A temperate rhamnaceous species with a non-enclosing stone and without physical dormancy

Abstract

The purpose of the present study was to investigate the dormancy break and germination requirements of seeds from the rhamnaceous vine Berchemia scandens. The fleshy fruit contains a two-locular stone with an endocarp described as ‘bony, thickish’. Scarified and non-scarified stones increased by about 30–50% in mass during imbibition over a 24-h period. The endocarp of the stone does not completely enclose the seeds and a soft tissue region is present. This region is the primary area of water entrance to the seed, as shown by dye-tracking and by sealing it. Freshly matured and overwintered seeds of B. scandens germinated to low percentages at all temperatures during 2 weeks of incubation in light, and they germinated from moderate to high percentages during 12–14 weeks of incubation in light. While cold stratification had a relatively modest effect on the promotion of total germination across most temperatures assessed (if seeds were left for long enough), it had a somewhat stronger effect on germination rate. Cold-stratified seeds germinated equally well in light and darkness. The class of dormancy found in seeds of B. scandens would be physiological. The anatomy of the stones readily allows water imbibition, showing that seeds of B. scandens lack physical dormancy, an uncommon trait in Rhamnaceae.

Germination responses to winter warm spells and warming vary widely among woody plants in a temperate forest

“…In contrast, fresh seeds of B. scandens, C. laevigata, E. fortunei, J. virginiana, Lonicera japonica, P. quinquefolia and V. vulpina germinated to low percentages, but cold-stratified seeds to moderate to high percentages across the temperature range. The germination responses in other populations of these same species have also been found to improve with cold stratification (Hidayati et al 2000;Bonner & Karrfalt 2008;Walck et al 2012;Rounsaville et al 2018). Ligustrum sinense and Lonicera maackii produced seeds that were mostly non-dormant when freshgerminating to higher percentages than the other species.…”

“… b Stone consisted of two (inseparable) locules; a locule contained a seed or was empty (Walck et al 2012). …”

“…We monitored the temperature and relative humidity in each incubator throughout the study using dataloggers (Tinytag Plus 2; Gemini Data Loggers, Chichester, UK) to make certain that both variables remained steady. Stone consisted of two (inseparable) locules; a locule contained a seed or was empty (Walck et al 2012).…”

Thermal niche for in situ seed germination by Mediterranean mountain streams: model prediction and validation for Rhamnus persicifolia seeds

“…Seeds of the Rhamnaceae have an investing embryo (Martin, 1946) and can be non-dormant or, following the dormancy classification system Baskin, 1998, 2004), show physiological (PD), physical dormancy (PY) or combined ( physical and physiological; PY + PD) dormancy. Physical dormancy is the most represented class in this family (61 % of the investigated species), followed by PY + PD (22 %), PD (12 %) and nondormancy (ND) (6 %; Walck et al, 2012). Mattana et al (2009) reported that germination of R. persicifolia seeds could be achieved, without any scarification, at warm temperatures (≥20 8C), excluding the presence of PY.…”

Filing considerably breaks seed dormancy of Berchemia discolour Hemsley

“…Application of the pre-treatment method of filing should be improved so as to achieve a better germination rate. Seed coat impermeability is not the only cause for prolonged and low germination for B. discolour and it is recommended that the seeds be chopped at the radicle end followed by soaking in cold water and drying in the sun for 24 h as a method to promote germination (Walck et al, 2012). Majaju and Zananga (2006), working on indigenous tree species in Zimbabwe, germinated a variety of trees and observed varied germination rates.…”