Ecological longevity of Polaskia chende (Cactaceae) seeds in the soil seed bank, seedling emergence and survival

Abstract

Soil seed banks are essential elements of plant population dynamics, enabling species to maintain genetic variability, withstand periods of adversity and persist over time, including for cactus species. However knowledge of the soil seed bank in cacti is scanty. In this study, over a 5-year period we studied the seed bank dynamics, seedling emergence and nurse plant facilitation of Polaskia chende, an endemic columnar cactus of central Mexico. P. chende seeds were collected for a wild population in Puebla, Mexico. Freshly collected seeds were sown at 25 °C and 12-h photoperiod under white light, far-red light and darkness. The collected seeds were divided in two lots, the first was stored in the laboratory and the second was use to bury seeds in open areas and beneath a shrub canopy. Seeds were exhumed periodically over 5 years. At the same time seeds were sown in open areas and beneath shrub canopies; seedling emergence and survival were recorded over different periods of time for 5 years. The species forms long-term persistent soil seed banks. The timing of seedling emergence via germination in the field was regulated by interaction between light, temperature and soil moisture. Seeds entered secondary dormancy at specific times according to the expression of environmental factors, demonstrating irregular dormancy cycling. Seedling survival of P. chende was improved under Acacia constricta nurse plants. Finally, plant facilitation affected the soil seed bank dynamics as it promoted the formation of a soil seed bank, but not its persistence.

What are the demographic consequences of a seed bank stage for columnar cacti?

“…Seed banks seem to be more widespread than previously thought as evidence suggests short term seed banks in the subtribe Stenocerinae (Myrtillocactus geometrizans, Polaskia chende, Stenocereus sp. and Stenocereus stelatus) (Ordoñez, 2008;Cano-Salgado et al, 2012;Álvarez-Espino et al, 2014;Ordoñez Salanueva et al, 2017) a pattern similar to that reported for many long-lived plants 408 including succulents, shrubs, and trees (Silvertown et al, 1993;409 Enright et al, 1995;Franco and Silvertown, 2004). Arid and of recruitment at any given time gives the impression of a slowly decreasing population that depends on survival (Holland and Molina-Freaner, 2013).…”

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

“…There are few studies that have submitted the seeds to environmental conditions and have examined their viability after different burial periods (Bowers 2000, 2005, Matías-Palafox 2007Olvera-Carrillo et al 2009, Cheib & Souza 2012, Goodman et al 2012, Álvarez-Espino et al 2014, Ordoñez-Salanueva et al 2017, Lindow-López et al 2018a, Aragón-Gastélum et al 2018 or have assessed the effective seed bank, extracting the seeds from the soil in different times of the year (Montiel & Montaña 2003). Only the studies of Bowers (2005) and Ordoñez-Salanueva et al (2017) shows two species (Mammillaria grahamii and Polaskia chende) capable of possessing a long-term, continuous seed bank (up to at least five years) according to the classification of Bakker et al (1996).…”

Potential impact of global warming on seed bank, dormancy and germination of three succulent species from the Chihuahuan Desert

“…The potential for soil seed bank formation was evaluated by burying the seeds and subsequently examining their germination percentage at regular intervals (Cheib and Garcia, 2012) following the design used by Ordóñez-Salanueva et al (2017). Forty-eight batches containing 55 seeds (2640 seeds) per species were made.…”

“…Physiological seed dormancy is expected in these species, because it is common in their families (Baskin and Baskin, 1998). Cactus seeds can enter secondary dormancy with cues from specific conditions such as darkness (Flores et al , 2006; Rojas-Aréchiga and Mandujano-Sánchez, 2017), and at specific times, according to variation of environmental factors (Álvarez-Espino et al , 2014; Ordóñez-Salanueva et al , 2017). Thus, some seeds of succulent species germinate in summer, the rainy season, but others can enter dormancy.…”

“…Seeds with physiological dormancy can cycle through a gradation of dormancy 'states' in response to their environment, during which the range of conditions in which the seeds are able to germinate widens and contracts (Long et al, 2015). Dormancy cycling has also been found in the cactus Polaskia chende from the Tehuacan Valley (Ordóñez-Salanueva et al, 2017). Dormancy cycling indicates that the ungerminated seeds are viable seeds in the soil seed bank of E. platyacanthus.…”