After-ripening, Light Conditions, and Cold Stratification Influence Germination of Marula [Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro] Seeds

Abstract

<jats:p>Marula [<jats:italic>Sclerocarya birrea</jats:italic> (A. Rich.) Hochst. subsp. <jats:italic>caffra</jats:italic> (Sond.) Kokwaro (Anacardiaceae)] is used in many African countries as a food crop and is also in demand for industrial purposes. The fruit pulp has high vitamin C levels and the nuts have a high protein and oil content. The fruit pulp is commercially used in the production of an alcoholic beverage (Amarula Cream) and the oil is gaining importance in the cosmetic industry. Although attempts are being made to domesticate this high-value indigenous tree, there is very limited information available on aspects of seed germination. Our study investigated the role of light, temperature, cold stratification, and after-ripening on seed germination of <jats:italic>S</jats:italic>. <jats:italic>birrea</jats:italic>. Temperatures between 25 and 35 °C favored germination of opercula-removed seeds under continuous dark conditions. White light completely inhibited seed germination with the inhibitory effect being reversed when seeds were transferred to dark conditions. This photoinhibitory effect on opercula-removed seeds was lost after 12 months of seed storage at room temperature in the dark. Cold stratification (5 °C) of intact seeds for 14 days significantly improved germination (65%) as compared with nonstratified seeds (32%). Pregermination treatments (acid scarification, boiling water, dry heat, soaking, and plant growth regulators) of <jats:italic>S. birrea</jats:italic> seeds did not promote germination. Seeds of <jats:italic>S. birrea</jats:italic> can be considered orthodox because they tolerated desiccation without significant loss of viability. Both intact and opercula-removed seeds readily imbibe water suggesting physiological rather than physical dormancy. The highest germination percentage was recorded under constant dark conditions at 25 °C for opercula-removed seeds exposed to an after-ripening period of 12 months. This study indicates that after-ripening, light conditions, and cold stratification are critical factors for germination of <jats:italic>S. birrea</jats:italic> seeds.</jats:p>

Unraveling the Effects of Cold Stratification and Temperature on the Seed Germination of Invasive Spartina alterniflora Across Latitude

“…In temperate and boreal regions, stratification helps break dormancy for seeds after the cold, wet, winter period ( Baskin and Baskin, 2014 ). For example, cold stratification has been shown to increase germination percentage and germination rate in species such as Arbutus unedo , Corylopsis coreana , Primula beesiana , and Sclerocarya birrea ( Moyo et al, 2009 ; Pipinis, 2017 ; Kim et al, 2018 ; Yang et al, 2020 ). Although longer stratification times are usually needed by species that experience longer winters ( Zhang et al, 2019 ), prolonged seed stratification may reduce germination and subsequent seedling survival ( Plyler and Carrick, 1993 ; Plyler and Proseus, 1996 ).…”

Effects of temperature and light on germination and early seedling development of the pine pink orchid (Bletia purpurea)

“…2006). Cold stratification (Baskin & Baskin 2001; Moyo et al. 2009; Han & Long 2010) and oscillating temperatures (Baskin & Baskin 2001, 2003) have also been shown to break dormancy and/or promote germination.…”

Seed (true seed plus endocarp) dormancy in Anacardiaceae in relation to infrafamilial taxonomy and endocarp anatomy

“…al. (1986),Lewis (1987), Holtzhausen et al (1990,Msanga (1998), Jøker and Erdey (2003),Gamémé et al (2004),Pritchard et al (2004),Moyo et al (2009),Dlamini (2010),Agbogan et al (2014) and Hamidou et al…”