Seed traits and germination in the Cactaceae family: A review across Americas

Abstract

Background: Cactaceae is the fifth taxonomic group with the highest proportion of threatened species and among the angiosperms, the most vulnerable to human disturbance. One way to contribute to the preservation of this family is to understand the processes that promote seed germination.
 Questions: Have the relationship between seed traits and cactus germination been documented? How common is dormancy and seed banks in Cactaceae? Are there general patterns in cacti germination response to temperature, light, water, salinity, phytohormones, hydration/dehydration cycles, mechanical or chemical scarification?
 Data description: A total of 333 studies on cactus germination with information on 409 taxa.
 Study site and dates: since 1939 to January 2020.
 Methods: A search of scientific articles in Google Scholar was performed with the words Cactaceae, cacti and cactus, in combination with various matters on germination in English, Spanish and Portuguese.
 Results: The main germination studies in cactus deal with photoblasticism (275 taxa), temperature (205 taxa) and seed longevity (142 taxa). Other lines of study in cactus germination (e.g., desiccation tolerance, vivipary, phytohormones, mechanical or chemical scarification, in vitro germination, hydration/dehydration cycles, water and saline stress, serotiny, storage in cold, high temperature tolerance and soil seed bank) include between 14 and 65 taxa. Cacti have only physiological dormancy and optimal germination for most species occur between 20 and 30 °C. Photoblasticism is strongly influenced by phylogeny with 80.9 % positive photoblastic species.
 Conclusions: Mexico, Brazil and Argentina are the three leading countries in the study of cactus germination.

Combined effect of temperature and water stress on seed germination of four Leptocereus spp. (Cactaceae) from Cuban dry forests

“…From our four species, L. ekmanii showed the lowest germinability and MGT, probably due to the presence of dormant seeds in a fraction of the seed lot, as in other cactus species (Barrios, et al, 2020; Rojas‐Aréchiga & Vázquez‐Yanes, 2000). Fast seed germination is a common phenomenon in the Cactaceae, with species with germination (at optimal temperature) in the first few days (De la Barrera & Nobel, 2003; Meiado, 2016; Parsons, Vandelook, & Janssens, 2014) or weeks (Seal et al, 2009) after sowing, except for species with seed dormancy (Olvera‐Carrillo et al, 2003).…”

“…The decrease in germination of Cuban Leptocereus species that inhabit dry or semi‐arid environments in response to decreasing water potential was stronger than that of other cactus species. In 28 cacti studied at −0.4 MPa water potential, the mean of germinability was about 50% (see Barrios, et al, 2020), with several species exhibiting a germinability between 55 and 100% at this water potential, for example, Ferocactus histrix (Flores et al, 2017), Gymnocalycium mostii (Gurvich et al, 2017), Trichocereus candicans (Mazzola, Cenizo, & Kin, 2013), Neobuxbaumia tetetzo and Neobuxbaumia macrochephala (Ramírez‐Padilla & Valverde, 2005), Pilosocereus arrabidae (Martins, Pereira, Carvalho, Barros, & De Andrade, 2012), Polaskia chichipe , Polaskia chende , Myrtillocactus schenckii and Escontria chiotilla (Guillén, Casas, & Rodríguez‐Morales, 2015), Mammillaria gaumeri (Cervera, Andrade, Simá, & Graham, 2006), Cereus jamacaru subsp. jamacaru (Meiado et al, 2010) and Selenicereus undatus (Ortiz, Gomes, Takahashi, Urbano, & Strapasson, 2014, respectively), or even an increase in seed germination at −0.4 MPa, for example, Pachycereus hollianus (Flores & Briones, 2001) and Echinocactus platyacanthus (Flores et al, 2017).…”

“…Temperature and water stress are the most important factors affecting seed germination (Baskin & Baskin, 2014). Although in most cacti the germination mainly occurs at water potentials between −0.6 and 0 MPa (Barrios, Sánchez, Flores, & Jurado, 2020), cactus seeds have developed adaptations to germinate with high temperatures and highly variable soil moisture in their habitats. Some cactus species from arid and semi‐arid environments can germinate even at −1 MPa (De la Barrera & Nobel, 2003; Guillén, Terrazas, De la Barrera, & Casas, 2011).…”

In vitro conservation and genetic diversity of threatened species of Melocactus (Cactaceae)

“…In this context, water availability, substrate preference, association with nursery plants, herbivory and competition are factors that make germination and the initial establishment of these plants naturally di cult (Godínez-Álvarez et al 2003;Machado 2009;Barrios et al 2020). Consequently, only a part of the seeds present in the soil would germinate.…”

Are wildfires affecting seed germination in cactus? An experimental assessment

“…Although the germination response to heat shock of many species from different regions has been widely studied, works have largely focused on trees, shrubs, forbs and grasses (e.g. Luna et al 2007;Dayamba et al 2008;Zuloaga-Aguilar et al 2010;Jaureguiberry & Díaz 2015;Arcamone & Jaureguiberry 2018;Zirondi et al 2019), whereas other growth forms of conspicuous regional importance, such as cacti, have rarely been assessed (Barrios et al 2020).…”