Polaskia chende

Name, habit and habitat

The accepted name is Polaskia chende (Rol.-Goss.) A.C.Gibson & K.E.Horak. Cereus chende is a historical name for this species. POWO describes a tree-like plant associated with dry shrubland. The seed study describes a cactus reaching less than 4 m, with the populations examined coming from the Caltepec region of Puebla, a dry landscape on volcanic substrate. [2-WWW] [Ordoñez-Salanueva et al. 2017]

Light and seed dormancy

Fresh seeds germinated at 70% in white light and 37% in far-red light, while no germination occurred in darkness. The experiment used 25 ± 1°C and a twelve-hour photoperiod. Viability assessed by cutting seeds exceeded 90%. The difference between viability and germination was associated with shallow dormancy that partly declined during after-ripening. [Ordoñez-Salanueva et al. 2017]

In the field experiment, seed bags were placed 1 cm deep beneath nurse shrubs and in open ground. They were recovered over 64 months and tested for germination. A living seed fraction persisted in both microsites. Changes in germination across sampling dates indicated dormancy cycles that can distribute seedling recruitment across several seasons. [Ordoñez-Salanueva et al. 2017]

Emergence beneath nurse shrubs

Separate plots were used to observe emergence and seedling survival. Maximum cumulative emergence reached 34% in the open and 61% beneath shrubs, with these values attained at different times. The study named the nurse shrub as Acacia constricta. Its cover provided a microsite in which a larger fraction of seeds reached the seedling stage. [Ordoñez-Salanueva et al. 2017]

After 20.5 months, all monitored seedlings in the open had died, while approximately 28% of the cohort remained beneath shrubs. At 60.5 months, about 6% of sheltered seedlings were still alive. Long seed persistence in soil and more favourable conditions for young plants beneath shrubs describe different components of population regeneration. A seed can remain dormant where seedling development soon ends. [Ordoñez-Salanueva et al. 2017]

Relevance to propagation

Evaluating a seed batch requires distinguishing viability, dormancy and germination capacity under specified light conditions. In the material studied, fresh seeds retained high viability although some remained dormant. Long-term burial was a method for examining the seed bank in natural soil. Those data concern population persistence, while germination conditions are described by the separate laboratory component of the experiment. [Ordoñez-Salanueva et al. 2017]

Materials from the author's archive

The species also appears in Konrad Szychowski's private material archive. [Kaktusy i Inne 2005a]