass, and width and mass. Seed germination started 3-6 days after sowing in those species with larger size and mass, whereas the smaller and lighter seeds of E. chiotilla and M. geometrizans required 15 days suggesting a delay in germination, thus seeds were nondormant. Seed size and germination response differences agree with hypothesis of appertaining to different phylogenetic clades

Fruits, seeds and germination in five species of Globose Cacteae (Cactaceae)

The morphological characteristics of fruits and seeds, and the germination responses of freshly matured seeds of five species of Cacteae (Coryphantha bumamma, C. clavata, C. cornifera, Ferocactus histrix and Mammillaria uncinata) were studied at room temperature under laboratory conditions. The aim of the study was to record the macro- and micro-morphology of fruits and seeds of these species and to investigate specific requirements for germination. Variance analysis detected significant differences (p80%) are observed on the sixth day in F. histrix and M. uncinata. It is concluded that some morphological characteristics of fruits and seeds can be used to support further systematic studies of Cactoideae genera and will contribute new knowledge for their potential use and conservation

Morphological seed traits and germination of six species of Pachycereeae (Cactaceae)

Morphological seed traits and germination responses of freshly matured seeds of six species of Pachycereeae: Escontria chiotilla, Myrtillocactus geometrizans, Neobuxbaumia mezcalaensis, N. multiareolata, Pachycereus grandis, and Stenocereus queretaroensis were studied at room temperature in laboratory conditions with the hypothesis that seed size affects germination. Seeds are different in shape and testa structure. Both, number of seeds per fruit and seed traits (length, width, width/length ratio, and mass) showed statistically significant differences. The highest correlation coefficients corresponded to seed length and width, length and mass, and width and mass. Seed germination started 3-6 days after sowing in those species with larger size and mass, whereas the smaller and lighter seeds of E. chiotilla and M. geometrizans required 15 days suggesting a delay in germination, thus seeds were nondormant. Seed size and germination response differences agree with hypothesis of appertaining to different phylogenetic clades

Fruits, seeds and germination in five species of Globose Cacteae (Cactaceae)

The morphological characteristics of fruits and seeds, and the germination responses of freshly matured seeds of five species of Cacteae (Coryphantha bumamma, C. clavata, C. cornifera, Ferocactus histrix and Mammillaria uncinata) were studied at room temperature under laboratory conditions. The aim of the study was to record the macro- and micro-morphology of fruits and seeds of these species and to investigate specific requirements for germination. Variance analysis detected significant differences (p80%) are observed on the sixth day in F. histrix and M. uncinata. It is concluded that some morphological characteristics of fruits and seeds can be used to support further systematic studies of Cactoideae genera and will contribute new knowledge for their potential use and conservation