Storage of short-lived seeds of Inga vera subsp. affinis in osmotic medium

Abstract

Inga vera subsp. affinis (Fabaceae) is a tree species native to riparian forests in Southeast Brazil and is key for the restoration of deforested areas. The species produce seeds that are highly recalcitrant. Extreme sensitivity to desiccation as well as vivipary are commonly observed in mature seeds, which also tend towards polyembryony. Past research has shown that typical strategies to store seeds are inapplicable to Inga vera as viability is completely lost when seeds are either dried to around 28% water content (wet basis) or stored at 5°C for a few weeks. Here, we examine the feasibility of storing the seeds under hydrated conditions but at reduced water potential. Freshly collected seeds were kept under conventional storage conditions (plastic bags in cold chamber, 5°C) and in polyethylene glycol (PEG) solutions (−1.6 and −2.4 MPa) at 10°C. Seed germination was assessed after various intervals of time, until all seeds had lost viability. Before storage, seeds attained 100% germination and produced an average of 1.8 normal seedlings per seed (due to polyembryony). Storage in PEG at −1.6 MPa maintained 90% germination (radicle protrusion) and one normal seedling per seed on average for more than 200 d. Osmotic storage likely slowed down metabolism within the seed and hence consumption of food reserves. The storage time achieved has practical applications for in situ restoration, but cannot address ex situ germplasm conservation. Extending shelf life for an additional 6 months allows tree nurseries to optimize the production of seedlings so that they can be planted during the wet season.